If you use Google Scholar, this bookmarklet will highlight the citations in your search results which have full text on IngentaConnect. Run your search and then click on the toolbar link to highlight the IngentaConnect results.
Use Google Scholar to search IngentaConnect. Highlight words on any web page and click the link, or enter words into the pop-up box. Your search will be executed on Google but the results will be limited to those available on IngentaConnect.
from the IngentaConnect Labs PowerTools page
They have a Firefox search plugin on their main Ingenta Labs page.