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   3225459篇
  免费   236921篇
  国内免费   8673篇
耳鼻咽喉   43431篇
儿科学   107810篇
妇产科学   89142篇
基础医学   456996篇
口腔科学   89822篇
临床医学   296033篇
内科学   630453篇
皮肤病学   75807篇
神经病学   264159篇
特种医学   124085篇
外国民族医学   1066篇
外科学   480905篇
综合类   67969篇
现状与发展   5篇
一般理论   1299篇
预防医学   250982篇
眼科学   72681篇
药学   235729篇
  11篇
中国医学   6573篇
肿瘤学   176095篇
  2019年   25372篇
  2018年   35828篇
  2017年   27554篇
  2016年   31673篇
  2015年   35649篇
  2014年   49137篇
  2013年   74620篇
  2012年   98799篇
  2011年   104578篇
  2010年   62948篇
  2009年   59976篇
  2008年   97812篇
  2007年   103690篇
  2006年   105652篇
  2005年   101234篇
  2004年   97945篇
  2003年   94551篇
  2002年   91127篇
  2001年   153450篇
  2000年   157341篇
  1999年   132735篇
  1998年   38339篇
  1997年   34175篇
  1996年   34203篇
  1995年   33157篇
  1994年   30553篇
  1993年   28449篇
  1992年   104017篇
  1991年   100541篇
  1990年   97700篇
  1989年   94347篇
  1988年   86275篇
  1987年   85041篇
  1986年   79658篇
  1985年   76304篇
  1984年   56932篇
  1983年   48241篇
  1982年   28732篇
  1981年   25761篇
  1979年   50758篇
  1978年   36131篇
  1977年   30619篇
  1976年   28562篇
  1975年   30259篇
  1974年   36042篇
  1973年   34358篇
  1972年   31975篇
  1971年   29753篇
  1970年   27419篇
  1969年   26148篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Objective The degree of Left Ventricular Mass Index (LVMI) regression following aortic valve replacement correlates with long-term survival. This study aims to assess the extent of LVMI regression at 3 months following aortic valve replacement (AVR) with different types and sizes of mechanical valves in rheumatic aortic valve disease. Methods The LVMI regression was studied in 34 consecutive patients, undergoing elective AVR for rheumatic aortic stenosis and/or regurgitation. They were grouped in A and B, matched in age, body surface area and pre-operative LVMI, receiving respectively a tilting disc and a bileaflet mechanical valve. The LVMI was calculated by M-mode echocardiography using the Devereux' formula pre-operatively and three months post-operatively. The trend of LVMI reduction was compared between the two groups and amongst the patients with stenotic, regurgitant and mixed aortic valve, pathologies; and receiving different sizes of valves. Results The mean preoperative LVMI was 199g±79.5 g/m2. At three months post aortic valve replacement, the mean LVMI was 130g±49.0 g/m2. There was a significant reduction of LVMI post-operatively (p=0.001) at three months follow-up. The extent of LVMI regression following surgery amongst the groups A and B did not vary significantly (p=0.92). The extent of LVMI regression did not vary significantly in patients with different aortic valve pathology nor with different sizes of the valves implanted. Conclusions There is a significant early LVMI regression following aortic valve replacement in rheumatic aortic valve disease. The type and the size of the mechanical prosthesis or the rheumatic pathology do not appear to influence this regression.  相似文献   
992.
993.
Renal fibrosis and the origin of the renal fibroblast.   总被引:4,自引:0,他引:4  
Many studies have determined that the extent of tubulointerstitialinvolvement, particularly fibrosis, correlates better with renalfunction than glomerular changes do, thus, the extent of tubulointerstitialdamage in any given renal biopsy has important implicationsfor the renal prognosis of the patient (summarized in [1]).Tubulointerstitial fibrosis is characterized by the accumulationof extracellular matrix components including collagen typesI, III, IV, proteoglycans and fibronectin. In recent years,much controversy has been created in the nephrology communityregarding the origin of matrix-producing cells in the kidney.Several possibilities exist, including activation of residentinterstitial fibroblasts, migrating haematopoietic or mesenchymalstem cells from the bone marrow, periadventitial cells and epithelial–mesenchymaltransition (EMT) of tubular epithelial cells. This review summarizesrecent data indicating the possible origin of matrix-producingcells in the kidney, and illustrates from a clinical point of  相似文献   
994.
There is insufficient evidence that the surgical treatment of asymptomatic infrarenal aneurysms > 5.5 cm. is beneficial to patients. This is the result of serious complications of aneurysm surgery and the dearth of information from randomized trials. Based on evidence from the literature we defined scenarios and translated data into natural frequency trees to improve understanding of the uncertainty of help versus harm due to treatment of aneurysms. Our analysis shows that the majority of patients can expect little on longevity from surgery while they are at risk of dying from surgery or suffering from serious morbidity. We conclude that, as long as uncertainty persist, patients should be treated in hospitals that can show very low surgical mortality and major morbidity rates. To further resolve the problem of uncertainty randomized trials for larger aneurysms should be performed. Important issues to discuss are the lower and upper limits of the diameter of the aneurysms and the age and risk profiles of the patients to be included in such trials.  相似文献   
995.
This study was performed to evaluate the surgical strategy in patients with calvarial tumours, in order to design and modify a robot-assisted trepanation system. A total of 75 patients underwent craniectomy for the treatment of calvarial tumours during the 10-year period from 1993 to 2002. The patients' complaints, the size, location and histology of the tumour, and the various cranioplasty techniques used were analysed retrospectively. In a second procedure several craniectomies at typical locations according to the study's results were performed in a laboratory setting using a hexapod robotic tool, constructed at the Helmholtz-Institute, RWTH Aachen University, and plastic model heads. The workflow was documented and the reproducibility and the accuracy of the procedure were registered. A total of 83 surgical procedures were performed on 75 patients. The majority (87 %) of lesions treated surgically were located in the frontal, temporal and anterior parts of the parietal region. Histological examination revealed benign lesions in 66 % of the patients and dural involvement in 46 %. According to these results craniectomies were performed using the robotic system. Mean positioning accuracy of the robotic system while milling was 0.24 mm, with a standard deviation of 0.04 mm, and maximum error under 1 mm. Craniectomies leaving a 1-mm layer of the tabula interna intact to ensure a healthy dura were performed in several regions successfully. The majority of calvarial tumours, requiring surgical treatment in our patients, were located in cosmetically relevant areas in which drilling can be carried out with the robotic trepanation system. Consequently, the surgical approach had to be planned carefully in order to achieve a good cosmetic outcome.  相似文献   
996.
997.
Malignancy larynx usually presents early, the common symptoms being hoarseness, pain thorat, cough and irritation of throat. An advanced malignancy is likely to be complicated by a pharyngo-cutaneous fistula. However it is an occurrence towards the end stage of the disease. Here we present a case of malignancy larynx primarily presenting as pharyngo-cutaneous fistula without any other symptoms.  相似文献   
998.
999.

Background  

Both diabetes and obesity syndromes are recognized to promote lumbar vertebral instability, premature osteodegeneration, exacerbate progressive osteoporosis and increase the propensity towards vertebral degeneration, instability and deformation in humans.  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