Journal indexes and abstracts can do two things. They can help you
- locate where a article was published if you have incomplete details
- locate articles written on a certain subject
To find a subject-specific index look at the list of on-line resources by subject
Some more general indexes:
ArticleFirst
Arts & Humanities Citation Index
ISI - Web of Science
Science Citation Index
Science in the Nineteenth-Century Periodical
Social Sciences Citation Index
Wellesley Index to Victorian Periodicals 1824-1900
ZETOC