If the database or search engine you are searching does not have built in tools for finding empirical research, the next best option is to add words to your search that would be used in empirical research. This is not always easy. For example, you can include the word "empirical" in your search, but that will not find nearly all of the empirical research on your topic. After all, if every empirical research article clearly said it was "empirical," we wouldn't need this guide!
The best bet is to include search terms that are used to describe empirical research methods. What those terms are will vary a lot by the discipline you are researching in.
You can add a number of terms related to research methods in an advanced search, adding "OR" between each term, to increase the proportion of empirical research in your results. This is not a perfect solution, so you need to evaluate each article for the characteristics of empirical research.
There are a lot of possible research methods words you might include in your search. Using a database's subjects can help you narrow it down.
Many databases assign "subjects" to each article. These subjects are standardized terms used to describe the article, which can include the research methods used. Databases have a subject terms list, sometimes called a "thesaurus," where you can look up the terms used in the database. Adding empirical research method-related subject terms can increase the proportion of empirical research in your results.
The most common database interface at our libraries is EBSCOhost. This video teaches how to look up an EBSCOhost database's subjects.