焊前预热既可以防止产生热裂纹,又可防止产生冷裂纹。
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Which certificate is always issued by the China Classification Society().
A. Loadline certificate
B. Safety equipment certificate
C. Safety construction certificate
D. Safety cargogear certificate
新古典综合派简单货币乘数模型的结论与凯恩斯的()是吻合的。
细菌细胞除基本结构外,还有诸如()、()和()等特殊结构。