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   13552篇
  免费   527篇
  国内免费   293篇
耳鼻咽喉   150篇
儿科学   22篇
妇产科学   16篇
基础医学   3180篇
口腔科学   49篇
临床医学   258篇
内科学   322篇
皮肤病学   6篇
神经病学   7686篇
特种医学   102篇
外科学   271篇
综合类   1041篇
预防医学   65篇
眼科学   162篇
药学   876篇
  1篇
中国医学   117篇
肿瘤学   48篇
  2023年   60篇
  2022年   66篇
  2021年   154篇
  2020年   184篇
  2019年   159篇
  2018年   135篇
  2017年   195篇
  2016年   194篇
  2015年   221篇
  2014年   334篇
  2013年   403篇
  2012年   449篇
  2011年   546篇
  2010年   494篇
  2009年   512篇
  2008年   554篇
  2007年   489篇
  2006年   549篇
  2005年   404篇
  2004年   399篇
  2003年   439篇
  2002年   372篇
  2001年   329篇
  2000年   306篇
  1999年   290篇
  1998年   291篇
  1997年   292篇
  1996年   251篇
  1995年   322篇
  1994年   284篇
  1993年   316篇
  1992年   252篇
  1991年   265篇
  1990年   239篇
  1989年   227篇
  1988年   252篇
  1987年   269篇
  1986年   345篇
  1985年   503篇
  1984年   466篇
  1983年   339篇
  1982年   317篇
  1981年   250篇
  1980年   239篇
  1979年   133篇
  1978年   89篇
  1977年   48篇
  1976年   42篇
  1975年   26篇
  1973年   26篇
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
1.
目的:探讨脊柱微创经皮椎间孔镜日间手术全程化管理模式的构建与效果。方法:选取2017年3月1日~2018年3月31日行经皮椎间孔镜下髓核摘除术的94例腰椎间盘突出症患者作为对照组,采取常规住院管理模式。选取2018年4月1日~2019年4月30日行经皮椎间孔镜下髓核摘除术日间手术的88例腰椎间盘突出症患者作为日间组,实施涵盖门诊、病房、出院后随访的全程化日间手术管理模式。比较两组临床效果。结果:两组患者术后各期视觉模拟评分法(VAS)、JOA、ODI评分较术前改善(P<0.05),两组术后各期VAS、JOA、ODI评分及并发症发生率比较差异无统计学意义(P>0.05)。日间组术前等待时间、住院时间、直接医疗费用低于对照组(P<0.01),患者满意度高于对照组(P<0.05)。结论:经皮椎间孔镜日间手术全程化管理模式应用于腰椎间盘突出症患者临床疗效较好,具有可行性、安全性、有效性,同时在提高医疗资源的利用率、降低住院费用方面具有明显优势。  相似文献   
2.
Circadian rhythms are 24-hour natural rhythms regulated by the suprachiasmatic nucleus, also known as the "master clock". The retino-hypothalamic tract entrains suprachiasmatic nucleus with photic information to synchronise endogenous circadian rhythms with the Earth’s light-dark cycle. However, despite the robustness of circadian rhythms, an unhealthy lifestyle and chronic photic disturbances cause circadian rhythm disruption in the suprachiasmatic nucleus’s TTFL loops via affecting glutamate and γ-aminobutyric acid-mediated neurotransmission in the suprachiasmatic nucleus. Recently, considerable evidence has been shown correlating CRd with the incidence of Alzheimer's disease. The present review aims to identify the existence and signalling of endocannabinoids in CRd induced Alzheimer's disease through retino-hypothalamic tract- suprachiasmatic nucleus-cortex. Immunohistochemistry has confirmed the expression of cannabinoid receptor 1 in the suprachiasmatic nucleus to modulate the circadian phases of the master clock. Literature also suggests that cannabinoids may alter activity of suprachiasmatic nucleus by influencing the activity of their major neurotransmitter γ-aminobutyric acid or by interacting indirectly with the suprachiasmatic nucleus’s two other major inputs i.e., the geniculo-hypothalamic tract-mediated release of neuropeptide Y and serotonergic inputs from the dorsal raphe nuclei. Besides, the expression of cannabinoid receptor 2 ameliorates cognitive deficits via reduction of tauopathy and microglial activation. In conclusion, endocannabinoids may be identified as a putative target for correcting CRd and decelerating Alzheimer’s disease.  相似文献   
3.
