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   2313篇
  免费   148篇
  国内免费   93篇
耳鼻咽喉   7篇
儿科学   12篇
妇产科学   3篇
基础医学   248篇
口腔科学   7篇
临床医学   89篇
内科学   113篇
皮肤病学   5篇
神经病学   934篇
特种医学   29篇
外科学   40篇
综合类   234篇
预防医学   52篇
眼科学   17篇
药学   481篇
中国医学   268篇
肿瘤学   15篇
  2023年   26篇
  2022年   23篇
  2021年   50篇
  2020年   51篇
  2019年   50篇
  2018年   44篇
  2017年   52篇
  2016年   47篇
  2015年   49篇
  2014年   85篇
  2013年   127篇
  2012年   107篇
  2011年   109篇
  2010年   90篇
  2009年   67篇
  2008年   118篇
  2007年   103篇
  2006年   70篇
  2005年   85篇
  2004年   74篇
  2003年   76篇
  2002年   56篇
  2001年   82篇
  2000年   44篇
  1999年   44篇
  1998年   38篇
  1997年   39篇
  1996年   29篇
  1995年   37篇
  1994年   37篇
  1993年   28篇
  1992年   43篇
  1991年   38篇
  1990年   36篇
  1989年   27篇
  1988年   33篇
  1987年   25篇
  1986年   47篇
  1985年   60篇
  1984年   50篇
  1983年   50篇
  1982年   46篇
  1981年   64篇
  1980年   36篇
  1979年   21篇
  1978年   9篇
  1977年   8篇
  1976年   4篇
  1974年   6篇
  1973年   5篇
排序方式: 共有2554条查询结果,搜索用时 31 毫秒
1.
A red-absorbing, water-soluble, and iodinated resorufin derivative (R1) that can be selectively activated with a monoamine oxidase (MAO) enzyme was synthesized, and its potential as a photodynamic therapy (PDT) agent was evaluated. R1 showed high 1O2 generation yields in aqueous solutions upon addition of MAO isoforms, and it was further tested in cell culture studies. R1 induced photocytotoxicity after being triggered by endogenous MAO enzyme in cancer cells with a much higher efficiency in SH-SY5Y neuroblastoma cells with high MAO-A expression. Additionally, R1 displayed differential cytotoxicity between cancer and normal cells, without any considerable dark toxicity. To the best of our knowledge, R1 marks the first example of a resorufin-based photosensitizer (PS) as well as the first anticancer drug that is activated by a MAO enzyme. Remarkably, the target PDT agent was obtained only in three steps as a result of versatile resorufin chemistry.  相似文献   
2.
目的探究生酮饮食结合抗癫痫药物对难治性癫痫患者发作频率、血清单胺类神经递质的影响。方法将2016年1月至2018年2月我院神经内科收治的72例难治性癫痫患儿纳入研究,所有患儿均在原有抗癫痫药物基础上进行至少3个月的生酮饮食治疗,于治疗后3、6、12个月时统计癫痫发作频率,复查脑电图评价脑部放电控制情况;于治疗6个月时采用韦氏儿童智力量表对患儿治疗前后的认知功能进行评价,测定事件相关电位P300及血清去甲肾上腺素(NE)、多巴胺(DA)、5-羟色胺(5-HT)水平。结果所有患儿均接受随访,治疗维持3、6、12个月的患者分别为72例、60例、38例。生酮饮食治疗3、6、12个月时临床发作控制有效率分别为40.3%、50%、55.3%,完全控制发作率分别为2.8%、18.3%、21.1%;脑电波减少有效率分别为50%、68.3%、76.3%;与治疗前比较,治疗6个月时患儿言语智商、操作智商、全量表智商得分未见显著性改变(P 0.05);与治疗前比较,治疗6个月时患儿N_2PL显著降低,P3波幅及血清NE、DA、5-HT等神经递质水平显著升高(P 0.05)。结论总体上生酮饮食结合抗癫痫药物治疗难治性癫痫有效,不仅可降低癫痫发作次数,也可一定程度改善患儿认知功能,其机制可能与其对神经递质的调控相关。  相似文献   
3.
