2. Cross-database retrieval refers to the retrieval in the journals, doctoral dissertations, newspapers, conferences, yearbooks, patents, standards, scientific and technological achievements, etc. 12 database (multiple selections are allowed) of HowNet, and the retrieval documents included are not limited to papers, including all literature contents.
3. The data of each database of HowNet can be retrieved independently, and its underlying databases are separated. But through knowledge nodes and knowledge elements, you can also link to related databases, such as searching for the word "polyethylene", searching for academic papers, and displaying academic papers. If you don't know the meaning of this word, you can look it up in reference books and dictionaries through knowledge elements.
4. If you need to search across databases or use knowledge elements, the premise is that the database you use has purchased the database you cross. Of course, you can also download by page.