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   21167篇
  免费   1646篇
  国内免费   68篇
耳鼻咽喉   198篇
儿科学   590篇
妇产科学   629篇
基础医学   2861篇
口腔科学   389篇
临床医学   2353篇
内科学   4400篇
皮肤病学   323篇
神经病学   1829篇
特种医学   851篇
外国民族医学   2篇
外科学   2325篇
综合类   440篇
一般理论   16篇
预防医学   2389篇
眼科学   435篇
药学   1445篇
中国医学   46篇
肿瘤学   1360篇
  2023年   116篇
  2022年   273篇
  2021年   508篇
  2020年   318篇
  2019年   469篇
  2018年   503篇
  2017年   376篇
  2016年   383篇
  2015年   475篇
  2014年   700篇
  2013年   895篇
  2012年   1334篇
  2011年   1416篇
  2010年   758篇
  2009年   654篇
  2008年   1126篇
  2007年   1218篇
  2006年   1122篇
  2005年   1069篇
  2004年   915篇
  2003年   868篇
  2002年   859篇
  2001年   467篇
  2000年   422篇
  1999年   365篇
  1998年   187篇
  1997年   135篇
  1996年   132篇
  1995年   165篇
  1994年   116篇
  1993年   127篇
  1992年   325篇
  1991年   279篇
  1990年   273篇
  1989年   283篇
  1988年   212篇
  1987年   209篇
  1986年   210篇
  1985年   218篇
  1984年   170篇
  1983年   135篇
  1982年   116篇
  1981年   106篇
  1979年   199篇
  1978年   154篇
  1977年   114篇
  1974年   134篇
  1973年   112篇
  1971年   98篇
  1970年   102篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
The development of a goitre in the retrosternal space may result in many different symptoms due to local compression. We describe a case in which such a goitre resulted in full-thickness ulceration of the oesophagus, which presented as a fatal haematemesis. We believe that such a complication has not been previously reported.  相似文献   
63.
In view of the current audiological need to obtain rapidly recorded and objective threshold information, particularly for frequencies below 1 kHz, we have developed an evoked potential technique based on the frequency following response. The technique involves the acquisition of a single captured epoch of EEG containing phase-locked responses to 1000 cycles of a continuous pure-tone stimulus. The captured epoch is partitioned into segments representing the responses to single cycles of the stimulus. The segments are then averaged to produce the period evoked potential. The process takes less than five seconds.  相似文献   
64.
65.
66.
Autonomy has been the central principle underpinning changes which have affected the practice of medicine in recent years. Medical education is undergoing changes as well, many of which are underpinned, at least implicitly, by increasing concern for autonomy. Some universities have embarked on graduate courses which utilize problem-based learning (PBL) techniques to teach all areas, including medical ethics. I argue that PBL is a desirable method for teaching and learning in medical ethics. It is desirable because the nature of ethical enquiry is highly compatible with the learning processes which characterize PBL. But it is also desirable because it should help keep open the question of what autonomy really is, and how it should operate within the sphere of medical practice and medical education.  相似文献   
67.
Pancreatic complications following cardiopulmonary bypass are infrequent but are associated with high mortality. All cases of pancreatic complications following cardiopulmonary bypass from 1972 to 1987 at a single institution were retrospectively reviewed. Of 5621 patients who underwent cardiopulmonary bypass, 25 (0.44%) sustained pancreatic complications. There were 15 cases of acute pancreatitis and 10 cases of pancreatic necrosis, with 11 deaths in the group reviewed, a mortality rate of 44%. Factors that were correlated with mortality associated with pancreatic complications in this study include preoperative hypotension, preoperative use of inotropic agents, and renal failure (preoperative and postoperative). Factors that have been previously associated with mortality from pancreatic complications in other studies, such as fluid sequestration, respiratory failure, sepsis, tachycardia, hypocalcemia, age greater than 55 years, and abnormal laboratory findings, were not found to be significantly associated with mortality in this study. Of the five patients for whom complete data were available, not one patient received greater than 800 mg of calcium per square meter of body surface area in the perioperative period. While the exact mechanism of pancreatic injury remains unclear, based on experimental studies and clinical correlation, it is likely that pancreatic ischemia remains a significant contributing factor. We conclude that no factor specifically associated with cardiopulmonary bypass was correlated significantly with mortality.  相似文献   
68.
Objective   To profile the expression of all known members of the matrix metalloproteinase ( MMP ), a disintegrin and metalloproteinase with thrombospondin motifs ( ADAMTS ), and tissue inhibitor of metalloproteinases ( TIMP s) gene families in normal cartilage and that from patients with osteoarthritis (OA).
Methods   Human cartilage was obtained from femoral heads at joint replacement for either osteoarthritis or following fracture to the neck of femur. Total RNA was purified and expression of genes assayed using quantitative real-time PCR.
Results   Several members of the above gene families were regulated in OA. Genes increasing in expression in OA were: at P  < 0.001, MMP-13 , MMP-28 , ADAMTS-16 ; at P  < 0.01, MMP-9 , MMP-16 , ADAMTS-2 , ADAMTS-14 and at P  < 0.05, MMP-2 , TIMP-3 , ADAMTS-12 . Genes decreasing in expression in OA were: at P  < 0.001, MMP-1 , MMP-3 , ADAMTS-1 ; at P  < 0.01, MMP-10 , TIMP-1 , ADAMTS-9 and at P  < 0.05, TIMP-4 , ADAMTS-5 , ADAMTS-15 . Correlation analysis revealed that groups of genes across the gene families are co-expressed in cartilage.
Conclusion   This is the first comprehensive expression profile of all known MMP , ADAMTS and TIMP genes in cartilage. Patterns of expression provide a foundation on which to understand mechanisms of gene regulation in OA and potentially for refining the specificity of anti-proteolytic therapies.  相似文献   
69.
BACKGROUND: Multicolored Asian lady beetles (Harmonia axyridis) have been used as a biological control agent against crop-destroying aphids in the United States. Outside their natural habitat, H. axyridis seeks refuge in homes during fall and winter, leading to patient complaints and symptoms of rhinitis, wheezing, and urticaria on exposure to the beetles. OBJECTIVE: To gain a better understanding of the character and spectrum of allergic disease provoked by exposure to home-infesting lady beetles. METHODS: Eight patients with allergic symptoms suspected of being caused by H. axyridis and consistent with an IgE-mediated process were identified and interviewed. A whole-body extract from H. axyridis was prepared. Western blots using the patients' serum identified specific IgE antibodies in the extract. Through a novel technique, immunohistochemical analysis using beetle sections overlayed with patient serum was performed. A random survey of allergists from across the United States was also performed to evaluate experience with cases of lady beetle allergy. RESULTS: Western blots revealed IgE binding to 5 proteins with molecular weights of approximately 8.6, 21, 28, 31, and 75 kDa. Specific IgE bound to proteins localized in the beetle's mouth and leg areas. The allergist survey revealed positive responses in North Central, Mid-Atlantic and New England states. CONCLUSION: In 8 patients with allergic symptoms on exposure to high levels of lady beetles, specific IgE bound to proteins from H. axyridis. There was also an increased frequency of suspected cases of lady beetle allergy in endemic areas.  相似文献   
70.
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