勇气并不总是咆哮。有时勇气是一天结束时那个轻声说"明天我再试一次"的声音。
"Courage doesn't always roar. Sometimes courage is the quiet voice at the end of the day saying 'I will try again tomorrow.'"
无人机不是玩具,而是改变行业的工具。
"The magic of books is that they can take you anywhere."
数学是解开宇宙秘密和理解支配它的基本法则的关键。