首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   4445篇
  免费   253篇
  国内免费   32篇
耳鼻咽喉   34篇
儿科学   278篇
妇产科学   48篇
基础医学   553篇
口腔科学   123篇
临床医学   313篇
内科学   895篇
皮肤病学   50篇
神经病学   264篇
特种医学   280篇
外科学   501篇
综合类   125篇
一般理论   1篇
预防医学   273篇
眼科学   387篇
药学   320篇
  1篇
中国医学   15篇
肿瘤学   269篇
  2023年   28篇
  2022年   33篇
  2021年   123篇
  2020年   75篇
  2019年   87篇
  2018年   106篇
  2017年   73篇
  2016年   84篇
  2015年   104篇
  2014年   166篇
  2013年   183篇
  2012年   300篇
  2011年   284篇
  2010年   186篇
  2009年   163篇
  2008年   236篇
  2007年   280篇
  2006年   253篇
  2005年   222篇
  2004年   223篇
  2003年   146篇
  2002年   131篇
  2001年   110篇
  2000年   94篇
  1999年   82篇
  1998年   55篇
  1997年   53篇
  1996年   55篇
  1995年   43篇
  1994年   26篇
  1993年   35篇
  1992年   40篇
  1991年   42篇
  1990年   44篇
  1989年   65篇
  1988年   38篇
  1987年   46篇
  1986年   42篇
  1985年   37篇
  1984年   30篇
  1983年   24篇
  1982年   19篇
  1981年   27篇
  1980年   23篇
  1979年   35篇
  1978年   14篇
  1977年   21篇
  1976年   16篇
  1975年   22篇
  1970年   13篇
排序方式: 共有4730条查询结果,搜索用时 328 毫秒
1.
2.
Purpose:Since the declaration of the lockdown due to COVID-19, the usage of digital devices has gone up across the globe, resulting in a challenge for the visual systems of all ages. The purpose of this study is to assess the impact of the lockdown on digital device usage, and consequently, the ocular surface health implications and circadian rhythm abnormalities related to digital eye strain.Methods:An open online survey was sent through various social media platforms and was open for a period of 2 weeks.Results:A total of 407 usable responses were obtained; the average age of respondents was 27.4 years. Typically, 93.6% of respondents reported an increase in their screen time since the lockdown was declared. The average increase in digital device usage was calculated at about 4.8 ± 2.8 h per day. The total usage per day was found to be 8.65 ± 3.74 hours. Sleep disturbances have been reported by 62.4% of people. Typically, 95.8% of respondents had experienced at least one symptom related to digital device usage, and 56.5% said that the frequency and intensity of these symptoms increased since the lockdown was declared.Conclusion:The study highlighted the drastic increase in use of digital devices after the initiation of the COVID-19 lockdown, and along with it, the slow deterioration of ocular health across all age groups. Awareness about prevention of digital eye strain should be stressed, and going forward, measures to bring these adverse effects to a minimum should be explored.  相似文献   
3.
4.
5.
6.
Coronary artery bypass grafts: visualization with MR imaging   总被引:1,自引:0,他引:1  
Gomes  AS; Lois  JF; Drinkwater  DC  Jr; Corday  SR 《Radiology》1987,162(1):175
  相似文献   
7.
The goals of this report are: 1) to review the number needed to treat (NNT) concept, which, although well established in many sectors of medicine, is still relatively new to the radiotherapy community; 2) to discuss several clinical radiotherapy examples illustrating the inherent advantages of the NNT approach; and 3) to discuss potential future roles of the NNT concept within radiotherapy.  相似文献   
8.
Poliomyelitis trends in Pondicherry, south India, 1989-91.   总被引:1,自引:1,他引:0       下载免费PDF全文
STUDY OBJECTIVES: To assess the poliomyelitis trend, including study of the epidemiological features, and to correlate this with the immunisation coverage of infants. DESIGN: Three annual lameness surveys in children aged 0-60 months employing cluster sampling methods and a series of five cross sectional surveys of immunisation coverage in children aged 12-23 months of age were undertaken. SETTING: Pondicherry, India, 1988-92. SUBJECTS: More than 10,000 children in the age group of 0-60 months took part in the three annual lameness surveys and samples of 210 children aged 12-23 months were covered each year in immunisation coverage surveys. MEASUREMENTS AND MAIN RESULTS: Altogether 50 of 11,461, 24 of 10,093, and 17 of 11,218 children surveyed during 1989, 1990, and 1991 respectively had become lame as a result of poliomyelitis, giving prevalences of 4.4, 2.4, and 1.5 per 1000 children for the three surveys. The corrected prevalences of poliomyelitis were 5.9, 3.2, and 2.0 per 1000 children during 1989, 1990, and 1991 respectively. The proportion of cases aged up to 36 months fell from 48% in 1989 to 12.5% in 1990 and 6% in 1991. The age at onset was less than 1 year in most. The median age at onset was 10.7 months. About 54% of the affected children had received three doses of oral poliomyelitis vaccine (OPV) before the onset of paralysis. In 1988 immunisation coverage for the third dose of OPV was 91% and in 1992 it was 97.6%. The drop out rate for the first versus the third dose of OPV fell from 6.3 in 1988 to 1.9% in 1992. CONCLUSION: Three successive annual lameness surveys showed that poliomyelitis was declining between 1989 and 1991. Five immunisation coverage surveys conducted from 1988 to 1992 showed high initial coverage followed by an improvement in the form of almost universal coverage for OPV.  相似文献   
9.
Background Extended trans septal (ETS) approach for mitral valve surgery often divides the artery to the Sino-Atrial node. The clinical implication of this is contentious. We analyzed our early results with ETS approach. Methods Between June 1998 and September 2003 eleven patients underwent mitral valve surgery by ETS approach. Six were females. Age ranged from 19 years to 67 years (median 40 years). Six underwent mitral valve replacement (MVR). Four underwent aortic and mitral (double) valve replacement (DVR). One had mitral valve repair. Three had additional procedures (tricuspid valve repair=1, Coronary artery bypass=1, Aorto bifemoral graft=1). Cardiopulmonary bypass ranged from 64 minutes to 77 minutes (median 72 minutes) for MVR and 112 minutes to 178 minutes (median 140 minutes) for DVR. Aortic cross clamp times ranged from 39 minutes to 52 minutes (median 47 minutes) for MVR and 74 minutes to 120 minutes (median 95 minutes) for DVR. Results There was no mortality or morbidity attributed to the ETS approach. One early death in emergency DVR was due to heart failure. Three patients needed seqeuntial pacing in the immediate post-operative period. Nine out of ten survivors were back to their preoperative rhythms on hospital discharge (6 sinus rhythm; 3 atrial fibrillation). One patient with preoperative trifascicular block who underwent reoperation to fix a paravalvular mitral leak needed a permanent pacemaker (VVI). The follow-up ranged from 1 month to 64 months (median 6 months) and is 100% complete. There was no late death or new arrhythmia. Conclusions Extended trans septal approach is safe. It gives excellent exposure of the mitral valve. division of the sinus node artery is not deleterious in the short to intermediate term. Presented at the 50th Annual Meeting of IACTS. New Delhi, Feb. 2004.  相似文献   
10.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号