Empirical research is published in scholarly, peer-reviewed journals and in books. Some library databases do not have a straightforward way to limit to empirical research.
PsycINFO includes a Methodology filter to limit results to empirical research studies.
How to do it:
Type your keywords into the search boxes, as below, and click Search:
At the results page, click all filters to see a list of options.

Scroll down to Methodology and click the arrow to see a list. Check the box next to empirical study. Next, click Apply to see the filtered list of results.

You may also want to limit by publication data and source type. Click Peer Reviewed to limit to that source type. Click All time to see options for limiting by year. There's an option to set a more specific time limit -- a custom range -- click All filters and look under Publication Date.