These databases are the key ones for searching for chemistry information. Scifinder and Reaxys allow searches not only using words but also by drawing a chemical structure or entering a molecular formula. Web of Science and Scopus cannot do the latter but they are more multidisciplinary for a broader topic search. Web of Science and Scopus also allow you to do citation searches (see who cited an interesting article) and can calculate an H-index for a topic or author.
Science of Synthesis (SynOne) is a comprehensive overview of the literature of organic synthesis reactions.
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