Perhaps you should try some spelling variations:
"modified objective optimization algorithms" » "modified objective optimisation algorithm", "modified objective estimation algorithms", "modified objective estimation algorithm", "modified multiobjective optimization algorithms"
"modified based approximation algorithms" » "modified one approximation algorithms", "modified time approximation algorithms", "modified male approximation algorithms"

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 based approximation algorithms") or ("modified objective optimization algorithms"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("modified based approximation algorithms") OR ("modified objective optimization algorithms")).
• Removing quotes may allow a broader search: (( modified based approximation algorithms ) or ( modified objective optimization algorithms )).
• Adding a wildcard symbol may retrieve word variants: (("modified based approximation algorithms") or ("modified objective optimization algorithms"))*.