Solo, the Oxford University Libraries' catalogue, covers the collections of most of the libraries, including all of the Bodleian libraries, and most departmental and college libraries, including Linacre library. Please note that college libraries normally admit only their own members, but if you trace unique material in a college library an email to the librarian will usually gain you admittance. You can find details of University libraries, along with their opening hours and admissions policy, here. Solo also gives you access to the University libraries' expanding collection of e-books. See here for a detailed guide to using Solo.
Outside Oxford, the most comprehensive guide for locating library books is WorldCat. If you can trace a book on WorldCat, Fiona can almost certainly obtain it for you on Inter-library loan.
You can access the contents of most of the e-journals that the University libraries subscribe to via Solo, using the Articles tab to search. If you don't find the article you're looking for, search for the journal title using the Oxford Collections tab, to see if the journal is available in printed form. Please note that you will need either to connect via the Oxford VPN or use your single-sign-on to access e-journals if you are outside the University network. A few e-journals are only available via specialist databases - ask Fiona for advice if you can't trace the e-journal you're looking for.
You can access the University libraries' collection of databases via the Databases A-Z list on Solo. It also covers other miscellaneous e-resources such as digital maps, directories and encyclopaedias. It is browsable by database title or subject. As with e-journals, you will need either to connect via the Oxford VPN or use your single-sign-on to access these resources outside the University network.
The best sources for news and magazine articles are Factiva and Nexis UK, both available via Databases A-Z. They both have a business bias, but cover many more general publications too. They both have extensive archives, so are good for retrieving articles no longer available on current newspaper and magazine websites.
ProQuest Dissertations and Theses (available via Databases A-Z) has the full text of many dissertations worldwide, and the British Library's Ethos service has a good coverage of full-text doctoral dissertations from UK universities. The Oxford Research Archive (ORA) has the full-text of recent Oxford theses, and don't forget Solo for printed copies of theses held in the University libraries. For further sources, see the Bodleian Libraries Theses page.
Open Access is a growing movement in scholarly research, offering free access to the text of articles, book chapters, theses and monographs held in institutional repositories. Google Scholar is the most popular search engine for finding Open Access material, or try the aggregator CORE. Oxford University Open Acess articles and theses are available on ORA.