Wikipedia has this comprehensive list of major academic databases and search engines. This list has over 50 titles neatly organized based on the discipline they target. From sociology to agriculture, almost all disciplines are covered. These search engines are especially useful for teachers, educators, and academic researchers looking for a quick access to articles published in academic journals and other scientific publications. These kind of documents and articles do not normally have a high visibility in normal search engines. You might want to book the page and keep it handy to use whenever needs be.
Click here to check the original list.