Also known as bibliometrics or informetrics, metrics (in this area) is the scientific study or statistical calculation of research output, such as books and articles.
Why Metrics are Important
Metrics, like citation count, can help to gauge the influence or impact of a researcher's article, or the body of work by an academic department or center.
Metrics like Journal Impact Factor can help to estimate a journal's influence or impact.
Metrics and visualizations can be used to identify research strengths and collaborations.
Applications for funding, promotion, or research positions may require a certain metric.
Caveats and Limitations
Citations counts can be misleading due to self-citations
A high citations count can include both positive and negative citations
Measures like the citation count and h-index score can vary between database/resources since they include different journals and years of coverage
Find the most cited journals in a field, the highest impact journals in a field, the leading journals in a field and the most published articles in the sciences, technology and social sciences. Added functionality available with personal account.
Includes Science, Social Sciences, Arts & Humanities and Emerging Sources Citation Indexes. Also includes Journal Citation Reports, and Conference Proceedings. Added functionality available with personal account.
Multidisciplinary search tool specifically for scholarly literature, including peer-reviewed papers, theses, books, preprints, abstracts and technical reports from all broad areas of research. Added functionality available with personal account.
Eigenfactor.org® is an academic research project co-founded by Jevin West and Carl Bergstrom and sponsored by the Bergstrom Lab in the Department of Biology at the University of Washington. We aim to use recent advances in network analysis and information theory to develop novel methods for evaluating the influence of scholarly periodicals and for mapping the structure of academic research. We are committed to broadly disseminating our research findings and technological developments, while respecting the confidentiality of the data sources we use.
The Scimago Journal & Country Rank is a portal that includes the journals and country scientific indicators developed from the information contained in the Scopus® database (Elsevier B.V.). These indicators can be used to assess and analyze scientific domains.
"The Metrics Toolkit provides evidence-based information about research metrics across disciplines, including how each metric is calculated, where you can find it, and how each should (and should not) be applied. You’ll also find examples of how to use metrics in grant applications, CV, and promotion packages."
Provided by the company that includes Altmetric Explorer, this is a freely available database of publications (and more) that can also display basic level metrics and altmetrics for researchers and their publications.
"scite uses deep learning to classify citation statements in three categories: those that provide disputing or supporting evidence, and others, which mention the cited study without providing evidence for its validity."
Becoming Metric-Wise by 
