Early Heinlein e.g. Have Spacesuit - Will Travel, Farmer In The Sky, The Rolling Stones or for non-juveniles, The Moon is a Harsh Mistress have lots of science.

Later works, less so.

Or even Star Trek to be honest. I don't know why Star Wars always gets passed off as "science fantasy" when it's a more grounded universe than Trek by far - space wizards notwithstanding (which Trek has plenty of.)

Even in a lot of hard SF, a lot of the science is wonky if it falls outside of the author's special interest or area of expertise. Relevant to Asimov, the only reason robots have "positronic" brains in his stories is that positrons were a new discovery at the time and it sounded cool and futuristic to him.