This is the 12461st most frequent Russian word.
китайских
"Китайских" means "Chinese" (adjective, plural or genitive singular).
The word 'китайских' is used here as an adjective describing the souvenirs, indicating their origin.
Я купил несколько китайских сувениров в магазине.
I bought several Chinese souvenirs at the store.
'Китайских' serves as an adjective modifying 'традициях,' specifying the subject matter related to China.
В университете есть курс о китайских традициях и культуре.
There is a course about Chinese traditions and culture at the university.
Here, 'китайских' is an adjective giving information about the philosophers, emphasizing their national or cultural identity.