目的:观察镇心省睡益智方水提液及其精油对β淀粉样前体蛋白基因/早老素基因(APP/PS1)双转基因小鼠学习记忆的影响并探讨其可能机制。方法:采用APP/PS1双转基因痴呆小鼠及同月龄相同遗传背景C57BL/6JNju小鼠2种小鼠。C57BL/6JNju小鼠作为正常组,APP/PS1双转基因痴呆小鼠随机分为模型组,镇心省睡益智方精油低、高质量浓度组(12.13,48.50 mg·L~(-1)),镇心省睡益智方水提液组(0.46 g·kg~(-1)),每组12只。每天给药1次,连续给药22 d。给药结束后采用跳台实验、Morris水迷宫实验对小鼠行为学能力进行检测,采用尼氏染色观察海马CA1区神经元变化,采用硫磺素(Th S)染色观察海马DG区老年斑(SP)沉积,采用免疫组化法检测小鼠脑组织中葡萄糖转运蛋白1(GLUT1),胰岛素受体底物-1(IRS-1)的表达,采用酶联免疫吸附测定(ELISA)检测小鼠海马组织中乙酰胆碱(ACH),γ-氨基丁酸(GABA),谷氨酸(GLU)含量的变化。结果:与正常组比较,模型组小鼠跳台实验潜伏期显著缩短,错误次数显著增加(P0.01),Morris水迷宫实验定位航行逃避潜伏期明显延长(P0.05,P0.01),海马CA1区神经元出现缺失,DG区出现明显的老年斑沉积(P0.05),ACH,GLUT1含量均显著下降(P0.01),GABA,GLU水平及IRS-1的表达均显著升高(P0.01);与模型组比较,各给药组均可显著延长小鼠跳台实验潜伏期、减少跳台错误次数(P0.01),明显降低定位航行小鼠逃避潜伏期(P0.05,P0.01),可一定程度保护小鼠海马CA1区神经元,减少DG区老年斑沉积(P0.05,P0.01),明显增加小鼠脑组织中ACH,GLUT1表达(P0.05,P0.01),显著降低GABA,GLU水平及IRS-1的表达(P0.01)。结论:镇心省睡益智方水提液及其精油能够改善APP/PS1小鼠的学习记忆行为,保护神经元,增加脑组织GLUT1的表达,减少脑组织IRS-1的表达,减少老年斑沉积,升高ACH含量,降低GABA,GLU含量,可能是其防治阿尔茨海默症的机制。  相似文献   
4.
Lateral habenula (LHb) hyperactivity plays a pivotal role in the emergence of negative emotional states, including those occurring during withdrawal from addictive drugs. We have previously implicated cocaine‐driven adaptations at synapses from the entopeduncular nucleus (EPN) to the LHb in this process. Specifically, ionotropic GABAA receptor (R)‐mediated neurotransmission at EPN‐to‐LHb synapses is reduced during cocaine withdrawal, due to impaired vesicle filling. Recent studies have shown that metabotropic GABABR signaling also controls LHb activity, although its role at EPN‐to‐LHb synapses during drug withdrawal is unknown. Here, we predicted that cocaine treatment would reduce GABABR‐mediated neurotransmission at EPN‐to‐LHb synapses. We chronically treated mice with saline or cocaine, prepared brain slices after two days of withdrawal and performed voltage‐clamp recordings from LHb neurons whilst optogenetically stimulating EPN terminals. Compared with controls, mice in cocaine withdrawal exhibited reduced GABAAR‐mediated input to LHb neurons, and a reduced occurrence of GABABR‐signaling at EPN‐to‐LHb synapses. We then assessed the underlying mechanism of this decrease. Application of GABABR agonist baclofen evoked similar postsynaptic responses in EPN‐innervated LHb neurons in saline‐ and cocaine‐treated mice. Release probability at EPN‐to‐LHb GABAergic synapses was also comparable between groups. However, incubating brain slices in glutamine to facilitate GABA vesicle filling, normalized GABABR‐currents at EPN‐to‐LHb synapses in cocaine‐treated mice. Overall, we show that during cocaine withdrawal, together with reduced GABAAR transmission, also GABABR‐mediated inhibitory signaling is diminished at EPN‐to‐LHb synapses, likely via the same presynaptic deficit. In concert, these alterations are predicted to contribute to the emergence of drug withdrawal symptoms, facilitating drug relapse.  相似文献   
5.
6.
Depression is one of the prevalent and persistent psychiatric illnesses. It brings heavy socioeconomic burden such as healthcare expenditures and even higher suicide rates. Despite many hypotheses about its mechanism have been put forward, so far it is still unclear, not to mention the precise and effective diagnostic or therapeutic methods. In this paper, the current conditions of pathological and pharmacological mechanism of depression were reviewed systematically. Firstly, the most recent hypotheses and metabolomics based research including hereditary, neurotransmitter systems, brain derived neurotrophic factor (BDNF), hyperactivity of the hypothalamic pituitary adrenal (HPA) axis and inflammatory as well as metabolomics were summarized. Secondly, the present situation and development on antidepressant drugs at home and abroad were reviewed. Finally, a conclusion and prospect on the pathological and pharmacological mechanism of depression were provided primarily.  相似文献   
7.
