是在Wikipedia 查 Maxwell's equations
查 divergent operator, curl operator
http://kyxk.net/bbsanc.php?path=%2Fgroups%2Fsci.faq%2FBrain%2Fcognition%2Fhuangdixinnao%2FM.1143897005.00
http://baike.baidu.com/view/150496.htm
http://baike.baidu.com/view/3965696.htm