If you want to find it for free, it is impossible, because the most authoritative way to know whether an article has been included in the three major searches is to enter these three databases and enter a text topic for query. However, these three databases are not open to the public for free, and you will be allowed to log in and use the query function when you enter. In order to avoid inquiries, only ask your friends who work in colleges and universities. Generally, some universities in China will buy mirror images of three databases for the convenience of downloading, and they can directly access the databases through the school intranet. If you still don't understand how to search, I suggest you search Baidu: EI Academic Conference Center, which has detailed instructions on EI query, and other databases are the same as EI.