Scopus is an abstract and citation database of research literature and quality web sources, including journals, conference proceedings, trade publications, abstracts, and patent records. It is a multidisciplinary resource covering materials from the humanities, sciences and social sciences. Scopus allows you to locate the most highly cited items and the articles that cite them.
IOPscience is an online service for all journal content published by the Institute of Physics. It contains more than 300,000 articles, from 1874 to the present day. Also includes pre-prints from eprintweb.org (a free service, based on the arXiv.org at Cornell University), and editorial and news from IOP community websites.
Major source of chemical and physical property data. It includes information on elements, inorganic compounds, organic compounds, physical constants, units and conversion factors, symbols, and nomenclature.