For many years, the scientific standard of length was a metal bar kept in a temperature controlled vault near paris . 多年来，长度的科学标准曾是一根金属棒，这根金属棒保存在巴黎附近的有温度调节的地下室里。
2.
As getting incision of underwater distributary channel in different period , debouch bar keeps short time and low - development 由于受到不同期水下分流河道的切割，河口坝保持时间较短而欠发育。
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