Royal Society of Chemistry www.rsc.org
The National Centre for Biotechnology Information advances science and health by providing access to biomedical and genomic information PubChem http://pubchem.ncbi.nlm.nih.gov/
The European Bioinformatics Institute https://www.ebi.ac.uk/chembldb/
SureChem integrating patent chemistry into the scientific community https://www.surechem.com/
ZINC, a free database of commercially-available compounds for virtual screening http://zinc.docking.org/search/structure.php
PATENTSCOPE you can search 35 million patent documents including 2.2 million published international patent applications http://patentscope.wipo.int/search/en/search.jsf
PubMed comprises more than 23 million citations for biomedical literature from MEDLINE, life science journals, and online books. http://www.ncbi.nlm.nih.gov/pubmed