There is a nice language tool available. It is an open source proofreading software for English, German and more languages:
The University College London offers an interactive self-learning course in Academic Writing in English. This app is availalbe for iOS and Android.
Find more at http://www.ucl.ac.uk/english-usage/apps/awe/index.htm
This blog post by Next Scientist gives you some tips to improve academic writing including 15 typical English grammar goofs: