for effective scientific writing
This is a collocation dictionary that can help you find the right word combinations. With subject-verb combinations and suitable adjectives and prepositions, this website can help you build an entire sentence around a single keyword. Caveat: it's limited to the most frequent words in English.
This website was not meant as a language aid, but it can be used as one very easily. Check the frequency of similar-sounding expressions: is it "on one hand" or "on the one hand"? Great both for general and for technical vocabulary.