The Howard-Tilton Memorial Library's landing page features a search bar that allows you to search most of its collections (both print and digital) in a single search. Be careful, though. This search tool's ability to aggregate results from numerous databases may return an overwhelming number of results.
A less wide-reaching alternative, Ebsco offers users the ability to search all the databases we get from them with a single search. You may still get a lot of results, but it may be a more manageable number.
Google Scholar searches the full-text content of scholarly content available freely on the Web and can be a powerful search tool. However, large numbers of results and limited ways to filter those results make this resource a challenging one to use effectively. You may find that many of the results are not relevant to your topic but occur in the results list because your search terms appear once or twice in a footnote or or an article. Whenever possible, it's better to search for keywords in an item's title, abstract, or subject headings (tags) in order to find items with high relevance.