层析系统为正丁醇∶冰醋酸∶水=4∶1∶5时,用纸层析法分离苯丙氨酸(F)、丙氨酸(A)和苏氨酸(T)时则它们的Rf值之间关系应为:
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
免费的网站请分享给朋友吧