Different schools have different requirements for the number of sci papers published. Some majors are more difficult, and you can graduate by publishing 1 sci paper. Some majors may need to publish 2-3 papers to graduate. Generally, it is enough to prepare 2-3 doctoral theses.

For example: Shanghai Jiaotong University doctoral thesis requirements:

Neo-Confucianism: publish (or hire) 2 academic papers, and publish (or hire) at least 1 in journals retrieved by SCI (Science Citation Index).

Engineering and Agronomy: publish (or hire) 2 academic papers, and publish (or hire) at least 1 paper in journals retrieved by SCI (Science Citation Index) or EI (Engineering Index). Papers published in EI retrieval journals should be in English (or its first foreign language).

Literature, law, economy and management: published (or hired) 2 academic papers in journals retrieved by SSCI (Social Science Citation Index) or CSSCI (China Social Science Citation Index).