The default list of filter categories in the left hand sidebar does not include all options. Click on the link labeled "Choose additional filters" to add categories to the list. Filters are available to focus your search results by article types, text availability, publication dates, species, languages, sex, subjects, journal categories, ages, and search fields.
Type of Article, Species, Sex, and Ages filters are based on terms added by indexers. When these filters are selected they remove very recent articles that have not yet been indexed. Always look at the most recent search results before adding these filters.
Activated Filters Display on Search Result Pages. Filters stay selected during the current search session until you change or clear them.