判断题
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7. What did the writer notice at a conference? A、One of...
单项选择题7. What did the writer notice at a conference? A、One of the men wore a cowboy shirt and jeans. B、None of the women wore sensible shoes. C、All the women were dressed in the same way. D、 All the men were dressed in the same way.
冲泡小青柑时,首先要去掉____。
问答题冲泡小青柑时,首先要去掉____。
已知某实验室采用《居住区大气中甲醛卫生检验标准方法-分光光度法》(GB／T 16129-1995)测定空气中甲...
问答题 已知某实验室采用《居住区大气中甲醛卫生检验标准方法-分光光度法》(GB／T 16129-1995)测定空气中甲醛含量，标准绘制甲醛标准曲线时，计算因子Bs为4.33μg/吸光度值。在某次甲醛测定中，测得吸光度为0.115，以水为参比，测得试剂空白值为0.021，采样时吸收液体积为5.0m1，分析时取样体积为2.0ml，采样流量为0.5L／min，采样时间为45min(大气压为101.3kPa，室温为20℃)，试求室内甲醛的浓度
