有些玫瑰是双瓣的，有些是单瓣的。

Some roses are double; others are single.

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目的：评价保留二尖瓣全瓣下结构对双瓣替换者术后左心功能的影响。

Objective: To evaluate the effect of preservation of the entire mitral subvalvular apparatus during double valve replacement on left ventricular functions.

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双瓣止回阀主要由阀体、阀瓣、阀杆及弹簧等重要零件组成，并采用薄型轻巧设计。

Double disc check valve consists of body, disc, valve rod and spring and other parts. The valve is designed with slim light weight.

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