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   381788篇
  免费   65911篇
  国内免费   19420篇
耳鼻咽喉   4349篇
儿科学   8074篇
妇产科学   4417篇
基础医学   47833篇
口腔科学   10048篇
临床医学   50030篇
内科学   65179篇
皮肤病学   11128篇
神经病学   27289篇
特种医学   13701篇
外国民族医学   137篇
外科学   44917篇
综合类   55451篇
现状与发展   74篇
一般理论   44篇
预防医学   26933篇
眼科学   9011篇
药学   37521篇
  309篇
中国医学   20073篇
肿瘤学   30601篇
  2024年   988篇
  2023年   4325篇
  2022年   11095篇
  2021年   15404篇
  2020年   15309篇
  2019年   18962篇
  2018年   19036篇
  2017年   19911篇
  2016年   20202篇
  2015年   24883篇
  2014年   27974篇
  2013年   28638篇
  2012年   28688篇
  2011年   30542篇
  2010年   26892篇
  2009年   20202篇
  2008年   20609篇
  2007年   18936篇
  2006年   18227篇
  2005年   16361篇
  2004年   11817篇
  2003年   11063篇
  2002年   9442篇
  2001年   7930篇
  2000年   7198篇
  1999年   6123篇
  1998年   3571篇
  1997年   3420篇
  1996年   2562篇
  1995年   2347篇
  1994年   1971篇
  1993年   1277篇
  1992年   1776篇
  1991年   1544篇
  1990年   1346篇
  1989年   1146篇
  1988年   987篇
  1987年   934篇
  1986年   715篇
  1985年   611篇
  1984年   337篇
  1983年   253篇
  1982年   180篇
  1981年   175篇
  1980年   117篇
  1979年   192篇
  1978年   94篇
  1976年   82篇
  1974年   104篇
  1973年   80篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The neural circuitry underlying movement detection was inferred from studies of amacrine cells under whole-cell patch clamp in retinal slices. Cells were identified by Lucifer yellow staining. Synaptic inputs were driven by "puffing" transmitter substances at the dendrites of presynaptic cells. Spatial sensitivity profiles for amacrine cells were measured by puffing transmitter substances along the lateral spread of their processes. Synaptic pathways were separated and identified with appropriate pre- and postsynaptic pharmacological blocking agents. Two distinct amacrine cell types were found: one with narrow spread of processes that received sustained excitatory synaptic current, the other with very wide spread of processes that received transient excitatory synaptic currents. The transient currents found only in the wide-field amacrine cell were formed presynaptically at GABAB receptors. They could be blocked with baclofen, a GABAB agonist, and their time course was extended by AVA, a GABAB antagonist. Baclofen and AVA had no direct affect upon the wide-field amacrine cell, but picrotoxin blocked a separate, direct GABA input to this cell. The narrow-field amacrine cell was shown to be GABAergic by counterstaining with anti-GABA antiserum after it was filled with Lucifer yellow. Its narrow, spatial profile and sustained synaptic input are properties that closely match those of the GABAergic antagonistic signal that forms transient activity (described above), suggesting that the narrow-field amacrine cell itself is the source of the GABAergic interaction mediating transient activity in the inner plexiform layer (IPL). Other work has shown a GABAB sensitivity at some bipolar terminals, suggesting a population of bipolars as the probable site of interaction mediating transient action. The results suggest that two local populations of amacrine cell types (sustained and transient) interact with the two populations of bipolar cell types (transient forming and nontransient forming). These interactions underlie the formation of the change-detecting subunits. We suggest that local populations of these subunits converge to form the receptive fields of movement-detecting ganglion cells.  相似文献   
992.
Dose-response curves for the elevation of homovanillic acid (HVA) levels, determined by high performance liquid chromatography using electrochemical detection, in the pre-frontal cortex and caudate of rats after acute treatment with 12 antipsychotic drugs are presented. The order of potency in both brain regions was: haloperidol fluphenazine > loxapine > trifluoperazine > thiothixene > molindone > clopenthixol > chlorpromazine > metoclopramide > thioridazine > clozapine > sulpiride. This ranking is roughly correlated with that based on clinical potencies. The relative elevation of the content of HVA was weaker in the pre-frontal cortex than in the caudate for all drugs tested, except clozapine at a high dose.  相似文献   
993.
