This is caused by the download of Thunder. After downloading, the asnx format file must be changed to PDF, and there is no way to change the ASNX format to PDF reader mode. That is to say, if you download ten documents, you can only open each document by changing the suffix to PDF. The solution is simple and normal, with no thunderbolt. Open the paper download option in the webpage, and then select "Save as" or "Save as Normal".