A method for predicting activity of traditional Chinese medi cine based on quantitative composition-activity relationship of neural network model Impact factors and model comparison of summer stomatal conductance of six common greening species in cities of Northern China A study on soil erodibility in a combined experimental trampling and simulated rainfall experiment on a Stipa bungeana steppe in Huanxian County, Gansu Province, China Comparison of three models of forest biomass estimation