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   6975篇
  免费   339篇
  国内免费   266篇
耳鼻咽喉   64篇
儿科学   69篇
妇产科学   9篇
基础医学   1373篇
口腔科学   12篇
临床医学   281篇
内科学   223篇
皮肤病学   16篇
神经病学   3744篇
特种医学   69篇
外科学   122篇
综合类   825篇
预防医学   88篇
眼科学   45篇
药学   415篇
中国医学   195篇
肿瘤学   30篇
  2023年   44篇
  2022年   50篇
  2021年   123篇
  2020年   124篇
  2019年   123篇
  2018年   112篇
  2017年   127篇
  2016年   143篇
  2015年   135篇
  2014年   211篇
  2013年   256篇
  2012年   328篇
  2011年   315篇
  2010年   328篇
  2009年   301篇
  2008年   347篇
  2007年   346篇
  2006年   342篇
  2005年   297篇
  2004年   286篇
  2003年   311篇
  2002年   242篇
  2001年   194篇
  2000年   182篇
  1999年   181篇
  1998年   162篇
  1997年   146篇
  1996年   139篇
  1995年   130篇
  1994年   130篇
  1993年   136篇
  1992年   100篇
  1991年   121篇
  1990年   99篇
  1989年   86篇
  1988年   90篇
  1987年   102篇
  1986年   181篇
  1985年   164篇
  1984年   74篇
  1983年   67篇
  1982年   51篇
  1981年   65篇
  1980年   52篇
  1979年   12篇
  1978年   8篇
  1977年   6篇
  1976年   5篇
  1974年   2篇
  1973年   3篇
排序方式: 共有7580条查询结果,搜索用时 15 毫秒
1.
2.
为了保证电子设备在复杂的电磁环境中正常运行,需要对其进行电磁防护。传统的电磁防护方法尽管已取得较好的防护效果,但是还存在一定的不足。为了弥补传统电磁防护的不足,本研究提出基于神经抗扰机制的电磁仿生方法,并具体提出基于神经元抗扰机制的新型方波发生器。采用最接近生物神经元电生理活动的数学模型Hodgkin-Huxley模型对新型方波发生器进行设计。利用Matlab的Simulink工具箱搭建方波发生器的仿真程序,分析方波信号占空比的特性,得到模型参数对占空比的影响程度。基于田口方法的望小特性优化方波发生器的模型参数,从而得到特定占空比。该方波发生器可为智能电子设备提供稳定可靠的方波信号。  相似文献   
3.
4.
The nervous system and the immune system individually play important roles in regulating the processes necessary to maintain physiological homeostasis, respond to acute stress and protect against external threats. These two regulating systems for maintaining the living body had often been assumed to function independently. Allergies develop as a result of an overreaction of the immune system to substances that are relatively harmless to the body, such as food, pollen and dust mites. Therefore, it has been generally supposed that the development and pathogenesis of allergies can be explained through an immunological interpretation. Recently, however, neuro-immune crosstalk has attracted increasing attention. Consequently, it is becoming clear that there is close morphological proximity and physiological and pathophysiological interactions between neurons and immune cells in various peripheral tissues. Thus, researchers are now beginning to appreciate that neuro-immune interactions may play a role in tissue homeostasis and the pathophysiology of immune-mediated disease, but very little information is available on the molecular basis of these interactions. Mast cells are a part of the innate immune system implicated in allergic reactions and the regulation of host–pathogen interactions. Mast cells are ubiquitous in the body, and these cells are often found in close proximity to nerve fibers in various tissues, including the lamina propria of the intestine. Mast cells and neurons are thought to communicate bidirectionally to modulate neurophysiological effects and mast cell functions, which suggests that neuro-immune interactions may be involved in the pathology of allergic diseases.  相似文献   
5.
Introduction: RNS60 is a novel immune-modulatory agent that has shown neuroprotective effects in amytrophic lateral sclerosis (ALS) preclinical models. RNS60 is administered by weekly intravenous infusion and daily nebulization. The objective of this pilot open-label trial was to test the feasibility, safety, and tolerability of long-term RNS60 administration in ALS patients. Methods: The planned treatment duration was 23 weeks and the primary outcomes were safety and tolerability. Secondary outcomes included PBR28 positron emission tomography (PET) imaging and plasma biomarkers of inflammation. Results: Sixteen participants with ALS received RNS60 and 13 (81%) completed 23 weeks of RNS60 treatment. There were no serious adverse events and no participants withdrew from the trial due to drug-related adverse events. There were no significant changes in the biomarkers. Discussion: Long-term RNS60 administration was safe and well-tolerated. A large, multicenter, phase II trial of RNS60 is currently enrolling participants to test the effects of RNS60 on ALS biomarkers and disease progression. Muscle Nerve 59 :303–308, 2019  相似文献   
6.

