Google Scholar is free to use on the internet, and has lots of full-text articles included. Google Scholar also allows you to search and explore papers that he cited other papers, and includes Web of Science citation counts and lists when ailable.
You can also set up your own researcher/scholar profile, and organize citations. The video below demonstrates five tips that will help you maximize your Google Scholar searches.
Google Scholar is also useful for Literature Reviews and intensive searching!
Google Scholar contains much more content in languages other than English and English content from more geographically diverse areas. That can be an advantage if you are performing a literature review.
Use "Related articles" and "Cited by" links to access articles that are similar or related to the article citation you are examining.
Related Articles finds articles written on similar topics.
Cited by lists all articles that cited the source article you are examining. Occasionally Google Scholar will also list Web of Science cited by counts.