Erase Thumbnail-pic in the post …

Hi there. When I am using thumbnails for the article-overview site, the thumbnail image is shown very big in the article itself above. It would be cool, if I could hide the source-code, so there will not be the big image at the articles-pages. Where can I find the code in order to hide it, so that there will only be the thumbnails in the overview-page?

Thank you for help.