Google Scholar
Encyclopedia
Google Scholar is a freely accessible web search engine
that indexes the full text of scholarly literature across an array of publishing formats and disciplines. Released in beta in November 2004, the Google Scholar index includes most peer-review
ed online journal
s of Europe and America's largest scholarly publishers. It is similar in function to the freely available Scirus
from Elsevier
, CiteSeerX
, and getCITED
. It is also similar to the subscription-based tools, Elsevier's Scopus
and Thomson ISI's Web of Science
. Its advertising slogan — "Stand on the shoulders of giants" — is a nod to the scholars who have contributed to their fields over the centuries, providing the foundation for new intellectual achievements.
In 2006, in response to release of Microsoft's Windows Live Academic
Search, a potential competitor for Google Scholar, a citation importing feature was implemented using bibliography managers
(such as RefWorks
, RefMan
, EndNote
, and BibTeX
). Similar features are also part of other search engines, such as CiteSeer
and Scirus
.
In 2007, Acharya announced that Google Scholar had started a program to digitize and host journal articles in agreement with their publishers, an effort separate from Google Books, whose scans of older journals do not include the metadata required for identifying specific articles in specific issues.
Using its "group of" feature, it shows the available links to journal articles. In the 2005 version, this feature provided a link to both subscription-access versions of an article and to free full-text versions of articles; for most of 2006, it provided links to only the publishers' versions. Since December 2006, it has provided links to both published versions and major open access repositories, but still does not cover those posted on individual faculty web pages; access to such self-archived non-subscription versions is now provided by a link to Google
, where one can find such open access articles.
Through its "cited by" feature, Google Scholar provides access to abstracts of articles that have cited the article being viewed. It is this feature in particular that provides the citation indexing previously only found in Scopus
and Web of Knowledge. Through its "Related articles" feature, Google Scholar presents a list of closely related articles, ranked primarily by how similar these articles are to the original result, but also taking into account the relevance of each paper.
, Google Scholar is not yet available to the Google AJAX API
.
Google Scholar’s legal database of US cases is extensive. Users can search and read published opinions of US state appellate and supreme court cases since 1950, US federal district, appellate, tax and bankruptcy courts since 1923 and US Supreme Court cases since 1791. Google Scholar embeds clickable citation links within the case and the How Cited tab allows lawyers to research prior case law and the subsequent citations to the court decision. The Google Scholar Legal Content Star Paginator extension inserts Westlaw and LexisNexis style page numbers in line with the text of the case.
and words included in a document's title. As a consequence the first search results are often highly cited articles.
(UI) is still in beta. The reviews recognize that its "cited by" feature in particular poses serious competition to Scopus and ISI Web of Knowledge, although it generally returns fewer results than subscription services. Another important issue is that the relative coverage of Google Scholar varies by discipline compared to other general databases.
A significant problem with Google Scholar is the secrecy about its coverage. Some publishers do not allow it to crawl their journals. Elsevier
journals were not included before mid-2007, when Elsevier began to make most of its ScienceDirect
content available to Google Scholar and Google's web search. As of February 2008 the absentees still included the most recent years of the American Chemical Society
journals. Google Scholar does not publish a list of scientific journals crawled, and the frequency of its updates is unknown. It is therefore impossible to know how current or exhaustive searches are in Google Scholar. Nonetheless, it allows easy access to published articles without the difficulties encountered in some of the most expensive commercial databases.
Google Scholar puts high weight on citation counts in its ranking algorithm and therefore is being criticised for strengthening the Matthew effect
; as highly cited papers appear in top positions they gain more citations while new papers hardly appear in top positions and therefore get less attention by the users of Google Scholar and hence fewer citations.
Google Scholar has problems identifying publications on the arXiv
preprint server correctly. Interpunctuation characters in titles produce wrong search results, and authors are assigned to wrong papers, which leads to erroneous additional search results. Some search results are even given without any comprehensible reason.
