By convenient sampling, 105 stable COPD patients from three hospitals in Beijing were recruited in this study.
采取便利抽样的方法，对在北京市某三家三甲医院就诊的105例稳定期COPD患者进行问卷调查。
The research object of the study is the domestic tourists, and we distribute questionnaires to the college student travelers on campus by convenient sampling.
本研究以国内旅游消费者为研究对象，通过便利抽样的方式对在校大学生旅游者发放问卷。
The research object of the study is the domestic tourists, and we distribute questionnaires to the college student travelers on campus by convenient sampling.
本研究以国内旅游消费者为研究对象，通过便利抽样的方式对在校大学生旅游者发放问卷。
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