See IALS Library's EU research guide.
EU primary legislation is on Westlaw UK and the EUR-Lex website, in original and consolidated amended versions. EUR-Lex is the easiest database to use for researching primary legislation.
EU secondary legislation (regulations, directives and so on) is on Westlaw UK and EUR-Lex, in original and consolidated amended versions. TIP: the consolidated versions are occasionally not quite up-to-date (the IALS EU research guide says how to check).
The decisions of the Court of Justice, the General Court (formerly 'Court of First Instance') and the now-defunct Civil Service Tribunal are on Westlaw UK, Lexis+® UK, EUR-Lex and the EU court website, Curia.
For national court decisions on matters of EU law, see Dec.nat, or the National Case Law collection on EUR-Lex.
Cases from national and EU courts concerning judicial cooperation in civil and commercial matters are available in the JURE database on EUR-Lex.
EUR-Lex has COM documents from 1960 onwards, under 'Preparatory Documents'.
The Archive of European Integration includes many old COM documents.
Westlaw UK has COM documents from around the mid-1990s onwards.
The entire Official Journal of the European Union / Official Journal of the European Communities is on EUR-Lex, right back to the 1950s.
Individual documents published in the L series of the Official Journal (directives, regulations, decisions and other EU secondary legislation) are on Westlaw UK, but they are not grouped by OJ issue.
Documents published in the C series of the Official Journal are on Westlaw UK from 1990 onwards (under 'Information and Notices').
For other EU official publications, try the Publications Office of the EU, other parts of the Europa website, or the Archive of European Integration.
Library Search can be used to search across numerous different online journal collections. Enter your search terms and select 'Articles'.
Alternatively, try the following sources individually (all except Find-eR can be accessed via IALS Law Databases page):
Westlaw UK: full-text articles or abstracts from UK and European/international law journals
Westlaw International Materials: full-text articles from European, international and US law journals
Lexis+® UK: full-text articles or abstracts from UK, European/international and US law journals
Index to Foreign Legal Periodicals (part of HeinOnline): index covering selected journals from all around the world, including international and comparative law titles; gives links to full-text articles, if available in other modules of HeinOnline
Find-eR, the European Commission's library catalogue: indexes journal articles from a range of European countries; filter search results by Resource Type 'Articles'; full text not available to external users
HeinOnline's Law Journals Library: thousands of full-text journals, mainly published in the US, but including a substantial number of articles on EU law
If you need more help...
See our research guide, Finding Journal Articles.
On Library Search, select All / Everything to find book chapters (as well as journal articles and entire books). If you select 'Books' on Library Search, it searches book titles, subject headings and other metadata, but does not search inside books.
Instead of using Library Search, you could search e-book collections one at a time. The following collections include a substantial number of titles focusing on EU law:
Oxford Scholarship Online (OSO)
Practical Law has an EU law section and a Brexit section, with legal updates, practice notes and other material designed with practitioners in mind.