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   5666篇
  免费   277篇
  国内免费   31篇
耳鼻咽喉   70篇
儿科学   148篇
妇产科学   131篇
基础医学   615篇
口腔科学   124篇
临床医学   436篇
内科学   1532篇
皮肤病学   22篇
神经病学   679篇
特种医学   311篇
外科学   792篇
综合类   11篇
预防医学   195篇
眼科学   56篇
药学   273篇
中国医学   9篇
肿瘤学   570篇
  2024年   6篇
  2023年   65篇
  2022年   95篇
  2021年   232篇
  2020年   121篇
  2019年   132篇
  2018年   205篇
  2017年   122篇
  2016年   168篇
  2015年   172篇
  2014年   267篇
  2013年   288篇
  2012年   478篇
  2011年   451篇
  2010年   221篇
  2009年   257篇
  2008年   364篇
  2007年   357篇
  2006年   363篇
  2005年   340篇
  2004年   286篇
  2003年   263篇
  2002年   199篇
  2001年   46篇
  2000年   54篇
  1999年   45篇
  1998年   37篇
  1997年   28篇
  1996年   21篇
  1995年   24篇
  1994年   13篇
  1993年   16篇
  1992年   27篇
  1991年   24篇
  1990年   18篇
  1989年   16篇
  1988年   19篇
  1987年   17篇
  1986年   9篇
  1985年   19篇
  1984年   13篇
  1983年   4篇
  1980年   5篇
  1979年   6篇
  1978年   7篇
  1976年   4篇
  1974年   4篇
  1972年   5篇
  1971年   5篇
  1966年   3篇
排序方式: 共有5974条查询结果,搜索用时 62 毫秒
991.
992.

Introduction

Several neurodegenerative brain proteinopathies, including Alzheimer's disease (AD), are associated with cerebral deposition of insoluble aggregates of α-synuclein. Previous studies reported a trend toward increased cerebrospinal fluid (CSF) α-synuclein (α-syn) concentrations in AD compared with other neurodegenerative diseases and healthy controls.

Methods

The pathophysiological role of CSF α-syn in asymptomatic subjects at risk of AD has not been explored. We performed a large-scale cross-sectional observational monocentric study of preclinical individuals at risk for AD (INSIGHT-preAD).

Results

We found a positive association between CSF α-syn concentrations and brain β-amyloid deposition measures as mean cortical standard uptake value ratios. We demonstrate positive correlations between CSF α-syn and both CSF t-tau and p-tau181 concentrations.

Discussion

Animal models presented evidence, indicating that α-syn may synergistically and directly induce fibrillization of both tau and β-amyloid. Our data indicate an association of CSF α-syn with AD-related pathophysiological mechanisms, during the preclinical phase of the disease.  相似文献   
993.
Neostigmine test (NT) is a pharmacological test, demonstrating a clinical improvement in patients affected by myasthenia gravis (MG). We aim to compare clinical evaluation and neurophysiological recordings by concentric-needle single-fiber electromyography (CN-SFEMG) in response to acute administration of neostigmine in ocular and generalized MG patients. Twenty-three MG patients (10 with ocular MG and 13 with generalized MG) were evaluated before and after 90 min neostigmine 0.5-mg administration. Clinical responsiveness was assessed by MG composite (MGC) scale. Neurophysiological evaluation by CN-SFEMG considered analysis of mean value of consecutive differences (MCD), single-pair jitter, and blocks. MGC scores significantly improved after NT in generalized MG patients (MGC 11.1?±?7.6 vs 9.1?±?6.7, p?=?0.02), whereas the improvement was not significant in the ocular group. CN-SFEMG recordings significantly improved after NT in generalized MG patients (MCD 58.9?±?18.8 vs 45.9?±?23.2 μs, p?=?0.003; single-pair jitter 49.8?±?26.9 vs 24.1?±?26.7%, p?=?0.0001; blocks 6.2?±?9.5 vs 2.6?±?7.4%, p?=?0.03) as well as in ocular MG patients (MCD 50.8?±?22.7 vs 40.1?±?22.9 μs, p?=?0.01; single-pair jitter 35.9?±?23.7 vs 20.0?±?25.1%, p?=?0.001). CN-SFEMG is a reliable tool to evaluate responsiveness to acute administration of neostigmine in MG. Moreover, neurophysiological modifications to NT could show subclinical improvement in ocular MG better than that of the clinical scale.  相似文献   
994.
995.
Journal of Neurology - In this independent, multicenter, retrospective study, we investigated the short-term persistence to treatment with first-line self-injectable or oral disease-modifying...  相似文献   
996.

Background

High frequency transcranial random noise stimulation (hf-tRNS) facilitates performance in several perceptual and cognitive tasks, however, little is known about the underlying modulatory mechanisms.

