Some people say 半脱产 to refer to part time study and 全脱产 as full time study for people who have a job. And the word for workers to go back to study is 进修.
半脱产学习 and 全脱产学习， or 半脱产进修 and 全脱产进修 are words specifically for people who have worked. Intuitively speaking, if you have never worked, you have no work(产) to get away with(脱).
全日制学习 is a broader term for everybody, including students who have never worked.
I'm not sure if these words are only used in some parts of China, but it is quite recognized in the northern China.
Searched some description and I pasted below:
学历中的脱产学习是在学习期间不参加工作的一种学习方式，办学的方式相当于全日制学习。 也就是参加工作后再去校内进行全日制学习的方式， 其管理模式与普通高校一样，学习期间不在原单位工作，不占用周六和周日的工休时间，对学生有正常的、相对固定的授课教室和管理要求，有稳定的寒暑假期安排。
而半脱产学习就是一边学习，一边工作， 即白天工作时间还是工作，在周一至周五的晚上和周末的休息时间来学习，这种利用业余时间学习的方式称为半脱产。
另外还有一种为不脱产学习，即不脱离工作岗位，利用闲暇之余进行学习。一边工作,一边利用工作之余的时间来学习上课，参加考试的一种学习方式。函授是成人教育中不脱产学习的主要形式。
Here also mentioned 函授 which is also widely recognized. This is a program type designed for workers to get a degree while work full time. You can also go to 夜大(night university) to get a degree. Basically they're the same.
In summary:
半脱产学习 means part time study, still work (normally this is supported by the company you work for, as you expect to get away from work when there is commitment required from the study, although the classes are normally conducted in the nights and weekends)
全脱产学习 means full time study, no work
函授 means part time study, full time work （this type of study is for people who doesn't have a degree but want to get one). Refer here.
Strictly speaking, 函授 might have people who is not working and never worked either, but this type of program is designed for full time workers and classes will be conducted in a way to cater for students who need to work full time. 函授 is probably less popular now, as it's easier for students to get a degree now.
Of course you can use a broader word, like 全日制，非全日制学习, however, those words don't differentiate the student types at all.
Like others suggested, 在职读书 is also a commonly recognized word, especially for higher educations (I feel) after degree because I often hear people talk about 在职研究生. I also feel 在职 is more modern than 脱产.
By the way, maybe a lot of people don’t study after degree but there are a lot of people do study in China when they have jobs, and a lot of them are company or corporate sponsored, and normally they don’t mix with full time students. And as I mentioned in the comment section, a master's degree normally requires 3 year full time study in China, and it's a big commitment, some people will simply get one from abroad. Guess that’s why you don’t see them in school. However, everything is changing, and in order to meet the demands, more and more study programs will be available for working class.
