浅滩上的潮水逐渐退去。The tidal stream or current gradually decreases in the shallows.潮水已经退去,他们走过岩石区的潮水潭。The tide was out and they walked among the rock pools.潮水小的时候强风可以让船只改变航向。Strong winds can turn boats when the tide is weak....
China was the first country in the world to synthesize crystalline insulin, a bioactive protein.中国在世界上最早用人工方法合成一种有生物活力的蛋白质--结晶胰岛素.Microorganisms can produce many beneficial bioactive substances through secondary metaboli...