Cyanidin-3-glucoside (C3G) is a well-known natural anthocyanin with antioxidant and anti-inflammatory properties. In this study, we explored the role and action mechanism of C3G in high glucose (HG)-induced damage of human nucleus pulposus cells (HNPCs). Cell viability was assessed by CCK-8 assay. TUNEL assay was performed for detecting apoptotic rate. Western blot was performed to determine the expression levels of cl-caspase-3, caspase-3, Bax, Bim, collagen II, aggrecan, MMP-3, MMP-13, and ADAMTS5. Reactive oxygen species (ROS) generation was analyzed using DCFH-DA staining. The Nrf2 was knocked down or overexpressed in HNPCs through transfection with si-Nrf2 or pcDNA3.0-Nrf2. C3G treatment (12.5, 25, and 50 μM) improved cell viability of HNPCs under HG condition. HG-induced cell apoptosis of HNPCs was attenuated by C3G with decreased apoptotic rate and relative levels of cl-caspase-3/caspase-3, Bax, and Bim. C3G treatment caused significant increase in expression levels of collagen II and aggrecan and decrease in the relative levels of MMP-3, MMP-13, and ADAMTS5. After treatment with C3G, ROS generation in HNPCs was markedly reduced. Treatment with N-acetylcysteine (NAC) reversed HG-induced cell apoptosis and extracellular matrix (ECM) degradation. C3G treatment induced the expression of Nrf2 and HO-1 in HG-induced HNPCs. Moreover, knockdown of Nrf2 reversed the inhibitory effect of C3G on ROS production. Summarily, C3G exerted a protective effect on ROS-mediated cellular damage in HNPCs under HG condition, which was attributed to the induction of the Nrf2/HO-1 signaling pathway.  相似文献   
4.
目的 探讨尾状核指数对帕金森病(PD)双侧苍白球内侧部(GPi)脑深部电刺激术(DBS)疗效的影响。方法 回顾性分析2018年8月至2020年12月双侧GPi-DBS治疗的36例PD的临床资料。术前应用MRI测量尾状核指数、Evans指数及第三脑室宽度。术前、术后6个月应用39项帕金森病问卷(PDQ-39)评分、统一帕金森病评定量表Ⅲ(UPDRS-Ⅲ)评分、左旋多巴等效日剂量(LEDD)评估疗效。根据术后6个月UPDRS-Ⅲ评分分为改善组(n=26)与恶化组(n=10)。结果 术后6个月,PDQ-39评分、UPDRS-Ⅲ评分、LEDD均明显降低(P<0.05)。恶化组尾状核指数、第三脑室宽度较改善组明显增大(P<0.05),而Evans指数无明显变化(P>0.05)。多因素logistic回归分析显示尾状核指数≥0.16(OR=1.76;95% CI 1.09~3.18;P=0.017)是PD术后UPDRS-Ⅲ评分恶化的独立影响因素。结论 双侧GPi-DBs明显改善PD症状,尾状核指数可用于评估PD病人双侧GPi-DBS后运动功能。  相似文献   
5.
Objective Neonatal exposure to propofol has been reported to cause neurotoxicity and neurocognitive decline in adulthood; however, the underlying mechanism has not been established.Methods SD rats were exposed to propofol on postnatal day 7(PND-7). Double-immunofluorescence staining was used to assess neurogenesis in the hippocampal dentate gyrus(DG). The expression of pAkt and p27 were measured by western blotting. The Morris water maze, novel object recognition test,and object location test we...  相似文献   
6.
目的探讨不同切口下白内障超声乳化吸除术治疗硬核白内障的效果及对患者视力水平的影响。方法将76例(86眼)硬核白内障患者按照手术切口大小分为研究组(39例,44眼)与对照组(37例,42眼)。研究组行1.8 mm微切口同轴超声乳化吸除术,对照组行3.0 mm标准切口白内障超声乳化吸除术。比较两组患者手术中有效超声乳化时间、超声乳化能量,比较术前、术后1 d、术后7 d、术后30 d患者眼压、患眼裸眼视力、角膜散光度、泪膜功能,比较两组术后并发症发生率。结果两组有效超声乳化时间与超声乳化能量比较差异无统计学意义(P>0.05)。术后1 d、7 d研究组及术后1 d对照组眼压显著低于术前(P<0.05或0.01),术后各时间点两组眼压比较差异无统计学意义(P>0.05);术后各时间点两组裸眼视力均较术前显著提升(P<0.01),研究组较对照组提升更显著(P<0.01);术后30 d研究组角膜散光度显著低于术前(P<0.01),术后1 d、7 d对照组角膜散光度显著高于术前(P<0.05或0.01),研究组术后各时点角膜散光度均显著低于对照组(P<0.05或0.01)。术后各时点两组泪膜破裂时间均显著短于术前(P<0.01),研究组显著长于对照组(P<0.05或0.01);术后1 d、7 d研究组及术后各时点对照组基础泪液分泌量均显著少于术前(P<0.05或0.01),研究组显著多于对照组(P<0.05或0.01)。两组并发症发生率比较差异无统计学意义(P>0.05)。结论1.8 mm同轴微创超声乳化吸除术治疗硬核白内障安全有效,术后患者眼压较为稳定,视力水平恢复较好,角膜散光度降低,泪膜功能恢复良好。  相似文献   
7.
