differential density sign的用法和样例：
- Expressions of Density Parameters of Biot Medium with Differential Density
- Discussion and analyse of the high density sign of middle cerebra artery
- Study of the Value of High Density Sign of Unilateral Middle Cerebral Artery in Diagnosis of Early Cerebral Infarction
- (ii) Based on an analysis of charge differential density,we observed that the charge and energy are transfered from the phenylethenyl to the indoline and rhodanine rings;
- The density of population in this city is very high.