随着化学工业的不断发展,各种高效杀虫剂,植物生长激素、昆虫性激素以及作物微量元素相继出现。施用时,需要稀释几万,几十万甚至几百万倍。科学家们为了用一种简便的符号来表示百万分之几的浓度,就把 PartPermillion 这句英语单词中的头 With the continuous development of the chemical industry, a variety of highly effective pesticides, plant growth hormones, insect sex hormones and crop trace elements have emerged. Application, you need to dilute tens of thousands, hundreds of thousands or even millions of times. Scientists in order to use a simple symbol to indicate the concentration of parts per million, put PartPermillion head in the English word