形变强化
参考答案：
金属经冷塑性变形后，其强度和硬度上升，塑性和韧性下降，这种现象称为形变强化。
Our new physics teacher got a pretty and lovely girl _____ .
A．in his thirty
B．in his thirty’s
C．in his thirtieth
D．in his thirties
口腔颌面部感染的主要途径是
A．牙源性感染
B．腺源性感染
C．损伤性感染
D．血源性感染
E．医源性感染
