which 引导定语从句时，它在从句中主要用作主语或宾语，但有时也可用作定语，在意义上大致相当于 this 或 that。给你几个例句，请注意体会：

We told him to consult the doctor, which advice he took. 我们叫他去看医生，他听取了我们的劝告。

He is studying economics, which knowledge is very important today. 他学经济学，这种知识现今很重要。

He lost his temper, at which point I decided to go home. 他发脾气了，这时我就决定回家了。

We arrived at noon, by which time the demonstration was over. 我们是中午到的，这时游行业已结束。

Tom spent four years in college, during which time he learned French. 汤姆上了四年大学，在此期间他学了法语。

I called him by the wrong name for which mistake I apologize. 我叫错了他的名字，为了这个错误我愿道歉。

He may possibly decide not to come, in which case there’s no problem. 他可能会决定不来，这样就没问题了。

注意，它与用作定语的关系代词 whose 用法不同——whose 引导定语从句时，它在意义上大致相当于 one's。如：

Wolves are highly social animals whose success depends upon cooperation. 狼是高度群体化的动物，它们的成功依赖于合作。

感觉下面的资料总结得不错（稍作改动），可以参考一下：

关系限定词which之后名词的语义特征

关系限定词which之后一般是个外延比先行项更为广泛的的抽象名词，比方说fact，case，event，situation，time，place，means，advice，failure，claim，statement等。

具体来讲：

1. 当先行项是主句中的名词成分时，关系限定词which之后的名词通常是前面名词成分的上位词；

2. 当先行项是整个主句所表示的一种情况时，

2.1 关系限定词which之后的名词是对前面情况的一种总结概括

2.2 关系限定词which之后的名词是对主句与从句之间潜在逻辑语义关系的一种明确。

例句：

1. Tom spent four years in college，during which time he learned French.

time是years的上位词

2.1 I called him by the wrong name，for which mistake I apologized.

先行项所表示的情况是对关系限定词which之后的名词的某种具体说明，即先行项回答了后面这一抽象名词所指内容“是什么”的问题。

2.2 It is suggested that a transformer be fixed to the fluorescent light，by which means electrical force can be changed.

关系限定词which之后的名词直接指明了主从句之间隐藏的内在逻辑关系，这里表示方式。