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   3342篇
  免费   190篇
  国内免费   6篇
耳鼻咽喉   33篇
儿科学   116篇
妇产科学   105篇
基础医学   544篇
口腔科学   44篇
临床医学   272篇
内科学   745篇
皮肤病学   40篇
神经病学   287篇
特种医学   300篇
外国民族医学   2篇
外科学   439篇
综合类   13篇
一般理论   1篇
预防医学   175篇
眼科学   39篇
药学   213篇
中国医学   2篇
肿瘤学   168篇
  2023年   21篇
  2022年   31篇
  2021年   53篇
  2020年   29篇
  2019年   38篇
  2018年   45篇
  2017年   42篇
  2016年   54篇
  2015年   60篇
  2014年   89篇
  2013年   107篇
  2012年   170篇
  2011年   152篇
  2010年   108篇
  2009年   100篇
  2008年   130篇
  2007年   178篇
  2006年   137篇
  2005年   142篇
  2004年   133篇
  2003年   131篇
  2002年   146篇
  2001年   101篇
  2000年   113篇
  1999年   101篇
  1998年   54篇
  1997年   31篇
  1996年   19篇
  1995年   17篇
  1994年   27篇
  1993年   22篇
  1992年   60篇
  1991年   68篇
  1990年   70篇
  1989年   79篇
  1988年   57篇
  1987年   51篇
  1986年   43篇
  1985年   54篇
  1984年   39篇
  1983年   25篇
  1982年   19篇
  1979年   43篇
  1978年   21篇
  1977年   16篇
  1975年   19篇
  1973年   18篇
  1972年   21篇
  1968年   19篇
  1965年   14篇
排序方式: 共有3538条查询结果,搜索用时 15 毫秒
21.
The clinical history of 1538 HIV positive patients was analyzed on the basis of the new CDC classification system of HIV disease and AIDS. This classification system combines three CD4 cell categories (1, 2, and 3) with three clinical categories (A, B, and C) into nine subgroups AI–C3. We examined the overall survival for all subgroups and the AIDS-free survival for subgroups Al–B3. AIDS-free survival for patients in subgroups Al, A2, and B1 was considerably longer than survival in patients from subgroups A3, B2, and B3 (P < 0.0001). According to these findings, the new CDC classification system could be simplified into three stages, stage I and II comprising the above mentioned six subgroups, and stage III comprising clinical AIDS defining categories C1, C2, and C3. These three stages correspond to different periods in the management of HIV positive patients, i.e., period of observation, period of prophylaxis, and period of treatment.Abbreviations AIDS acquired immunodeficiency syndrome - CDC Centers for Disease Control - HIV Human immunodeficiency virus Correspondence to: E.B. Helm  相似文献   
22.
We observed that culture medium conditioned with fetal rat long bones stimulated cyclic AMP production by canine renal cortical membranes. This cyclase-stimulating activity (CSA) was retained by an ultrafiltration membrane with a molecular weight cutoff of 5000; three biologically active peaks with an approximate molecular weight of 18,000-25,000, 9000-12,000, and 4000-6000 were separated by high-performance liquid chromatography. The biologic activity was destroyed by trypsin digestion. The stimulation of adenylate cyclase by the medium and by the three peaks was inhibited by [N-leu8,18,Tyr34]parathyroid hormone-(3-34)-amide and by [Tyr34]parathyroid hormone-(7-34)amide. Preincubation of the bone culture medium and of the three peaks with an antibody raised against human parathyroid hormone-(1-34) did not decrease the biologic activity more than incubation with nonimmune serum. However, the biologic activity of the three active peaks was significantly suppressed after preincubation with an antiserum directed against the N-terminal region of the parathyroid hormone-related peptide of malignancy. The release of CSA into the bone culture medium was enhanced by parathyroid hormone induction and by 1,25-dihydroxycholecalciferol. It was decreased by calcitonin. We conclude that fetal murine bones in culture release peptides that stimulate the adenylate cyclase of renal cortical membranes. These peptides are antigenically similar to the parathyroid hormone-related peptide of malignancy. Their release from bones is modulated by hormones that control bone resorption.  相似文献   
23.
