Most databases do not have a way to search by whether or not an article uses empirical research. The only absolute way to determine if an article uses empirical research is to check the METHODS section, however, you can usually find some keywords in the ABSTRACT that will let you know if an article used empirical research.
*Remember, smaller case studies can also ask their subject to take a survey, then go in-depth with the interview questions - making this qualitative rather than empirical research.
**Look for charts and graphs, percentages reported out, etc.