Perhaps you should try some spelling variations:
"modified network approximation algorithm" » "modified network approximation algorithms", "certified network approximation algorithm", "defined network approximation algorithm", "modified near approximation algorithm"
"modified invasive ventilation algorithm" » "modified invasive estimation algorithm", "modified invasive estimation algorithms", "modified invasive evolution algorithm", "modified adaptive ventilation algorithm", "modified passive ventilation algorithm"

Try widening your search to All Fields.

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("modified network approximation algorithm") or ("modified invasive ventilation algorithm"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("modified network approximation algorithm") OR ("modified invasive ventilation algorithm")).
• Removing quotes may allow a broader search: (( modified network approximation algorithm ) or ( modified invasive ventilation algorithm )).
• Adding a wildcard symbol may retrieve word variants: (("modified network approximation algorithm") or ("modified invasive ventilation algorithm"))*.