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PubChem provides information on the biological activities of small molecules. It is a component of NIH's Molecular Libraries Roadmap Initiative. PubChem is organized as three linked databases within NCBI: PubChem Substance, PubChem Compound, and PubChem BioAssay. PubChem also provides a fast chemical structure similarity search tool. A self-paced PubChem tutorial is available.
As of December 2022, ChemIDplus and Drug Information Portal Content are only available through PubChem.