Perhaps you should try some spelling variations:
significantly improve » significantly improved (Expand Search)
significantly vary » significantly larger (Expand Search), significantly worse (Expand Search), significantly less (Expand Search)
improve decrease » improve disease (Expand Search), improved urease (Expand Search), improves disease (Expand Search)
vary decrease » a decrease (Expand Search)

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

• Removing quotes may allow a broader search: (( significantly vary decrease ) OR ( significantly improve decrease )).