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PubMed (Database Instruction)

This guide will assist you in using PubMed's new interface. PubMed is a free database that contains more than 30 million citations and abstracts of peer-reviewed biomedical literature.

Improving your search in PubMed

By taking the time to format your search correctly you can greatly improve how you communicate with the search engine and ultimately get much better results.                                                                                         

Here are some key points. 


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Boolean & PubMed

Use Boolean operators to structure how your search terms are used in PubMed.

  • AND retrieves results that include all the search terms.   Ex. Mother AND Father
  • OR retrieves results that include at least one of the search terms.  Ex. Sister OR Brother OR Sibling
  • NOT excludes the terms from your search.  Ex. Aunt NOT cousin 
    NOTE: use NOT cautiously as you may exclude something useful.

Rules for use:

  • Always put operators in ALL CAPS so they are considered instructions and not terms
  • Operators are processed from left to right
  • Use parentheses ( ...) to nest terms that should be processed as a unit before being considered in the overall search (same as math)
    Ex. (terminal OR end-stage) AND liver disease
  • If Boolean operators are not used, PubMed will automatically add AND between terms.
    Ex. disease Acid reflux = disease AND acid reflux
  • Can use special characters in place of operators Ex. AND = & (ampersand ),  OR = | (pipe)

More about Boolean and PubMed

Phrase searching

There are a couple of ways to search for phrases (terms that have more than one word) within PubMed.

  1. Place phrases within double quotes  "..."   Ex. "intensive care unit"
  2. Separate with a hyphen ...-...(no spaces).   Ex. critical-care
  3. Use a field tag  Ex. Intensive Care unit[tiab] = "intensive care unit" in the title or abstract

By doing this you are instructing the search to treat the phrase as a single unit. 

Rules for use

  • While contained within double quotations, hyphenated or tagged, Automatic Term mapping will not be applied
  • If PubMed cannot find results using the phrase it will convert it to single terms Ex. (Intensive AND Care AND Unit) and apply Automatic term mapping

More about Phrase searching in PubMed

Wildcards & Truncation

PubMed's Automatic Term Mapping is very efficient looking for plurals and related terms but sometimes applying a wildcard into your search term can be very useful. Wildcards are used when you want to search for terms that have a common beginning. We use an asterisk * as the wildcard

 Ex. Nurs* = nurse, nurses, nursing, nursery, etc.

Rules for use: 

  • There must be a minimum of 4 characters before the wildcard
  • Use wildcards within double quotation marks, with hyphens or field tags
  • The truncated term must be the last word if in a phrase
  • Wildcards will inhibit the use of automatic term mapping and MeSH

More about Truncation in PubMed

Field Tags (Field Codes)

Field tags allow us to focus the search within certain aspects of a result, such as a title, authors, journal name, subjects, and so on. There are over 50 field tags that can be used in combination to focus your search. 

Ex. Smith[au] = only results with an author named ‘smith’
Ex. nurse[ta] = only results where the journal's title includes the term ‘nurse’

Rules for use: 

  • Field tags are placed directly after the term (space or no space)  Ex. Term [au] or Term[au]
  • Enclosed within square brackets [..]
  • In lower case or uppercase  Ex. [AU] or [au]
  • The use of field tags will inhibit automatic term matching

More about Field Tags

Searching by authors, journals & dates

Searching for an
  • Best format: Last name First initial  Ex. Smith J

  • Omit punctuation, suffixes, etc.

  • Less is more - PubMed will auto-truncate  Ex. Smith J*

  • Add field tag: [au]  Ex. Smith J[au]

Searching for a
  • Use full name, abbreviation, or ISSN

  • PubMed applies Automatic Term Mapping

  • Add field tag: [ta]  Ex. Journal of Gastric Cancer[ta]

Searching for a
  • Best format : yyyy/mm/dd (month and day are optional)

  • Add field tag: [dp]  Ex. 2018[dp]

  • Date range format: yyyy:yyyy   Ex. 2015:2020

  • Relative date range format: 

    • term="last X years"[dp]     Ex. Acid reflux="last 5 years"[db]

    • term="last X months"[dp]

    • term="last X days"[dp] 

More about searching by Author, Journal, or Date