目的应用巢式病例对照研究方法，探讨原发性肝癌（HCC）的危险因素。
Purpose To explore the risk factors of hepatocellular carcinoma (HCC) with the aid of nested case control study.
方法应用1∶1配对的病例对照研究方法，调查和分析家庭环境中与儿童哮喘有关的暴露因素。
Methods A 1:1 matched case-control study was performed exposure to analyse some exposure factors in home environment that related with asthma.
方法采用1：1病例对照研究方法对合肥市及定远县50对老年性白内障及对照进行问卷调查。
Methods a 1:1 matched case-control study with 50 pairs on risk factors of cataract was carried out in Hefei city and Dingyuan county.
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