A.Peking Univ AND hosp B.Peking Univ SAME hosp C.Peking Univ WITH hosp D.Peking Univ NEAR hosp
A.PubMed B.SinoMed C.EMBASE D.CINAHL
A.肝炎?疫苗 B.肝炎%疫苗 C.肝炎*疫苗 D.肝炎$疫苗