先求（相对）标准不确定度△ Y／Y= sqr(（△L）^2+(△m/2)^2+(△L0/2)^2+(△m0/2)^2)再求标准不确定度△ Y=Y* sqr(（△L）^2+(△m/2)^2+(△L0/2)^2+(△m0/2)^2)
