Eclipse artifact searching depends on repository's index file. It seems you did not download the index file.
Go to Window -> Prefrences -> Maven and check "Download repository index updates on start". Restart Eclipse and then look at the progress view. An index file should be downloading.
After downloading completely, artifact searching will be ready to use.
UPDATE You also need to rebuild your Maven repository index in 'maven repository view'.
In this view , open 'Global Repositories', right-click 'central', check 'Full Index Enable', and then, click 'Rebuild Index' in the same menu.
A 66M index file will be downloaded.
~ Answered on 2012-12-28 02:33:36