There are three main types of descriptive methods: observational methods, case-study methods and survey methods.

描述性研究法一共分为三类：观察法，案例分析法以及调研法。

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However, problems in these projects include a lack of dynamic observations, differences in observational methods, and data integration.

这些计划存在的主要问题是缺少动态的监测、研究方法不统一、数据整合困难等。

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However, problems in these projects include a lack of dynamic observations, differences in observational methods, and data integration.

这些计划存在的主要问题是缺少动态的监测、研究方法不统一、数据整合困难等。

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