Perhaps you should try some spelling variations:
acoustic materials » acoustic metamaterials, plastic materials, elastic materials
acoustic material » acoustic metamaterial, acoustic metamaterials, plastic material
basic materials » basic material, plastic materials, elastic materials

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

• If you are trying to use Boolean operators, they must be ALL CAPS: %((basic materials) OR (((acoustic material) OR (acoustic materials))))%22.
• Adding a wildcard symbol may retrieve word variants: %((basic materials) or (((acoustic material) or (acoustic materials))))%22*.