sample field survey 抽样现场调查
In this paper, the main factors affecting tunnel erosion and their mechanism were studied based on field survey and data from sample analysis.
本文以野外调查和资料分析为基础，分析研究了影响洞穴侵蚀的主要因素和机理。
Methods Field observation and survey in the 16 sample hospitals chosen by the means of comprehensive index evaluation.
方法对采用综合指数法抽取的16所样本中医院用观察法实地调查。
To enlarge the sample size, the data were collected via a variety of methods in both field survey and net survey, at last 411 valid questionnaires were collected.
为扩大样本量，笔者采取了实地和网络调查相结合的多种灵活方式，最终收集到了411份有效问卷。
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