Perhaps you should try some spelling variations:
sach tri » sach tai, sach tren, sach truc
tri thuc » tri tue
thuc dan » thuc hanh, hoc dan, thuc vat
dan khoi » dang khoi, dan hoi, dan khai
khoi pho » khoi tho, khoi khoa, hoc pho
tren hoc » truyen hoc, trung hoc, triet hoc
cao khoa » lao khoa, bao khoa, cac khoa
te sach » toc sach
khoa he » hoa he, khoa hoc, khong he

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( te sach tri thuc dan khoi pho thong ) or ( ((tu cach) OR (tu cac)) tren hoc cao khoa he thong ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( te sach tri thuc dan khoi pho thong ) OR ( ((tu cach) OR (tu cac)) tren hoc cao khoa he thong )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( te sach tri thuc dan khoi pho thong ) or ( ((tu cach) OR (tu cac)) tren hoc cao khoa he thong ))".
• Adding a wildcard symbol may retrieve word variants: (( te sach tri thuc dan khoi pho thong ) or ( ((tu cach) OR (tu cac)) tren hoc cao khoa he thong ))*.