活血化瘀法治疗实验性腹膜炎   总被引:2,自引:0,他引:2       下载免费PDF全文
本实验在大白鼠腹膜炎的早期单独使用丹参为主的活血化瘀药进行治疗,以加速渗出的纤维蛋白(原)的吸收,促进腹腔内感染的清除与消散。实验结果表明给药组动物的死亡率明显低于对照组,其病理改变也明显减轻,从而为在腹膜炎治疗的早期和中期应用活血化瘀药提供了实验依据。  相似文献   
994.
背景 感染性休克患者存在肾脏血液灌注异常,严重时可诱发急性肾损伤(AKI),严重威胁患者生命安全;彩色多普勒超声(CDU)可用于评估肾脏血流变化,但有关其在感染性休克患者AKI评估中价值的研究较少。目的 通过CDU评价感染性休克患者AKI的发生情况及其血流动力学改变。方法 选取2019年6月至2021年7月徐州市中心医院收治的105例确诊为感染性休克的患者并纳入感染组,选取同期健康体检者58例并纳入对照组,收集受试者一般资料。采用CDU检查受试者肾脏血流动力学指标[肾动脉管腔内径(D)、收缩期血流峰值速度(Vs)、舒张末期血流速度(Vd)、阻力指数(RI)、搏动指数(PI)],比较感染组与对照组的一般资料及肾脏血流动力学指标。根据感染组患者入院72 h内发生AKI与否将其分为AKI组及非AKI组,比较AKI组与非AKI组肾脏血流动力学指标。应用受试者工作特征(ROC)曲线分析肾脏血流动力学指标对感染性休克患者发生AKI的预测价值。应用单因素分析及多因素Logistic回归分析探讨感染性休克患者发生AKI的影响因素。以AKI由轻到重的程度将患者分为AKIⅠ组、AKIⅡ组、AKIⅢ组,比较...  相似文献   
995.
目的 探讨胃癌根治术术后肺部并发症(PPCs)的相关危险因素,为PPCs的个体化防治提供相应的对策。 方法 回顾性分析2019年1月至2021年3月兰州大学第二医院普通外科443例胃癌患者的临床资料,统计患者的临床病理特征,采用二分类Logistic回归分析胃癌根治术PPCs的危险因素。 结果 443例胃癌根治术PPCs的发生率为18.1%(80/443),其中肺部感染的发生率为12.4%(55/443),胸腔积液的发生率为11.7%(52/443),发生PPCs较未发生PPCs住院时间延长。Logistic回归分析显示,年龄≥60岁(OR=0.42495%CI: 0.241~0.746)、糖尿病史(OR=0.31895%CI: 0.146~0.693)、每分钟最大通气量(MVV)(%)<85%(OR=0.50995%CI: 0.297~0.874)、术中失血量≥200 mL(OR=0.49695%CI: 0.276~0.797)和术后吻合口并发症(OR=4.03895%CI: 1.250~13.049)是胃癌根治术发生PPCs的独立危险因素。 结论 对于年龄≥60岁、糖尿病史、MVV(%)<85%、术中失血量≥200 mL、术后吻合口并发症的胃癌患者,应注意预防PPCs的发生。  相似文献   
996.
目的 探讨芪苈强心胶囊联合尼可地尔对射血分数保留性心力衰竭患者心功能及细胞因子的影响。方法 连续入选2019年10月至2020年10月诊断为射血分数保留性心力衰竭的患者共90例,随机分为观察组(45例)与对照组(45例)。对照组给予常规抗心力衰竭药物加芪苈强心胶囊治疗,观察组在对照组治疗基础上,加用尼可地尔治疗。比较两组患者一般临床资料、细胞因子水平、心功能各项指标。随访1年患者心功能情况、细胞因子水平以及不良心脑血管事件(MACCEs)发生情况。结果 两组患者接受治疗1年后脑钠肽(BNP)、左室舒张末期内径、白细胞介素(IL)-1β、IL-6、肿瘤坏死因子-α(TNF-α)均降低,射血分数(EF)值较治疗前升高,差异有统计学意义(P<0.05)。组间对比发现,两组患者入院时基础BNP、细胞因子、超声心能指标(LVEF、左室舒张末期内径、左房内径)差异无统计学意义(P>0.05);接受治疗1年后观察组IL-1β、IL-6、TNF-α、BNP、左室舒张末期内径低于对照组,EF值高于对照组,差异有统计学意义(P<0.05)。随访1年对照组共有7例发生终点事件,观察组共有4...  相似文献   
997.
