If you're looking for a specific item, the easiest way to track it down is by using the library catalogue, iDiscover. Type a few words from the article's title into the search box. If the article is available online (and many of them are) then you should be able to get to it directly by clicking 'Full text available'. If it isn't online, then iDiscover will tell you where copies of the print journal can be found.
If you're looking for articles on a given topic, add a few keywords to the search box on iDiscover. Be careful with your search terms, and try synonyms if you're not getting the results you hoped for.
Encyclopedia and bibliographies give a useful starting point to find background information on your topic. They often list other useful books and articles on a topic. The most useful ones for Classics are:
L'Année philologique an essential bibliographic resource for all Classical disciplines. Useful for finding books and articles on specific subjects or on particular ancient authors. It can be searched using a range of criteria, e.g. modern author, ancient author, keyword, subject, date, etc. Useful for decoding abbreviations used for journal titles.
Oxford reference Online brings together many of OUP's most popular reference titles into a single, cross-searchable, collection. It includes the Oxford Classical Dictionary, the Oxford Companion to Classical Civilization, Who's who in the Classical World and the Pocket Oxford Latin Dictionary.
New Pauly Online provides comprehensive coverage of the ancient world from the prehistory of the Aegean (2nd millennium BCE) to Late Antiquity (600-800 CE).
Perseus Project Digital library of resources for the study of the ancient world and beyond. Includes texts and translations of many core ancient authors. Provides online Greek and Latin lexica (Liddell & Scott, and Lewis & Short). Also morphological analyses, English to Greek and Latin word searches, vocabulary tools, and context searches. The TLG links to the Perseus LSJ and Greek morphological analysis tool.
Search for the journal by title in the ejournals libguide.
If the relevant year is covered, click on the link to the journal and navigate to the article.
Use the abstract and indexing databases to carry out a general subject search.
All University of Cambridge PhD theses from 1970 onwards are searchable from the Theses catalogue.
Apollo (the University of Cambridge data repository) holds full-text digital versions of several hundred Cambridge PhD theses. This is a rapidly growing collection deposited on a voluntary basis.
You can also access theses from outside the University: