Stephen Hawking knew what he wanted to do by the time he was eight years old. His parents lived in London where his father was researching medicine. He did not want to follow his father as his paren
关于化学反应与能量变化的叙述不正确的是A．在化学反应中只有燃烧才能放出热量B．物质的缓慢氧化均放出热量C．物质发生化学反应的同时伴随着能
在下图所示的实例中，通过热传递改变物体内能的是( )
烯烃与氢气加成生成烷烃，但烷烃不一定都能由烯烃与氢气加成得到。下列烷烃不能由烯烃和氢气通过加成反应制得的是（ ）A.正戊烷B.异戊烷C.新戊
How about taking ___ short break?I want to make ___ call. A.the;a B.a;the C.the;th
依次填入下列各句横线处的词语，最恰当的一组是 ①要解决我国法律服务市场监管_______的问题，就必须完善相关立法，改革法律服务市场的监管体制和
In January , 2004, the United States successfully launched “Spirit”, a Mars Exploration Rover, _____ a new milestone in the history of mankind. A. it marked B. marking C.
关于质点,下列描述中正确的是( )A．质点就是体积很小的物体B．只有低速运动的物体才可看成质点，高速运动的物体不可看作质点C．任何物
