A new feature will soon be added to the PubMed database.  It will be a “Results by year” timeline which will be displayed when 10,000 or more citations are retrieved. If you mouse over the bars in the timeline, you will display the number of citations for each year included.   If you click on an individual bar, you will display the results for that year.

A second discovery  tool, the “PMC images search” tool will display images from citations where the search resulted in a minimum of 250 citations, filters were not applied and Boolean operators are not part of the search strategy.  The search will retrieve a minimum of 4 relevant images.  See here for examples of these new features.