【单选题】有四个直齿圆柱齿轮:1)m1=5mm,z1=20,【图片】;2)m2=2.5mm,z2=40,【图片】;3)m3=5mm,z3=40,【图片】;4)m4=2.5mm,z4=40,【图片】。试问哪两个齿轮的渐开线齿廓形状相同?( )
【单选题】我国颁布实行的壬戌学制是在( )。A.B.1903年C.1912年D.1922年
【单选题】处于高弹态的高聚物,下列哪些单元不能运动( )。
【单选题】有四个直齿圆柱齿轮:1) m = 5mm,z = 20,α = 20° 2) m = 5mm,z = 40,α = 20° 3) m = 2mm,z = 50,α = 20° 4) m = 5mm,z = 20,α = 25°。其中,渐开线齿廓形状相同的是()
【单选题】According to the passage, the danger of nuclear power lies in______.
【单选题】根据下列文章,请回答 31~35 题。 Mobile Phones Mobile phones should carry a label if they proved to be a dangerous source of radiation, according to Robert Bell, a scientist. And no more mobile phone transmitter t...
A.
they should be banned immediately.
B.
the use of them should be restricted.
C.
all transmitter towers should be torn down.
D.
a warning label should be attached.
【单选题】我国经正式颁布并在全国范围内实际推行的学制中,修业年限最长的个是( )