1. Look for your topic in an appropriate database e.g. Web of Science.
2. Search for your topic e.g. sample Search: "clock proteins" and sleep (in Topic field)
3. Click Search.
4. Once on a results list page, click on arrow by Source Titles (in far left column).
5. You will see the journal titles listed which have articles on this topic. Do some journal names include much content in this subject area?? e.g. Chronobiology International, Journal of Biochemistry, Journal of Biological Rhythms etc.
6. You could take a few journal titles e.g. top 6 and then look up the Impact Factors for them to make your own rank order.