羟基乙叉二膦酸酸洗后预膜液的选择较少有人研究，而适当的预膜钝化是防止酸洗后金属表面返锈的必要措施。
There is little study on the selection of liquid of pre - filming after the acid wash by hydroxy ethidine phosphonic acid (HEDP).
但是，目前大部分的研究集中于如何在教学活动中运用情感策略，而对于教材中如何体现情感因素却较少有人研究，理科教材尤为严重。
But most of the research focuses on how to apply the affective factor in the teaching process, but not in the textbooks, especially in science textbooks.
定时器最小定时引起的同步偏差已有众多学者研究，信号周期飘移下的同步采样则较少有人涉足。
Synchronous deviation caused by limitation of the timer has already been studied by numerous scholars, however, Synch-sampling in the instance of signal cycle instability has been less discussed.
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