as mentioned above,如上所述,一般做插入语
As mentioned above,an object has positive charge when it has lost electrons.
如上所述,物体失去电子时带正电荷.
as is mentioned above,如上所述,也做插入语
As is mentioned above,substances are constantly undergoing physical and chemical changes .
如上所述,物质总是在进行着物理变化和化学变化.
因此,它们之间没有区别