一种积分变换，它来源于函数的傅里叶积分表示。积分 (1) 称为? 的傅里叶积分。周期函数在一定条件下可以展成傅里叶级数。(An integral transformation that derives from the Fu Liye integral representation of a function. Integral (1) is called the Fu Liye integral of F more. The periodic function can be expanded into Fourier series under certain conditions)