Google Scholar is vulnerable to spam
. Researchers from the University of California, Berkeley
and Otto-von-Guericke University Magdeburg demonstrated that citation counts on Google Scholar can be manipulated and complete non-sense articles created with SCIgen
were indexed from Google Scholar. They concluded that citation counts from Google Scholar should only be used with care especially when used to calculate performance metrics such as the h-index
or impact factor
. Although Google Scholar does not compute the h-index itself, several downstream web sites use its data. The practicality of manipulating h-index calculators by spoofing
Google Scholar was demonstrated in 2010 by Cyril Labbe from Joseph Fourier University
, who managed to rank "Ike Antkare" ahead of Albert Einstein
by means of a large set of SCIgen
-produced documents citing each other (effectively an academic link farm
).
Google Scholar is also not able to shepardize case law, as Westlaw
and Lexis
can.
Web search engine
A web search engine is designed to search for information on the World Wide Web and FTP servers. The search results are generally presented in a list of results often referred to as SERPS, or "search engine results pages". The information may consist of web pages, images, information and other...
that indexes the full text of scholarly literature across an array of publishing formats and disciplines. Released in beta in November 2004, the Google Scholar index includes most peer-review
Peer review
Peer review is a process of self-regulation by a profession or a process of evaluation involving qualified individuals within the relevant field. Peer review methods are employed to maintain standards, improve performance and provide credibility...
ed online journal
Academic journal
An academic journal is a peer-reviewed periodical in which scholarship relating to a particular academic discipline is published. Academic journals serve as forums for the introduction and presentation for scrutiny of new research, and the critique of existing research...
s of Europe and America's largest scholarly publishers. It is similar in function to the freely available Scirus
Scirus
Scirus is a comprehensive science-specific search engine. Like CiteSeerX and Google Scholar, it is focused on scientific information. Unlike CiteSeerX, Scirus is not only for computer sciences and IT and not all of the results include full text. It also sends its scientific search results to...
from Elsevier
Elsevier
Elsevier is a publishing company which publishes medical and scientific literature. It is a part of the Reed Elsevier group. Based in Amsterdam, the company has operations in the United Kingdom, USA and elsewhere....
, CiteSeerX
CiteSeerX
CiteSeerX is a public search engine and digital library and repository for scientific and academic papers with a focus on computer and information science. It is loosely based on the previous CiteSeer search engine and digital library and is built with a new open source infrastructure, SeerSuite,...
, and getCITED
GetCITED
GetCITED is a website database that lists publication and citation information on academic articles whose information is entered by members. It aims to include not only journal articles but also book chapters and other publications, both peer-reviewed and non-reviewed...
. It is also similar to the subscription-based tools, Elsevier's Scopus
Scopus
Scopus, officially named SciVerse Scopus, is a bibliographic database containing abstracts and citations for academic journal articles. It covers nearly 18,000 titles from over 5,000 international publishers, including coverage of 16,500 peer-reviewed journals in the scientific, technical, medical,...
and Thomson ISI's Web of Science
Web of Science
ISI Web of Knowledge is an academic citation indexing and search service, which is combined with web linking and provided by Thomson Reuters. Web of Knowledge coverage encompasses the sciences, social sciences, arts and humanities. It provides bibliographic content and the tools to access, analyze,...
. Its advertising slogan — "Stand on the shoulders of giants" — is a nod to the scholars who have contributed to their fields over the centuries, providing the foundation for new intellectual achievements.
History
Google Scholar arose out of a discussion between Alex Verstak and Anurag Acharya, both of whom were then working on building Google's main web index.In 2006, in response to release of Microsoft's Windows Live Academic
Windows Live Academic
Live Search Academic was a Web search engine for scholarly literature which existed from 2006–2008; it was part of Microsoft's Live Search group of services. It was similar, rather than equivalent, to Google Scholar in that the users are required to login before accessing the service...
Search, a potential competitor for Google Scholar, a citation importing feature was implemented using bibliography managers
Reference management software
Reference management software, citation management software or personal bibliographic management software is software for scholars and authors to use for recording and utilising bibliographic citations . Once a citation has been recorded, it can be used time and again in generating bibliographies,...
(such as RefWorks
RefWorks
RefWorks is a web-based commercial citation manager — an application for managing references, retrieving bibliographic information, and designing texts in terms of their literature references...
, RefMan
Reference Manager
Reference Manager is a commercial reference management software package sold by Thomson Reuters. It was the first commercial software of its kind, originally developed by Ernest Beutler and his son, Earl Beutler, in 1982 through their company Research Information Systems...
