In New PubMed: Subject Filters
With the rollout of new PubMed, some features have changed such as the location of pre-populated subject filters.
In old PubMed, on your results page you could limit your search to specific, popular subject areas relatively easily with a full listing of options.
In new PubMed, this functionality is buried under several clicks and does not have the full list of subject searches.
All previous subject filters still exist in new PubMed but have not been added to the results page. In order to access these pre-populated searches, you have to search the PubMed FAQs to find and to enable them.