请问文章引用的数字如果上标时需要与前面的单词一个空格吗

请问文章引用的数字如果上标时需要与前面的单词一个空格吗 比如 researchers found that smoking is good for some people.
researchers found that smoking is good for some people_1.
这里的1是上标。_ 代表空格
还是没有空格？如下所示。 researchers found that smoking is good for some people1.

有空格