【简答题】穿衣镜是利用 ________成等大的虚像 制成的;放大镜是利用 ________ 镜可以成正立放大的虚像的原理制成的;汽车的观后镜是利用 ________ 镜来达到扩大视野的目的;太阳灶是利用凹面镜能把太阳光 ________ 在焦点的性质制成的.
【简答题】太阳灶是用 ______面镜制成的,它可以使照在表面的太阳光 ______在一点,凹面镜的面积越大汇聚的太阳光就越 ______,温度也就越 ______,利用它不仅可以烧水、煮饭,还可以发电、冶炼,所以它是既节约燃料又不 ______的环保型能源.
【单选题】Which of the following is NOT true about the deck crane?
A.
Deck cranes are able to pick up and land permitted loads anywhere within its working radius.
B.
Deck cranes have a strong adaptation for any kind of cargoes.
C.
Deck cranes have been replaced by derricks on many modern ships.
D.
Deck cranes are easy to operate because its rotary angle can reach 360 degrees.
【简答题】太阳灶是用_________ 面镜制成的,它可以使照在表面的太阳光_________在一点,凹面镜的面积越大会聚的太阳光就越_________ 温度也就越_________,利用它不仅可以烧水、煮饭,还可以发电、冶炼,所以它是既节约燃料又不_________的环保型能源。
【多选题】旅游从业人员直接为旅游者提供服务,其()决定了旅游服务的安全程度。
【简答题】S1:How many security levels are there?Do you know the differences?S2:Yes,there are three security levels .Levels means the normal level at which ships and port facilities normally operate;Level 2 is t...
【简答题】Cranes have replaced derricks on many modern ships. Positioned between the holds, often on a platform(平台) which can be rotated through 360° the deck crane provides an immediately operational unit requ...
【单选题】下列有关麦克斯韦方程组的说法中,不正确的是( )。
D.
静电场和恒定磁场的基本方程可视为麦克斯韦方程组的特例