, EndNote
EndNote
EndNote is a commercial reference management software package, used to manage bibliographies and references when writing essays and articles. It is produced by Thomson Reuters.- Features :...
, and BibTeX
BibTeX
BibTeX is reference management software for formatting lists of references. The BibTeX tool is typically used together with the LaTeX document preparation system...
). Similar features are also part of other search engines, such as CiteSeer
CiteSeer
CiteSeer was a public search engine and digital library for scientific and academic papers. It is often considered to be the first automated citation indexing system and was considered a predecessor of academic search tools such as Google Scholar and Microsoft Academic Search. It was replaced by...
and Scirus
Scirus
Scirus is a comprehensive science-specific search engine. Like CiteSeerX and Google Scholar, it is focused on scientific information. Unlike CiteSeerX, Scirus is not only for computer sciences and IT and not all of the results include full text. It also sends its scientific search results to...
.
In 2007, Acharya announced that Google Scholar had started a program to digitize and host journal articles in agreement with their publishers, an effort separate from Google Books, whose scans of older journals do not include the metadata required for identifying specific articles in specific issues.
Features and specifications
Google Scholar allows users to search for digital or physical copies of articles, whether online or in libraries. “Scholarly” searches will appear using the references from “’full-text journal articles, technical reports, preprints, theses, books, and other documents, including selected Web pages that are deemed to be “scholarly.’” Harry Homan should win it. Because most of Google Scholar's search results link directly to commercial journal articles, a majority of the time users will only be able to access a brief summary of the articles topics, as well as small amounts of important information regarding the article, and possibly have to pay a fee to access the entire article. Google Scholar is as easy to use as with the regular Google web search, especially with the helpfulness of the "advanced search" option, which can automatically narrow search results to a specific journal or article. The most relevant results for the searched keywords will be listed first, in order of the author's ranking, the number of references that are linked to it and their relevance to other scholarly literature, and the ranking of the publication that the journal appears in.Using its "group of" feature, it shows the available links to journal articles. In the 2005 version, this feature provided a link to both subscription-access versions of an article and to free full-text versions of articles; for most of 2006, it provided links to only the publishers' versions. Since December 2006, it has provided links to both published versions and major open access repositories, but still does not cover those posted on individual faculty web pages; access to such self-archived non-subscription versions is now provided by a link to Google
Google
Google Inc. is an American multinational public corporation invested in Internet search, cloud computing, and advertising technologies. Google hosts and develops a number of Internet-based services and products, and generates profit primarily from advertising through its AdWords program...
, where one can find such open access articles.
Through its "cited by" feature, Google Scholar provides access to abstracts of articles that have cited the article being viewed. It is this feature in particular that provides the citation indexing previously only found in Scopus
Scopus
Scopus, officially named SciVerse Scopus, is a bibliographic database containing abstracts and citations for academic journal articles. It covers nearly 18,000 titles from over 5,000 international publishers, including coverage of 16,500 peer-reviewed journals in the scientific, technical, medical,...
and Web of Knowledge. Through its "Related articles" feature, Google Scholar presents a list of closely related articles, ranked primarily by how similar these articles are to the original result, but also taking into account the relevance of each paper.
, Google Scholar is not yet available to the Google AJAX API
Google AJAX APIs
Google AJAX APIs is a JavaScript library to integrate rich, multimedia, search, or feed-based Internet content into web applications/pages, organized by Google. They can be used by third parties to place rich Ajax content on web pages.-External links:*...
.
Google Scholar’s legal database of US cases is extensive. Users can search and read published opinions of US state appellate and supreme court cases since 1950, US federal district, appellate, tax and bankruptcy courts since 1923 and US Supreme Court cases since 1791. Google Scholar embeds clickable citation links within the case and the How Cited tab allows lawyers to research prior case law and the subsequent citations to the court decision. The Google Scholar Legal Content Star Paginator extension inserts Westlaw and LexisNexis style page numbers in line with the text of the case.
