Leasing Journal Citations (MEDLINE®/PubMed® including OLDMEDLINE)
MEDLINE, the primary component of PubMed®, is the NLM's premier citation database. MEDLINE's subject scope is biomedicine and health, broadly defined to encompass those areas of the life sciences, behavioral sciences, chemical sciences, and bioengineering.
MEDLINE citation data comprises approximately 91% of the data distributed to MEDLINE/PubMed licensees. The other categories of records that reside in PubMed and are distributed to licensees are:
- the out-of-scope citations from a few selectively indexed MEDLINE journals (primarily covering general science and general chemistry) for which the life sciences articles are indexed for MEDLINE;
- in-process citations which provide a record for an article before it is indexed with MeSH and added to MEDLINE or converted to out-of-scope status;
- some citations in the OLDMEDLINE subset that have not yet been updated with current vocabulary and converted to MEDLINE status;
- some citations in PubMed that precede the date a journal was selected for MEDLINE indexing if the citations are submitted after late 2003 to NLM electronically by the publishers;
- starting in summer 2005, prospective citations to articles from non-MEDLINE journals that submit full text to PubMed Central and are thus cited in PubMed.
NLM now exports over 98% of PubMed records to MEDLINE/PubMed licensees. The approximately 2% of the records not exported to MEDLINE/PubMed licensees are those tagged [PubMed - as supplied by publisher] in PubMed. These are mostly records recently added directly to PubMed via electronic submission from a publisher, most of which are soon to proceed to the next stage, at which time the record will be exported. Most other non-exported records are either: older citations for the relatively few non-MEDLINE journals in PubMed; citations to MEDLINE journals prior to their date of selection for MEDLINE which were submitted electronically by the publishers before late July 2003; or citations electronically submitted for articles that appear on the Web in advance of the journal issue's release (i.e., ahead of print citations). Following publication of the completed issue, the item will be queued for issue level review and released in In-Data-Review status. All "publisher-supplied" citations have not been reviewed for accurate bibliographic data. Also see the Fact Sheet "MEDLINE, PubMed, and PMC (PubMed Central): How are they different?".
The <PubmedData> group of elements that reside in PubMed records are not distributed to NLM licensees.
NLM does not provide search software.
Specifications and Access
NLM distributes MEDLINE/PubMed in XML format via ftp. See MEDLINE Characters for information on use of diacritical marks and UTF-8 encoding. Links to the DTDs and other information/documentation, including MEDLINE/PubMed XML data element descriptions, are available. Also see MEDLINE/PubMed Data.
A completely maintained MEDLINE/PubMed baseline database now containing over 25 million records is available each December.
Each year's baseline database is a complete reload for continuing licensees. The current (2015) baseline database requires 113.9 GB disk space uncompressed; 15.8 GB compressed. Subsequent update files distributed after the baseline files contain new, revised, and deleted records. They are generally available seven days each week and should be applied by licensees regularly.
In addition to, or instead of, mounting the XML data locally, licensees have access to the MEDLINE/PubMed Baseline Repository (MBR) Query Tool which is available from a link on the MBR main page. The MBR home page contains links to various freely accessible resources; however the Query Tool is restricted to NLM’s registered MEDLINE/PubMed licensees. The MBR Query Tool provides Web access to the baseline databases 2002 and forward. It permits searching by MeSH Headings, Subheadings, MeSH Heading/Subheading combinations, Names of Substances (MeSH Supplementary Concept Records), and PMID. Users can limit or filter by Date Created, Date Completed, Date Last Revised, Publication Year, and Status. Citations retrieved are available in both XML Format and PubMed’s MEDLINE ASCII Display Format.
Sample NLM Data
Sample MEDLINE/PubMed data are available. A license agreement is not needed for sample data.
To request a license, complete and submit the License Request Form after reading and accepting the electronic License Agreement for NLM Data.
The end of the each MEDLINE production year is mid-November and the new year's baseline files will be available for complete reload approximately one month later. Depending on the time of year, prospective licensees may wish to consider waiting until December to first get the data to avoid a reload of the new year's files shortly after initial receipt of the data. See Additional Information below.
Alternatives to Leasing
MEDLINE/PubMed may be downloaded for personal use and a single copy of downloaded data may be redistributed. Small amounts of MEDLINE/PubMed data may be retrieved from PubMed for redistribution without entering into a formal licensing agreement. See Information on Copyright for additional details.
MEDLINE/PubMed update files contain new and revised versions of records, and deleted records. Update files are generally available to licensees at noon EST Tuesday-Saturday. During several weeks each November and December only records in in-data-review and in-process status are distributed as NLM prepares for and performs annual data maintenance. Various types of maintenance actions, sometimes affecting large numbers of records, also take place during the year. Thus, licensees should process the revised records as well as new and deleted records in the update files regularly.
Announcements and documentation for licensees are posted at the Information for Licensees of NLM Data page. Licensees are also encouraged to read the NLM Technical Bulletin and to subscribe to NLM's e-mail alert, NLM-Announces.
The MeSH Vocabulary, a companion database for MEDLINE, may be downloaded at no cost after completion of a brief Memorandum of Understanding.
The IndexCatalogue data may be downloaded at not cost (no license required).
- The List of Serials Indexed for Online Users (download in XML format; does not cover the OLDMEDLINE subset journal titles or other non-MEDLINE journal titles in PubMed)
- LocatorPlus, the NLM online catalog and NLM Catalog, an Entrez database
- Serfile may be leased from NLM
- PubMed journals files (contains limited journal information; updated daily)
- NLM Catalog for basic journal information similar to data found in PubMed journals list (available in the Entrez Utilities; updated daily).
Also see the NLM FAQ: Finding NLM® Serials Data and MEDLINE® Indexed Journals. For additional information about MEDLINE/PubMed, see the MEDLINE/PubMed Resources Guide.