Impact Metrics and Scholarly Attribution

Google Scholar Metrics uses the H-Index formula to rank journals. The Metrics Home Page lists the top 100 h5-index ranked publications in English.

"The h5-index is the h-index for articles published in the last 5 complete years. It is the largest number h such that h articles published in 2010-2014 have at least h citations."

Because disciplines have varying publishing models and expectations, comparing journal citation indices across research areas is not recommended. However, Google Scholar Metrics also provides h5-index ranked lists by subject area. Researchers can select language, discipline category, and, if desired, a subject sub-category.

By clicking on the h5-index for each journal, one can access the references for the most cited articles and the number of times each article was cited within that 5-year period.

Clicking on the Cited by number within each reference provides a list of those articles.

Clicking on an article name can lead to a source and sometimes full text. 

Caveat: Google Scholar Metrics is limited to articles indexed in Google Scholar, a database that does not have set journal inclusion parameters. For best results, multiple sources and methods should be used in identifying the most significant journals and articles in a research area.

The Eigenfactor™ Score uses a network of citation data to assess the relative importance of journals in the science and social science communities. Journals with many citations from influential journals are rated as influential themselves.

The Article Influence™ Score determines the average influence of a journal's articles.

Score calculation is based on the citations received over a five year period, but it also considers which journals have contributed these citations so that highly cited journals will influence the network more than lesser cited journals. References from one article in a journal to another article from the same journal are removed, so that Eigenfactor Scores are not influenced by journal self-citation.

Since the number and frequency of citations vary by discipline, the Eigenfactor algorithm adjusts for these differences.

In addition to articles from scholarly journals, Eigenfactor also includes newspaper articles, theses, popular magazines and other items in its reference material.

Eigenfactor scores can also be viewed within ISI Journal Citation Reports.

SCImago Journal and Country Rank, or SJR, is a measure of scientific influence of scholarly journals that accounts for both the number of citations received by a journal and the importance or prestige of the journals where such citations come from.

The SJR indicator, which is inspired by the Google PageRank algorithm, was developed for extremely large and heterogeneous journal citation networks. It is a size-independent indicator and it ranks journals by their ‘average prestige per article’ and can be used for journal comparisons in science evaluation processes.

SJR calculation uses data provided by Scopus.

ISI Journal Citation Reports (JCR) offers a means to statistically compare and evaluate some of the world's leading journals.

• Delivers quantifiable statistical information based on citation data. 
• Provides a variety of impact and influence metrics, including the Journal Impact Factor and Eigenfactor®
• Includes rank-in-category tables, journal self-citations, and Impact Factor boxplots

JCR provides comparison data for how journals rank among other titles in a subject category and by citation value and impact factor. One can also retrieve historical trend data for several years to see the direction of the impact. However a specific article can trigger a measurement that is a one-time spike.

Using JCR

Go to ISI Journal Citation Reports.

You can see that it offers a choice of two collections - the JCR Science Edition (which includes medicine) and the JCR Social Sciences Edition, and that you will need to specify a year. 

The database can be viewed by journal groupings (of subject, publisher, or country of origin); searched for a specific journal; or accessed in its entirety.

Searching the Science Edition, year 2011; and selecting to view journals by Subject Category, provides an opportunity to choose from a long list of categories. Selecting "Computer Science - Artificial Intelligence" and clicking on Submit provides 111 results, sorted alphabetically by journal title.

The list can be resorted by the following options.

Sorting by Impact Factor, for example, can give a better idea of the most important journals in the field.

Clicking on a journal's name gives more specific information about that journal, including the option to view various graphs.

Click on the Impact Factor Trend Graph. 

Information such as this can help you see how a journal's impact factor has changed over time. Comparisons with other journals might indicate rising or decreasing influence. However, due to differences in databases and algorithms, more than one type of ranking index should be consulted in the overall analysis of a journal's significance in a field. 

By studying journal impact metrics, such as those presented in this database, scholarly researchers and academic organizations can make better informed decisions about the importance of the journals they purchase and publish in.

Caveat: JCR metrics are limited to articles indexed in Web of Science. For best results, multiple sources and methods should be used in identifying the most significant journals and articles in a research area.

Essential Scientific Indicators

Essential Scientific Indicators (ESI) visually ranks authors, institutions, countries, and journals, and links to influential papers to help identify top researchers or institutions in specific fields. This tool is best used to compare metrics beyond journals. To access ESI, look to its tab at the top of the main Web of Science page.

When you land on the main page for ESI, you will see the following:

The default page is under the tab Indicators, set to rank top papers by research field with an optional and interactive global map for visualization. The other options are Authors, Institutions, Journals, Countries-Territories, and Research Fronts, and you can add multiple filters.

The tab Field Baselines looks at the annualized expected citation rates for papers in a research field. This can be broken up by Citation Rates, the yearly averages of citations per paper; Percentiles, which define levels of citation activity; or Field Rankings, which provide 10-year citation rates and aggregate counts of highly cited papers.

The tab Citation Thresholds looks at the minimum number of citations within a research field, obtained by ranking papers in descending order by citation count and then selecting the top fraction or percentage of papers. This can be broken up by ESI Thresholds, which shows the number of citations received by the top 1% of authors and institutions and the top 50% of countries and journals in a 10-year period; Highly Cited Thresholds, which shows the minimum number of citations received by the top 1% of papers from each of 10 database years; or Hot Paper Thresholds, which shows the minimum number of citations received during the most recent two-month period by the top 0.1% of papers from the past two years.

Thomson Reuter's guide to Journal Evaluation & Highly Cited Research: http://wokinfo.com/media/pdf/JEHCR