Repeatability is the cornerstone of science and it is particularly important for systematic reviews. However, little is known on how database and search engine choices influence replicability. Here, we present a comparative analysis of time-synchronized searches at different locations in the world, revealing a large variation among the hits obtained within each of the several search terms using different search engines. We found that PubMed and Scopus returned geographically consistent results to identical search strings, Google Scholar and Web of Science varied substantially both in the number of returned hits and in the list of individual articles depending on the search location and computing environment. To maintain scientific integrity and consistency, especially in systematic reviews, action is needed from both the scientific community and scientific search platforms to increase search consistency. Researchers are encouraged to report the search location, and database providers should make search algorithms transparent and revise access rules to titles behind paywalls.

中文翻译：

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一项比较分析显示科学文献的检索具有不可复制性

可重复性是科学的基石，对于系统评价尤其重要。但是，对于数据库和搜索引擎的选择如何影响可复制性知之甚少。在这里，我们对世界上不同地点的时间同步搜索进行了比较分析，揭示了使用不同搜索引擎在多个搜索词中的每个词中获得的匹配之间的巨大差异。我们发现，PubMed和Scopus将地理上一致的结果返回到相同的搜索字符串，而Google Scholar和Web of Science的返回命中数和单个文章的列表在很大程度上取决于搜索位置和计算环境而有所不同。为了保持科学的完整性和一致性，尤其是在系统评价中，科学界和科学搜索平台都需要采取行动来提高搜索的一致性。鼓励研究人员报告搜索位置，数据库提供商应使搜索算法透明，并修改对付费墙后面标题的访问规则。