%
% Articles in Citable Items
The % of Articles in Citable Items emphasizes a journal's original research by calculating the percentage of articles that count toward the total Citable Items. For example, in 2013, Nature has 829 articles and 28 reviews for a total Citable Items of 857. 96% of the Citable Items are original research.
+
+ (plus sign)
The plus sign indicates that the citation counts for translated and original language versions of the same journal have been combined.
•
• (small bullet)
In journal rankings, the small bullet indicates that complete source data were not available for a particular title before the JCR processing deadline (usually mid-February of the JCR year).
5
5-Year Journal Impact Factor
The 5-year journal Impact Factor, available from 2007 onward, is the average number of times articles from the journal published in the past five years have been cited in the JCR year. It is calculated by dividing the number of citations in the JCR year by the total number of articles published in the five previous years.
A
Aggregate Cited Category Graph
Shows the distribution by cited year of citations to articles published in journals in the category in the JCR year.
Aggregate Cited Half-Life
Aggregate Cited half-life is the median age, in years, of items in any journal in the category that were cited during the JCR year.
Aggregate Citing Category Graph
Shows the distribution by cited year of citations from journals in the category made in the JCR year.
Aggregate Citing Half-Life
The median age of articles cited by journals in the category in the JCR Year based on aggregated journal data.
Aggregate Immediacy Index
The aggregate Immediacy Index indicates how quickly articles in a subject category are cited.
Aggregate Impact Factor
The aggregate Impact Factor for a subject category is calculated the same way as the Impact Factor for a journal, but it takes into account the number of citations to all journals in the category and the number of articles from all journals in the category. An aggregate Impact Factor of 1.0 means that that, on average, the articles in the subject category published one or two years ago have been cited one time.
Article
An article is a significant item published in a journal covered by Journal Citation Reports®. Editorials, letters, news items, and meeting abstracts are usually not counted as articles because they are not generally cited. The Articles column in the table you see on the Journal Summary page or Journal page counts research articles, review articles, notes, and corrections/retractions. Articles and Reviews are counted separately in the Journal Source Data section of the Journal page.
Article Influence Score
The Article Influence Score determines the average influence of a journal's articles over the first five years after publication. It is calculated by multiplying the Eigenfactor Score by 0.01 and dividing by the number of articles in the journal, normalized as a fraction of all articles in all publications. This measure is roughly analogous to the 5-Year Journal Impact Factor in that it is a ratio of a journal’s citation influence to the size of the journal’s article contribution over a period of five years.
The equation is as follows:
where X = 5-year Journal Article Count divided by the 5-year Article Count from All Journals.
The mean Article Influence Score for each article is 1.00. A score greater than 1.00 indicates that each article in the journal has above-average influence. A score less than 1.00 indicates that each article in the journal has below-average influence.
Average Journal Impact Factor Percentile
The Average Journal Impact Factor Percentile takes the sum of the JIF Percentile for each category under consideration, and then calculates the average from those values.
Where N = number of categories.
C
Citation
A citation is the formal acknowledgment of intellectual debt to previously published research. It generally contains sufficient bibliographic information to uniquely identify the cited document.
Cited-Only Journals (Journals with only Cited Journal information)
Some of the journals listed in JCR are not citing journals, but are cited-only journals. This means that the references in these journals are not included in the database. This is significant when comparing journals because self-citations from cited-only journals are not included in JCR data. Self-citations often represent a significant percentage of the citations that a journal receives. Cited-only journals may be ceased journals, suspended journals, or superseded titles. Any journal that appears elsewhere in JCR, but not in the Citing Journal Listing, is a cited-only journal.
Cited Half-life
Median age of the articles that were cited in the JCR year. Half of a journal's cited articles were published more recently than the cited half-life.
Cited Journal Data
Cited Journal data show how many citations a journal received in the JCR year.
Cited Journal Graph
The Cited Journal Graph shows the distribution by cited year of citations to articles published in a journal.
