Register for free. Click sources for metrics. "Scopus is the largest abstract and citation database of peer-reviewed literature: scientific journals, books and conference proceedings. Delivering a comprehensive overview of the world's research output in the fields of science, technology, medicine, social sciences, and arts and humanities, Scopus features smart tools to track, analyze and visualize research."
"CiteScore metrics from Scopus are comprehensive, transparent, current and free metrics for serial titles in Scopus. Search or browse below to find a source and see associated metrics. Use the annual metrics for reporting, and track the progress of 2017 metrics with CiteScore Tracker 2017. Be sure to use qualitative as well as the below quantitative inputs when presenting your research impact, and always use more than one metric for the quantitative part."
For a book:
Look for reviews in scholarly publications. Search for the title of the book in library databases considered important to the relevant discipline (for example, ScienceDirect for the sciences or the MLA International Bibliography for literature). The existence of reviews is a good sign, but also read what the reviews say about the work.
Find out how often the book has been cited through Google Scholar. When looking at the number of citations, consider the age of the book and compare it to other works on the subject. (A newer book will probably have fewer citations than an older, well-known one.)
Look at the publisher. Scholarly publishers like university presses are more selective about the works they publish. However, just because a work is of high quality does not mean it necessarily has had an impact on its field.
For an article:
Look at the journal. Is the article published in a highly regarded journal in the discipline? Usually, the best ranked journals will publish quality works from highly respected scholars in the field. However, just because something is of high quality does not mean it has made an impact on the field, so the quality of the journal should not be your only criterion. For more information on evaluating journals, take a look at Cabell's Directories.
Find out how many times the article has been cited using Google Scholar. The database is large and diverse and will give a more complete picture how your original source has permeated the scholarly literature in the discipline and how influential the original article is to the scholarly community.
Finding Citations in Scopus:
When looking at a single information record in Scopus, you can view who has cited the record in the "Cited by" box in the upper right.