For Civs: Maya is a great option, as is Han. Greece is a good all-around civ with strong bonuses that can help in any direction. Anything that lets you play "tall" (mostly cities, few towns, lots of specialists) rather than "wide" (few cities, lots of towns), is going to benefit a science victory, so Khmer, which doesn't on the face of it look particularly great for Science on its own, is good for setting up a path to Majapahit (who is great for Exploration science) and onto Meiji Japan for Modern. But there are a lot of options.
For Leaders, Confucius is a clear standout. If you expect to be playing mostly peacefully, Himiko, Queen of Wa is outstanding. If you're going more warlike, then Trung Trac, whose Science bonus is no joke and who can also fight with the best of them.
Hope that helps!