做meta分析，你还不会用这个数据库进行选题？
What Is ClinicalTrials.gov?
ClinicalTrials.gov is a Web-based resource that provides patients, their family members, health care professionals, researchers, and the public with easy access to information on publicly and privately supported clinical studies on a wide range of diseases and conditions. The Web site is maintained by the National Library of Medicine (NLM)at the National Institutes of Health (NIH). Information on ClinicalTrials.gov is provided and updated by the sponsor or principal investigator of the clinical study. Studies are generally submitted to the Web site (that is, registered) when they begin, and the information on the site is updated throughout the study. In some cases, results of the study are submitted after the study ends. This Web site and database of clinical studies is commonly referred to as a "registry and results database."
What Information Can I Find on ClinicalTrials.gov?
Disease or condition
Intervention (for example, the medical product, behavior, or procedure being studied)
Title, description, and design of the study
Requirements for participation (eligibility criteria)
Locations where the study is being conducted
Contact information for the study locations
Links to relevant information on other health Web sites, such as NLM's MedlinePlus® for patient health information and PubMed® for citations and abstracts of scholarly articles in the field of medicine
Some records also include information on the results of the study, such as:
Description of study participants (the number of participants starting and completing the study and their demographic data)
Outcomes of the study
Summary of adverse events experienced by study participants
看完了网站的介绍，接下来，教大家如何使用：
登录网址：https://www.clinicaltrials.gov/ct2/home
输入自己感兴的干预或者疾病
选择限定条件
选择好了参数后，点击search
然后看结果，我们可以知道那些试验已经完成了，而且有结果有数据，但是文章还没有发表，可以抢先进行发表meta分析，即使别人做过了，有新的试验出来，而且结果与原先的meta分析结果相反，那就完全写更新的meta了。
这里还有很多参数，大家可以根据自己的情况进行限定