Using the method combining systemic sampling and cluster sampling together, we select 972 persons to be the inquisition object, collecting 890 valid questionnaire, with 91.6% efficiency .

调查采用分层整群抽样的方法，选取972人作为调查对象，得有效调查问卷890份，有效率为91.6%。

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All patients suffering cancer of these two groups underwent systemic mediastinal and hilar lymph node sampling.

比较两组手术时间、术后住院时间、术后留置引流管时间、清扫的淋巴结总数等指标。

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