1 Molecules Molecules Molecules molecules Molecules 1420-3049 Molecular Diversity Preservation International molecules-14-02254 10.3390/molecules14062254 molecules14062254 Editorial Full Open Access Journals Have Increased Impact Factors Lin Shu-Kun Molecular Diversity Preservation International (MDPI), Matthaeusstrasse 11, CH-4057 Basel, Switzerland; Tel. +41-79 322 3379; Fax: +41-61 302 8918; E-mail: lin@mdpi.org; http://www.mdpi.org/lin 22 6 2009 14 6 2254 2255 20 6 2009 © 2009 by the authors; licensee Molecular Diversity Preservation International, Basel, Switzerland 2009

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 2009

Impact factors of four MDPI journals (adapted from the Journal Citation Report (JCR), Edition 2008, Copyright 2009 by Thomson Reuters).

We are pleased to report the increase of the impact factors of MDPI journals during 2007 and 2008 (see Figure 1). In 2005 and part of 2006, the use of a two tier publication system, whereby we offered full Open Access publication to those authors willing to contribute financially to support this option, while providing the alternative choice of free publication withoutOpen Access for those authors who preferred not to pay [1,2], resulted in the obviously decreased impact factors seen in 2006 [3,4]. In early 2007, a full Open Access publishing policy was instituted and we can now begin to clearly see the effect of the full Open Access policy in the steady recovery of the impact factors of the affected journals.

On the other hand, the two tier publication system (Open Access and non-Open Access) was only briefly applied to the journal Sensors and we thus see a continuous increase of the impact factor in recent years. The 2008 impact factor of the journal Sensors is 1.870.

We also observed an interesting phenomenon: two Molecules papers were retracted because they had also been published elsewhere. Nevertheless, these withdrawn papers were cited elsewhere, while the non-Open Access papers were not. We have now added a watermark to the original PDF files of withdrawn papers, clearly identifying their status, in order to prevent further citation of such papers [5].

Since October 2008, all MDPI journals have been published at the new server www.mdpi.com. Just recently we published the 5000th paper in a MDPI journal and Molecules alone has published over 2000 papers. As we wrote in our editorial [6], the year 2009 will be a more successful year for the journal Molecules and for all the other MDPI journals, including several newly launched journals.

References Lin S.-K Open Access and Author's Open Choice Molecules 2005 10 583 584 10.3390/10060583 Lin S.-K. Delayed Open Access or Permanent Non-Open Access Molecules 2006 11 496 497 10.3390/11070496 Lin S.-K. Non-Open Access and Its Adverse Impact on Molecules Molecules 2007 12 1436 1437 10.3390/12071436 Lin S.-K. Full Open Access Publishing Policy Imposed in 2007: Molecules Publishes Many More Papers This Year ― More than 2000 Pages Published up to Issue 8 Molecules 2007 12 2001 2002 10.3390/12082001 Lin S.-K. McPhee D.J. Citation of Two Retracted Papers Shows Both the Impact Advantage and an Unintended Consequence of Open Access Molecules 2007 12 2190 2192 10.3390/12092190 Lin S.-K. McPhee D.J. Molecules' Highlights in 2008 and a Look Forward to 2009 Molecules 2009 14 584 585 10.3390/molecules14010584