OneSearch is a good place to start - use it to get an idea of the amount of literature there is on your subject.
However most researchers need to use specialist databases because they
You should search several different databases because:
Use your subject guide to identify the specialist databases we recommend for your subject.
In many subjects, books are a vital source of information.
Union catalogues bring together the catalogues of many different libraries.
Older books Search our electronic book collections, which include many texts from the 19th and 20th centuries and before.
Theses and dissertations are not indexed in most subject databases, so you should look for them separately. They matter because they often contain cutting-edge information, or go into more detail than any work the author may have published.
Grey literature includes reports, conference proceedings, standards and patents, government publications and many other important documents which aren’t books or journal articles.