[{"title":"( 3 个子文件 12.36MB ) 机械设计和机械原理ppt","children":[{"title":"机械设计与原理2","children":[{"title":"第九章 轮系.ppt <span style='color:#111;'> 2.96MB </span>","children":null,"spread":false},{"title":"第八章 齿轮机构.ppt <span style='color:#111;'> 12.21MB </span>","children":null,"spread":false},{"title":"第七章 凸轮机构.ppt <span style='color:#111;'> 3.37MB </span>","children":null,"spread":false}],"spread":true}],"spread":true}]