Abstract：
In this paper, we study two types of second-order nonlinear differential equations with variable coefficients and mixed delays. Based on Krasnoselskii\'s fixed point theorem, the existence results of positive periodic solution are established. It should be pointed out that the equations we studied are more general. Therefore, the results of this paper have better applicability.
摘要：
在本文中,我们研究了两类具有变系数和混合时滞的二阶非线性微分方程。基于Krasnoselskii的不动点定理，建立了正周期解的存在性结果。应该指出的是，我们所研究的方程是更一般的。因此,本文的成果具有较好的适用性。