Background

Chronic stress exposure increases the risk of developing various neuropsychiatric illnesses. The behavioral sequelae of stress correlate with dendritic hypertrophy and glutamate-related synaptic remodeling at basolateral amygdala projection neurons (BLA PNs). Yet, though BLA PNs are functionally heterogeneous with diverse corticolimbic targets, it remains unclear whether stress differentially impacts specific output circuits.

Methods

Confocal imaging was used to reconstruct the morphology of mouse BLA PNs with the aid of retrograde tracing and biocytin staining. The synaptic activity in these neurons was measured with in vitro electrophysiology, and anxiety-like behavior of the mice was assessed with the elevated plus maze and open field test.

Results

Chronic restraint stress (CRS) produced dendritic hypertrophy across mouse BLA PNs, regardless of whether they did (BLA→dorsomedial prefrontal cortex [dmPFC]) or did not (BLA?dmPFC) target dmPFC. However, CRS increased the size of dendritic spine heads and the number of mature, mushroom-shaped spines only in BLA?dmPFC PNs, sparing neighboring BLA→dmPFC PNs. Moreover, the excitatory glutamatergic transmission was also selectively increased in BLA?dmPFC PNs, and this effect correlated with CRS-induced increases in anxiety-like behavior. Segregating BLA?dmPFC PNs based on their targeting of ventral hippocampus (BLA→ventral hippocampus) or nucleus accumbens (BLA→nucleus accumbens) revealed that CRS increased spine density and glutamatergic signaling in BLA→ventral hippocampus PNs in a manner that correlated with anxiety-like behavior.

Conclusions

Chronic stress caused BLA PN neuronal remodeling with a previously unrecognized degree of circuit specificity, offering new insight into the pathophysiological basis of depression, anxiety disorders, and other stress-related conditions.  相似文献   
7.
8.
Subjective tinnitus is the most common type of tinnitus, which is the manifestation of pathological activities in the brain. It happens in a substantial portion of the general population and brings significant burden to the society. Severe subjective tinnitus can lead to depression and insomnia and severely affects patients’ quality of life. However, due to poor understanding of its etiology and pathogenesis, treatment of subjective tinnitus remains challenging. In recent decades, a growing number of studies have shown that subjective tinnitus is related to lesion-induced neural plasticity of auditory and non-auditory central systems. This article reviews cellular mechanisms of neural plasticity in subjective tinnitus to provide further understanding of its pathogenesis.  相似文献   
9.
Due to novel gene therapy opportunities, genetic screening is no longer restricted to familial cases of ALS (FALS) cases but also aplies to the sporadic populations (SALS). Screening of four main genes (C9orf72, SOD1, TARDBP and FUS) identified the causes in 15% of Amyotrophic Lateral Sclerosis (ALS) patients (two third of the familial cases and 8% of the sporadic ones) but their respective contribution to ALS phenotype varies according the age of disease onset. The genetic overlap between ALS and other diseases is expanding and includes frontotemporal dementia, Paget's Disease of Bone, myopathy for adult cases, HSP and CMT for young cases highlighing the importance of retrieving the exhaustive familial history for each indivdual with ALS. Incomplete disease penetrance, diversity of the possible phenotypes, as well as the lack of confidence concerning the pathogenicity of most identified variants and/or possible oligogenic inheritance are burdens of ALS genetic counseling to be delivered to patients and at risk individuals. The multitude of rare ALS genetic causes identifed seems to converge to similar cellular pathways leading to inapropriate response to stress emphacising new potential therapeutic options for the disease.  相似文献   
10.
目的:本研究旨在阐明肾细胞癌下调蛋白1(DRR1)在小鼠大脑组织中的表达谱及相关生物学功能。方法:首先,通过real time RT-PCR的方法明确在不同发育阶段的小鼠大脑组织中DRR1的表达水平;利用免疫荧光染色法检测DRR1在原代培养的神经干细胞以及神经元中的表达情况。其次,采用real time RT-PCR的方法分别检测DRR1在诱导分化前后的神经干细胞中的表达水平。最后,利用慢病毒感染的方法在原代培养的神经干细胞以及神经元中分别上调或者下调DRR1的表达,进而评价DRR1对原代培养的神经干细胞的分化以及神经元的突起形成的影响。结果:DRR1在各个发育阶段的小鼠大脑组织中均有表达,并且其表达水平随发育呈逐渐上升趋势。DRR1在分化前后的神经干细胞中均表达,但在诱导分化后的细胞中的表达水平显著高于其分化前的表达水平(P<0.01)。同时,过表达DRR1可促进神经干细胞的分化。DRR1在分化成熟的原代神经元的树突以及轴突均有表达,且DRR1的表达水平影响神经元的突起形成(P<0.01)。结论:DRR1在各发育阶段的小鼠大脑及分化前后的神经干细胞中均有表达,其作用与神经干细胞分化调控以及神经元突起形成有关。  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