parts per billion (ppb) 中文意思是什麼
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Among the asthmatic chinese children, the level of nitric oxide is about 80 parts per billion ( ppb ) while for normal children it is only 29ppb
結果發現患有哮喘的華人兒童中，一氧化氮的濃度為80ppb ，正常兒童則只有29ppb 。
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