Ranking algorithm
While most academic databases and search engines allow users to select one factor (e.g. relevance, citation counts, or publication date) to rank results, Google Scholar ranks results with a combined ranking algorithm in a "way researchers do, weighing the full text of each article, the author, the publication in which the article appears, and how often the piece has been cited in other scholarly literature". Research has shown that Google Scholar puts high weight especially on citation countsCitation impact
Citation is the process of acknowledging or citing the author, year, title, and locus of publication of a source used in a published work. Such citations can be counted as measures of the usage and impact of the cited work. This is called citation analysis or bibliometrics...
and words included in a document's title. As a consequence the first search results are often highly cited articles.
Limitations and criticism
Some searchers consider Google Scholar of comparable quality and utility to commercial databases, even though its user interfaceUser interface
The user interface, in the industrial design field of human–machine interaction, is the space where interaction between humans and machines occurs. The goal of interaction between a human and a machine at the user interface is effective operation and control of the machine, and feedback from the...
(UI) is still in beta. The reviews recognize that its "cited by" feature in particular poses serious competition to Scopus and ISI Web of Knowledge, although it generally returns fewer results than subscription services. Another important issue is that the relative coverage of Google Scholar varies by discipline compared to other general databases.
A significant problem with Google Scholar is the secrecy about its coverage. Some publishers do not allow it to crawl their journals. Elsevier
Elsevier
Elsevier is a publishing company which publishes medical and scientific literature. It is a part of the Reed Elsevier group. Based in Amsterdam, the company has operations in the United Kingdom, USA and elsewhere....
journals were not included before mid-2007, when Elsevier began to make most of its ScienceDirect
ScienceDirect
ScienceDirect is one of the largest online collections of published scientific research in the world. It is operated by the publisher Elsevier and contains nearly 10 million articles from over 2,500 journals and over 6,000 e-books, reference works, book series and handbooks issued by Elsevier...
content available to Google Scholar and Google's web search. As of February 2008 the absentees still included the most recent years of the American Chemical Society
American Chemical Society
The American Chemical Society is a scientific society based in the United States that supports scientific inquiry in the field of chemistry. Founded in 1876 at New York University, the ACS currently has more than 161,000 members at all degree-levels and in all fields of chemistry, chemical...
journals. Google Scholar does not publish a list of scientific journals crawled, and the frequency of its updates is unknown. It is therefore impossible to know how current or exhaustive searches are in Google Scholar. Nonetheless, it allows easy access to published articles without the difficulties encountered in some of the most expensive commercial databases.
Google Scholar puts high weight on citation counts in its ranking algorithm and therefore is being criticised for strengthening the Matthew effect
Matthew effect (sociology)
In sociology, the Matthew effect is the phenomenon where "the rich get richer and the poor get poorer". Those who possess power and economic or social capital can leverage those resources to gain more power or capital. The term was first coined by sociologist Robert K...
; as highly cited papers appear in top positions they gain more citations while new papers hardly appear in top positions and therefore get less attention by the users of Google Scholar and hence fewer citations.
Google Scholar has problems identifying publications on the arXiv
ArXiv
The arXiv |Chi]], χ) is an archive for electronic preprints of scientific papers in the fields of mathematics, physics, astronomy, computer science, quantitative biology, statistics, and quantitative finance which can be accessed online. In many fields of mathematics and physics, almost all...
preprint server correctly. Interpunctuation characters in titles produce wrong search results, and authors are assigned to wrong papers, which leads to erroneous additional search results. Some search results are even given without any comprehensible reason.
Google Scholar is vulnerable to spam
Spam (electronic)
Spam is the use of electronic messaging systems to send unsolicited bulk messages indiscriminately...
. Researchers from the University of California, Berkeley
University of California, Berkeley
The University of California, Berkeley , is a teaching and research university established in 1868 and located in Berkeley, California, USA...
and Otto-von-Guericke University Magdeburg demonstrated that citation counts on Google Scholar can be manipulated and complete non-sense articles created with SCIgen
SCIgen
SCIgen is a program created by scientists at the Massachusetts Institute of Technology that randomly generates nonsense in the form of computer science research papers, including graphs, diagrams, and citations...
were indexed from Google Scholar. They concluded that citation counts from Google Scholar should only be used with care especially when used to calculate performance metrics such as the h-index
H-index
The h-index is an index that attempts to measure both the productivity and impact of the published work of a scientist or scholar. The index is based on the set of the scientist's most cited papers and the number of citations that they have received in other publications...
or impact factor
Impact factor
The impact factor, often abbreviated IF, is a measure reflecting the average number of citations to articles published in science and social science journals. It is frequently used as a proxy for the relative importance of a journal within its field, with journals with higher impact factors deemed...
