Here's an example of how wildly different the numbers can be. The search is for "Sinn RN" as author.
|Scopus||Web of Science||Harzing|
Publish or Perish is freeware, created by an Australian academic to help her with her own research portfolio. You must download the software onto your computer. Publish or Perish searches Google Scholar and calculates a number of metrics that include:
Dr. Harzing's web site offers links to interesting articles about how to use and interpret these numbers.
ResearcherID incorporates EndNote Web, which allows you to import article citations that aren't indexed by Web of Science. Articles added in this fashion won't be incorporated into your times cited or h-index. ResearcherID provides you with a permanent URL which you can distribute.
ORCID, Open Researcher & Contributor ID, is a non-profit group trying to solve the author disambiguation problem. They hope to create a researcher registry that will use the linking power of the Internet to uniquely identify authors and contributors.