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   530256篇
  免费   27666篇
  国内免费   496篇
耳鼻咽喉   6681篇
儿科学   16921篇
妇产科学   12541篇
基础医学   92623篇
口腔科学   12349篇
临床医学   48539篇
内科学   95518篇
皮肤病学   11869篇
神经病学   34016篇
特种医学   19756篇
外国民族医学   53篇
外科学   78103篇
综合类   7625篇
现状与发展   2篇
一般理论   107篇
预防医学   38587篇
眼科学   11939篇
药学   41421篇
  1篇
中国医学   1126篇
肿瘤学   28641篇
  2019年   3898篇
  2018年   5735篇
  2017年   4133篇
  2016年   4877篇
  2015年   5368篇
  2014年   7117篇
  2013年   10508篇
  2012年   15598篇
  2011年   17414篇
  2010年   9972篇
  2009年   8835篇
  2008年   15744篇
  2007年   17461篇
  2006年   16950篇
  2005年   16279篇
  2004年   15903篇
  2003年   15272篇
  2002年   14798篇
  2001年   22430篇
  2000年   22972篇
  1999年   18920篇
  1998年   5232篇
  1997年   4364篇
  1996年   4397篇
  1995年   4124篇
  1992年   14413篇
  1991年   15817篇
  1990年   15951篇
  1989年   15625篇
  1988年   14309篇
  1987年   14202篇
  1986年   13170篇
  1985年   12687篇
  1984年   9394篇
  1983年   8000篇
  1982年   4177篇
  1979年   8938篇
  1978年   6382篇
  1977年   5150篇
  1976年   5504篇
  1975年   6613篇
  1974年   7420篇
  1973年   7160篇
  1972年   6597篇
  1971年   6309篇
  1970年   5887篇
  1969年   5467篇
  1968年   5161篇
  1967年   4621篇
  1966年   3963篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Carotid cavernous fistulae: indications for urgent treatment   总被引:5,自引:0,他引:5  
Angiographic and clinical data from 155 patients with carotid cavernous fistulae were retrospectively reviewed to determine angiographic features associated with increased risk of morbidity and mortality. These features included presence of a pseudoaneurysm, large varix of the cavernous sinus, venous drainage to cortical veins, and thrombosis of venous outflow pathways distant from the fistula. Clinical signs and symptoms that characterized a hazardous carotid cavernous fistula included increased intracranial pressure, rapidly progressive proptosis, diminished visual acuity, hemorrhage, and transient ischemic attacks. Cortical venous drainage from the carotid cavernous fistula is secondary to occlusion or absence of the normal venous outflow pathways and is associated with signs and symptoms of increased intracranial pressure and an increased risk of intraparenchymal hemorrhage. Angiographic demonstration of a cavernous sinus varix, with extension of the sinus into the subarachnoid space, is associated with an increased risk of fatal subarachnoid hemorrhage. Identification of these high-risk features provides a basis for making decisions about treatment.  相似文献   
993.
994.
The results of combined medical and surgical management of 66 patients with active prosthetic valve endocarditis (APVE) are analyzed. Between 1970 and 1985, 3510 patients were operative survivors of mitral, aortic or double mitral-aortic valve replacement. Cumulative follow-up was 15,640 patient-years (mean 4.4 years). The overall annual incidence of reoperation for APVE was 0.42 +/- 0.05% (0.34 +/- 0.08% for biological and 0.46 +/- 0.06% for mechanical prostheses, p = n.s.). Early APVE occurred in 21 patients and 45 patients had late APVE. Indications for surgery were heart failure in 92%, systemic emboli in 5% and persistent sepsis in 3% of patients. Overall operative mortality (less than 30 days) was 38% (25/66). (Early APVE 52% and late APVE 31%). Anatomical location, valve design and number of prostheses implanted did not correlate with a higher operative risk. Overall endocarditis-related mortality was 56% (37/66). Uni and multivariate stepwise logistic regression analysis identified: 1) date of surgery (p = 0.01), 2) renal failure (p = 0.03) and 3) early APVE (p = 0.03) as predictors of endocarditis-related death. Actuarial survival at 1, 5 and 10 postoperative years was 41 +/- 6%, 30 +/- 6% and 24 +/- 7% respectively. This study confirms the high lethality of APVE. However, with adequate and aggressive combined medical and surgical management, some patients can be saved.  相似文献   
995.
Zero-order release of oxprenolol hydrochloride was obtained by controlling the swelling and erosion of the matrix. This formulation involves only mixing of drug, hydroxypropylmethylcellulose (HPMC), and sodium carboxymethylcellulose (Na CMC) at the ratio of 1:0.4:1.6, respectively, and compressing the mixture directly into tablets. The in vitro release pattern from this optimized matrix tablet was reproducible. Accelerated stability studies revealed that the optimized formulation remains stable for an approximately 2-year shelf life. This sustained-release (SR) tablet was evaluated in dogs, and for comparison a conventional (CV) formulation was also given at the same dose level. Plasma oxprenolol levels were monitored by a sensitive and specific high-performance liquid chromatographic (HPLC) method. Significant differences in the pharmacokinetic parameters, i.e., lower C max, higher values of t max, MRT, AUC, and plasma concentration at 24 hr, and nearly constant plasma levels over 12 hr, indicated that the SR matrix tablet is superior to the CV rapid-releasing formulation. The in vitro release parameters and in vivo pharmacokinetics correlated well.  相似文献   
996.
997.
998.
Valves in the subclavian and internal jugular veins were studied in 100 autopsy cases (52 men and 48 women; range, 18 to 91 years old; mean, 67 years). In 87 cases, valves were present in all 4 veins, and in 13 cases, valves anatomically were absent from 16 veins, 9 of which were the left internal jugular vein. The average distance from the valve to the junction with the innominate vein was 1.7 cm for the subclavian vein and 0.3 cm for the internal jugular vein. Cuspid height averaged 0.9 cm. Valves were bicuspid in 347 (90%) and unicuspid in 39 (10%); unicuspid valves were more common in the internal jugular vein than in the subclavian vein. Catheter-induced trauma was observed in 4 cases and implied in 4 more. These findings may have important implications concerning the failure, in some cases, of closed-chest cardiac resuscitation to maintain forward blood flow at adequate pressure.  相似文献   
999.
Walking after stroke. Measurement and recovery over the first 3 months   总被引:4,自引:0,他引:4  
Sixty surviving patients had their walking ability and speed assessed regularly over the first 3 months after an acute stroke. Sixty-four matched controls were studied to allow categorisation of speed as 'slow' or 'normal'. Fourteen patients never had any significant loss of walking speed; fifteen patients never recovered the ability to walk and one patient remained dependent upon verbal support. Of the 30 showing significant recovery, only 10 regained normal speed, and 8 remained dependent upon a physical aid at 3 months. Plotting individual recovery curves of walking speed over time showed the wide range of change which may be expected. It is argued that timing of gait over 10 metres is a valid reliable measure that is currently underused.  相似文献   
1000.
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