. Although Google Scholar does not compute the h-index itself, several downstream web sites use its data. The practicality of manipulating h-index calculators by spoofing
Spoofing attack
In the context of network security, a spoofing attack is a situation in which one person or program successfully masquerades as another by falsifying data and thereby gaining an illegitimate advantage.- Spoofing and TCP/IP :...
Google Scholar was demonstrated in 2010 by Cyril Labbe from Joseph Fourier University
Joseph Fourier University
Université Joseph Fourier , often known as UJF, is a French university situated in the city of Grenoble and focused on the fields of sciences, technologies and health...
, who managed to rank "Ike Antkare" ahead of Albert Einstein
Albert Einstein
Albert Einstein was a German-born theoretical physicist who developed the theory of general relativity, effecting a revolution in physics. For this achievement, Einstein is often regarded as the father of modern physics and one of the most prolific intellects in human history...
by means of a large set of SCIgen
SCIgen
SCIgen is a program created by scientists at the Massachusetts Institute of Technology that randomly generates nonsense in the form of computer science research papers, including graphs, diagrams, and citations...
-produced documents citing each other (effectively an academic link farm
Link farm
On the World Wide Web, a link farm is any group of web sites that all hyperlink to every other site in the group. Although some link farms can be created by hand, most are created through automated programs and services. A link farm is a form of spamming the index of a search engine...
).
Google Scholar is also not able to shepardize case law, as Westlaw
Westlaw
Westlaw is one of the primary online legal research services for lawyers and legal professionals in the United States and is a part of West. In addition, it provides proprietary database services...
and Lexis
Lexis
Lexis may refer to:*Lexis , the total bank of words and phrases of a particular language, the artifact of which is known as a lexicon*Lexis *Lexis.com, part of the LexisNexis online information database-People with the name:...
can.
See also
- Academic databases and search engines
- Citation indexCitation indexA citation index is a kind of bibliographic database, an index of citations between publications, allowing the user to easily establish which later documents cite which earlier documents. The first citation indices were legal citators such as Shepard's Citations...
- CiteSeerXCiteSeerXCiteSeerX is a public search engine and digital library and repository for scientific and academic papers with a focus on computer and information science. It is loosely based on the previous CiteSeer search engine and digital library and is built with a new open source infrastructure, SeerSuite,...
- getCITEDGetCITEDGetCITED is a website database that lists publication and citation information on academic articles whose information is entered by members. It aims to include not only journal articles but also book chapters and other publications, both peer-reviewed and non-reviewed...
- Institute for Scientific InformationInstitute for Scientific InformationThe Institute for Scientific Information was founded by Eugene Garfield in 1960. It was acquired by Thomson Scientific & Healthcare in 1992, became known as Thomson ISI and now is part of the Healthcare & Science business of the multi-billion dollar Thomson Reuters Corporation.ISI offered...
's Web of ScienceWeb of ScienceISI Web of Knowledge is an academic citation indexing and search service, which is combined with web linking and provided by Thomson Reuters. Web of Knowledge coverage encompasses the sciences, social sciences, arts and humanities. It provides bibliographic content and the tools to access, analyze,... - Live Search Academic
- Microsoft Academic Search
- ScirusScirusScirus is a comprehensive science-specific search engine. Like CiteSeerX and Google Scholar, it is focused on scientific information. Unlike CiteSeerX, Scirus is not only for computer sciences and IT and not all of the results include full text. It also sends its scientific search results to...
- ScopusScopusScopus, officially named SciVerse Scopus, is a bibliographic database containing abstracts and citations for academic journal articles. It covers nearly 18,000 titles from over 5,000 international publishers, including coverage of 16,500 peer-reviewed journals in the scientific, technical, medical,...
- Google Scholar and Academic LibrariesGoogle Scholar and academic librariesGoogle Scholar and Academic Libraries is a web-based scholarly search engine, a citation analysis tool and a gateway to materials on the web that are open access. As well as this it connects to library journal subscriptions and book collections. It has been described as a "blended" resource for...