The ArticlesPlus searchbox on the first page of this Guide will help you with basic research in Classics.
For in-depth research, however, use L'Annee Philologique, the main research database for Classics.
And don't worry about the French title; a loose translation is "The year in Classical Studies." The database is very international in scope, with an English interface and many English-language sources.
The Ancient Greek and Roman Philosophy section of the Philpapers website has links to thousands of well-categorized papers and articles on all periods of ancient philosophy.
Please note: links to most of the scholarly journal articles will work correctly if you are on-campus. If you are off-campus, however, you will need to note the citation for the article, then go to ALICE and do a Periodical Title search for the journal, and navigate till you get to the article itself.
If you wind up on a site that asks you to PAY for an article, DON'T DO IT! We can almost always provide you with the article free of charge, either from our own holdings or via Interlibrary Loan.