Search Operators

Search operators AND, OR, NOT, and SAME may be used to combine terms in order to broaden or narrow retrieval.

Case does not matter when using search operators. For example, OR, Or, and or returns the same results.



Boolean Operators


Use AND to find records containing all terms separated by the operator.


Use OR to find records containing any of the terms separated by the operator.


Use NOT to exclude records containing certain words from your search.



Use SAME to find records where the terms separated by the operator appear in the same sentence. A sentence is defined as the title of a record or a sentence in the abstract.

Using the SAME operator instead of AND is a good way to narrow your search.


Search Operator Precedence

If you use different operators in your search, the search is processed according to this order of precedence:

  1. SAME
  2. NOT
  3. AND
  4. OR


copper OR lead AND algae finds all records in which both lead AND algae are present as well as all records in which the word copper is present.

(copper OR lead) AND algae finds all records in which the word algae is present together with either copper or lead.


Use of Parentheses

Use parentheses to override operator precedence. The expression inside the parentheses is executed first.

(cadmium AND gill*) NOT Pisces finds records containing both cadmium and gill (or gills), but excludes records containing the word Pisces.

(salmon OR pike) SAME virus find records containing salmon or pike within the same sentence as virus.


AND Examples

Beverage AND bottle finds records containing both terms.

Beverage AND bottle AND beer finds records containing all three terms.


OR Example

Beverage OR bottle finds records containing either beverage or bottle (or both).


NOT Example

Beverage NOT bottle finds records containing beverage but excludes records containing bottle.


SAME Example

Beverage SAME bottle finds records in which these two terms must appear in the same sentence.