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，而在(－∞,∞)上定义的非周期函数?，显然不能用三角级数来表示。但是傅里叶建议把?表示成所谓傅里叶积分的方法(An integral transform that is derived from the Fourier integral representation of a function. IntegralFourier integral . The periodic function can develop a Fourier series under certain conditions, and the non-periodic function defined oncan obviously not be represented by a trigonometric series. However, Fourier proposed to representas a method of so-called Fourier integration.)