With 100 specialized search engines for academic research listed, you are certain to find some new ones. Some of my favorites are included in this list. The list is organized into helpful catagories by subject or discipline. One of my favorites for History is listed here, the David Rumsey Historical Map Collection. The collection has over 30,000 images, searchable by keyword.
There is a wealth of research to suggest that vocabulary knowledge is the single best predictor of student academic achievement across all curriculum areas. via Feedly