Ocean Science (2005-present) and Ocean Science Discussions (2004-present) – Preprints, articles [PDF], supplements, online discussion | European Geosciences Union.

Oil & Gas Science and Technology – Revue de l’IFP Energies nouvelles, former title: Revue de l’Institut Francais du Petrole – Articles (1997-2021) [PDF].

Open Analytical Chemistry Journal, The – (2007-2015) | Bentham Open.

Open Biochemistry Journal, The – (2007-2018) | Bentham Science Publishers.

Open Ceramics – (2020-present) | European Ceramic Society | Elsevier.

Open Chemical Engineering Journal, The – (2007-present) | Bentham Open.

Open Chemical Physics Journal, The – (2008-2013) | Bentham Open.

Open Clinical Biochemistry Journal, The – (2008-2018) | formerly Open Clinical Chemistry Journal, The | Bentham Open.

Open Inorganic Chemistry Journal, The – (2007-2009) | Bentham Open.

Open Macromolecules Journal, The – (2007-2014) | Bentham Open.

Open Materials Science Journal, The – (2007-2019) | Bentham Open.

Open Material Sciences – (2014-2019) | de Gruyter | triggered content at Portico.

Open Medicinal Chemistry Journal, The – (2007-present) | Bentham Open.

Open Mineralogy Journal, The – (2007-2011) | Bentham Open.

Open Nanoscience Journal, The – (2007-2014) | Bentham Open.

Open Organic Chemistry Journal, The – (2007-2015) | Bentham Open.

Open Physical Chemistry Journal, The – (2007-2014) | Bentham Open.

Open Spectroscopy Journal, The – (2007-2015) | Bentham Open.

Open Thermodynamics Journal, The – (2007-2013) | Bentham Open.

Open Toxicology Journal, The – (2007-2013, 2021) | Bentham Open.

Optical Materials: X – (2019-present) | Elsevier.

Optical Nanoscopy – Articles (2012-2014) | principles, development, and applications of optical imaging with spatial resolution substantially better than half the wavelength of light | Springer.

Organic & Biomolecular Chemistry ( Org. Biomol. Chem. ) – Issue #1 of each volume (2000-present) [PDF] | Royal Society of Chemistry.

Organic and Medicinal Chemistry Letters – (2011-2014) | SpringerOpen journal.

Organic Chemistry Frontiers – All issues (2014-2015); Issue #1 of each volume (2016-present) [PDF] | the Chinese Chemical Society and the Royal Society of Chemistry.

Organic Chemistry Highlights ( Org. Chem. Highlights ) – Short reviews (2004-present) [HTML] | e-journal. Also: abstract database.

Organic Chemistry Insights – (2008-2016) | Libertas Academica, SAGE Publications | available from the CLOCKSS archive.

Organic Materials – (2019-present) | synthesis, characterization and application of molecular and polymeric materials | Thieme.

Organic Photonics and Photovoltaics – (2013-2019) | de Gruyter | triggered content at Portico.

Organic Syntheses – Procedures for synthesis (1921-present) [HTML, PDF].

Oriental Journal of Chemistry ( Orient. J. Chem. ) – (2008-present) | international journal of pure and applied chemistry | Oriental Scientific Publishing Co., Bhopal, India.

Oxford Open Materials Science – (2021-present) | Oxford University Press.