Citing Half-Life
Median age of articles cited by the journal in the JCR year.
Citing Journal Data
Citing journal data show how many citations a journal made to other journals (including itself) in the JCR year.
E
Eigenfactor® Metrics
Like the Impact Factor, the Eigenfactor Score and Article Influence® Score use citation data to assess and track the influence of a journal in relation to other journals. Eigenfactor Metrics are available only for JCR years 2007 and later. You can learn more about Eigenfactor Score and Article Influence Score at www.eigenfactor.org. Eigenfactor Metrics, Eigenfactor Score, Article Influence® Score are Licensed Marks used with permission from the University of Washington The Eigenfactor® Algorithm-2008, was developed by the Metrics Eigenfactor Project: a bibliometric research project conducted by Professor Carl Bergstrom and his laboratory at University of Washington.
Eigenfactor® Score
The Eigenfactor Score calculation is based on the number of times articles from the journal published in the past five years have been cited in the JCR year, 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.
I
Immediacy Index
The Immediacy Index is the average number of times an article is cited in the year it is published. The journal Immediacy Index indicates how quickly articles in a journal are cited. The aggregate Immediacy Index indicates how quickly articles in a subject category are cited. The Immediacy Index is calculated by dividing the number of citations to articles published in a given year by the number of articles published in that year. Because it is a per-article average, the Immediacy Index tends to discount the advantage of large journals over small ones. However, frequently issued journals may have an advantage because an article published early in the year has a better chance of being cited than one published later in the year. Many publications that publish infrequently or late in the year have low Immediacy Indexes. For comparing journals specializing in cutting-edge research, the immediacy index can provide a useful perspective.
ISSN / eISSN
International Standard Serial Number, a unique number that identifies a journal. The format is four numbers, a hyphen (-), three numbers, and then a check character that may be a number or X. For example, 0010-4620
J
Journal Citation Indicator
The Journal Citation Indicator (JCI) is based on the mean category normalized citation impact (CNCI) for the journal. CNCIs are calculated at the document level and are based on citations from all documents in the three previous years and the JCR Year to articles and reviews published in the previous three years. The JCI is normalized for document type, publication year, and category. The average JCI for any category is 1. A JCI of 2 indicates that a journal is receiving twice the expected number of citations for the average journal in the category. A JCI of 0.5 indicates a journal is receiving half the expected number of citations for the average journal in the category. As citations distributions are skewed towards larger numbers of papers with fewer citations, the majority of journals in a category may have a JCI < 1.
JCI Rank
Journals within a category are sorted in descending order by Journal Citation Indicator (JCI) resulting in the Category Ranking. A separate rank is shown for each category in which the journal is listed in JCR.
JCI Quartile
In Journal Citation Reports, we provide quartile rankings based on rank for the Journal Citation Indicator. Quartiles are defined as the following:
| Q1 | 0.0 < Z ≤ 0.25 | Highest ranked journals in a category |
| Q2 | 0.25 < Z ≤ 0.5 | |
| Q3 | 0.5 < Z ≤ 0.75 | |
| Q4 | 0.75 < Z | Lowest ranked journals in a category |
Z is defined as:
Z=(X/Y)
Where X is the journal rank in category and Y is the number of journals in the category.
JCR Year
The year of the JCR edition displayed in the top right-hand corner of the page. Each JCR year contains one year of citation data. You select the JCR year on the Welcome page.
Journal Impact Factor
The Journal Impact Factor is defined as all citations to the journal in the current JCR year to items published in the previous two years, divided by the total number of scholarly items (these comprise articles, reviews, and proceedings papers) published in the journal in the previous two years. Though not a strict mathematical average, the Journal Impact Factor provides a functional approximation of the mean citation rate per citable item. A Journal Impact Factor of 1.0 means that, on average, the articles published one or two years ago have been cited one time. A Journal Impact Factor of 2.5 means that, on average, the articles published one or two years ago have been cited two and a half times. The citing works may be articles published in the same journal. However, most citing works are from different journals, proceedings, or books indexed in Web of Science Core Collection.