The aim of this study was to characterize the role of the efflux transporter Mrp2 (Abcc2) in the pharmacokinetics of orally and intravenously administered pravastatin in rats. Eight Mrp2-deficient TR- rats and eight wild-type rats were given an oral dose of 20 mg/kg pravastatin. Four TR- animals and four wild-type animals were studied after intravenous administration of pravastatin (5 mg/kg). The TR(-) rats showed a 6.1-fold higher mean area under the plasma concentration-time curve (AUC) of pravastatin (p < 0.001) after oral administration and a 4.7-fold higher AUC (p < 0.01) after intravenous administration of pravastatin as compared with the wild-type animals. The mean systemic (total) clearance of pravastatin was 4.6-fold higher (39.2 versus 8.50 l/h/kg, p < 0.001) and the mean V 4.3-fold higher (14.1 versus 3.29 l/kg, p < 0.01) in the wild-type rats. The mean renal clearance of pravastatin in the TR(-) rats was 16.5-fold increased as compared with the wild-type animals (0.695 versus 0.042 l/h/kg, p < 0.05). The increased systemic exposure to oral pravastatin in the TR- rats was associated with a greater inhibitory effect on 3-hydroxy-3-methylglutaryl CoA reductase, as shown by smaller lathosterol to cholesterol concentration ratios. These results suggest that the reduced biliary pravastatin excretion in the Mrp2-deficient TR- rats is partly compensated for by increased urinary excretion of pravastatin. Furthermore, intestinal Mrp2 does not appear to play a major role in the oral absorption of pravastatin in normal rats.  相似文献   
24.
BACKGROUND: Coronary artery calcium (CAC) provides evidence of coronary atherosclerosis and has significant prognostic power. Although prior studies have documented a relationship between CAC and hemodynamically significant coronary artery stenosis, the results have not been conclusive. METHODS AND RESULTS: We evaluated 126 consecutive patients who underwent electron beam computed tomography CAC scoring by use of the Agatston method and stress myocardial perfusion imaging (MPI) within 3 months of each other. The analysis revealed no correlation between absolute CAC score and age- and gender-adjusted CAC scores with MPI. Overall, 18% of patients had abnormal MPI results irrespective of their CAC. CONCLUSION: CAC scoring and stress MPI should be thus considered complementary approaches rather than exclusionary in the evaluation of the patient at risk for coronary artery disease.  相似文献   
25.
Coronary thrombolysis is an attractive approach for salvaging jeopardized, ischemic myocardium. The advent of second- and third-generation clot-selective thrombolytic agents will make this approach safer and more widely applicable in the future. However, residual stenoses and reocclusion are common after the thrombolytic therapy. In addition to thrombolysis, future management of coronary thrombosis may include adjunctive pharmacologic therapy such as calcium-channel antagonists, beta-blockers, or oxygen free radical scavengers, and/or mechanical interventions such as balloon or laser angioplasty, or bypass surgery.  相似文献   
26.
Summary The aim of the study was to use a novel combination of two methods for the simultaneous evaluation of two effects of oral cisapride in 10 diabetic patients with autonomic neuropathy; gastric emptying time was measured by following radio-opaque markers and orocaecal transit time by the sulphasalazine-sulphapridine method. The study was of double-blind, randomized, placebo-controlled, cross-over design.It was possible to evaluate the effect of a prokinetic drug on gastric emptying and orocaecal transit times using these two noninvasive techniques at the same time. Cisapride significantly reduced both the gastric emptying (1.2 h versus 2.1 h) and orocaecal tansit (5.9 h versus 7.7 h) times.  相似文献   
27.
28.
29.
30.
One hundred and sixty-four patients admitted to a psychogeriatric unit were given a combination of four different cognitive tests: the Mini Mental State Examination (MMSE), the Abbreviated Mental Test Score, The Felix Post Unit Score and the compilation of tests recommended by the MRC Alzheimer's Disease Workshop. The tests were compared with respect to their ability to sort accurately cases of dementia and depression, and the effects of age and education on test score and misclassification rate with diagnosis controlled for. The MMSE had a very high misclassification rate for the poorly educated and depressed group. The logistical discriminant functional analysis selected only eight items as the best discriminators between organic/ functional or dementia/depression groups. Only one of these eight was not either a memory or orientation test. The value of simply adding up tests of different aspects of cognitive function in dementia assessment or screening is questioned.  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