Due to my line of work, I find myself having to use both these services frequently, despite avoiding google as much as I can. I see a lot of alternatives out there for internet searching, but when it comes to specific fields, alternatives tend to be scarce.
In my experience, best with science, math, and technology stuff:
https://arxiv.org/
But I’ve found it to be very good for finding scientific articles.
It is fairly good for what it is, lots of things missing but I will certainly take it. Use it often. Recommend.