目的 探讨地佐辛复合舒芬太尼在腰硬联合麻醉剖宫产术后镇痛中的应用效果,以为剖宫产术后麻醉药物的合理选择提供参考.方法 选取2018年10月至2019年10月收治的130例腰硬联合麻醉剖宫产术产妇作为研究对象,以随机数字表法将其分为对照组和观察组,各65例.两组均行剖宫产术,对照组采用舒芬太尼进行术后镇痛,观察组采用地佐辛复合舒芬太尼进行术后镇痛.比较两组的麻醉效果.结果 观察组术后4、12、24 h的VAS评分低于对照组,RSS评分高于对照组(P<0.05).术前,两组的NE、Cor、ET-1水平无明显差异(P>0.05);术后24 h,观察组的NE、Cor、ET-1水平低于对照组(P<0.05).观察组的初乳时间早于对照组,术后4、12、24 h的PRL水平高于对照组(P<0.05).术前,两组的NPY、SP、β-EP水平无明显差异(P>0.05);术后24 h,观察组的NPY、SP、β-EP水平低于对照组(P<0.05).结论 地佐辛复合舒芬太尼应用在腰硬联合麻醉剖宫产术后有助于提高镇痛、镇静效果,减轻产妇的应激反应,改善早期泌乳情况,下调神经递质水平,值得临床推广和应用.  相似文献   
8.
目的:探讨高温条件下急性力竭运动对大鼠下丘脑单胺类神经递质的影响。方法:16只雄性SD大鼠经适应性跑台训练后随机分为常温运动组(E)和高温运动组(HE),每组8只。E组和HE组大鼠分别在常温环境(23℃,约50%相对湿度)和高温环境(33℃,约50%相对湿度)中进行一次性力竭跑台运动。两组大鼠均在急性力竭运动后即刻宰杀。记录大鼠实验前后肛温(Tr)变化及力竭运动时间,运用高效液相色谱法测试大鼠下丘脑单胺类神经递质。结果:HE组大鼠急性力竭运动时间显著小于E组(P<0.01),而Tr显著高于E组(P<0.01);HE组大鼠下丘脑去甲肾上腺素(NE)浓度显著高于E组(P<0.01);两组大鼠5羟色胺(5-HT)、多巴胺(DA)、5羟色胺与多巴胺比值(5HT/DA)之间无显著性差异(P>0.05),但HE组大鼠5-HT和DA代谢产物5羟色氨酸(5-HIAA)与3,4-二羟基苯乙酸(DOPAC)均显著低于E组(P<0.05)。结论:(1)高温环境明显降低大鼠运动能力,大鼠核心温度升高是影响高温环境中运动能力的关键性因素,而非下丘脑单胺类神经递质的变化。(2)高温环境在一定程度上减弱了力竭运动对大鼠下丘脑单胺类神经递质的影响。  相似文献   
9.
Several selective antagonists for adenosine A2A receptors (A2AR) are currently under evaluation in clinical trials (phases I to III) to treat Parkinson's disease, and they will probably soon reach the market. The usefulness of these antagonists has been deduced from studies demonstrating functional interactions between dopamine D2 and adenosine A2A receptors in the basal ganglia. At present it is believed that A2AR antagonists can be used in combination with the dopamine precursor L-DOPA to minimize the motor symptoms of Parkinson's patients. However, a considerable body of data indicates that in addition to ameliorating motor symptoms, adenosine A2AR antagonists may also prevent neurodegeneration. Despite these promising indications, one further issue must be considered in order to develop fully optimized antiparkinsonian drug therapy, namely the existence of (hetero)dimers/oligomers of G protein-coupled receptors, a topic that is currently the focus of intense debate within the scientific community. Dopamine D2 receptors (D2Rs) expressed in the striatum are known to form heteromers with A2A adenosine receptors. Thus, the development of heteromer-specific A2A receptor antagonists represents a promising strategy for the identification of more selective and safer drugs.  相似文献   
10.
目的观察司来吉兰对帕金森病(PD)模型大鼠黑质纹状体内酪氨酸羟化酶(TH)及胶质细胞源性神经营养因子(GDNF)表达的影响,探讨司来吉兰对多巴胺能神经元的保护作用及机制。方法 72只健康雄性SD大鼠随机分为对照组、模型组和司来吉兰组,每组均设4 d和8 d 2个亚组,各12只。模型组和司来吉兰组采用颈背部皮下注射鱼藤酮制备PD模型,对照组皮下注射等体积葵花油。之后司来吉兰组每日灌胃咪多吡0.5 mg/kg,模型组和对照组每日灌胃等体积生理盐水,4 d和8 d组分别连续灌胃4 d和8 d。采用免疫组化法和Western blotting法检测黑质纹状体TH和GDNF表达水平。结果免疫组化法和Western blotting法检测结果均显示,对照组大鼠黑质纹状体可见多量TH阳性细胞表达和少量GDNF阳性细胞表达,8 d和4 d组差异均无统计学意义。模型组TH和GDNF阳性细胞表达均明显低于对照组(均P<0.05),8 d和4 d组差异均无统计学意义。司来吉兰组TH阳性细胞表达低于对照组而高于模型组,GDNF阳性细胞表达高于对照组和模型组(均P<0.05),且8 d组均高于4 d组(均P<0.05)。结论司来吉兰可减轻PD模型大鼠黑质纹状体多巴胺能神经元的损伤,其作用机制可能与增加GDNF表达有关。  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