Below is not an exhaustive list. It depends what subject realm(s) your topic fits within.
You are encouraged to use LibrarySearch (see bottom of this page) and to also search in different databases within the subject area of your particular topic.

You can select an appropriate databases from the U of T Libraries homepage by clicking "Databases" on the homepage below the simple search or in the horizontal submenu, then refer to "Databases by Subject",  select an appropriate subject area and perform your searches in the "best bets" databases.  

You can also use LibrarySearch from the Library homepage, while it's not exhaustive, it searches many databases at once.

• use the "Advanced Search" so that you can enter synonymous terms more easily for each key concept/main theme 

You can use a similar search formula in a subject specific database (such as those listed above) and in fact, you can search for those terms more specifically in the following fields, subject, abstracts, titles or even "anywhere except full text" (which encompasses the following 3 fields and is an option in certain databases).  Different search results will rise to the top in a subject-specific database search.