Journal Citation Reports has released 2009 data of Journals Impact Factor. This year report covers more than 7000 journals around the world. Some definitions should be known before taking a look at.

• 5-Year Journal Impact Factor is the average number of times articles from a journal published in the past five years have been cited in the JCR year. For journals in subjects where citation activity continues to rise through several years, this metric allows more of their total citation activity to be included in a critical performance metric.
• Eigenfactor™ Metrics, comprising the Eigenfactor™ Score and Article Influence™ Score, use JCR citation data to assess the influence of a journal in relation to other journals. These metrics, based on five years of citation activity, consider not just the count of citations but the structure of the citation network.Eigenfactor Metrics are available only for JCR years 2007 and later. More information…
• Journal Self Cites provides analyses of journal self citations and their contribution to the Journal Impact Factor calculation.
• Rank-in-Category reveals the ranking of a journal in its subject categories based on the Journal Impact Factor. An accompanying Impact Factor box plotdepicts the distribution of Impact Factors for all journals in a category. More information…

Here are 10 top journals of the report in terms of the highest impact factor

Mark	Rank	Abbreviated Journal Title (linked to journal information)	ISSN	JCR Data						EigenfactorTM Metrics
				Total Cites	Impact Factor	5-Year Impact Factor	Immediacy Index	Articles	Cited Half-life	EigenfactorTM Score	Article InfluenceTM Score
	1	CA-CANCER J CLIN	0007-9235	8528	87.925	60.000	8.304	23	3.7	0.04227	20.887
	2	ACTA CRYSTALLOGR A	0108-7673	14394	49.926	20.635	0.438	48	>10.0	0.04597	6.995
	3	NEW ENGL J MED	0028-4793	216752	47.050	51.410	14.557	352	7.5	0.67401	19.870
	4	NAT REV MOL CELL BIO	1471-0072	24057	42.198	38.260	6.307	75	4.4	0.19100	22.008
	5	ANNU REV IMMUNOL	0732-0582	15517	37.902	41.485	14.792	24	7.6	0.05977	21.382
	6	PHYSIOL REV	0031-9333	19371	37.726	37.838	4.219	32	8.3	0.05731	15.879
	7	CHEM REV	0009-2665	80350	35.957	34.284	3.978	178	8.4	0.20940	12.137
	8	NATURE	0028-0836	483039	34.480	32.906	8.209	866	8.9	1.74951	18.054
	9	NAT GENET	1061-4036	69988	34.284	29.768	8.411	209	6.6	0.33311	15.608
	10	REV MOD PHYS	0034-6861	27005	33.145	41.344	16.522	46	>10.0	0.08135	24.372

(Source: http://admin-apps.isiknowledge.com/JCR/JCR)

– For more details about other journals, it can be referred and downloaded by PDF file here JCR-2009-Impact-Factor

– This is the list of new journals with first impact factor released by Thomson Reuters 09jcrnewtitles

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