Gear drawing standards - part 1: for spur, helical, double helical and rack.

齿轮制图标准。第1部分：正齿。螺旋齿。双螺旋齿和齿条。

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When carries various chemical modifications on double helical molecular of optically active, we can always gain derivatives which have specific properties.

在具有光学活性的螺旋分子母体上进行各种化学修饰，可以获得许多具有特殊性能的衍生物。

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Objective To evaluate the clinical value of double helical ct angiography (DHCTA) and coronary artery calcification (CAC) detection in diagnosis of coronary heart disease (CHD).

目的评价双层螺旋ct血管造影(DHCTA)与冠状动脉钙化(CAC)积分诊断冠心病(CHD)的临床价值。

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Dr Watson, co-discoverer with Francis Crick of the double-helical structure of DNA, was responsible for suggesting the human-genome project in the first place.

ECONOMIST: The big beasts of genomics