If you get too few results, you can:
In any case it is advisable to search Embase, the European counterpart of PubMed.
Depending on the subject both sources each contain a third part of unique references and a third part they have in common.
Embase is very suitable for finding pharmacological references.
Other important search engines are:
If you get too many results you can:
PubMed offers many options for targeted searches.
The best known of these is the entrance: Clinical Queries. Clinical Queries filters are search strategies that help to limit the search results to specific types of clinical studies. For example, you can search for articles about therapy, diagnosis, prognosis, etc.
In the PubMed start screen you will find Clinical Queries under the heading 'Find'.
In the video below you can see how the Clinical Queries work.
To be able to reference, deduplicate or screen your articles, it is useful to export your results.
You do this by clicking on 'Send to' after performing your search. Here you will see - among other things - the option to export your files to a 'citation manager' (reference management program).