How does Google Scholar work?
Just like the Google Search Engine, Google Scholar uses Googlebots which are Google's web-crawling robots to collect documents from the web, filter out the results, and make them available via the Google Scholar interface. For more information on Googlebots see http://www.google.com/bot.html.
DISTINGUISHING BETWEEN SCHOLARLY AND POPULAR SOURCES
Google Scholar uses a built in algorithm that makes a calculated guess at what it thinks is a scholarly source. Google is not releasing the parameters for what it considers to be scholarly or not. You will need to look at the source and decide if it is scholarly or popular. For more information, check out our tutorial on Evaluating Sources at: http://tutorial.lib.umn.edu/infomachine.asp?moduleID=9.
Google Scholar ranks sources according to relevance. According to the Google Scholar website, this relevance ranking takes into account the full text of each source as well as the source's author, the publication in which the source appeared and how often it has been cited in scholarly literature.
Google Scholar also automatically analyzes and extracts citations and presents them as separate results, even if the documents they refer to are not online. This means your search results may include citations of older works and seminal articles that appear only in books or other offline publications.
A FEW THINGS TO KEEP IN MIND WHEN IT COMES TO RANKING:
1. Google Scholar may offer several versions of the same article. This depends on who is providing access to the article; the publisher, the author personal website, another indexing services, etc.
2. Relevancy rankings cannot be re-sorted by date.
3. The information that Google Scholar is gathering is coming from the many different places. This means there is no real control over how often web resources might change. This means something that was ranked highly today may not be there next week.