Web of Science is the most complete and comprehensive citation tracking database with coverage from 1900 to the present. It provides thorough coverage of ~5900 major journals. Includes cited author searching. Abstracts, keywords, and additional subject categories are included and searchable from 1991+.
Video Tutorial: http://scientific.thomson.com/support/recorded-training/wos/
Provides International coverage of journal articles, selected web sites, and patents in the sciences and social sciences; provides citation tracking from 1996 to the present.
Interactive Tutorial: http://help.scopus.com/robo/projects/schelp/tutorials/sc_menu.html
Google has a specialized interface for searching the journal literature called Google Scholar that provides access topeer-reviewed papers, theses, books, abstracts and articles, from academic publishers, professional societies, preprint repositories, universities and other scholarly organizations. Although it is not as standardized, thorough, or reliable as BIOSIS, Web of Science and other literature databases, Google Scholar has a simple interface that many find convenient and easy to use.