Perhaps you should try some spelling variations:
chai khoa » thai khoa, chi khoa, pham khoa
khoa hoc » hoa hoc
thu sach » tu sach, thuat sach, thuoc sach
vat khoa » da khoa, tai khoa, vat hoc
tu cach » tu cac
su sach » so sach, vu sach
ta chai » ta chat, ta chi, ta hai
xin vat » sinh vat, dien vat, dinh vat

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( ((tu cach) or (su sach)) ta chai khoa hoc ) or ( ((thu sach) or (thu hoach)) xin vat khoa hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( ((tu cach) OR (su sach)) ta chai khoa hoc ) OR ( ((thu sach) OR (thu hoach)) xin vat khoa hoc )).
• Adding a wildcard symbol may retrieve word variants: (( ((tu cach) or (su sach)) ta chai khoa hoc ) or ( ((thu sach) or (thu hoach)) xin vat khoa hoc ))*.