Google's advanced search allows you to search by domain name (on bottom line of the advanced search form).
Entering .edu, .gov or .org into this line will only return results from educational, organizational or US government sites. You will still have to evaluate the sites for authority, accuracy, currency, and objectivity.
Google Scholar eliminates the commercial parts of Google and points to more scholarly information.
Pick one or two search engines and learn how to use them well. Refer to the HELP features to make sure you can create a search that will find the most relevant items and eliminate marginal and unhelpful sites.
Consider using Google Scholar. A Google Scholar search eliminates the advertising and commercial sites and helps you locate scholarly items.
Use critical thinking skills and evaluate the websites you find.