This issue publishes a special issue on a certain subject. This issue occupies the number of the main issue, but it is published on a certain topic. When searching, some special issues will be marked with special issues, which are weaker than the main issue, and some will be the same as the main issue without special issues. The special issue of many units is the same as the regular issue, and some only recognize the regular issue but not the special issue. You need to ask your unit yourself. If you are in a hurry to publish SCI, you can visit paper net, Tao Tao, where you can arrange a quick publication.