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   12650篇
  免费   1100篇
  国内免费   28篇
耳鼻咽喉   151篇
儿科学   352篇
妇产科学   316篇
基础医学   1583篇
口腔科学   280篇
临床医学   1525篇
内科学   2407篇
皮肤病学   148篇
神经病学   960篇
特种医学   875篇
外国民族医学   2篇
外科学   1573篇
综合类   381篇
一般理论   8篇
预防医学   1386篇
眼科学   174篇
药学   825篇
中国医学   9篇
肿瘤学   823篇
  2021年   166篇
  2020年   121篇
  2019年   188篇
  2018年   210篇
  2017年   160篇
  2016年   152篇
  2015年   174篇
  2014年   307篇
  2013年   421篇
  2012年   565篇
  2011年   603篇
  2010年   315篇
  2009年   286篇
  2008年   466篇
  2007年   555篇
  2006年   527篇
  2005年   532篇
  2004年   471篇
  2003年   462篇
  2002年   453篇
  2001年   426篇
  2000年   404篇
  1999年   335篇
  1998年   173篇
  1997年   161篇
  1996年   148篇
  1995年   167篇
  1994年   133篇
  1993年   128篇
  1992年   325篇
  1991年   277篇
  1990年   267篇
  1989年   291篇
  1988年   226篇
  1987年   214篇
  1986年   222篇
  1985年   233篇
  1984年   172篇
  1983年   134篇
  1982年   118篇
  1981年   100篇
  1979年   197篇
  1978年   155篇
  1977年   115篇
  1975年   98篇
  1974年   133篇
  1973年   108篇
  1972年   94篇
  1971年   95篇
  1970年   99篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
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   
32.
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   
33.
34.
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   
35.
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   
36.
37.
Conclusion  The ACCF/ASNC AC for SPECT MPI provides recommendations for the appropriate use of SPECT MPI. After the publication of the AC document in 2005, the AC has been used by nuclear cardiology practices with many clinical studies evaluating the list of indications in routine clinical practice. From these data. ASNC recommends minor but important changes to the indication list, suggesting the addition of 6 new indications and the modification of the definitions for “chest pain syndrome” and “CHD high risk.”. An objective review of existing indications focused on only those indications that had significant variability among the reviewers (n=20). These indications were reviewed in the presence of existing and new evidence-based data, and ASNC recommends that the grades for 6 indications be re-evaluated. The AC for SPECT MPI will require periodic review as new evidence becomes available or as clinical practice evolves. ASNC recognizes the importance of these criteria to improve the quality of patient care, and it will continue to play a key role in assembling the information for this ongoing review. From the current summary of evidence, ASNC consensus opinions, and ASNC recommendations in this document, ASNC strongly recommends that the AC guidelines be reviewed Prepared by the American Society of Nuclear Cardiology Quality Assurance Subcommittee for Quality in Imaging Standards. Reviewed by members of the American Society of Nuclear Cardiology Quality Assurance Committee. Approved by the American Society of Nuclear Cardiology Board of Directors, September 6, 20.  相似文献   
38.
BACKGROUND: A hypertensive response to exercise (HRE) is associated with false-positive stress echocardiograms and myocardial perfusion single photon emission computed tomography (myocardial perfusion imaging [MPI]) defects even in the absence of coronary artery disease (CAD). Transient ischemic dilation (TID) of the left ventricle on stress MPI is a marker of severe CAD and future cardiac events. This study evaluated the association between an HRE and TID. METHODS AND RESULTS: Blinded quantitative TID assessment was performed in 125 patients who had an HRE and a summed stress score (SSS) of less than 4, as well as 125 control patients with an SSS of less than 4 and without an HRE matched for age, gender, and resting systolic blood pressure. Cardiac comorbidities, pretest Framingham risk, and exercise results were recorded. TID was defined as a stress-to-rest volume ratio of 1.22 or greater. An HRE was associated with a high prevalence of TID and significantly more TID than no HRE (25.6% vs 11.2%; odds ratio, 3.00 [95% confidence interval, 1.41-6.38]). TID was more prevalent even in subgroups with a low pretest probability CAD, including those without diabetes mellitus or angina. On conditional logistic regression analysis, an HRE was found to be independently associated with TID after consideration of other clinical and exercise MPI variables (odds ratio, 2.72 [95% confidence interval, 1.01-7.31]). CONCLUSION: An HRE is associated with a high prevalence of TID in patients without other significant perfusion defects, possibly as a result of global subendocardial ischemia induced by the HRE.  相似文献   
39.
40.
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