It is not likely that you will find all the articles you want in one database. For most research, it will be necessary to look in two or three databases to be sure you have found the appropriate materials.
Each database has its own search terms so it may be necessary to use different words to search for the same idea each time you start researching in a new database.
The following two options are not really indexes to journal articles. They are enormous collections of journals with full text access to the articles included in each journal. They do not offer searching options that are as focused as those above so the results lists can be very large. It is highly recommended that you use them with caution and very focused search terms.
Dissertations & Theses Full Text - Provides indexing and full-text access to doctoral dissertations and master theses completed at accredited institutions. Full text coverage varies.
When full text is available, the content of the dissertation might be useful for finding search terms. The bibliography can be useful for locating additional sources to search in library databases or request via Interlibrary Loan.