R ” 是取化基,如乙氧基 、 甲氧基及它们的环氧和烷氧同系物或卤基.R " is a replaceable function , e . g . acetoxy, methoxy, their acyloxy and alkoxy homologs or halo.通过选择特定的同系物混合物, 可以达到应用性能的优化.By selection of specific homologous mixtures, application ...
Overhead, the chopper roared and the big blades churned the air.头顶上，直升机在呼啸，巨大的螺旋桨叶片搅动着空气。There were ominous dark clouds gathering overhead.不祥的阴霾在头顶上汇聚。She turned on the overhead light and looked around the little room.她打...