What are you looking for?
If you want to do more general subject searching and explore around a topic use Bibliographic Databases (also known as Abstracting and Indexing Services). See the 'Databases' tab for more information.
JSTOR contains the full-text of many of the classic journals, some as far back as the 1880s.
If you want to be alerted about new journal issues and tables of contents then sign up for the Zetoc service.
When searching in databases think about your keywords, and synonyms for these words.
Use truncation and Boolean operators.
Your search will develop over time, keep a note of what search terms you have used and what has / hasn't worked.