The UK’s national thesis service provided by the British Library. You can search for theses submitted to UK institutions. Note that abstracts are not included for all theses. Full text is available if the thesis has been digitised.
DART-Europe is a partnership of research libraries and library consortia to improve global access to European research theses. There is access to over 828,730 full-text research theses from 619 Universities sourced from 28 European countries. No password required.
WorldCat is the world's largest network of library content and services including theses and dissertations from over 70,000 library catalogues worldwide. It lets you search the collections of libraries in your community and thousands more around the world. You may also find article citations with links to their full text; authoritative research materials, such as documents and photos of local or historic significance; and digital versions of rare items that aren't available to the public.
No password required.
To search for theses or dissertations, go to the Advanced Search and select 'Thesis/dissertations' under 'Content'.