强调句型是不是定语从句

当然不是，强调句型是用来强调非谓语部分的
Mary bought the book in the store yesterday.
强调主语：It was Mary that bought the book in the store yesterday.
就是Mary昨天在店里买了书。
强调宾语：It was the book that Mary bought in the store yesterday.
Mary昨天在店里就是买了这本书。

强调地点状语：It was in the store that Mary bought the book yesterday.
Mary昨天就是在这家店里买了书。

强调时间状语：It was yesterday that Mary bought the book in the store.
Mary就是昨天在店里买了书。

强调句型中的It是没有实在含义的，It be...that 只是一个句型。判断是否是强调结构，就把It be...that去掉，如果句子意思通顺，就是强调结构，否则，就不是。

请比较：
It is the factofy that I visited last year. 这是强调句型，“去年，我参观的就是这个工厂。”
This is the factofy that I visited last year. 这是定语从句，这就是我去年参观的工厂。

如果有不理解，在追问！忘采纳！

强调句型不是定语从句
因为在强调句型中，that 不做成分，it is that ,it is who 去掉不能是病句，而定语从句中，that ,who必须充当成分

这要看是英语还是国语，国语这句话就成立，而英语就不一定，因为英语语法你有这种叫倒装句语法的存在导致了强调句不一定是定语从句。