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   3470173篇
  免费   282916篇
  国内免费   13970篇
耳鼻咽喉   48450篇
儿科学   111234篇
妇产科学   90845篇
基础医学   548465篇
口腔科学   93761篇
临床医学   307882篇
内科学   614407篇
皮肤病学   91465篇
神经病学   294173篇
特种医学   137129篇
外国民族医学   394篇
外科学   541660篇
综合类   102778篇
现状与发展   23篇
一般理论   2218篇
预防医学   289392篇
眼科学   79441篇
药学   240533篇
  23篇
中国医学   9799篇
肿瘤学   162987篇
  2021年   55157篇
  2020年   35180篇
  2019年   58248篇
  2018年   71513篇
  2017年   54416篇
  2016年   60075篇
  2015年   74317篇
  2014年   108658篇
  2013年   174066篇
  2012年   91426篇
  2011年   91682篇
  2010年   116905篇
  2009年   121348篇
  2008年   79777篇
  2007年   83464篇
  2006年   94058篇
  2005年   89944篇
  2004年   91752篇
  2003年   82937篇
  2002年   73324篇
  2001年   104568篇
  2000年   97280篇
  1999年   97526篇
  1998年   65413篇
  1997年   63063篇
  1996年   61028篇
  1995年   56440篇
  1994年   50731篇
  1993年   47204篇
  1992年   69706篇
  1991年   66910篇
  1990年   64297篇
  1989年   63438篇
  1988年   59419篇
  1987年   57857篇
  1986年   55195篇
  1985年   55145篇
  1984年   49732篇
  1983年   45782篇
  1982年   42220篇
  1981年   39689篇
  1980年   37397篇
  1979年   41856篇
  1978年   36497篇
  1977年   33457篇
  1976年   30819篇
  1975年   30062篇
  1974年   31285篇
  1973年   30092篇
  1972年   28368篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
991.
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   
992.
993.
BG Aktuell     
This paper gives an overview of the changes in the sector of accident insurance companies over recent months and a prognosis for the changes that can still be expected, especially with reference to the election results.  相似文献   
994.
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   
995.
11C-乙酸盐PET显像在肾脏肿瘤诊断中的作用   总被引:5,自引:1,他引:4  
目的探讨^11C-乙酸盐PET显像在肾脏肿瘤诊断中的作用及其与^18F-脱氧葡萄糖(FDG)肾肿瘤显像的关系。方法29例疑肾肿瘤患者行^11C-乙酸盐PET早期及延迟显像,其中22例1周内行^18F—FDG PET显像。所有患者均有手术病理检查或CT、随访结果。患者静脉注射^11C-乙酸盐后即刻采集肾脏部位早期图像,以反映肾皮质血流灌注;10min后采集延迟图像,以反映^11C-乙酸盐在肾皮质内的代谢。观察^11C-乙酸盐在人体内的分布,并比较^11C-乙酸盐与^18F—FDG肾肿瘤显像的阳性率及其与病理类型、分级的关系。结果^11C-乙酸盐在人体内以胰腺摄取最高,并可能经胰液分泌人肠道。肾皮质对^11C-乙酸盐摄取随时间而变化,延迟相大部分原发肾皮质肿瘤(13例中分级Ⅰ~Ⅱ为12例)对^11C-乙酸盐摄取高于正常肾皮质,阳性率为76.9%(10/13例);而^18F—FDG显像仅为30.8%(4/13例)。6例肾盂输尿管移行细胞癌^11C-乙酸盐显像阳性仅2例;其中5例行^18F—FDG显像,均阳性。1例肾血管平滑肌脂肪瘤^11C-乙酸盐早期及延迟显像均清晰显示,2例输尿管炎症对^11C-乙酸盐无摄取。结论^11C-乙酸盐PET显像对恶性程度较低的肾皮质肿瘤显像阳性率较高,可弥补^18F—FDG显像的不足。  相似文献   
996.
997.
998.
To investigate the phenotypic consequences of a deranged lymphangiogenesis in relation to tissue fluid accumulation and the possible role of inflammation in the pathogenesis of lymphoedema, we measured determinants of transcapillary fluid filtration and inflammatory mediators in the interstitial fluid in genetically engineered Chy mice, a model for primary congenital lymphoedema (Milroy's disease). Although initial lymphatics were not present in dermis in any of the areas studied (fore paw, hind paw, thigh and back skin) interstitial fluid pressure ( P if), measured with micropipettes, and tissue fluid volumes were significantly increased only in the areas with visible swelling – the fore and hind paw, whereas interstitial colloid osmotic pressure (COPif) was increased in all the skin areas examined. A volume load of 15% of body weight resulted in a more pronounced increase in P if as well as a four-fold increase in interstitial fluid volume in Chy relative to wild-type (wt) mice, showing the quantitative importance of lymphatics for fluid homeostasis during acute perturbations. A similar level of proinflammatory markers in interstitial fluid in early established lymphoedema (3–4 months) in Chy and wt suggests that inflammation does not have a major pathogenetic role for the development of lymphoedema, whereas a reduced level of the immunomodulatory cytokine interleukin (IL)-4 may result in a reduced immunological defence ability and thus lead to the increase in inflammatory cytokines IL-2 and IL-6 observed at a later stage (11–13 months). Our data suggest that primary lymphoedema results in a high interstitial fluid protein concentration that does not induce an interstitial inflammatory reaction per se , and furthermore shows the paramount importance of the initial lymphatics in tissue fluid homeostasis, especially during perturbations of transcapillary fluid balance.  相似文献   
999.
1000.
BACKGROUND: An augmented reality tool for computer assisted surgery named X-Scope allows visual tracking of real anatomical structures in superposition with volume rendered CT or MRI scans and thus can be used for navigated translocation of bony segments. METHODS: In a feasibility study X-Scope was used in orthognathic surgery to control the translocation of the maxilla after Le Fort I osteotomy within a bimaxillary procedure. The situation achieved was compared with the pre-operative situation by means of cephalometric analysis on lateral and frontal cephalograms. RESULTS: The technique was successfully utilized in 5 patients. Maxillary positioning using X-Scope was accomplished accurately within a range of 1mm. The tool was used in all cases in addition to the usual intra-operative splints. A stand-alone application without conventional control does not yet seem reasonable. CONCLUSION: Augmented reality tools like X-Scope may be helpful for controlling maxillary translocation in orthognathic surgery. The application to other interventions in cranio-maxillofacial surgery such as Le Fort III osteotomy, fronto-orbital advancement, and cranial vault reshaping or repair may also be considered.  相似文献   
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