真空值
参考答案：
作用在液面上的绝对压强小于大气压强时，在数值上不足于大气压强的那一部分差值称真空值，用Pv表示。
十二指肠球部穿透性溃疡的腹痛特点是()十二指肠球部溃疡的腹痛特点是()
A．进食-疼痛-缓解
B．疼痛-进食-缓解
C．呕吐酸酵宿食
D．腹痛放射至左肩左上臂内侧
E．腹痛放射至右肩、背部
-That actor often joins in different activities in Beijing. Do you know __________?
-For 5 years.[ ]
A. how soon he will come back
B. how long he has stayed there
C. when he went there
D. how long has he been there
