Method 15 hospitals and 2 937 residents were selected and studied through random and systematic sampling methods in Hainan Province.
方法 采用分层抽样和随机抽样方法对15家 医疗机构和2 937名疟区居民进行流行病学调查。
Methods Systematic sampling method was used in field Oncomelania investigation, and laboratory and field simulating drowning methods were also performed to observe survival of Oncomelania.
方法应用系统抽样法进行现场查螺，现场和实验室模拟水淹实验观察钉螺存活情况。
A method of systematic sampling has been adopted for Ailuropoda melanoleuca in Foping Nature Reserve.
已对佛坪自然保护区的大熊猫采用系统采样的方法。
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