说明：  此文档是PDF版的偏微分方程解的几道算例（差分、有限元）含matlab程序，包含各种差分格式，比如向前、向后、六点、精确值和数值解的比对图，对自由振动问题的时间和空间网格剖分后的模拟图
(This document is a PDF version of the partial differential equation solution of several examples (difference, finite element) + including Matlab program, including various difference formats, such as forward, backward, six point, accurate value and numerical solution of the comparison chart, the free vibration problem of time and space mesh after the division of the simulation chart!)