牙斑如果不清除就会导致牙齿蛀蚀和牙龈疾病。When not removed, plaque causes tooth decay and gum disease.牙齿和牙龈之间会滋生牙斑。Deposits of plaque build up between the tooth and the gum.需刷牙以去除牙斑.It is necessary to remove plaque by brushing one's tee...
方法: 用溴代及胺化反应合成了四甲基吡嗪衍生物.METHODS: The target compound was prepared by the bromination and amination reaction.用溴—甲醇溶解Al_2O_3, 其回收率在91%以上.If Al 2 O 3 is dissolved by Br 2 - CH 3 OH, its Recovery rate is above 91 %.用溴比用氯时产出率...
Elevational and latitudinal trends were not pronounced.海拔和纬度的变化趋势不明显.This latitudinal distinction means one thing - cold weather.此纬度上的差别就意味着一件事 --- 更冷的天气.The deep latitudinal structural belt shows the transposition relat...
Rows of stalls are given over to restaurants running off gas cylinders.数排摊位都让位给了使用煤气罐的饭店。A wander around any market will reveal stalls piled high with vegetables.随便到哪个市场逛逛，都能看见蔬菜堆得老高的菜摊。The majority of stalls charged a f...
A new high activity , lowcost catalyst and the optimal reaction conditions were found by experiments.通过实验找到了一种新型、高效 、 廉价的催化剂,以及最佳反应条件.The project involves harvesting rainwater using special lowcost containers and digging...