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Medline Glossary


AIM journals: Core clinical medical journals indexed for Abridged Index Medicus and available in most medium sized hospital or medical center libraries.

Boolean search: Means of combining search statements or sets using the logical operators "OR" to expand a search and "AND" to restrict a search to articles that contain two or more specified elements together.

Explode: permits simultaneous searching of both a broad subject and the narrower subjects classed under it (e.g., searching "Antiviral Agents" will retrieve articles on antiviral agents in general, new antiviral agents not yet assigned a MeSH heading, plus individual drugs such as "Acyclovir" or Zidovudine" classed as antiviral agents in Medline). Because indexing norms require that the most specific subject heading available be applied, normally an article indexed under the specific heading would not also be indexed under the broader heading; thus, searching only the broad subject would result in lost references which have been indexed under the more specific heading.

Fields: labeled divisions of a Medline record; most fields are directly searchable, separately or as specified in an "expert search", set off by periods (e.g., random$.ti,ab,sh,pt. or alberta.ti,ab,sh,in.). Medline fields include:

Mapping: a computer process whereby the search system matches a term entered to the closest subject headings in the database.

Medline: An electronic index to the contents of biomedical and health sciences journals published since 1966. Medline includes Index Medicus, the Index to Dental Literature, and the International Nursing Index.

MeSH: Medical Subject Headings, the thesaurus for Medline; a controlled vocabulary providing consistent terminology for concepts covered by the database.

Post-qualification: Used with existing broad subject heading search statements to focus the search and reduce the number of postings while increasing their relevance. To restrict a subject heading to focus, preface the set number with an asterisk (*) (e.g., if set 1 is Tuberculosis and you wish to find only papers where this is a central focus, create a new search statement by entering "*1"). To focus a search by the use of subheadings after the set has been created, enter the set number followed by a forward slash and the two-letter subheading designators desired (e.g., if set 1 is Tuberculosis, and you wish to restrict your search to "prevention and control" and "transmission", enter "1/pc,tm").

Restrict to focus: A choice offered following selection of a subject heading to be searched; choosing "all documents" at this point will retrieve all references indexed with a particular subject heading; choosing "Restrict to focus" will retrieve only references where this concept is a central focus of the article. Note that some MeSH headings, such as geographical names or headings relating to experimental design, are almost never designated under "restrict to focus".

Scope note: Defines a particular MeSH heading and explains its parameters, provides synonyms covered by the heading, year a MeSH heading was adopted by Medline, previous indexing for the MeSH heading, and cross references to other possibly relevant MeSH headings.

Subheadings: Generic terms to narrow and focus a MeSH subject heading search; on OVID systems, the scope of each subheading is presented on the right hand panel of the search screen where subheadings are selected. One or several headings may be selected at a time, and "all subheadings" may be selected.

Textword: Exact words found in the title and/or abstract fields; useful for searching if no MeSH heading exists for a specific concept. Textword searching requires the use of synonyms and by-passes the mapping feature that allows "restrict to focus" and subheading selection. Generally, prefer thesaurus searching (i.e., using the subject or MeSH headings).

Tree: Classified listing of subject headings, showing broader and narrower concepts. Can be searched selectively using the "Tools" function on OVID.

Truncation: Means searching for all variations based on a word stem. The truncation symbol on OVID is $. (e.g., predict$=predict, predicts, prediction, predicting,etc.)