In cases where technology is very recently introduced into the educational system, as is the case of most developing countries, studies have mainly focused on the first two stages, that is, on knowledge of an innovation and attitudes about it.

【翻译】在科技（教学手段）被刚刚引入教育系统的情况下，研究主要集中在前两个阶段，即对创新的认知和态度，这对大多数发展中国家而言都是一样的。

【分析】主句：studies have mainly focused on the first two stages, 其次：

1. that is（意为“即”）为插入语，后面具体解释哪两个阶段：on knowledge of an innovation and attitudes about it.

2. In cases where technology is very recently introduced into the educational system, 一个含有定语从句的介词短语，作地点状语。定语从句where technology is very recently introduced into the educational system 修饰cases。In cases where 一般翻译成：“在......情况下”。

3. as is the case of most developing countries,  是as 引导的非限制性定语从句，位置灵活，在句首、句中、句末均可，as 指代整个主句的内容。as is the case of 一般理解为：“像......一样；对......而言是一样的”。

关系代词as和which究竟有哪些区别？

关系代词as与which引导的非限制性定语从句，其先行词都可以是整个主句，指代主句的整个意思，但as和which具有不同的词义和用法。其区别如下：

1. as引导的从句表示说话人的看法、态度、解释或评论

引导定语从句时，as仍具有“正如，像，由……可知”等意思，翻译时有时可不必译出。所以，as定语从句常含有这些动词：see, know, hear, watch, remember, say, tell, show, expect, guess等，这类动词与as连用几乎成了一种固定搭配。as引导的定语从句可以置于句首、句中或句尾。如：

As is often the case, girls like dolls while boys like guns. 女孩子喜欢玩具而男孩子喜欢枪，这是常见的情况。

The famous magician Liu Qian, as we all know, is from Taiwan. 众所周知，著名魔术师刘谦是台湾人。

There is a net bar around here, as I remember. 我记得这儿附近有一家网吧。

2. which引导的定语从句对主句所叙述的事情进行补充说明，表明事物的状态或结果

which指前面主句所提到的这件事，常译为“这一点，这件事”等。这时它所引导的定语从句与主句之间常含有并列、因果关系。注意，它引导的从句不像as那样位置灵活，它只能位于主句的后面。如：

She tore up my photos, which (=and that) upset me.她撕碎了我的照片，这使我很不安。

He changed his mind again, which made us all angry. 他又改变了主意，这使我们大家都生气了。

3. 在定语从句中作限定语或介词的宾语时，要用which，不用as

Jenny might come, in which case I'll ask her. 詹妮可能会来，要是那样的话我就去问她。

She graduated from a local middle school, after which she went to Beijing University. 她毕业于当地的一所中学，之后她去了北京大学。

4. 当定语从句是否定含义或含有一个复合宾语时，用which而不用as

He pretended not to know me, which I didn't understand. 他假装不认识我，这是我搞不明白的。

He admires everyone in his class, which I find quite strange. 他羡慕班里的每个学生，我认为太奇怪了。

【特别提示】

as引导非限制性定语从句的最大特点是位置灵活；其次，as有以下常见的、而which不具备的“固定表达”：

as we all know 众所周知    

as I can remember 正如我所记得的

as often happens 正如经常发生的那样     

as we expect 正如我们预料的那样

as you see 这一点你明白

as was expected 正如预料的那样

as can be seen 看得出来     

as may be imagined 正如可以想象的那样

as has been said above 如上所述

as we all can see 正如我们都能看到的那样

as everybody can do 正如人人都能做到的那样

as is often the case 像经常发生的情况那样

as is the case of ... 像......一样；对......而言是一样的

that is 不是定语从句，而是插入语，意为“那就是”，“即”。相当于“that is to say, namely, 或者破折号——”。如果非要用定语从句修饰stages的话，那么which are后面不要on。