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   901239篇
  免费   62367篇
  国内免费   2343篇
耳鼻咽喉   12481篇
儿科学   28722篇
妇产科学   26186篇
基础医学   126749篇
口腔科学   24707篇
临床医学   74875篇
内科学   183445篇
皮肤病学   18992篇
神经病学   71559篇
特种医学   36501篇
外国民族医学   336篇
外科学   142373篇
综合类   19047篇
一般理论   247篇
预防医学   64652篇
眼科学   20145篇
药学   63896篇
中国医学   1805篇
肿瘤学   49231篇
  2018年   9084篇
  2017年   7182篇
  2016年   7709篇
  2015年   8754篇
  2014年   12400篇
  2013年   19260篇
  2012年   25735篇
  2011年   27350篇
  2010年   16624篇
  2009年   15836篇
  2008年   26197篇
  2007年   27818篇
  2006年   28001篇
  2005年   27528篇
  2004年   26364篇
  2003年   25532篇
  2002年   25112篇
  2001年   41398篇
  2000年   42587篇
  1999年   36303篇
  1998年   9975篇
  1997年   9157篇
  1996年   9092篇
  1995年   8457篇
  1994年   8089篇
  1993年   7589篇
  1992年   28224篇
  1991年   27007篇
  1990年   26435篇
  1989年   25378篇
  1988年   23581篇
  1987年   23188篇
  1986年   22264篇
  1985年   21169篇
  1984年   15819篇
  1983年   13486篇
  1982年   8091篇
  1979年   14598篇
  1978年   10213篇
  1977年   8630篇
  1976年   8149篇
  1975年   8962篇
  1974年   10700篇
  1973年   10191篇
  1972年   9661篇
  1971年   8921篇
  1970年   8585篇
  1969年   8029篇
  1968年   7686篇
  1967年   7090篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
Chronic obstructive pulmonary disease (COPD) is characterised by a local pulmonary inflammatory response to respiratory pollutants and by systemic inflammation. Tumour necrosis factor (TNF)-alpha has been implicated in systemic effects of COPD and operates by binding the p55 (R1) and p75 (R2) TNF-alpha receptors. To investigate the contribution of each TNF-alpha receptor in the pathogenesis of COPD, the present study examined the effects of chronic air or cigarette smoke (CS) exposure in TNF-alpha R1 knockout (KO) mice, TNF-alpha R2 KO mice and wild type (WT) mice. CS was found to significantly increase the protein levels of soluble TNF-alpha R1 (by four-fold) and TNF-alpha R2 (by 10-fold) in the bronchoalveolar lavage of WT mice. After 3 months, CS induced a prominent pulmonary inflammatory cell influx in WT and TNF-alpha R1 KO mice. In TNF-alpha R2 KO mice, CS-induced pulmonary inflammation was clearly attenuated. After 6 months, no emphysema was observed in CS-exposed TNF-alpha R2 KO mice in contrast to WT and TNF-alpha R1 KO mice. CS-exposed WT and TNF-alpha R1 KO mice failed to gain weight, whereas the body mass of TNF-alpha R2 KO mice was not affected. These current findings suggest that both tumour necrosis factor-alpha receptors contribute to the pathogenesis of chronic obstructive pulmonary disease, but tumour necrosis factor-alpha receptor-2 is the most active receptor in the development of inflammation, emphysema and systemic weight loss in this murine model of chronic obstructive pulmonary disease.  相似文献   
53.
    
Summary A patient with early bilateral nuclear cataracts and subsequent diagnosis of Fanconi–Bickel syndrome is described. Despite impaired galactose and glucose metabolism, cataracts have been reported in only few cases with this disorder. We conclude that Fanconi–Bickel syndrome should be considered in the differential diagnosis of neonatal cataracts. The pathogenesis of this complication has not been fully elucidated. Electronic supplementary material Supplementary material is available for this article at  相似文献   
54.
OBJECTIVES: To evaluate a novel method for localization of subdural electrodes in presurgical assessment of patients with drug-resistant focal epilepsy. METHODS: We studied eight consecutive patients with posterior epilepsy in whom subdural electrodes were implanted for presurgical evaluation. Electrodes were detected on post-implantation brain CT scans through a semiautomated procedure based on a MATLAB routine. Then, post-implantation CT scans were fused with pre-implantation MRI to localize the electrodes in relation to the underlying cortical structures. The reliability of this procedure was tested by comparing 3D-rendered MR images of the electrodes with electrode position as determined by intraoperative digital photography. RESULTS: In each patient, all electrodes could be correctly localized and visualized in a stereotactic space, thus allowing optimal surgery planning. The agreement between the procedure-generated images and the digital photographs was good according to two independent raters. The mean mismatch between the 3D images and the photographs was 2 mm. CONCLUSIONS: While our findings need confirmation on larger samples including patients with anterior epilepsy, this procedure allowed to localize subdural electrodes and to establish the spatial relationship of each electrode to the underlying brain structure, either normal or damaged, on brain convessity, basal and medial cortex. SIGNIFICANCE: Being simple, rapid, unexpensive, and reliable, this procedure holds promise to be useful to optimize epilepsy surgery planning.  相似文献   
55.
Abstract Guillain-Barré syndrome (GBS) is a disease of the peripheral nervous system, which is caused by aberrant immune responses directed against some components of peripheral nerves. GBS is rarely accompanied by cardiovascular involvement. We describe a case of acute neuropathy complicated by sudden heart failure and left ventricular dysfunction which had a presumably neurogenic origin. Pathogenesis of acute heart failure is probably due to transitorial stunned myocardium and neurogenic cardiac injury. We show a rare case of transitorial and acute cardiac dysfunction by echocardiography and laboratory markers of heart failure.  相似文献   
56.
A case of seminoma in a monorchid adult guinea fowl (Numida meleagris) is described. Grossly, a right enlarged testis, which was soft in consistency, and white to pale in colour with few spots of haemorrhages was observed. Histologically, the testicle revealed diffusely spread sheets of tumour cells. The cells were large pleomorphic with eccentrically placed hyperchromic nuclei. Mitotic figures were evident. A scanty fibrous stroma, containing lymphocytes and histiocytes, separating the groups of tumour cells, along with few areas of haemorrhages were observed. Occurrence of seminoma in guinea fowl is unusual and hence reported.  相似文献   
57.
58.
59.
Vitiligo and psoriasis are both common skin disorders. However, psoriasis strictly confined to pre-existing vitiligo areas is rare and suggests a causal relationship. We report here on two patients with a strict anatomical colocalization of vitiligo and psoriasis. The histopathological examinations showed typical changes for both diseases together with a dense infiltrate of CD4+ and CD8+ T cells. By immunohistochemistry, intracytoplasmatic granzyme B and tumour necrosis factor alpha (TNF-alpha) were detected within the T-cell population, suggesting the functional activity of these cells and the creation of a local T helper 1 (Th1)-cytokine milieu. Additionally, in one patient we could identify anti-melanocytic T cells by tetramer staining and enzyme-linked immunospot (ELISPOT) analysis. These skin-infiltrating lymphocytes might trigger, by the local production of Th-1 cytokines such as TNF-alpha and interferon-gamma (IFN-gamma), the eruption of psoriatic plaques in patients with a genetic predisposition for psoriasis.  相似文献   
60.
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