在观察性研究中,我们常常不得不依赖于无法直接检验的假设。
The most dangerous thing is not failure, but complacency.
煤炭开采的创新不仅仅是关于开采,而是更智能、更安全、更尊重环境地开采。
Liberty means responsibility. That is why most men dread it.
"Every act of creation is first an act of destruction."