Perhaps you should try some spelling variations:
nghien cac » nghiep cach, nghien cuu, nghiep cay
doanh khoa » toan khoa
cong toan » cong tan, cong hoan, cong tuan
cac thoi » cac toi, cac hop, cac tro
thoi tap » toi tap, hoc tap, thoi dai
cac cong » cua cong
khoa hoc » hoa hoc
mai khoi » mai khoa, tai khoa, cac khoi
nhan tai » hang tai, van tai, toan tai
mai hoi » dai hoi, lai hoi, mai doi
va nhan » van nhan, ca nhan, va phan

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: tu cac thoi tap, nghien cac cong toan doanh khoa hoc ((mai hoi) OR (mai khoi)) va nhan tai~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu cac thoi tap, nghien cac cong toan doanh khoa hoc ((mai hoi) OR (mai khoi)) va nhan tai".
• Adding a wildcard symbol may retrieve word variants: tu cac thoi tap, nghien cac cong toan doanh khoa hoc ((mai hoi) OR (mai khoi)) va nhan tai*.