Perhaps you should try some spelling variations:
"learning-based co implantation technique" » "learning-based co floatation technique", "learning-based co inhalation technique", "learning-based novel implantation technique", "learning-based code implantation technique", "learning-based no2 implantation technique", "learning-based two implantation technique"
"learning-based co imputation techniques" » "learning-based co augmentation techniques", "learning-based co segmentation techniques", "learning-based co floatation technique", "learning-based co limitation techniques", "learning-based code imputation techniques", "learning-based no2 imputation techniques", "learning-based two imputation techniques"

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("learning-based co imputation techniques") OR ("learning-based co implantation technique"))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"learning-based co imputation techniques\") OR (\"learning-based co implantation technique\"))*".
• Removing quotes may allow a broader search: (( learning-based co imputation techniques ) OR ( learning-based co implantation technique ))*.