[godelski]

If we're talking about fundamental physics I'll mention fusion research. If you go to the DOE Chinese citizens are highly restricted around locations like NIF. You don't need any kind of clearance to work at NIF, but people have different restrictions. Same is true for CERN. China doesn't have full access to everything that happens at CERN, which is a fairly open lab.

Most research isn't classified, but that doesn't mean most research is open.