Thickening is the usual first step in sludge disposal processing.
污泥处置过程中,浓缩通常是第一道工序。
The first step in protein synthesis is transcription.
蛋白质合成的第一步是转录。
It is the reverse of the propagation step in addition polymerization.
这一过程是加聚反应历程中链增长步序的逆过程。
📖 牛津释义
step in
intervene (to help or hinder sb/sth) 干预(以帮助或阻止某人[某事物]); 介入
If the police had not stepped in when they did there would have been serious violence. 当时若警方迟一些干预就会发生严重的暴力事件了.