Perhaps you should try some spelling variations:
decreased teaching » decreased reactive (Expand search)
teaching object » teaching subject (Expand search), teaching project (Expand search), learning object (Expand search)
decrease not » decrease of (Expand search), decrease akt (Expand search), decrease at (Expand search)
not decrease » to decrease (Expand search), not increase (Expand search), and decrease (Expand search)
by decreased » is decreased (Expand search), _ decreased (Expand search), to decreased (Expand search)
in decrease » in decreased (Expand search), on decrease (Expand search), pain decrease (Expand search)
decrease by » decreased by (Expand search), decrease of (Expand search), decrease _ (Expand search)

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (( decrease in decrease NOT decrease ) OR ( decrease by decreased teaching object ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( decrease in decrease not decrease ) OR ( decrease by decreased teaching object ))~".
• Adding a wildcard symbol may retrieve word variants: (( decrease in decrease not decrease ) OR ( decrease by decreased teaching object ))*.