Objective

In this study we compared the effects of hf-tRNS to those of anodal and cathodal tDCS in a global motion direction discrimination task. An equivalent noise (EN) paradigm was used to assess how hf-tRNS modulates the mechanisms underlying local and global motion processing.

Method

Motion coherence threshold and slope of the psychometric function were estimated using an 8AFC task in which observers had to discriminate the motion direction of a random dot kinematogram presented either in the left or right visual hemi-field. During the task hf-tRNS, anodal and cathodal tDCS were delivered over the left hMT+. In a subsequent experiment we implemented an EN paradigm in order to investigate the effects of hf-tRNS on the mechanisms involved in visual motion integration (i.e., internal noise and sampling).

Results

hf-tRNS reduced the motion coherence threshold but did not affect the slope of the psychometric function, suggesting no modulation of stimulus discriminability. Anodal and cathodal tDCS did not produce any modulatory effects. EN analysis in the last experiment found that hf-tRNS modulates sampling but not internal noise, suggesting that hf-tRNS modulates the integration of local motion cues.

Conclusion

hf-tRNS interacts with the output neurons tuned to directions near to the directional signal, incrementing the signal-to-noise ratio and the pooling of local motion cues and thus increasing the sensitivity for global moving stimuli.  相似文献   
997.
Schizophrenia (SCZ) is a common and severe mental disorder. Genetic factors likely play a role in its pathophysiology as well as in treatment response. In the present study, we investigated the effects of several single nucleotide polymorphisms (SNPs) within 9 genes involved with antipsychotic (AP) mechanisms of action. Two independent samples were recruited. The Korean sample included 176 subjects diagnosed with SCZ and 326 healthy controls, while the Italian sample included 83 subjects and 194 controls. AP response as measured by the positive and negative syndrome scale (PANSS) was the primary outcome, while the secondary outcome was the SCZ risk. Exploratory analyses were performed on (1) symptom clusters response (as measured by PANSS subscales); (2) age of onset; (3) family history; and (4) suicide history. Associations evidenced in the primary analyses did not survive to the FDR correction. Concerning SCZ risk, we partially confirmed the associations among COMT and MAPK1 genetic variants and SCZ. Finally, our exploratory analysis suggested that CHRNA7 and HTR2A genes may modulate both positive and negative symptoms responses, while PLA2G4A and SIGMAR1 may modulate respectively positive and negative symptoms responses. Moreover, GSK3B, HTR2A, PLA2G4A, and S100B variants may determine an anticipation of SCZ age of onset. Our results did not support a primary role for the genes investigated in AP response as a whole. However, our exploratory findings suggested that these genes may be involved in symptom clusters response.  相似文献   
998.
999.
Erectile dysfunction could be an early sign of endothelial dysfunction and, therefore, of cardiovascular disease, with which it shares many risk factors. Among reversible risk factors, physical inactivity is one of the most important. Regular physical exercise has been shown to improve erectile function through different mechanisms involving glucose and lipid metabolism, regulation of arterial pressure, production of nitric oxide and hormonal modulation. Furthermore, exercise shows a synergistic effect with the drugs commonly used in the treatment of impotence. Since many patients with erectile dysfunction may have underlying cardiovascular disease, the evaluation of individual cardiovascular risk is mandatory before prescribing physical exercise. When exercise is not contraindicated, the most appropriate protocol must be chosen, considering the individual characteristics of the patient. Both aerobic and anaerobic/resistance protocols have proven effective. However, meta‐analytic studies show that aerobic exercise with moderate‐to‐vigorous intensity is the most effective in improving erection. Testosterone is an important modulator of physical performance, and its blood levels must always be evaluated in patients with erectile dysfunction.  相似文献   
1000.
The cytomorphologic evaluation of serous cavity specimens can quickly determine the cause of an effusion as well as the presence or absence of a neoplastic process. Ancillary tests such as immunohistochemistry and fluorescence in situ hybridization are frequently used to help to definitively identify malignant cells, determine a site of origin, and distinguish between malignant and reactive mesothelial proliferations. In recent years, microRNAs (miRNAs) have been increasingly evaluated in cytologic specimens, including those from serous cavities. The examination of miRNA is attractive because of the stability of miRNA in such specimens and data suggesting that miRNA can provide prognostic and therapeutic information in addition to its role in diagnosis. Furthermore, miRNAs exist within extracellular exosomes, and this allows for their analysis in specimens that contain only rare malignant cells, degenerated cells, or obscuring components. This review discusses the technical aspects of specimen processing for miRNA analysis, recent studies of miRNA expression in malignant serous cavity specimens, and the potential importance of miRNA expression analysis for serous cavity specimens in the near future.  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