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   33076篇
  免费   1742篇
  国内免费   147篇
耳鼻咽喉   350篇
儿科学   733篇
妇产科学   581篇
基础医学   6262篇
口腔科学   743篇
临床医学   2616篇
内科学   6263篇
皮肤病学   854篇
神经病学   3404篇
特种医学   1424篇
外科学   4580篇
综合类   151篇
一般理论   14篇
预防医学   1658篇
眼科学   721篇
药学   2315篇
中国医学   21篇
肿瘤学   2275篇
  2022年   161篇
  2021年   345篇
  2020年   293篇
  2019年   488篇
  2018年   570篇
  2017年   437篇
  2016年   564篇
  2015年   651篇
  2014年   781篇
  2013年   1170篇
  2012年   1626篇
  2011年   1748篇
  2010年   1176篇
  2009年   1127篇
  2008年   1883篇
  2007年   1920篇
  2006年   1791篇
  2005年   1916篇
  2004年   1793篇
  2003年   1761篇
  2002年   1842篇
  2001年   341篇
  2000年   266篇
  1999年   386篇
  1998年   502篇
  1997年   412篇
  1996年   367篇
  1995年   337篇
  1994年   289篇
  1993年   258篇
  1992年   209篇
  1991年   204篇
  1990年   170篇
  1989年   161篇
  1988年   169篇
  1985年   157篇
  1984年   181篇
  1983年   161篇
  1982年   198篇
  1981年   169篇
  1978年   135篇
  1933年   170篇
  1932年   180篇
  1931年   167篇
  1930年   169篇
  1929年   147篇
  1928年   163篇
  1927年   144篇
  1926年   158篇
  1925年   139篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
Two recently discovered genes, the recombination activating genes 1 and 2 (RAG-1 and RAG-2), are necessary to perform variable (V), diversity (D), and joining (J) recombination. They synergistically activate VDJ recombination to generate immunocompetent lymphocytes. Disruption of either gene results in a maturation arrest at a very early B and T cell progenitor stage. Expression and downregulation of RAG's are closely associated with interleukin 7, sIgM and TCR-CD3 complex, respectively. Assessment of RAG mRNA expression is a valuable marker in identifying the genotypic maturation status of leukemias and lymphomas. Persistent RAG expression in otherwise mature lymphoid proliferations may explain puzzling biological and clinical observations such as multiple rearrangements in lymphomas with a mature phenotype. Lack of RAG expression in Hodgkin's disease with abundant Reed-Stern-berg cells is consistent with a mature phenotype of the latter. Availability of a anti-RAG-1 monoclonal antibody in the near future will facilitate RAG analysis of lymphomas.  相似文献   
72.
73.
74.
We investigated non-rapid eye movement (non-REM) sleep in patients with newly diagnosed Parkinson's disease (PD) who had never previously received dopaminergic medication. There were no significant differences in the conventional sleep parameters between de novo patients with PD and a healthy control group, but the length of stage 1 sleep and the number of awakenings increased significantly upon administration of dopaminergic drugs. Analyzing the quantitative electroencephalogram (EEG), we observed a significant reduction in the low-delta frequency range and a nonsignificant increase in the sigma frequency range in de novo patients with PD. The dopaminergic medication also nonsignificantly reduced the low-delta and sigma frequencies, the latter to the level of the controls. Possible mechanisms that may account for the observed differences are discussed. It is suggested that Parkinson's disease as well as the application of dopaminergic drugs exerts a desynchronizing effect on the sleep EEG that is reflected in a disruption of sleep continuity.  相似文献   
75.
This study showed that, in chickens, the negative effects of phytate-phosphorus in a low inorganic phosphorus diet could be completely reversed through the additive effects of reduced dietary calcium and increased cholecalciferol. In the future, perhaps greater reliance on more readily available plant phosphorus sources may be instituted in developing countries, where cheap sources of inorganic phosphorus are difficult to obtain.  相似文献   
76.
Summary Thoracoscopic surgery is decidedly expanded by the ability to perform pulmonary wedge resections of the lung by using the Endo-GIA-stapler. In addition to thoracoscopic biopsies, since July 1991 we have carried out wedge resections in 12 patients suffering from spontaneous pneumothorax (nine) or peripheral bronchial carcinoma (three). Postoperatively one air fistula persisted over 9 days. The chest tube was removed within 48 h in all other patients. There was no other major complication. The postoperative hospitalization period lasted 4.6 days (1–9 days). Operating time was 44 min (30–70 min). The benefit for the patient consists in the little-impaired breathing mechanics, the short hospital stay, and the favorable cosmetic result.  相似文献   
77.
Renal lesions have repeatedly been described in Wilson’s disease (WD). We investigated the excretion of total protein, albumin, low (LMW) and high molecular weight (HMW) proteins, N-acetyl-β-D-glucosaminidase (NAG), and calcium, as well as creatinine clearance, in 24-h urine samples of 41 patients with WD aged 6 – 37 (mean 17) years who had been treated for a period of 0 – 15 (mean 4.5) years with D-penicillamine (900 mg/day). The amount of all protein excreted was significantly increased compared with controls, 39% of patients presenting with total proteinuria more than two standard deviations from the mean of controls. The changes in protein excretion depended on the duration of treatment. LMW proteinuria was elevated almost exclusively in the first 2 years after the start of treatment, indicating early tubular damage. This is supported by an initially high excretion of β2-microglobulin, NAG, and calcium. Increased excretion of HMW proteins, including albumin, persisted over longer periods, which suggests glomerular injury in some patients, possibly related to the use of D-penicillamine. Creatinine clearance remained roughly within normal limits. We propose that renal function should regularly be checked in patients with WD. Received October 26, 1995; received in revised form August 27, 1996; accepted September 20, 1996  相似文献   
78.
79.
Identification of antiarrhythmic drugs and their metabolites in urine   总被引:1,自引:0,他引:1  
Identification of the antiarrhythmic drugs ajmaline, aprindine, diltiazem, disopyramide, flecainide, gallopamil, lidocaine, lorcainide, mexiletine, phenytoin, prajmaline, propafenone, quinidine, sparteine, tocainide and verapamil and their metabolites in urine is described. After acid hydrolysis of the conjugates, extraction and acetylation, the urine samples were analysed by computerized gas chromatography-mass spectrometry. Using ion chromatography with the selective ions m/z 58, 72, 84, 86, 136, 224, 266, and 426, the possible presence of antiarrhythmic drugs and/or their metabolites was indicated. The identity of positive signals in the reconstructed ion chromatograms was confirmed by a visual or computerized comparison of the stored full mass spectra with the reference spectra. The ion chromatograms, reference mass spectra and gas chromatographic retention indices (OV-101) are documented. The method presented is integrated in a general screening procedure (general unknown analysis) for several groups of drugs.  相似文献   
80.
Tranexamic acid has been advocated for patients with severe bleeding tendency due to thrombocytopenia not responding to platelet transfusions. Macroscopic haematuria is a well-known contraindication for its use in such patients. We present three clinical cases with microscopic haematuria, in whom tranexamic acid caused problems of clot formation in the urinary tract, indicating that microscopic haematuria should also be considered as a contraindication for tranexamic acid.  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