Japanese Patent Office website. (I won’t post the URL here, just search it on Baidu yourself)
Click the “IPDL” icon on the left side of the page. (IPDL is Japan's Industrial Property Digital Library)
Click "Patent & Utility Model Gazette DB" to enter the search page.
On the search page, 12 numbers can be entered at the same time. You only need to enter 1 number. For example, for the number 2004112866, what needs to be entered is: enter "A" in the first box, indicating the file type; enter 2004-112866 in the second box, and then click the "search" button.
Then click "JP 20-112866 A" on the left in the search results page that appears and it's OK.