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   5080篇
  免费   407篇
  国内免费   15篇
耳鼻咽喉   34篇
儿科学   118篇
妇产科学   100篇
基础医学   845篇
口腔科学   126篇
临床医学   411篇
内科学   867篇
皮肤病学   84篇
神经病学   902篇
特种医学   270篇
外科学   611篇
综合类   81篇
一般理论   1篇
预防医学   369篇
眼科学   63篇
药学   370篇
中国医学   2篇
肿瘤学   248篇
  2021年   58篇
  2019年   46篇
  2018年   83篇
  2017年   58篇
  2016年   91篇
  2015年   93篇
  2014年   120篇
  2013年   147篇
  2012年   210篇
  2011年   230篇
  2010年   135篇
  2009年   141篇
  2008年   190篇
  2007年   219篇
  2006年   187篇
  2005年   199篇
  2004年   149篇
  2003年   146篇
  2002年   156篇
  2001年   155篇
  2000年   159篇
  1999年   120篇
  1998年   83篇
  1997年   81篇
  1996年   56篇
  1995年   57篇
  1994年   61篇
  1992年   90篇
  1991年   89篇
  1990年   98篇
  1989年   85篇
  1988年   91篇
  1987年   83篇
  1986年   84篇
  1985年   80篇
  1984年   60篇
  1983年   72篇
  1982年   59篇
  1981年   54篇
  1980年   61篇
  1979年   77篇
  1978年   66篇
  1977年   66篇
  1976年   59篇
  1975年   46篇
  1974年   58篇
  1973年   53篇
  1972年   58篇
  1971年   55篇
  1968年   48篇
排序方式: 共有5502条查询结果,搜索用时 15 毫秒
71.
1. In a series of rats subjected to hemorrhage and shock a high negative correlation was found between the portal and peripheral venous oxygen saturations and the arterial blood pressure on the one hand, and the blood amino nitrogen levels on the other, and a high positive correlation between the portal and the peripheral oxygen saturations and between each of these and the blood pressure. 2. In five cats subjected to hemorrhage and shock the rise in plasma amino nitrogen and the fall in peripheral and portal venous oxygen saturations were confirmed. Further it was shown that the hepatic vein oxygen saturation falls early in shock while the arterial oxygen saturation showed no alteration except terminally, when it may fall also. 3. Ligation of the hepatic artery in rats did not affect the liver''s ability to deaminate amino acids. Hemorrhage in a series of hepatic artery ligated rats did not produce any greater rise in the blood amino nitrogen than a similar hemorrhage in normal rats. The hepatic artery probably cannot compensate to any degree for the decrease in portal blood flow in shock. 4. An operation was devised whereby the viscera and portal circulation of the rat were eliminated and the liver maintained only on its arterial circulation. The ability of such a liver to metabolize amino acids was found to be less than either the normal or the hepatic artery ligated liver and to have very little reserve. 5. On complete occlusion of the circulation to the rat liver this organ was found to resist anoxia up to 45 minutes. With further anoxia irreversible damage to this organ''s ability to handle amino acids occurred. 6. It is concluded that the blood amino nitrogen rise during shock results from an increased breakdown of protein in the peripheral tissues, the products of which accumulate either because they do not circulate through the liver at a sufficiently rapid rate or because with continued anoxia intrinsic damage may occur to the hepatic parenchyma so that it cannot dispose of amino acids.  相似文献   
72.
73.
74.
75.
76.
77.
Electromagnetic navigation during flexible bronchoscopy   总被引:5,自引:0,他引:5  
BACKGROUND: Flexible bronchoscopy is routinely utilized in the diagnosis and treatment of various lung diseases. Nondiagnostic bronchoscopy leads to more invasive interventions, such as transthoracic needle aspiration, mediastinoscopy or even thoracotomy. Electromagnetic navigation is a novel technology that facilitates approaching peripheral lung lesions, which are difficult to sample by conventional means. The navigation system involves creating an electromagnetic field around the chest and localizing an endoscopic tool using a microsensor overlaid upon previously acquired CT images. OBJECTIVES: To determine the practicality, accuracy and safety of real-time electromagnetic navigation, coupled with previously acquired 3D CT images, in locating artificially created peripheral lung lesions in a swine model. METHODS: Peripheral lung lesions were created in four swine models by insertion of a metal tube (1 x 10 mm) via a transthoracic approach. An electromagnetic field was created by placing the animal on an electromagnetic location board. A position sensor incorporated into the distal tip of a dedicated tool was used to navigate to the various target lesions. Information gathered in real time during bronchoscopy was presented on a monitor simultaneously by displaying previously acquired CT images. Upon reaching the target lesion, biopsies were performed and the functionality and safety of the superDimension/Bronchus System was observed and documented. RESULTS: The registration accuracy expressed by the fiducial target registration error, expressing both the registration quality and the stability of fiducial (registration) points, was 4.5 mm on average. No adverse effects, such as pneumothorax or internal bleeding, were encountered in any of the animals in this study. CONCLUSIONS: Real-time electromagnetic positioning technology coupled with previously acquired CT images is an accurate technology added to standard bronchoscopy to assist in reaching peripheral lung lesions and performing biopsies.  相似文献   
78.
We have evaluated the fibrinogen/fibrin fragment E antigen assay as a diagnostic test in patients with clinically suspected venous thrombosis by comparing the results of this assay with venography in 272 patients. The result of the fragment E antigen assay was elevated in 79 of 80 patients with positive venograms for recent venous thrombosis (sensitivity 99%) and within the normal range in 161 of 192 patients with normal venograms (specificity 84%). The fragment E assay was also evaluated in 130 medical and surgical controls without evidence of venous thrombosis by leg scanning and the test was found to be relatively nonspecific. However, in the patient group under study, a correct clinical diagnosis of no thrombosis, based on a normal fragment E result, was made in 161 of 162 cases (negative predictive value of 99%). Therefore, a normal test result effectively excludes a diagnosis of venous thrombosis in clinically symptomatic patients. The assay, as currently performed, is technically demanding and takes 24 hr to complete. Therefore, it will have to be simplified before it can be applied to clinical practice.  相似文献   
79.
80.
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