Perhaps you should try some spelling variations:
imputation techniques » implantation technique, augmentation techniques, segmentation techniques
indication technique » inhalation technique, reduction technique, truncation technique
code indication » novel indication
gas sensor » gas sensors
based code » based anode

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( learning-gas sensor imputation techniques ) or ( learning-based code indication technique ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( learning-gas sensor imputation techniques ) OR ( learning-based code indication technique )).
• Adding a wildcard symbol may retrieve word variants: (( learning-gas sensor imputation techniques ) or ( learning-based code indication technique ))*.