Use also the following general search engines and databases:
On the Hesburgh Lbraries page, change the setting on the left of the search form to ND Catalog.
Type in subject keywords, e.g. 'Early Modern Ireland'.Let's say you wish to browse through recent titles, but only those available in online format, make sure the 'Sort by' section has 'date newest', and select either 'Online' or 'e-book' to filter your results.
If the book that you need is not available in digital form, please ask a librarian for help.