The existence theorem of a class of periodic boundary value problems for first order nonlinear integrodifferential equations is obtained through the method of lower and upper solutions.是什么意思_The existence theorem of a class of periodic boundary value problems for first order nonlinear integrodifferential equations is obtained through the method of lower and upper solutions.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句