Employing cyto‐, myelo‐, and chemoarchitectural staining techniques, we analyzed the structure of the hippocampal formation in the banded mongoose and domestic ferret, species belonging to the two carnivoran superfamilies, which have had independent evolutionary trajectories for the past 55 million years. Our observations indicate that, despite the time since sharing a last common ancestor, these species show extensive similarities. The four major portions of the hippocampal formation (cornu Ammonis, dentate gyrus, subicular complex, and entorhinal cortex) were readily observed, contained the same internal subdivisions, and maintained the topological relationships of these subdivisions that could be considered typically mammalian. In addition, adult hippocampal neurogenesis was observed in both species, occurring at a rate similar to that observed in other mammals. Despite the overall similarities, several differences to each other, and to other mammalian species, were observed. We could not find evidence for the presence of the CA2 and CA4 fields of the cornu Ammonis region. In the banded mongoose the dentate gyrus appears to be comprised of up to seven lamina, through the sublamination of the molecular and granule cell layers, which is not observed in the domestic ferret. In addition, numerous subtle variations in chemoarchitecture between the two species were observed. These differences may contribute to an overall variation in the functionality of the hippocampal formation between the species, and in comparison to other mammalian species. These similarities and variations are important to understanding to what extent phylogenetic affinities and constraints affect potential adaptive evolutionary plasticity of the hippocampal formation.  相似文献   
8.
Epilepsy, characterized by recurrent seizures and abnormal electrical activity in the brain, is one of the most prevalent brain disorders. Over two million people in the United States have been diagnosed with epilepsy and 3% of the general population will be diagnosed with it at some point in their lives. While most developmental epilepsies occur due to genetic predisposition, a class of “acquired” epilepsies results from a variety of brain insults. A leading etiological factor for epilepsy that is currently on the rise is traumatic brain injury (TBI), which accounts for up to 20% of all symptomatic epilepsies. Remarkably, the presence of an identified early insult that constitutes a risk for development of epilepsy provides a therapeutic window in which the pathological processes associated with brain injury can be manipulated to limit the subsequent development of recurrent seizure activity and epilepsy. Recent studies have revealed diverse pathologies, including enhanced excitability, activated immune signaling, cell death, and enhanced neurogenesis within a week after injury, suggesting a period of heightened adaptive and maladaptive plasticity. An integrated understanding of these processes and their cellular and molecular underpinnings could lead to novel targets to arrest epileptogenesis after trauma. This review attempts to highlight and relate the diverse early changes after trauma and their role in development of epilepsy and suggests potential strategies to limit neurological complications in the injured brain.  相似文献   
9.
《Clinical neurophysiology》2019,130(5):727-738
ObjectiveFunctional processes in the brain are segregated in both the spatial and spectral domain. Motivated by findings reported at the cortical level in healthy participants we test the hypothesis in the basal ganglia of Parkinson’s disease patients that lower frequency beta band activity relates to motor circuits associated with the upper limb and higher beta frequencies with lower limb movements.MethodsWe recorded local field potentials (LFPs) from the subthalamic nucleus using segmented “directional” DBS leads, during which patients performed repetitive upper and lower limb movements. Movement-related spectral changes in the beta and gamma frequency-ranges and their spatial distributions were compared between limbs.ResultsWe found that the beta desynchronization during leg movements is characterised by a strikingly greater involvement of higher beta frequencies (24–31 Hz), regardless of whether this was contralateral or ipsilateral to the limb moved. The spatial distribution of limb-specific movement-related changes was evident at higher gamma frequencies.ConclusionLimb processing in the basal ganglia is differentially organised in the spectral and spatial domain and can be captured by directional DBS leads.SignificanceThese findings may help to refine the use of the subthalamic LFPs as a control signal for adaptive DBS and neuroprosthetic devices.  相似文献   
10.
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