There are search engines for everything, it seems, including scholarly research. Search engines for scholarly research have their own set of advantages and disadvantages.
- Access is free
- Include material from multiple publishers, so makes searching easier
- Full-text provided if freely available
- Full-text not guaranteed
- Searching options might be more limited compared to publishers' own sites
- Lack of transparency about what's actually included
- No quality filters
Academic search engines are good for getting an overview of a topic and if you don't have access to resources available through subscription, then they're great. If you do have access to resources available through subscription, you should use them instead.
The best academic search engines
Google Scholar is to academic search engines as Google is to regular search engines; it's Google applied to scholarly research. As of January 2018, it covered 348 million articles, and so probably has a few more than that now. Google Scholar uses the Google search interface so it's easy to use. If full-text is available, then it's well signposted. Quality can be a bit inconsistent at times however (see the Open Access Publishers page)
This is fancier, with more bells and whistles than Google Scholar. The bells and whistles are good if you're a researcher, but perhaps less so if you're simply looking for full-text articles, of which Microsoft Academic has significantly fewer (220 million, last time someone counted). Full-text is not so well signposted here, but it does have a nicer interface than Google Scholar however.
Update 06/05/2021 Microsoft Academic is closing down at the end of 2021
The Bielefeld Academic Search Engine is hosted by Bielefeld University in Germany and covers only open access material. The good news is that the majority of indexed material should be available as full-text, the bad news is BASE covers fewer articles than both Google Scholar and Microsoft Academic.
A little complicated perhaps, but this site aims to be a visual interface for the world's scientific knowledge. In practice that means creating maps from search results that give cluster together similar papers by topicc and so help to identify key concepts in a field. It uses the BASE search engine, so many items are full-text
CORE is similar to, but slightly larger than BASE and contains around 25,000,000 full-text articles mostly from open access sources
Dimensions offers similar bells and whistles to Microsoft Academic and has a nice interface with lots of options to refine youe search, one of which is open or closed access.
Other academic search engine are available - see the links and resources page for other resources