JSTOR provides access to full-text academic electronic journals in various disciplines including economics and finance, political science, history, literature, anthropology, mathematics, sociology, statistics, and education.
See https://about.muse.jhu.edu/resources/freeresourcescovid19/ for a list of scholarly presses offering free access to all their journals or ebooks on Project MUSE through June. Butler normally has full ejournal but not ebook access to MUSE.
Google Scholar provides a simple way to broadly search for scholarly literature. From one place, you can search across many disciplines and sources: peer-reviewed papers, theses, books, abstracts and articles, from academic publishers, professional societies, preprint repositories, universities and other scholarly organizations.
This group of online indexes provides access to biographies, bibliographies and critical analysis of authors, much of it full-text. The database is searchable by Author Name, Title, Genre, Literary Movement or Literary Themes, or a combination of criteria to create more powerful searches.
Literature Criticism Online is designed to provide easy access - new users may simply enter an author or title and find a wealth of content, while experienced researchers may broaden or narrow their results via cross-searches on names of critics, journal titles, topics and more.