说出电波传播的主要方式,并说出电波在自由空间的传播损耗与哪些因素有关?
测量电阻时,万用表量程挡位(),可提高测量精度。 ["应选择较高挡位","应选择较低挡位","随意选择","应选择直流挡"]
飞机上装有几部WXR(). ["1部","2部","3部","4部"]
在After Effects 6.5中如何将一段影片倒放?() ["Time Stretch","Time Remapping","Time-Reverse Keyframes","Time Difference"]
用万用表测量电阻时,万用表挡位开关应置于()挡。 ["“A”","“V”","“Ω”","“L”"]
轴的直径φ20,今实测得的尺寸为φ19.995,其轴线的直线度误差为0.015,试根据泰勒原则,判断这根轴是否合格。