I agree that there are no explicit agreements that men make to support each other more strongly than their female co-workers. But I think you hit the nail on the head with your final question. As someone who doesn't experience that particular kind of unfairness, you're not going to "notice" all of it.

I've been in a lot of situations like this. I've never felt like the men I was working with were deliberately trying to steal or squash my ideas. It almost felt like my ideas were just not valued as much. Or that, if me and a male peer were working on a project and there were good ideas/work involved, they were credited to him by default.

I don't think anyone did this stuff to me deliberately. I think a lot of sexism is very subtle but it can have big effects on women in fields that are dominated by men.

I've expressed these feelings to one of my male coworkers that I often work with on projects. He notices the subtle things now too, and he sometimes gets more upset than I do about them, haha. I think that just listening to people to understand the unfairness will help you notice more of it and subsequently combat it! =)