A lot of museums already have back-issues of exhibition catalogs located online for free. Many more are adding them! This is not a comprehensive list.
Multi-Search/EBSCO Discovery Service Great place to get started for most research topics.
Google Scholar Use Google Scholar to connect to full-text articles provided by UGA Libraries via the "View It @ UGA" links in the margin. Google Scholar searches across many scholarly disciplines and sources.
Libkey Nomad: Free Chrome browser extension that connects UGA resources with scholarly articles you find in PubMed, Wikipedia and hundreds of scholarly publisher websites. Also locates Open Access versions of articles.
More online resources
Databases by Subject List of databases and other resources provided by UGA Libraries.
Databases by Title An A-Z list of databases provided by UGA Libraries.
Ebooks Search the GIL-Find catalog to find ebooks. Filter by "Full Access Online."
The Libraries may be able to buy ebooks for class papers or projects. Please fill out the Suggest a Purchase form. Some e-textbooks and other ebooks are excluded from purchase by libraries.
FIND IT @ UGA
Most library databases include the FIND IT @ UGA button, which you can use to locate online access for specific citations.
Even if one can't access a print monograph or exhibition catalog, a book review of that book/catalog may be available.
Many of the major art databases index book (and exhibition) reviews, namely Art & Architecture Source, Bibliography of the History of Art / International Bibliography of Art, Avery Index to Architectural Periodicals, and ArtBibliographies Modern. CAA Reviews, an online-only publication of the College Art Association, includes reviews of art and architecture monographs, exhibitions, essays, and lists dissertations by year, all organized by subject and time period. The Art Libraries Society of North America publishes its art book reviews online: ARLIS/NA Reviews. ARLIS/NA's Multimedia & Technology Reviews reviews websites, online publications, and other products and resources of use to arts researchers that are online. Also, Bookforum reviews a good number of art books, with some reviews available at its website, and The Art Book Review is a free online resource. Photobook reviews are available from Aperture Magazine.
One can also use Multisearch, to do a search, entering as many keywords as you'd like contained in the book title in question, and select Book Review under Content Type on the left-hand side.
For canonical art historical titles, The Burlington Magazine published a series of articles on important 20th-century texts in art history called Art History Reviewed. Just do a title search for Art History Reviewed in Art & Architecture Source and you will see a listing of the specific articles and books reviewed. Burlington is available online in JSTOR, minus the last half a dozen years.