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   1419076篇
  免费   100288篇
  国内免费   3029篇
耳鼻咽喉   21022篇
儿科学   44154篇
妇产科学   41566篇
基础医学   198887篇
口腔科学   42073篇
临床医学   118688篇
内科学   277919篇
皮肤病学   32782篇
神经病学   112875篇
特种医学   57438篇
外国民族医学   466篇
外科学   221913篇
综合类   32400篇
现状与发展   6篇
一般理论   459篇
预防医学   96359篇
眼科学   34033篇
药学   105991篇
  3篇
中国医学   3266篇
肿瘤学   80093篇
  2018年   12454篇
  2015年   12826篇
  2014年   17929篇
  2013年   27069篇
  2012年   35493篇
  2011年   37327篇
  2010年   22262篇
  2009年   21691篇
  2008年   36104篇
  2007年   39382篇
  2006年   40052篇
  2005年   38916篇
  2004年   37890篇
  2003年   36700篇
  2002年   36164篇
  2001年   68451篇
  2000年   70030篇
  1999年   59298篇
  1998年   15829篇
  1997年   14579篇
  1996年   13893篇
  1995年   13062篇
  1994年   12223篇
  1993年   11441篇
  1992年   45377篇
  1991年   43822篇
  1990年   43074篇
  1989年   41920篇
  1988年   39125篇
  1987年   38500篇
  1986年   36944篇
  1985年   35020篇
  1984年   26238篇
  1983年   22222篇
  1982年   13334篇
  1981年   12217篇
  1979年   25222篇
  1978年   18034篇
  1977年   15651篇
  1976年   14063篇
  1975年   16133篇
  1974年   18938篇
  1973年   18442篇
  1972年   17596篇
  1971年   16463篇
  1970年   15571篇
  1969年   14959篇
  1968年   14051篇
  1967年   12528篇
  1966年   11692篇
排序方式: 共有10000条查询结果,搜索用时 640 毫秒
911.
Bulletin of Environmental Contamination and Toxicology - Elevated metal concentrations occur throughout the coastal zone due to urbanization and various anthropogenic activities. The lethal...  相似文献   
912.
 Because the immunomodulatory effects of antibiotics could possibly influence the degree of the systemic and local response to infection, knowledge of their intrinsic influence on the host's inflammatory response appears to be essential. Therefore, this study investigated the effects of frequently used antimicrobial agents (β-lactams, quinolones gentamicin, vancomycin and metronidazole) on the in-vitro tumor necrosis factor (TNF)-α and interleukin (IL)-6 production of isolated human peripheral blood mononuclear cells (PBMNC), cultured with or without endotoxin, in comparison with those effects obtained in a whole-blood assay system. In the presence of ciprofloxacin, ofloxacin, gentamicin, vancomycin, and metronidazole, a significant inhibition of the endotoxin-stimulated TNF-α production of human peripheral blood mononuclear cells (PBMNC) was found at therapeutic levels. Only ofloxacin showed a significant inhibitory influence on the endotoxin-induced IL-6 production of PBMNC. In the whole-blood assay, significant effects were not detectable. None of the antibiotics showed cytotoxicity. It is concluded that, at present, the direct immunological effects of antibiotics should be interpreted carefully with regard to the experimental conditions, and regardless of the therapeutic implications. To assess the potential direct immunomodulatory effect of antimicrobial agents, different cell culture procedures should be used. Received: October 19, 2001 / Accepted: February 15, 2002  相似文献   
913.
914.
915.
916.
Intracranial pathology is a common and important complication in extremely low birth weight babies. Lenticulostriate vasculopathy (LSV) is an abnormal finding on cranial ultrasounds of sick babies and has been associated with congenital infection, chromosomal aberration and twin-to-twin transfusion. We describe a previously unreported situation of LSV being detected in both donor and recipient twin. This pair of monochorionic, diamniotic twins was admitted to the Neonatal Intensive Care Unit at 28 weeks of gestation. The mother underwent an emergency caesarean section because ultrasound and Doppler studies showed stage III twin-to-twin transfusion syndrome. The first twin weighed 998 g and second twin weighed 600 g. The first twin had an uneventful stay, whereas the second twin needed prolonged continuous positive airway pressure and indomethacin for patent ductus arteriosus. Both of them developed LSV. The clinical significance of this condition on the neuro-developmental outcome of a neonate has not yet been fully determined.  相似文献   
917.
Static analysis with finite element of a realistic femur nail bone-implant system in a typical proximal femoral fracture under physiological load bearing situations provides results for stress, displacement and strain. The question to be answered is, if simulation with the finite element analysis is able to explain biomechanically clinical observed patterns of failure. Surface-Reconstruction with CT database of a proximal femur and reconstruction with CT based density data was done. Next steps were to unite the bone structure with the Proximal Femoral Nail and to model two relevant fractures (31-A2.2 and A2.3 according AO). After modelling of geometry, isotropic material behaviour and load application numeric calculation of the femur-nail system with FE-software was performed. FE simulation mainly shows an axial dislocation of the femoral head screw with nearly no dislocation of the antirotation screw. This so-called z-effect therefore means: (1) Tilting of the proximal main fragment around the sagittal axis between the screws and (2) relative movement of both screws in the frontal plane. Relative movement of the two screws against each other could be the reason for implant failure, the so called cut out. Furthermore simulation shows different gliding of the screws explaining the so called z-telescoping. The analyzed stress patterns have to be relativized, because isotropic material behaviour of cancellous bone was assumed. Further examinations for this issue are necessary.  相似文献   
918.
OBJECTIVE: To determine the safety and the long-term results of primary stent placement for localized distal aortic occlusive disease. DESIGN: Retrospective observational study. PATIENTS AND METHODS: From July 1998 to July 2005 17 patients (14 female and 3 men, mean age 57 years (39-80)) were treated for intermittent claudication. Five of these patients underwent additional endovascular treatment of focal iliac lesions. RESULTS: Technical success defined as residual stenosis of less than 50% or a trans-stenotic systolic pressure gradient <10% was achieved in 14 of 17 (82%) patients. Major complications included dissection at the puncture site in one patient and thrombosis of additional iliac stents in another patient. Both of these complications were successfully treated. During a mean follow-up of 27 months (range 1-86), four patients had recurrence of symptoms due to in-stent restenoses (n=2), femoral (n=1) or iliac occlusion (n=1), respectively. By Kaplan-Meier analysis, primary aortic hemodynamic patency was 83% at 3 years. Secondary aortic hemodynamic patency was 100%. The primary clinical patency was 68% at 3 years. CONCLUSION: Primary stent placement for distal aortic stenoses is an alternative to surgical treatment because of its high patency and relatively low complication rates.  相似文献   
919.
920.
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