function load_big_pic(){
   //顶图
   document.getElementById("p01").style.backgroundImage="url(image/p01.jpg)";

   //外框背景
   document.getElementById("back01").style.backgroundImage="url(image/back01.jpg)";
   document.getElementById("back02").style.backgroundImage="url(image/back02.jpg)";
   document.getElementById("back03").style.backgroundImage="url(image/back03.jpg)";
   document.getElementById("back04").style.backgroundImage="url(image/back04.jpg)";
}