For the most part, contemporary philosophical research is conducted by way of essay-length papers published in academic journals. Philosophers do still publish monographs in order to provide a longer or more detailed argument on a subject—but many monographs begin their lives as journal articles. The American Philosophical Association keeps a fairly thorough (though still incomplete) list of journals here. Below is an incomplete selection of some of the more well-regarded generalist journals (which publish essays on a wide range of philosophical topics for a general audience) and specialty journals.
Select the most important 2-3 terms related to your topic. Put the word AND between each new term; this tells the database to look for resources with ALL your terms.
metaphysics AND epistemology
Use quotation marks ( " " ) around phrases (two or more words); this tells the database to look for the words in that specific order.
"Zeno's Paradox"
Use an asterisk (*) to find multiple endings of one word. Using ethic* as a search term will include results that refer to ethics, ethical, ethically, etc.
ethic*