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   5586篇
  免费   241篇
  国内免费   28篇
耳鼻咽喉   74篇
儿科学   143篇
妇产科学   111篇
基础医学   559篇
口腔科学   122篇
临床医学   401篇
内科学   1543篇
皮肤病学   25篇
神经病学   666篇
特种医学   319篇
外科学   801篇
综合类   15篇
预防医学   190篇
眼科学   57篇
药学   263篇
中国医学   10篇
肿瘤学   556篇
  2024年   8篇
  2023年   69篇
  2022年   116篇
  2021年   234篇
  2020年   119篇
  2019年   130篇
  2018年   200篇
  2017年   119篇
  2016年   160篇
  2015年   171篇
  2014年   261篇
  2013年   281篇
  2012年   468篇
  2011年   425篇
  2010年   216篇
  2009年   252篇
  2008年   361篇
  2007年   344篇
  2006年   360篇
  2005年   338篇
  2004年   286篇
  2003年   261篇
  2002年   205篇
  2001年   44篇
  2000年   38篇
  1999年   43篇
  1998年   35篇
  1997年   27篇
  1996年   24篇
  1995年   23篇
  1994年   13篇
  1993年   15篇
  1992年   21篇
  1991年   21篇
  1990年   15篇
  1989年   12篇
  1988年   14篇
  1987年   6篇
  1986年   9篇
  1985年   18篇
  1984年   13篇
  1983年   5篇
  1982年   4篇
  1980年   5篇
  1979年   6篇
  1978年   10篇
  1976年   5篇
  1972年   4篇
  1969年   5篇
  1966年   3篇
排序方式: 共有5855条查询结果,搜索用时 13 毫秒
981.

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   
982.
983.
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   
984.
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   
985.
986.
987.
Abnormal levels of beta amyloid (Aβ42) and tau protein concentrations in the cerebral spinal fluid (CSF) have been largely described in Alzheimer’s disease (AD). Thus, CSF analysis of these biomarkers has been incorporated in recent AD diagnostic criteria, and it is increasingly performed for neurodegenerative dementia diagnostic workout in clinical setting. Nevertheless, the precise biomarkers CSF features in neurodegenerative dementia, either AD or Frontotemporal dementia (FTD), are still not fully clear today. This is mainly due to lack of CSF clear cutoff values due to a well-known intersite (but even intrasite) variability of CSF procedures, ranging from collection to analysis. Applying CSF biomarker ratios, rather than their single values could represent a useful tool, especially for the differential diagnosis of different forms of dementia. We explored clinical values of six CSF ratios (by combining Aβ42 and tau) in order to better discriminate between AD and FTD; we identified Aβ42/p-Tau181 ratio as a potential good candidate for helping differentiating AD from FTD in the clinical practice.  相似文献   
988.

Aim

To analyze the impact of 18F-fluorodeoxyglucose-PET/CT (PET/CT) in the radiotherapy (RT) planning strategy in HNC, correlating CT-scan and PET/CT performances.

Materials and methods

Inclusion criteria were: age >18 years old, histologically proven head and neck cancer (HNC), patients candidate to definitive RT ± chemotherapy, stage of disease by means of PET/TC and CT-scan performed at our Cancer Care Center.

Results

Sixty patients were analyzed. The following primary tumor sites were investigated: nasopharynx (13%), oropharynx (42%), oral cavity (32%) and larynx non-glottic (13%). Globally, PET/CT findings caused changes on nodal radiation treatment volumes in 10% of all the population of study. Specifically, in 5 cases out of 19 oral cavity tumors (26%), PET/CT detected neck-nodes positive (not detected at CT-scan). These findings have allowed to change the patients management, including PET/CT neck-nodes positive in the high-risk RT volumes.

Conclusion

In the RT planning strategy, the present findings support the use of PET/CT to improve upfront regional staging of HNC disease, particularly for oral cavity tumors. Further investigations are advocated to evaluate if this strategy could impact on long-term outcomes in terms of local control and overall survival.
  相似文献   
989.

Purpose

The aim of our study was to evaluate factors influencing effectiveness of percutaneous microwave ablation (MWA) in patients with small hepatocellular carcinoma (HCC) (<3 cm).

Materials and methods

Between December 2007 and August 2015, 49 patients with 65 previously histological typed HCC were treated in a total of 61 sessions. Tumours were subdivided into central (>3 cm from the capsule) (n = 22) and peripheral (<3 cm from the capsule) (n = 43). Imaging follow-up was performed at 1, 3, 6, and 12 months after treatment, then annually. Mean follow-up period was 18 months (range 1–55). Location of the lesion, age, sex, and underlying disease of the patients was analyzed and related with efficacy.

Results

Technical success was obtained in all cases. Residual disease was registered in 21 lesions (32.3 %): 13 were peripheral and 8 were central. Twelve of them were retreated with percutaneous MWA. Local recurrence was recorded in 8 lesions (12.3 %): 5 were retreated with MWA. No significant difference in terms of effectiveness was observed in lesions located in a central position and those situated in the peripheral position. Age, sex, and underlying disease not influenced results. Only one major complication was observed. The rate of minor complications was 24.5 %. Mortality at 30 days was 0 %.

Conclusions

Our results encourage the role of MWA in the treatment of small HCC. More numerous series and randomized studies are necessary to state the role of MWA and to select cases in which MWA may be more effective and safer than RFA.
  相似文献   
990.

Introduction

We investigated the clinical differences between familial and sporadic frontotemporal dementia (FTD), screening for mutations in known FTD genes.

Methods

We diagnosed 22 affected individuals belonging to eight families and 43 sporadic cases with FTD in Apulia, Southern Italy, in 2 years. Mutations in common causative FTD genes (GRN, MAPT, VCP, and TARDBP) and C9ORF72 expansions were screened.

Results

Behavioral variant of FTD was the most common clinical subtype (50% and 69% in familial and sporadic cases, respectively). Social conduct impairment/disinhibition, loss of insight, and inflexibility were the most frequent clinical features observed at onset. One new mutation was identified in GRN in family A.

Discussion

Disease onset in sporadic FTD was more frequently characterized by a clustering of behavioral symptoms with apathy and loss of personal hygiene. Mutations in common causative FTD genes are not a major cause of familial and sporadic FTD in the Southern Italian population.  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