简述心功能的分级标准。
Ⅰ级:体力活动不受限制,日常活动不出现症状。Ⅱ级:体力活动稍受限制,日常活动可出现症状,休息时无症状。Ⅲ级:体力活动明显受限,轻微日常活动即有症状,但休息时可无症状。Ⅳ级:不能从事任何体力活动,休息时亦有症状。
Modern physicists still look mostly at things we can't see. Either very small things in quantum physics or very big things like galaxies. Puting them together is the main problem of modem physics. The universe of space and time described by Einste