When someone develops a new theory on physics, which is barely on schetch (so there are no measurements, nor simulations) with just a mathematical and conceptual description, in which scientific journals people use to publish these theories?
Can you please elaborate a bit more your question? In what domain of physics? I guess that you are thinking about Mathematical Physics journals (Journal of Mathematical Physics or Journal of Physics A: Mathematical and Theoretical for instance). Also journals of the American Physical Society accept this kind of papers but what journal depends on the domain we are talking about...).
If it is only in a very conceptual stage it might be quite tough to pass peer review. Why not try it with the arxiv preprint archive first? It's out and published and you can still submit to a regular journal later.
For groundbreaking ideas you can try any journal of course, today with the more online-oriented publishing style it is even ok to submit a short article to a high class journal and put details and calculations in the arbitrary long supplemental material.