【简答题】The railway station has always been a fascinating place, representing departure as well as ______. (arrive)
【多选题】关于惯性环节的频率特性,下列说法正确的是:
B.
对数幅频特性由两条直线构成,斜率分别为0与-1,转折频率为1/T。
C.
对数相频特性的0至-90度范围内中心对称的曲线
D.
对数幅频特性是一条光滑曲线,有两条渐近线,斜率分别为0与-1,转折频率为1/T。
【单选题】以下有关生物化石的叙述,错误的是( )
A.
早期形成的地层中,成为化石的生物都很低等
【单选题】下列关于 SN1 反应历程,叙述错误的是( )
D.
生成重排产物和产物外消旋化是SN1反应历程的判断依据
【单选题】There is always the ____of an earthquake in this region, but so far there has been no sign of trouble
【单选题】As discovered by expedition scientists, Antarctica has not always been so cold as it is today, so has the Arctic.
【判断题】惯性环节 的对数幅频特性曲线的转折频率是 。( )