Not sure how many. But I know a significant amount of scientific papers are published in other languages than English, e.g. in Chinese language on Wanfang Data

Not sure how many. But I know a significant amount of scientific papers are published in other languages than English, e.g. in Chinese language on Wanfang Data (www.wanfangdata.com - affiliate of Chinese Ministry of Science and Technology). This is probably the case in many other non-English languages.