Not academic, but possibly of interest to many, is the BBC Learning English website page a

http://bbc.co.uk/learningenglish

At the top of the site, there is a language selection button.

Navigation through the courses and lessons is provided in several languages.

There are many books on academic writing methods, but not many that look comprehensively at common phrases used in research writing. This University of Manchester (UK) website looks useful:

http://www.phrasebank.manchester.ac.uk/

The site ' aims to provide you with examples of some of the phraseological ‘nuts and bolts’ of writing organised according to the main sections of a research paper or dissertation'... and states that ' the items in the Academic Phrasebank are mostly content neutral and generic in nature'. 

Topic headings include: Being Critical, Being Cautious, and many more. Each topic is introduced by an overview of usage for the topic. I highly recommened reading these passages and also the main introduction here: About Academic Phrasebank . 

Astronomy Thesaurus - covers English, French, German, Italian, and Spanish.

CAB Thesaurus - multi-lingual coverage of life sciences, technology and social sciences.

ERIC (Educational Resources Information Center) Thesaurus - based in USA, covers bibliographic citations and digests, sponsored by the U.S. Department of Education.

Ethnographic Thesaurus - based in USA; covers folklore, ethnomusicology, ethnology, and related fields.

European Thesaurus on International Relations and Area Studies - based in Europe; covers international relations and area studies, and the languages English, French, German, Spanish, Italian, Polish, Czech, Croatian and Russian (English or German interface).

Getty Art & Architecture Thesaurus - based in USA; covers fine art, architecture, decorative art, and material culture.

Getty Thesaurus of Geographic Names - covers all nations of the world, including vernacular and historical names, coordinates, place types, etc.

Getty Union List of Artist Names - based in USA; covers artists and architects, including variant names, pseudonyms, and language variants.

LC Thesaurus for Graphic Material   - covers terms terms related to graphic materials.

Medical Subject Headings (MeSH) - covers medicine and health.

Public Health Language - based in the UK.

Thesaurus for the Social Sciences - based in Germany, covers terms in German - English - French.

UNESCO Thesaurus - covers "the fields of education, culture, natural sciences, social and human sciences, communication and information"

Visual Thesaurus - a commercial site that gives a sneak preview of a potnetially very useful service. The main service is not free unfortunately.

See also: Taxonomies & Controlled Vocabularies SIG of ASI .

The Science Dictionary - A "specialized science search engine that queries billions of the web's top science pages for scientific information"

Online Life Science Dictionary - based in Japan.

World of Science - "Online Science for All" b ased in India.

Babylon Science & Technology - "The World's Best Online Dictionary"

Biology Online - "Run by enthusiasts from all around the world"

Opposite Dictionary - "Find opposite of a word in seconds. Largest opposites dictionary"

Pronounciation Dictionary - "All the words in the world. Pronounced" based in Spain.

Science Dictionary - " The World's Largest Online Science Dictionary" b ased in the USA.