A search for 'cognitive therapy' in Library Search returns the following catalogue results. Note the type of content. There is a mixture of print and electronic texts and commentary.
This search finds matches in book and journal titles. For more granular searching within the content of books and journals you should use the Articles + more feature of Library Search and the research databases.
A search for 'wellbeing AND exercise AND impact' in Library Search Articles + more returns the following results.
In addition to all the content in the Catalogue tab, there is also a wide range of content from various full text resources, with journal articles that match your search terms.
Articles + more search is often a good starting point for introductory material, but if you want to research the global literature on a topic, and go beyond quick full text results, then you should follow up with a database search. You can tailor your search more precisely using all the sophisticated functionality available on the research databases.