Powered by Thomson Reuters, the Web of Science Core Collection database is a collection of several cross-searchable databases:
You can search one or more of these databases from the Web of Science interface.
You can search for current and retrospective information, by topic, author, etc. in over 12,000 multidisciplinary journals, 50,000 books, and over 160,000 conference proceedings.
The Web of Science is particularly good for citation searching, that is, to discover how many times a particular author or article has been cited and by whom, and to locate later works which cite a specific article.