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   4061篇
  免费   278篇
  国内免费   6篇
耳鼻咽喉   49篇
儿科学   67篇
妇产科学   92篇
基础医学   494篇
口腔科学   82篇
临床医学   576篇
内科学   654篇
皮肤病学   47篇
神经病学   340篇
特种医学   159篇
外国民族医学   3篇
外科学   831篇
综合类   21篇
一般理论   4篇
预防医学   309篇
眼科学   37篇
药学   277篇
中国医学   9篇
肿瘤学   294篇
  2023年   18篇
  2022年   61篇
  2021年   156篇
  2020年   78篇
  2019年   116篇
  2018年   130篇
  2017年   126篇
  2016年   99篇
  2015年   146篇
  2014年   214篇
  2013年   253篇
  2012年   373篇
  2011年   424篇
  2010年   250篇
  2009年   200篇
  2008年   311篇
  2007年   292篇
  2006年   270篇
  2005年   209篇
  2004年   185篇
  2003年   137篇
  2002年   125篇
  2001年   16篇
  2000年   15篇
  1999年   20篇
  1998年   20篇
  1997年   9篇
  1996年   5篇
  1995年   6篇
  1994年   8篇
  1993年   2篇
  1992年   9篇
  1991年   4篇
  1990年   4篇
  1989年   8篇
  1988年   8篇
  1987年   6篇
  1986年   5篇
  1985年   2篇
  1984年   4篇
  1983年   3篇
  1982年   5篇
  1980年   1篇
  1979年   4篇
  1977年   1篇
  1976年   2篇
  1975年   1篇
  1973年   1篇
  1972年   1篇
  1965年   1篇
排序方式: 共有4345条查询结果,搜索用时 15 毫秒
11.
We have investigated the relative contributions of oxygen and glucose deprivation to ischaemic neurodegeneration in organotypic hippocampal slice cultures. Cultures prepared from 10-day-old rats were maintained in vitro for 14 days and then deprived of either oxygen (hypoxia), glucose (hypoglycaemia), or both oxygen and glucose (ischaemia). Hypoxia alone induced degeneration selectively in CA1 pyramidal cells and this was greatly potentiated if glucose was removed from the medium. We have also characterised the effects of both pre-and post-treatment using glutamate receptor antagonists and the sodium channel blocker tetrodotoxin (TTX). Neuronal death following either hypoxia or ischaemia was prevented by pre-incubation with CNQX, MK-801 or tetrodotoxin. MK-801 or CNQX also prevented death induced by either hypoxia or ischaemia if added immediately post-insult, however, post-insult addition of TTX prevented hypoxic but not ischaemic damage. Organotypic hippocampal slice cultures are sensitive to both NMDA and non-NMDA glutamate receptor blockade and thus represent a useful in vitro system for the study of ischaemic neurodegeneration paralleling results reported using in vivo models of ischaemia.  相似文献   
12.
13.
14.
15.
The Authors describe two monochorionic twins affected by Niemann-Pick disease type C with a clinical picture beginning in the neonatal age and with a progressive mental deterioration, loss of speech and spasticity started at 30 months. The importance of cultured skin fibroblasts is emphasized. The evidence of a defective intracellular cholesterol esterification is established as an intrinsic feature of Niemann-Pick disease type C.  相似文献   
16.
OBJECTIVE: To examine the clinical significance of acoustic data recorded by the SNAP home polysomnography system (SNAP Laboratories, Glenview, IL). STUDY DESIGN AND SETTING: Retrospective analysis of SNAP data from 59 patients undergoing evaluation for sleep apnea at the University of Nebraska Medical Center and an associated private practice in Omaha, NE. RESULTS: Snoring did not correlate with anthropometric variables such as body mass index and neck circumference. Statistical analysis showed no correlation between respiratory disturbance index and the maximum or average loudness of snoring. Average loudness was predictive of the presence of sleep apnea. Spectral analysis of snoring sonography found that the proportion of snoring events associated with a palatal source correlated strongly with the loudness of snoring. CONCLUSION: These data suggest that analysis of snoring has limited utility in the evaluation of the patient with sleep apnea but may be able to select patients who would benefit from palatal procedures to reduce snoring.  相似文献   
17.
