Search filters are:
Commonly, search filters limit search results by:
They are sometimes available at the click of a button in library databases, but don't let that deceive you! A lot of work goes into developing an effective search strategy for filters, and they often include various combinations of subject headings, textwords, and wildcards.
PubMed - Randomized Controlled Trials
randomized controlled trial.pt.
controlled clinical trial.pt.
1 or 2 or 3 or 4 or 5 or 6 or 7 or 8
exp animals/ not humans.sh.
9 not 10