Help / Building Complex Search Queries

If you not are yet familiar with basic or advanced search, please visit the respective tutorials:

Using multiple boolean operators in a single query

For example:

sleep AND (disorder OR therapy) NOT wake

looks for items with sleep and all or any of the words disorder or therapy, but not containing wake. Please note the use of parentheses (), which is used to group the subquery.

Also, since AND operator is always implicitly implied, the query is similar to:

sleep (disorder OR therapy) NOT wake

Without the parentheses, the following

sleep disorder OR therapy NOT wake

is similar to

(sleep OR disorder) AND (sleep OR therapy) AND (sleep NOT wake)

To avoid confusion, familiarize yourself with using parentheses to group subqueries.

Query Syntax


Use wildcard operator ? to replace a single character, or * to replace zero or more characters. For example use wom?n to look for woman or women.

Respira* includes item with respiration and respiratory, for example.


Using proximity ~ operator, you can search for a phrase with a specific maximum word distance between words. For example (combining with NOT operator):

"acute respiratory"~1 NOT "acute respiratory"

includes "acute upper respiratory" and "acute lower respiratory" but not "acute respiratory".

Term Boosting

You can boost a specific search term or phrase using the boost ^ operator. For example, combining with proximity operator as in the previous section, you can search for "acute respiratory", but with preference to "acute upper respiratory":

"acute respiratory"~1 OR "acute upper respiratory"^10

Notice that the number of results is similar to the following:

"acute respiratory"~1

But the order of the results is different, with the former give preference to "acute upper respiratory".

Advanced Field Search

In advanced search, you can search specifically in a particular field. Such fields are available as field keyword when you build the query manually.

Exact Field

Some fields, like MeSH term (available as mesh_term keyword), has an exact sub-field keyword, in which you can use to search for exact phrase. For example, the following looks for items with MeSH terms like "Infant", "Infant, Newborn", or any MeSH terms with "Infant" in it:


While the following looks for items that contain exact "Infant" MeSH term.


See the next section on fields with exact sub-field keyword.

Field Keywords

Below are advanced search fields and their field keyword equivalent:

Search field Keyword Exact field Value*
Title title No free form
Abstract abstract No free form
Journal journal No free form, exact ISSN
Journal journal_name Yes free form. See Advanced search**
Journal issue date journal_issue_date No "2012-01-01", "[2012-01-01 TO 2012-12-31]"
Journal issue date (year) journal_issue_year No "2009"
Journal issue date (month) journal_issue_month No "Aug", "3"
Journal issue date (day) journal_issue_day No "3", "29"
Fulltext fulltext No "yes" or "no"
Author author No free form, "Ahmad Sarji S"
MeSH term mesh_term Yes "Infant", "Infant, Newborn", "Infant, Newborn*"
Publication type publication_type Yes "journal article"
Publication date date_created No "2012-01-01", "[2012-01-01 TO 2012-12-31]"
PMID pmid No free form, "22210969", "222*"
Page page No free form, "10", "1-107"
Place of publication place_of_publication No See Advanced search**
Publisher publisher No See Advanced search**
Age group age_group No See Advanced search**
Coverage coverage No See Advanced search**
Health care delivery delivery No See Advanced search**
Ethnicity ethnicity No See Advanced search**
Gender gender No See Advanced search**
Primary care setting primary_care_setting No See Advanced search**
Special group special_group No See Advanced search**
Study design study_design No See Advanced search**
Subject system subject_system No See Advanced search**
Subject subgroup subject_subgroup No See Advanced search**
State state No See Advanced search**
  • Some fields in Advanced search provide more example queries.
  • * free form - accepts any form of queries as in the previous sections
  • ** You can enter a few letters in a particular search field, and suggestions will be generated for you to pick from.
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