Reaxys covers organic, inorganic and organometallic chemistry. Reaxys also supports synthesis planning, and provides information on millions of substances and their structure and reactions; chemical, physical and bioactivity property data; and references from over 200 years of primary literature. It includes the Beilstein (organic chemistry) database and the Gmelin (inorganic and organometallic chemistry) database. It iss a web-based workflow solution for chemists such as synthesis planning tools and commercial availability linking.
ISI Web of Science is a multidisciplinary science database, providing citations covering over 10,000 high-impact journals in the sciences, social sciences, arts, and humanities. It also contains international proceedings for over 120,000 conferences, and has strong coverage of chemical and related sciences (1945+, updated weekly).
PubMed is a freely available database provided by the US National Center for Biotechnology Information (NCBI). it includes over 18 million citations from medical/life science journals (1948+).
PubChem is a freely available database provided by NCBI, a database of chemical molecules and their activities against biological assays. It provides information such as description, the molecular weight and formula, the structure, and more advanced information, such as bioactivity results, synonyms, chemical actions, etc. It contains links to ToxNet and PubMed.
ChemSpider is a freely available database provided by the Royal Society of Chemistry, the richest single source of structure-based chemistry information.