Manyothernewtechniquesarenowavailablethatenablemoreresearch___(do)inthetesttubetoseeifchemicalsproduceharmfulbiologicaleffects.
BeforetheSmithsmovedtoNewYork,theylivedinaquiet___(neighbor)ofBoston.
质点沿x轴作简谐振动，其运动学方程x=cos()At，则速度表达式为()
在下列叙述中正确的是（）
Expertshavefoundthatnormalsleepcanbedividedintofive______stages
