The Engineering Index Annual abstract number is found at the beginning of each abstract.

在每篇ei摘要的开头，是工程索引年刊的文摘号。

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As with abstract classes, you can define any number of method signatures.

对于抽象类，可以定义任意数目的方法签名。

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As with abstract classes, you can define any number of method signatures.

对于抽象类，可以定义任意数目的方法签名。

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