根据文献的主题特征，利用各类主题目录或关键词索引进行检索的途经属于。
参考答案：主体途径
---Stanly has graduated from the university.
---It’s no wonder that I can’t see him these days. He ___ in the city for six years.
A．has stayed
B．had stayed
C．stayed
D． has been staying
直接导致癫痫患者发作的是（）
A.脑电图上有痫样放电
B.CT或MRI上有病灶
C.癫痫病理灶
D.致痫灶
E.脑电图上有局灶改变
