Research Rabbit is a discovery engine. It bills itself as "the Spotify of papers".
It is an invaluable tool for exploring new areas and writing literature reviews. It allows you to uncover new and classic papers related to your area of research easily and quickly. It also shows links between authors- making maps of collaborations and related works.
Research Rabbit is free, easy to use, and constantly adding new papers. Research Rabbit will also send you a weekly digest of new papers that it has discovered that may be relevant to your research.
