hiphotos.baidu.com/zhidao/pic/item/7aec54e736d12f2e53ce0c5f4ec2d562843568c2.com/zhidao/wh%3D450%2C600/sign=27e7e5844610b912bf94fefaf6cdd035/7aec54e736d12f2e53ce0c5f4ec2d562843568c2.jpg" /> 材料力学和结构力学的弯矩图画法不同