Journal Impact Factor - Subject Category
This is the Subject Category to which the journal is assigned in the Web of Science and JCR.
JIF Rank
Journals within a category are sorted in descending order by Journal Impact Factor (JIF) resulting in the Category Ranking. A separate rank is shown for each category in which the journal is listed in JCR.
JIF Quartile
In Journal Citation Reports, we provide quartile rankings based on rank for the Journal Impact Factor. Quartiles are defined as the following:
| Q1 | 0.0 < Z ≤ 0.25 | Highest ranked journals in a category |
| Q2 | 0.25 < Z ≤ 0.5 | |
| Q3 | 0.5 < Z ≤ 0.75 | |
| Q4 | 0.75 < Z | Lowest ranked journals in a category |
Z is defined as:
Z=(X/Y)
Where X is the journal rank in category and Y is the number of journals in the category.
Journal Impact Factor Percentile
The Journal Impact Factor Percentile transforms the rank in category by Journal Impact Factor into a percentile value, allowing more meaningful cross-category comparison. It’s calculated by using the following formula:
Where:
- N is the number of journals in the category
- R is the Descending Rank
Journal Title Change
The Journal Title Changes page lists title changes occurring in the past two years (that is, the JCR year and the preceding year). The listing is in alphabetical order by journal title. To view this list, click the Journal Title Changes link on the Journal page or the Journal Summary List page.
N
Non-Traditional
References types that are deemed to be non-traditional are non-research materials that include the following:
- Acts
- Act Releases
- Annals of Congress
- Archaeological Digs & Sites
- Bills & Resolutions
- Briefs & Litigations
- Codes
- Congressional Globe
- Congressional Record
- Court Cases
- Court Decisions
- Court Reports
- Debates
- Depositions
- Docket Nos.
- Hansard
- Hearings
- Laws
- Legislative Documents & Reports
- Maps
- National & State Constitutions
- Press Releases
- Register of Debates
- Regulations
- Rules
- Statutes
- Testimonies
- UK Parliament
- U.N. Docs. & Treaties
- URL
- DOI
- Databases
Normalized Eigenfactor® Score
The Normalized Eigenfactor Score is the Eigenfactor score normalized, by rescaling the total number of journals in the JCR each year, so that the average journal has a score of 1. Journals can then be compared and influence measured by their score relative to 1. For example, if a journal has a Normalized Eigenfactor Score of 5, that journal is considered to be 5 times as influential as the average journal in the JCR.
P
Publication Frequency
Frequency of publication data categorize the journals in the subject category according to their publication schedule. Subject categories that have a large number of frequently published journals tend to have a high Immediacy Index.
R
Review
An item is classified as a review if it meets any of the following criteria: it cites more than 100 references it appears in a review publication or a review section of a journal the word review or overview appears in its title the abstract states that it is a review or survey
S
Self-Citation
A self-citation is a reference to an article from the same journal. Self-citations can make up a significant portion of the citations a journal gives and receives each year. You can compare self-citing rates and self-cited rates to supplement your journal evaluation.
Subject Category
Each journal in JCR is assigned to at least one subject category, indicating a general area of science or the social sciences. Journals may be included in more than one subject category; therefore, when comparing journals across related categories, it is possible to see the same journal title in different categories.
T
Total Cites
The total number of times that a journal has been cited by all journals included in the database in the JCR year. Citations to journals listed in JCR are compiled annually from the JCR years combined database, regardless of which JCR edition lists the journal and regardless of what kind of article was cited or when the cited article was published. Each unique article-to-article link is counted as a citation. Citations from a journal to an article previously published in the same journal are compiled in the total cites. However, some journals listed in JCR may be cited-only journals, in which case self-cites are not included.