Accessed through the NCBI Bookshelf, the Help Manual contains documentation for many NCBI resources, including PubMed, PubMed Central, the Entrez system, Gene, SNP and LinkOut. All chapters can be downloaded in PDF format.
This resource organizes NCBI information, resources, data, and tools and utilities on genomes including sequences, maps, chromosomes, assemblies, and annotations. Sequence and map data from the whole genomes of organisms. The genomes represent both completely sequenced organisms and those for which sequencing is in progress.