压力性尿失禁(stress urinary incontinence,SUI)是指喷嚏、咳嗽、大笑或运动等腹压增高而无逼尿肌收缩的情况下出现的不自主漏尿,该病严重影响患者生活质量及身心健康。中国成年女性SUI的患病率约18.9%,在50~59岁年龄段可高达28.0%。我国2017年女性压力性尿失禁治疗指南推荐的保守治疗主要包括生活方式干预(行为治疗)、盆底肌训练(pelvic floor muscle training, PFMT)、盆底肌生物反馈、电刺激治疗、药物治疗及抗尿失禁子宫托等。针灸治疗尿失禁临床具有良好的效应,但由于缺乏高质量临床研究证据,尚未被指南推荐。因此,我们对相关文献进行检索,发现近5年针灸治疗SUI的随机对照研究数量明显增加,次髎、中髎、会阳、骶四穴、秩边等尾骶部腧穴在临床上的运用日益受到关注,考虑可能与针刺刺激阴部神经丛,从而调节盆底肌肌力、改善尿控能力效应有关。基于此,我们希望对针灸治疗SUI的系统评价进行更新,并评价不同针灸取穴方案对SUI疗效的影响,以期为SUI的临床治疗提供参考意见。  相似文献   
998.
Histamine is known to cause a substantial increase in the permeability of venules to both water and proteins. However, this increase is transient, i.e., the initially elevated permeability returns toward control levels, or "recovers," even during continuous histamine stimulation. In this investigation, we attempted to identify the possible chemical signal(s) initiating the permeability recovery process in single venules of rat mesentery. Specifically, we tested whether histamine's binding to H2 receptors and/or the production of prostacyclin by endothelial cells was involved in this process. To achieve this aim, the time course of endothelial cells was involved in this process. To achieve this aim, the time course of histamine-induced changes in permeability to alpha-lactalbumin was measured in the presence of H2 receptor antagonist (cimetidine) or of prostacyclin synthetase inhibitor (tranylcypromine), respectively. Permeability of individually perfused microvessels was measured using fluorescence microscopy. The results demonstrated that permeability recovery was not affected by the H2 receptor antagonist but was suppressed or even abolished by the prostacyclin synthesis inhibitor. Therefore, these results suggest that the production of prostacyclin by endothelial cells might serve as one chemical signal to initiate the permeability recovery process, whereas histamine's binding to H2 receptors is not involved in this phenomenon.  相似文献   
999.
The regional and cellular localization of the two subtypes of dopamine receptors, D1 and D2, have been ascertained in rat forebrain by use of fluorescent dopaminergic antagonist ligands. (R,S)-5-(4'-aminophenyl)-8-chloro-2,3,4,5-tetrahydro-3- methyl-[1H]-3-benzazepin-7-ol, the 4'-amino derivative of the high-affinity D1-specific antagonist SCH 23390, and the D2 selective antagonist N-(p-aminophenethyl)spiperone were chemically derivatized using the fluorescent compound tetramethylrhodamine. The modification of these antagonist ligands has allowed the specific, cellular resolution of the D1 and D2 receptor binding sites in intact, highly organized regions of forebrain slices in a very rapid experimental time frame. The regional localization of receptors labeled by the fluorescent probes is in agreement with previous receptor autoradiography studies. Moreover, the specific cellular binding patterns for both receptors can now be compared and contrasted to one another in the same tissue by using these fluorescent ligands. D1 receptor sites are most evident within the striatum and exhibit regions of intense "patch" fluorescence corresponding to receptor reactivity in cells and their processes. The distribution of D1 receptor binding is highly analogous to the pattern of dopamine terminal histofluorescence in the caudate nucleus. D2 receptor sites are less prevalent overall and may be localized to a subpopulation of the D1 fluorescent neurons in the caudate nucleus and nucleus accumbens regions.  相似文献   
1000.
Advances in microsurgery have produced multiple options for microsurgical restoration of distal digital function. However, because of the complexity of most mutilating hand injuries, these possibilities can be readily overlooked. A surgical awareness of these options for "like" tissue transplantation is now necessary for complete mutilating hand injury care. These "minor" aesthetic and functional microsurgical procedures can be major factors in overall patient acceptance and utilization of the reconstructed hands.  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