Problem with modules

I have unlocked some modules, and some of them are avail, but the other ones, (weapons specifically, emp missiles etc) do not show on my build screen. Am I missing some thing here?

some modules are race specific (not many) so you need to be building a hull from the appropriate race in order to have them listed, and all modules are specific to a particular hull type, so if you unlock a frigate module, it will not show up for use on a cruiser, for example.
Is that what you are seeing?

race and hull size specific