D: DOAL>>>Directory of Open Access Journals is used for multiple searches on various subjects such as mathematics, English, Sciences. and so on. This database offers only journals and articles based on your searches. From the looks of it, there’s also a segment for a controlled vocabulary search. I don’t see any unique features, it’s pretty much shows similar formats from any other regular databases.
M: MathSciNet>>> Is used primarily for math related subjects. It offers a wide variety of information mostly from textbooks and others from mostly articles/journals and such. It also has a controlled vocabulary search. The database has one or two unique features, one of them is that it has an option to choose where you want to get information from books, articles, journals, and such. Another is that you can choose a time period of which you want to look in.