It uses scholar as a search engine, but then it replaces the links in the results. 
e.g.<p><pre><code>    http:&#x2F;&#x2F;link.springer.com&#x2F;link-to-paper
</code></pre>
becomes:<p><pre><code>    http:&#x2F;&#x2F;link.springer.com.sci-hub.io&#x2F;link-to-paper
</code></pre>
As far as I can tell, it works for some articles.