已知函数f(x)＝(ax－1)ex，a∈R. (1)当a＝1时，求函数f(x)的极值； (2)若函数f(x)在区间(0,1)上是单调增函数，求实数a的取值范围．
如图所示为一段直光导纤维，它的折射率为n，从它的一端射入的光线必须满足θ________才能使入射光线全部从另一端射出.（光导纤维的外部为真空）
The basin _______ water soon. You can’t pour more in. A. is full with B. fills with C. is filled of D. is filled with
No matter how long your life is, you will, at best, be able to read only a few books of all that have been written, and the few you do read should include the best. It is to be expected that the selec
材料一：“承派周恩来先生来渝洽商，甚为欣慰。惟目前各种重要问题，均待与先生面商，时机迫切，仍盼先生能与周恩来先生惠然偕临，则重要的问
History has witnessed great changes in the styles of Western art. During the Middle Ages, a conventional artist would mainly aim to represent __31__ (religion) themes. A feeling of respect and love
被称为“地球之肺”的是（ ） A．热带雨林 B．热带草原 C．热带沙漠 D．亚寒带针叶林
关于火车转弯处内外铁轨间的高度关系，下列说法中正确的是 A．内、外轨一样高，以防列车倾倒造成翻车事故 B．因为列车转弯处有向内倾倒的可能，
的曲线如图所示，那么方程
的曲线是 ( )
对称，选C