| 1 | O&G Open 🔗 | 2024- | Ovid | 7 |
| 2 | Obesity Medicine 🔗 | 2016- | Clinical Key | 29 |
| 3 | Obesity Pillars 🔗 | 2022- | Clinical Key | 5 |
| 4 | Obesity Research & Clinical Practice 🔗 | 2007- | Clinical Key | 35 |
| 5 | Obstetric Anesthesia Digest 🔗 | 2001- | Ovid | 40 |
| 6 | Obstetrical & Gynecological Survey 🔗 | 1995- | Ovid | 2 |
| 7 | Obstetrical and Gynecological Survey 🔗 | 1995- | Ovid | 36 |
| 8 | Obstetrics and Gynecology 🔗 | 1995- | Ovid | 29 |
| 9 | Obstetrics and Gynecology Clinics 🔗 | 2007- | Clinical Key | 38 |
| 10 | Obstetrics, Gynaecology and Reproductive Medicine 🔗 | 2007- | Clinical Key | 34 |
| 11 | Occupational and Environmental Medicine 🔗 | 1944- | BMJ | 31 |
| 12 | Occupational Medicine 🔗 | 1996- | Oxford | 60 |
| 13 | Ocular Immunology and Inflammation 🔗 | 1997- | Taylor & Francis | 44 |
| 14 | Ocular Oncology and Pathology 🔗 | 2015- | Karger | 37 |
| 15 | Ocular Surface 🔗 | 2007- | Clinical Key | 65 |
| 16 | Oncologist, The 🔗 | 2000- | Oxford | 38 |
| 17 | Oncology and Translational Medicine 🔗 | 2015- | Ovid | 8 |
| 18 | Oncology Research and Treatment 🔗 | 1998- | Karger | 31 |
| 19 | Oncology Times 🔗 | 2001- | Ovid | 68 |
| 20 | One Health 🔗 | 2015- | Clinical Key | 5 |
| 21 | Open Forum Infectious Diseases 🔗 | 2014- | Oxford | 39 |
| 22 | Operative Neurosurgery 🔗 | 2005- | Oxford | 44 |
| 23 | Operative Neurosurgery 🔗 | 2005- | Ovid | 7 |
| 24 | Operative Techniques in Orthopaedics 🔗 | 2007- | Clinical Key | 52 |
| 25 | Operative Techniques in Otolaryngology - Head and Neck Surgery 🔗 | 2007- | Clinical Key | 32 |
| 26 | Operative Techniques in Sports Medicine 🔗 | 2007- | Clinical Key | 39 |
| 27 | Operative Techniques in Thoracic and Cardiovascular Surgery: A Comparative Atlas 🔗 | 2007- | Clinical Key | 31 |
| 28 | Ophthalmic Plastic & Reconstructive Surgery 🔗 | 2000- | Ovid | 34 |
| 29 | Ophthalmologica 🔗 | 1998- | Karger | 42 |
| 30 | Ophthalmology 🔗 | 2007- | Clinical Key | 45 |
| 31 | Ophthalmology Science 🔗 | 2021- | Clinical Key | 42 |
| 32 | Optometry & Vision Science 🔗 | 2000- | Ovid | 29 |
| 33 | OR Nurse 🔗 | 2007- | Ovid | 71 |
| 34 | Oral and Maxillofacial Surgery 🔗 | 2007- | Clinical Key | 30 |
| 35 | Oral and Maxillofacial Surgery Cases 🔗 | 2015- | Clinical Key | 40 |
| 36 | Oral Oncology 🔗 | 2007- | Clinical Key | 33 |
| 37 | Oral Oncology Reports 🔗 | 2022- | Clinical Key | 7 |
| 38 | Oral Surgery, Oral Medicine, Oral Pathology and Oral Radiology 🔗 | (2012-2015) | Clinical Key | 35 |
| 39 | Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology and Endodontology 🔗 | (2007-2011) | Clinical Key | 31 |
| 40 | ORL Journal for Oto-Rhino-Laryngology, Head and Neck Surgery 🔗 | 1998- | Karger | 33 |
| 41 | Orthopaedic Nursing 🔗 | 2001- | Ovid | 48 |
| 42 | Orthopaedics & Trauma 🔗 | 2009- | Clinical Key | 28 |
| 43 | Orthopaedics & Traumatology: Surgery & Research 🔗 | 2010- | Clinical Key | 34 |
| 44 | Orthopedic Clinics of North America 🔗 | 2007- | Clinical Key | 54 |
| 45 | Orthoplastic Surgery 🔗 | 2020- | Ovid | 6 |
| 46 | Orthoplastic Surgery 🔗 | 2020- | Clinical Key | 40 |
| 47 | Osteoarthritis and Cartilage 🔗 | 2007- | Clinical Key | 32 |
| 48 | Osteoarthritis and Cartilage Open 🔗 | 2019- | Clinical Key | 6 |
| 49 | Osteoarthritis Imaging 🔗 | 2021- | Clinical Key | 4 |
| 50 | Osteoporosis and Sarcopenia 🔗 | 2015- | Clinical Key | 5 |
| 51 | OTA International 🔗 | 2018- | Ovid | 8 |
| 52 | Otolaryngologic Clinics of North America 🔗 | (2007-2014) | Clinical Key | 28 |
| 53 | Otolaryngology Case Reports 🔗 | 2016- | Clinical Key | 34 |
| 54 | Otology & Neurotology 🔗 | 2001- | Ovid | 30 |
| 55 | Otology & Neurotology Open 🔗 | 2021- | Ovid | 9 |
| 56 | Oxford Medical Case Reports (OMCR) 🔗 | 2014- | Oxford | 38 |
| 57 | Oxford Open Immunology 🔗 | 2020- | Oxford | 37 |