The National Center for Biotechnology Information (NCBI) provides a comprehensive suite of database resources for molecular biology research. These resources include Entrez, a powerful integrated database retrieval system; PubMed and PubMed Central for accessing biomedical literature; LocusLink for curated gene information; BLAST and its variants for sequence similarity searches; UniGene for gene-oriented sequence clusters; ProtEST for protein sequence comparisons; the Trace Archive for sequencing data; HomoloGene for gene orthologs and homologs; dbMHC for clinical applications of the Major Histocompatibility Complex; RefSeq for curated and computationally derived sequences; specialized tools like OrfFinder, Spidey, and Electronic PCR; dbSNP for single nucleotide polymorphisms; Entrez Genomes for genome-scale analysis; Clusters of Orthologous Groups (COGs) for protein families; Retroviral genotyping tools and the SARS Coronavirus resource; Map Viewer for genomic maps; Model Maker for transcript model construction; Evidence Viewer for gene model analysis; the Cancer Chromosome Aberration Project (CCAP) for chromosomal aberration data; SAGEmap and Gene Expression Omnibus (GEO) for gene expression data; OMIM for genetic disorders; and the Molecular Modeling Database (MMDB) and Conserved Domain Database (CDD) for protein structure and domain information. These resources are accessible through the NCBI home page and offer extensive functionalities for researchers in various fields of biology and medicine.The National Center for Biotechnology Information (NCBI) provides a comprehensive suite of database resources for molecular biology research. These resources include Entrez, a powerful integrated database retrieval system; PubMed and PubMed Central for accessing biomedical literature; LocusLink for curated gene information; BLAST and its variants for sequence similarity searches; UniGene for gene-oriented sequence clusters; ProtEST for protein sequence comparisons; the Trace Archive for sequencing data; HomoloGene for gene orthologs and homologs; dbMHC for clinical applications of the Major Histocompatibility Complex; RefSeq for curated and computationally derived sequences; specialized tools like OrfFinder, Spidey, and Electronic PCR; dbSNP for single nucleotide polymorphisms; Entrez Genomes for genome-scale analysis; Clusters of Orthologous Groups (COGs) for protein families; Retroviral genotyping tools and the SARS Coronavirus resource; Map Viewer for genomic maps; Model Maker for transcript model construction; Evidence Viewer for gene model analysis; the Cancer Chromosome Aberration Project (CCAP) for chromosomal aberration data; SAGEmap and Gene Expression Omnibus (GEO) for gene expression data; OMIM for genetic disorders; and the Molecular Modeling Database (MMDB) and Conserved Domain Database (CDD) for protein structure and domain information. These resources are accessible through the NCBI home page and offer extensive functionalities for researchers in various fields of biology and medicine.