关键词: 微分方程, 正周期解, 不动点定理, 状态依赖

Abstract: In this paper ,we are concerned with the existence of positive periodic solutions to
the differential equations with state-dependent delay
x′(t) = −A(t, x(t))x(t) + B(x(t))F(x(t −  (t, x(t)))).
Using Krasnoselskii fixed point theorem, we establish some sufficient condition for the existence
and nonexistence of positive !-periodic solutions to the above equation .

Key words: Differential equtions, Positive periodic solution, Fixed point theorem, State- dependent