Medical Subject Headings: Controlled vocabulary thesaurus produced by the NATIONAL LIBRARY OF MEDICINE. It consists of sets of terms naming descriptors in a hierarchical structure that permits searching at various levels of specificity.Subject Headings: Terms or expressions which provide the major means of access by subject to the bibliographic unit.MEDLINE: The premier bibliographic database of the NATIONAL LIBRARY OF MEDICINE. MEDLINE® (MEDLARS Online) is the primary subset of PUBMED and can be searched on NLM's Web site in PubMed or the NLM Gateway. MEDLINE references are indexed with MEDICAL SUBJECT HEADINGS (MeSH).Abstracting and Indexing as Topic: Activities performed to identify concepts and aspects of published information and research reports.Catalogs, LibraryNational Library of Medicine (U.S.): An agency of the NATIONAL INSTITUTES OF HEALTH concerned with overall planning, promoting, and administering programs pertaining to advancement of medical and related sciences. Major activities of this institute include the collection, dissemination, and exchange of information important to the progress of medicine and health, research in medical informatics and support for medical library development.Information Storage and Retrieval: Organized activities related to the storage, location, search, and retrieval of information.PubMed: A bibliographic database that includes MEDLINE as its primary subset. It is produced by the National Center for Biotechnology Information (NCBI), part of the NATIONAL LIBRARY OF MEDICINE. PubMed, which is searchable through NLM's Web site, also includes access to additional citations to selected life sciences journals not in MEDLINE, and links to other resources such as the full-text of articles at participating publishers' Web sites, NCBI's molecular biology databases, and PubMed Central.Abbreviations as Topic: Shortened forms of written words or phrases used for brevity.MEDLARS: A computerized biomedical bibliographic storage and retrieval system operated by the NATIONAL LIBRARY OF MEDICINE. MEDLARS stands for Medical Literature Analysis and Retrieval System, which was first introduced in 1964 and evolved into an online system in 1971 called MEDLINE (MEDLARS Online). As other online databases were developed, MEDLARS became the name of the entire NLM information system while MEDLINE became the name of the premier database. MEDLARS was used to produce the former printed Cumulated Index Medicus, and the printed monthly Index Medicus, until that publication ceased in December 2004.Terminology as Topic: The terms, expressions, designations, or symbols used in a particular science, discipline, or specialized subject area.Vocabulary, Controlled: A specified list of terms with a fixed and unalterable meaning, and from which a selection is made when CATALOGING; ABSTRACTING AND INDEXING; or searching BOOKS; JOURNALS AS TOPIC; and other documents. The control is intended to avoid the scattering of related subjects under different headings (SUBJECT HEADINGS). The list may be altered or extended only by the publisher or issuing agency. (From Harrod's Librarians' Glossary, 7th ed, p163)Unified Medical Language System: A research and development program initiated by the NATIONAL LIBRARY OF MEDICINE to build knowledge sources for the purpose of aiding the development of systems that help health professionals retrieve and integrate biomedical information. The knowledge sources can be used to link disparate information systems to overcome retrieval problems caused by differences in terminology and the scattering of relevant information across many databases. The three knowledge sources are the Metathesaurus, the Semantic Network, and the Specialist Lexicon.Databases, Bibliographic: Extensive collections, reputedly complete, of references and citations to books, articles, publications, etc., generally on a single subject or specialized subject area. Databases can operate through automated files, libraries, or computer disks. The concept should be differentiated from DATABASES, FACTUAL which is used for collections of data and facts apart from bibliographic references to them.Automatic Data Processing: Data processing largely performed by automatic means.Periodicals as Topic: A publication issued at stated, more or less regular, intervals.Natural Language Processing: Computer processing of a language with rules that reflect and describe current usage rather than prescribed usage.Medical Informatics: The field of information science concerned with the analysis and dissemination of medical data through the application of computers to various aspects of health care and medicine.Chronology as Topic: The temporal sequence of events that have occurred.Internet: A loose confederation of computer communication networks around the world. The networks that make up the Internet are connected through several backbone networks. The Internet grew out of the US Government ARPAnet project and was designed to facilitate information exchange.Cataloging: Activities performed in the preparation of bibliographic records for CATALOGS. It is carried out according to a set of rules and contains information enabling the user to know what is available and where items can be found.United StatesSoftware: Sequential operating programs and data which instruct the functioning of a digital computer.Algorithms: A procedure consisting of a sequence of algebraic formulas and/or logical steps to calculate or determine a given task.Libraries, MedicalOptic Flow: The continuous visual field seen by a subject through space and time.Databases, Factual: Extensive collections, reputedly complete, of facts and data garnered from material of a specialized subject area and made available for analysis and application. The collection can be automated by various contemporary methods for retrieval. The concept should be differentiated from DATABASES, BIBLIOGRAPHIC which is restricted to collections of bibliographic references.Information Systems: Integrated set of files, procedures, and equipment for the storage, manipulation, and retrieval of information.