Entrez: The NCBI Search and Discovery Engine

Abstract

About 2.7 million unique users a day come to the NCBI website to explore data resources as diverse as the PubMed database of published scientific articles, the PubMed Central (PMC) database of full text articles and books, the GenBank database of DNA and protein sequences, the dbSNP database of genetic variation, or the PubChem database of chemical structures. They search and retrieve records in each very different database, but also follow the connections between them such as the article in PubMed where the DNA sequence in GenBank was reported, or the protein that would be altered by a variation in dbSNP. While the names of the individual databases are household words in biomedicine and biomedical researchers just assume they have ready access to them all and can easily navigate through the relationships among the database as a matter of course, a great deal of design, engineering, and software development has gone into making this possible. Underlying the search and retrieval of these databases is the Entrez search and retrieval engine.