From 1-1-1981 to 3-31-1985, 367 subjects (227 males and 140 females) were examined by means of TL-201 myocardial scintigraphy for diagnostic purpose. A follow-up period, 5 years maximum, was run in order to assess the prognostic value of the three equivalents of transient myocardial ischemia which can be demonstrated by the test (angina, reversible hypoperfusion, and ST-T segment changes). The end points were myocardial infarction and/or sudden death. Three-hundred fifty-four patients complied (96%). During the observation period 9 severe ischemic events (SIE) occurred: 5 myocardial infarctions and 4 sudden deaths. As far as the predictivity of SIE is concerned, the "t" test for independent samples showed a statistically significant difference between the group of patients with no signs of ischemia and the group with positive scintiscan (p less than 0.05) and with the three equivalents of ischemia all together (p less than 0.05). Moreover, in the sub-group of patients with pathological scintigraphic results the probability for SIE to occur was statistically different in the patients with no hypoperfusion in the region supplied by the anterior descending coronary artery and in those with pathological scintigraphic findings in that region (p less than 0.05). In our opinion, the above data demonstrate the pathological signs noticeable with stress myocardial TL-201 scintiscan to have prognostic value.  相似文献   
18.
Summary Diffuse distribution of small, faintly staining, beaded deposits of rat immunoglobulin M (IgM) around the glomerular capillary blood vessels, and a more intensely staining larger deposition in the mesangium, were observed on the kidney sections of normal rats. As glomerular-fixed nephritogenic antigens are known to be present on the epithelial aspect of the glomerular basement membrane (GBM), especially at the soles of foot processes and at the slit pores, it was assumed that the IgM antibodies were directed against these antigens. Investigation by immunofluorescent antibody double-staining techniques of rat kidney sections obtained from normal and rabbit anti-FX1A-injected rats stained for the nephritogenic antigen showed that a number of antigenic sites in the glomeruli and in the mesangium shared antibody hits by heterologous rabbit IgG and autologous rat IgM antibodies. Most sites in the glomeruli stained specifically for rat IgM or rabbit IgG, but preferentially for the latter. The intensely fluorescent mesangial deposits stained mainly for rat IgM, indicating that at these sites the antigenic material was virtually saturated, while areas at the entry to the mesangial space also stained for rabbit IgG, indicating that at these locations free nephritogenic epitopes were still available for reaction with the anti-FX1A antibody. Western blot analysis have shown that the rabbit anti-rat FX1A IgG and the rat anti-rat KF3 IgM antibodies are directed against the same renal tubular-derived antigen with a molecular weight of 70,000. These experimental findings collectively demonstrate that the heterologous IgG and autologous IgM antibodies are directed against the same nephritogenic antigen, which is found in the glomeruli, the mesangium and the proximal convoluted tubules. Thus, the IgM autoantibody has a possible physiological role but, in addition, there is evidence of active immunophagocytic events, manifested in a rapid and continuous entrapment and expulsion of macromolecules after their processing by the mesangial cells of normal and passive Heymann nephritis rats.  相似文献   
19.
Human immunodeficiency virus (HIV)-related opportunistic infections continue to occur in patients who are newly diagnosed with HIV infection, those in the early course of highly active antiretroviral therapy or nonadherent to HIV care, and other immunosuppressed individuals. One of the most common opportunistic infections in these patients is Pneumocystis pneumonia. CD8+ T cells are recruited to the lung after P. carinii infection and have been associated with both lung injury and host defense. This variability may be due to subpopulations of CD8+ T cells recruited to the lung. We have previously shown using adoptive transfer studies that in vivo-generated T-cytotoxic-1 (Tc1) CD8+ T cells, defined by the secretion of gamma interferon (IFN-gamma), have effector activity against Pneumocystis spp. in vitro as well as in vivo. To better understand the mechanisms of these effects, we generated, expanded, and tested Tc1 and Tc2 CD8+ T cells specific for P. murina ex vivo. Tc1-polarized CD8+ T cells secreted higher levels of IFN-gamma and granulocyte-macrophage colony-stimulating factor (GM-CSF) and lower levels of interleukin-4 (IL-4), IL-5, IL-10, and IL-13 than Tc2 CD8+ T cells when stimulated with P. murina antigen. Moreover, Tc1 CD8+ T cells demonstrated enhanced effector activity in a macrophage-mediated killing assay which was independent of cell contact. The augmentation in macrophage-mediated P. murina killing was significantly abrogated when GM-CSF was neutralized in the Tc1 CD8+ T cells. These data support the possibility that antigen-specific GM-CSF secretion is critical for effector activity of P. murina-specific Tc1 CD8+ T cells in vitro.  相似文献   
20.
Although no prospective epidemiological studies have evaluated the relationship between family interactions and the development of borderline personality disorder (BPD), there is considerable evidence for the central role of family interactions in the development of BPD. This paper describes the role of family interactions or processes, especially those that might be regarded as invalidating or conflictual, negative or critical, and the absence of more validating, positive, supportive, empathic interactions, in the development of BPD. Perhaps more importantly, the proposed model considers how these parental and family behaviors transact with the child's own behaviors and emotional vulnerabilities, resulting in a developmental model of BPD that is neither blaming of the family member with BPD nor of her or his parents and caregivers, and has important and specific implications for both prevention and intervention.  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