Traditionally, Web of Science and Scopus have been the two most widely used databases for bibliometric analyses. However, during the last few years some new scholarly databases, such as Dimensions, have come up. Several previous studies have compared different databases, either through a direct comparison of article coverage or by comparing the citations across the databases. This article aims to present a comparative analysis of the journal coverage of the three databases (Web of Science, Scopus and Dimensions), with the objective to describe, understand and visualize the differences in them. The most recent master journal lists of the three databases is used for analysis. The results indicate that the databases have significantly different journal coverage, with the Web of Science being most selective and Dimensions being the most exhaustive. About 99.11% and 96.61% of the journals indexed in Web of Science are also indexed in Scopus and Dimensions, respectively. Scopus has 96.42% of its indexed journals also covered by Dimensions. Dimensions database has the most exhaustive journal coverage, with 82.22% more journals than Web of Science and 48.17% more journals than Scopus. This article also analysed the research outputs for 20 selected countries for the 2010–2018 period, as indexed in the three databases, and identified database-induced variations in research output volume, rank, global share and subject area composition for different countries. It is found that there are clearly visible variations in the research output from different countries in the three databases, along with differential coverage of different subject areas by the three databases. The analytical study provides an informative and practically useful picture of the journal coverage of Web of Science, Scopus and Dimensions databases.

传统上，Web of Science和Scopus是两个用于文献计量分析的最广泛使用的数据库。但是，在最近几年中，出现了一些新的学术数据库，例如Dimensions。以前的一些研究通过直接比较文章覆盖率或通过比较整个数据库的引文来比较不同的数据库。本文旨在对这三个数据库（Web of Science，Scopus和Dimensions）的期刊覆盖率进行比较分析，以描述，理解和可视化它们之间的差异。使用三个数据库的最新主日记列表进行分析。结果表明，数据库的期刊覆盖率存在显着差异，其中Web of Science的选择性最高，Dimensions的范围最为详尽。在Web of Science中被索引的期刊中，分别约有99.11％和96.61％在Scopus和Dimensions中也被索引。Scopus的索引期刊中有96.42％也包含在Dimensions中。Dimensions数据库具有最详尽的期刊覆盖范围，期刊比Web of Science多82.22％，比Scopus多48.17％。本文还分析了三个数据库中针对20个选定国家在2010-2018年期间的研究成果，并确定了数据库引起的不同国家研究成果的数量，排名，全球份额和主题领域构成的变化。结果发现，在三个数据库中，来自不同国家的研究成果存在明显可见的变化，并且三个数据库对不同学科领域的覆盖范围也有所不同。