You can search for primary research articles in a similar way that you search for other peer-reviewed articles. From your list of results, you can sift through to look for primary research.
If you have hundreds or thousands of results and want to try to focus your search on primary research articles, there are three different techniques to try.
Important! From your list of results, you will still need to examine each article to see if it is primary research and not a synthesis of others' research.
All of these results are generally primary research articles, but keep in mind that while all case studies are primary research, not all primary research is in the form of a case study, so you will likely be missing some primary research articles on your topic by searching this way.