如果字符串中含有"这样的字符，需要`""'来定义。

字符串的标准形式是`""'，当不引起误会时，可简作""。

是否有相应的帮助文件？

help strings

补：    In addition to double quotes for enclosing strings, Stata also allows compound double quotes:  `" and "'.  You can type "string" or you can type `"string"', although users seldom type `"string"'.  Compound double quotes are of special interest to programmers because they nest and provide a way for a quoted string to itself contain double quotes (either simple or compound).  

help quotes