Web of Science
Web of Science (previously known as (ISI) Web of Knowledge) is an online subscription-based scientific citation indexing service maintained by Thomson Reuters that provides a comprehensive citation search. It gives access to multiple databases that reference cross-disciplinary research, which allows for in-depth exploration of specialized sub-fields within an academic or scientific discipline.
Background and history
A citation index is built on the fact that citations in science serve as linkages between similar research items, and lead to matching or related scientific literature, such as journal articles, conference proceedings, abstracts, etc. In addition, literature which shows the greatest impact in a particular field, or more than one discipline, can be easily located through a citation index. For example, a paper's influence can be determined by linking to all the papers that have cited it. In this way, current trends, patterns, and emerging fields of research can be assessed. Eugene Garfield, the "father of citation indexing of academic literature," who launched the Science Citation Index (SCI), which in turn led to the Web of Science, wrote:
Citations are the formal, explicit linkages between papers that have particular points in common. A citation index is built around these linkages. It lists publications that have been cited and identifies the sources of the citations. Anyone conducting a literature search can find from one to dozens of additional papers on a subject just by knowing one that has been cited. And every paper that is found provides a list of new citations with which to continue the search.
The simplicity of citation indexing is one of its main strengths. 
Search and analysis
Web of Science is described as a unifying research tool which enables the user to acquire, analyze, and disseminate database information in a timely manner. This is accomplished because of the creation of a common vocabulary, called ontology, for varied search terms and varied data. Moreover, search terms generate related information across categories.
Acceptable content for Web of Knowledge is determined by an evaluation and selection process based on the following criteria: impact, influence, timeliness, peer review, and geographic representation.
Web of Science employs various search and analysis capabilities. First, citation indexing is employed, which is enhanced by the capability to search for results across disciplines. The influence, impact, history, and methodology of an idea can be followed from its first instance, notice, or referral to the present day. This technology points to a deficiency with the keyword-only method of searching.
Second, subtle trends and patterns relevant to the literature or research of interest, become apparent. Broad trends indicate significant topics of the day, as well as the history relevant to both the work at hand, and particular areas of study.
Expanding the coverage of Web of Science, in November 2009 Thomson Reuters introduced Century of Social Sciences. This service contains files which trace social science research back to the beginning of the 20th century, and Web of Science now has indexing coverage from the year 1900 to the present. As of 3 September 2014[update], the multidisciplinary coverage of the Web of Science encompasses over 50,000 scholarly books, 12,000 journals and 160,000 conference proceedings. The selection is made on the basis of impact evaluations and comprise open-access journals, spanning multiple academic disciplines. The coverage includes: the sciences, social sciences, arts, and humanities, and goes across disciplines. However, Web of Science does not index all journals, and its coverage in some fields is less complete than in others.
Furthermore, as of September 3, 2014 the total file count of the Web of Science was 90 million records, which included over a billion cited references. This citation service on average indexes around 65 million items per year, and it is described as the largest accessible citation database.
Titles of foreign-language publications are translated into English and so cannot be found by searches in the original language.
- Conference Proceedings Citation Index covers more than 160,000 conference titles in the Sciences starting from 1990 to the present day
- Science Citation Index Expanded covers more than 8,500 notable journals encompassing 150 disciplines. Coverage is from the year 1900 to the present day.
- Social Sciences Citation Index covers more than 3,000 journals in social science disciplines. Range of coverage is from the year 1900 to the present day.
- Arts & Humanities Citation Index covers more than 1,700 arts and humanities journals starting from 1975. In addition, 250 major scientific and social sciences journals are also covered.
- Index Chemicus lists more than 2.6 million compounds. The time of coverage is from 1993 to present day.
- Current Chemical Reactions indexes over one million reactions, and the range of coverage is from 1986 to present day. The INPI archives from 1840 to 1985 are also indexed in this database.
- Book Citation Index covers more than 60,000 editorially selected books starting from 2005.
Since 2008, the Web of Science hosts a number of regional citation indices. The Chinese Science Citation Database, produced in partnership with the Chinese Academy of Sciences, was first one in a language other than English. It was followed in 2013 by the SciELO Citation Index, covering Brazil, Spain, Portugal, the Caribbean and South Africa, and more 12 countries of Latin America; and by the Korea Citation Index (KCI) in 2014, with updates from the South Korean National Research Foundation.
The seven citation indices listed above contain references which have been cited by other articles. One may use them to undertake cited reference search, that is, locating articles that cite an earlier, or current publication. One may search citation databases by topic, by author, by source title, and by location. Two chemistry databases, Index Chemicus and Current Chemical Reactions allow for the creation of structure drawings, thus enabling users to locate chemical compounds and reactions.
Abstracting and indexing
The following types of literature are indexed: scholarly books, peer reviewed journals, original research articles, reviews, editorials, chronologies, abstracts, as well as other items. Disciplines included in this index are agriculture, biological sciences, engineering, medical and life sciences, physical and chemical sciences, anthropology, law, library sciences, architecture, dance, music, film, and theater. Seven citation databases encompasses coverage of the above disciplines.
Limitations in the use of citation analysis
As with other scientific approaches, scientometrics and bibliometrics have their own limitations. Recently, a criticism was voiced pointing toward certain deficiencies of the journal impact factor (JIF) calculation process, based on Thomson Reuters Web of Science, such as: journal citation distributions usually are highly skewed towards established journals; journal impact factor properties are field-specific and can be easily manipulated by editors, or even by changing the editorial policies; this makes the entire process essentially nontransparent.
Regarding the more objective journal metrics, there is a growing view that for greater accuracy it must be supplemented with an article-level metrics and peer-review. Thomson Reuters replied to criticism in general terms by stating that "no one metric can fully capture the complex contributions scholars make to their disciplines, and many forms of scholarly achievement should be considered."
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- "Chinese Science Citation Database".
- "Thomson Reuters Collaborates with SciELO to Showcase Emerging Research Centers within Web of Knowledge".
- "Thomson Reuters Collaborates with National Research Foundation of Korea to Showcase the Region's Research in Web of Science".
- San Francisco Declaration on Research Assessment: Putting science into the assessment of research, December 16, 2012
- Thomson Reuters Statement Regarding the San Francisco Declaration on Research Assessment 
- About Web of Science
- Web of Science
- Searching the Citation Indexes (Web of Science) Harvard College Library. 2010. (archive)
- MIT Web of Science video tutorial. 2008.