PQDD ProQuest Digital Dissertations
. PQDD (ProQuest Digital Dissertations) ???UMI ??????????????,?DAO (Dissertation Abstracts Ondisc)???????:??1000?????150???????,???????????????????????????:????????????? . PQDD??????:. 1??????,?1861???; 2????,????; 3?1997???????????????????,??????24???????4??????4.7???????1.2????????. ??PQDD
449 views • 22 slides