Web of Science indexes the content of over 12,000 journals in the sciences (8,500 journals), social sciences (3,000), and the humanities (1,700) with its coverage is strongest in the natural sciences, health sciences, engineering, computer science, materials sciences.. It includes more than 50 million scholarly articles published from 1987 to the present. It also indexes over 120,000 conference proceedings.
Journal Citation Reports (JCR): For each of the 74 million articles included in the primary index, Web of Science also makes searchable the hundreds of millions of cited references contained in those articles – creating a “web” of scholarly knowledge. JCR enables users to find articles that cite a common source, for example an important and well-respected article in a particular field. The frequency with which articles are cited is used to create journal impact factors for the 12,000 journals it indexes in Web of Science. While there is some controversy over how accurate journal impact factors are, they are one measure of a journal’s importance in a field of study.