JSTOR is an indispensable database for academic research. Of its more than 2,000 journals, mainly in the humanities and the social sciences, there are 139 philosophy journals. In addition, there are more than 6,500 open access ebooks from 85 academic publishers. Articles date from the 19th century up to what is called a "moving wall" of 3 to 5 years between the current issue and what is available on JSTOR. (Many publishers have similar restrictions to access, ranging from months to years.) In addition, JSTOR has what they call the Text Analyzer. Drag and drop your text in JSTOR's Text Analyzer, and it will suggest books and articles relevant to your paper.
ProQuest's Philosophy collection has more than 165 philosophy journals. It also includes The Philosopher's Index and more than 1,000 dissertations from the 1860s to the present.
Religion and Philosophy Collection (EBSCOhost)
Ebsco's Religion & Philosophy Collection is a full-text database for theology and philosophy research. It includes more than 200 full-text journals and magazines.
Project Muse provides access to the full text of 32 philosophy journals and over 600 other academic journals, and thousands of book titles from major university presses. In addition, Project Muse provides Open Access to thousands of books and journals.
Nietzsche-Studien is the major publication in the field of Nietzsche studies. It reflects the entire spectrum of research on Nietzsche, from philosophy to literary studies and political theory.
Oxford Academic bring together the world's leading scholars to evaluate the current thinking in a field or topic and explores the major debates. NYPL has the entire collection of the Oxford Handbook series in philosophy, of which there are 26.