The links above will either go to a page that lists magazines or to one where you can search for magazines.
If you just want to know the professional magazines or anthologies that publish science fiction short stories -- which meet Science Fiction & Fantasy Writers of America qualifications -- here are 21 markets from sfwa.org: (they are not all currently open to submissions, however):
- Analog Science Fiction and Fact (guidelines)
- Apex (guidelines)
- Asimov’s Science Fiction (guidelines)
- Bull Spec (guidelines)
- Cicada (guidelines)
- Clarkesworld Magazine (guidelines)
- Cosmos (guidelines)
- Cricket (guidelines)
- Dark Wisdom (guidelines)
- Flash Fiction Online (guidelines)
- Grantville Gazette (guidelines)
- Lightspeed Magazine (guidelines)
- The Magazine of Fantasy and Science Fiction (guidelines)
- Nature (guidelines)
- Odyssey (guidelines)
- Orson Scott Card’s InterGalactic Medicine Show (guidelines)
- The Pedestal Magazine (guidelines)
- Redstone Science Fiction (guidelines)
- Strange Horizons (guidelines)
- Tor.com (guidelines)
- Writers of the Future Anthology (rules)