这是链接地址:http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TG8-4VPM5F5-4&_user=10&_coverDate=05%2F01%2F2009&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1466122393&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=68e343ee388cba5b8e0c59b2017b3f0c&searchtype=a