建筑学中，拱道或门口的拱心石，是把建筑整体连接在一起来防止它倒塌的石头。

In architecture, a keystone in an archway or doorway is the stone that holds the whole thing together, and keeps it from collapsing.

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计划中的大号拱心石石油管道将用于运输产自加拿大油沙的重原油。

The proposed Keystone XL pipeline would carry heavier crude oil produced from tar sands in Canada.

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但有一个人一如既往地稳定，成为支撑桥梁的拱心石——他就是维迪奇。

But if there's been one constant, the keystone holding up the bridge, it's Vidic.

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