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Health & Medical Literature Searching

A step by step guide to the literature searching process & techniques

Why would i use a database?

Databases allow you to do different kinds of searches.

Basic keyword search: similar to a library catalogue or Google search where you use whatever keywords you think describe your topic.

Subject heading search:  use the thesaurus terms (also known as controlled vocabulary) of the database to find all articles tagged with specifically assigned subject headings.

Combined keyword & subject heading search:  for advanced research, use combined searching  to ensure retrieval of current and relevant  resources to support your research.  Start with your own basic keywords as concepts but also find out what the thesaurus term in the database is for that concept and combine them. 

Free text vs Thesaurus or MeSH searching

Using both Keyword  & Thesaurus terms in a database search will help you in the following ways.

Using a Database Thesaurus

About Thesaurus Terms:  A database thesaurus or controlled vocabulary is an index used to assign subject information to the research articles contained in database. The main thesaurus used in Medicine is called MeSH (Medical Subject Headings). MeSH is an index of medical terms used by specific databases  to classify all medical research.  When searching databases always check to see which controlled vocabulary is used. For detailed understanding of MeSH, follow this MEDLINE/PubMed Medical Subject Heading  tutorial.

Learn more about searching with subject headings on different databases


Subject Vocabulary

Subject Search Tutorials

Medline Complete & Cinahl MeSH / Cinahl Headings

Cochrane Library MeSH


Thesaurus of


Index terms

PubMed MeSH
SCOPUS  No thesaurus


Combining search terms in your search strategy with AND / OR

Once you have formulated your question, isolated your concepts & decided on your keywords &/or  thesaurus terms, combining terms is the next step:

How to combine terms for best results: use boolean operators AND,  OR,  NOT

  • AND  - all terms must be present. Used when you want to combine different concepts to find articles that include both concepts. Use NOT with caution because you may end up missing something important.

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  • OR  - either of the terms must be present. Use when you want to combine similar concepts  or  combine  several synonyms keywords and the equivalent subject heading


  • NOT - terms excluded from search. Use after you have combined terms using AND/OR for cases when you get many results and you wish to eliminate an unwanted subset from your results: e.g.(animals AND cloning) NOT sheep. Use NOT with caution because you may end up missing something important.

Using Truncation & Wildcards for Keyword Searching

When you use keywords to augment your search strategy, databases have advanced tricks to save you time & help you include as many related terms as possible.Always check database help for symbols used.

Truncation for Keyword Searching is a search technique where possible word endings are replaced by a symbol. The database will search for all possible variations of the word.

Frequently used truncation symbols include the asterisk (*), a question mark (?) or a dollar sign ($)

Example: to find all possible endings related to the word cardiac, enter root cardi*  to retrieve cardiac, cardiovascular, cardiology, cardiomyopathy, etc


Wildcards for Keyword Searching: In addition to truncation, in some databases wildcards can be used in keyword searches. The wildcard is represented by a question mark ? or a hash tag # placed in the middle of a word to account for possible different spellings of the same word.

Use the ? wildcard to replace an unknown character in your term so that your search returns all alternate spellings for that word. 

 Example: Type analy?e to find all citations containing analyze & analyse.

Add the # wildcard in your search term where an alternate spelling may contain an extra character. This search finds all citations of the word that appear with or without the extra character.

Example:  Enter p#ediatric to find all citations containing pediatric or paediatric.