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   109271篇
  免费   8693篇
  国内免费   5088篇
耳鼻咽喉   483篇
儿科学   2648篇
妇产科学   766篇
基础医学   9395篇
口腔科学   792篇
临床医学   14071篇
内科学   9873篇
皮肤病学   411篇
神经病学   18931篇
特种医学   6869篇
外国民族医学   7篇
外科学   15929篇
综合类   18731篇
现状与发展   5篇
一般理论   1篇
预防医学   5448篇
眼科学   1076篇
药学   9955篇
  68篇
中国医学   4532篇
肿瘤学   3061篇
  2024年   249篇
  2023年   1772篇
  2022年   2687篇
  2021年   5051篇
  2020年   4439篇
  2019年   3415篇
  2018年   3373篇
  2017年   3805篇
  2016年   4013篇
  2015年   3912篇
  2014年   6746篇
  2013年   8019篇
  2012年   6381篇
  2011年   6938篇
  2010年   5881篇
  2009年   5568篇
  2008年   5595篇
  2007年   5688篇
  2006年   5378篇
  2005年   4739篇
  2004年   3917篇
  2003年   3689篇
  2002年   2797篇
  2001年   2480篇
  2000年   1981篇
  1999年   1717篇
  1998年   1486篇
  1997年   1499篇
  1996年   1212篇
  1995年   1002篇
  1994年   916篇
  1993年   691篇
  1992年   665篇
  1991年   519篇
  1990年   469篇
  1989年   425篇
  1988年   399篇
  1987年   348篇
  1986年   391篇
  1985年   484篇
  1984年   446篇
  1983年   292篇
  1982年   362篇
  1981年   319篇
  1980年   291篇
  1979年   165篇
  1978年   105篇
  1977年   91篇
  1976年   87篇
  1975年   45篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Brain Research Institute, Russian Academy of Medical Sciences, Moscow. Institute of Biological Research, Belgrade, Yugloslavia. Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 114, No. 7, pp. 56–58, July, 1992.  相似文献   
992.
The in situ thermal protein denaturation and its correlation with direct hyperthermic cell injury in Dunning AT-1 prostate tumor cells were investigated in this study. The in situ thermal protein denaturation was studied using both Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The FTIR spectra at different temperatures show changes in protein secondary structure (from alpha helix to extended beta sheet) during in situ thermal protein denaturation within AT-1 cells. Calorimetric studies using DSC show that endothermic heat release is associated with the in situ thermal protein denaturation. Furthermore, both the secondary structure changes detected by FTIR and the calorimetric changes detected by DSC were quantified and the kinetics of the overall in situ thermal protein denaturation was derived under different heating conditions. The onset temperature where the overall in situ thermal protein denaturation is first detectable was found to be scanning rate dependent (approximately 41 degrees C at 2 degrees C min(-1) and approximately 44 degrees C at 5 degrees C min(-1)). The kinetics of the overall in situ thermal protein denaturation was derived from both DSC and FTIR measurements and was fit using kinetic and statistical models. The kinetic data determined by FTIR and DSC under the same heating conditions match well with each other. The activation energy of the overall in situ thermal protein denaturation is found to be strongly dependent on the temperature range considered (the activation energy ranges from approximately 110 kJ mol(-1) between 44 and 90 degrees C to approximately 750 kJ mol(-1) between 44 and 50 degrees C). However, its dependence on heating rate is negligible. Several denaturation peaks, including a dominant one between approximately 62 and 65 degrees C, are identifiable from both the DSC and the FTIR results. To investigate directly the relationship between thermally induced cell injury and the in situ thermal protein denaturation, both acute (propidium iodide dye exclusion, assessed 3-h postthermal treatment) and chronic (clonogenics, assessed 7-day postthermal treatment) cell injury were quantified using AT-1 cells prepared under the same conditions as for the DSC protein studies. Comparisons of the results from the cell injury studies and the DSC protein denaturation studies show that the overall in situ thermal protein denaturation correlates well with both the acute and the chronic cell injury, which suggests that overall in situ thermal protein denaturation is an important mechanism of direct hyperthermic cell injury in AT-1 cells at the macromolecular level.  相似文献   
993.
目的观察中药珍珠散协同爱宝疗浓缩液治疗重度官颈糜烂临床疗效和药物经济学效益。方法将有生育要求的Ⅲ度官颈糜烂患者111例随机分为治疗组和对照组,治疗组用中药珍珠散联合爱宝疗浓缩液治疗,对照组则单用爱宝疗浓缩液治疗,均每3d治疗一次。45d后,比较两组疗效、疗程及治疗费用。结果治疗组治愈率明显高于对照组(67.9%vs36.4%),差异有统计学意义(P〈0.05)。治疗组费用明显低于对照组[(371.6±138.4)vs(483.6±36.6)]元(P〈0.01)。治疗组治疗时间比对照组显著缩短[(32.4±12.1)vs(44.0±3.3)]d(P〈0.01)。治疗组中提前结束治疗患者多于对照组(35/56vs6/55,P〈0.05)。治疗组与对照组均未见副作用发生。结论珍珠散协同爱宝疗浓缩液治疗重度官颈糜烂疗效好,药物经济学效益高,值得临床推广。  相似文献   
994.
为了探讨硫酸软骨素酶ABC对脊髓损伤后损伤局部瘢痕形成和脊髓传导功能修复的影响,本研究首先制作大鼠脊髓全横断损伤动物模型,并将其分为脊髓损伤组(A组)和脊髓损伤治疗组(B组)。在观察期内对动物的行为学表现进行BBB评分;用免疫荧光组织化学方法观察损伤4周后硫酸软骨素酶ABC对损伤局部的硫酸软骨素蛋白聚糖(CSPGs)的裂解作用;用辣根过氧化物酶(HRP)示踪法观察损伤8周后神经纤维的再生情况。结果显示:A组与B组之间动物的行为学评分B组优于A组,有显著性差异(P<0.01);B组动物脊髓内硫酸软骨素蛋白聚糖阳性物质的表达明显低于A组,具有显著性差异(P<0.05),而硫酸软骨素核心蛋白的表达无显著性差异(P>0.05);HRP示踪法显示B组脊髓损伤头端可见少量HRP标记的神经元胞体和纤维。本研究结果提示硫酸软骨素酶ABC能够裂解CSPGs中的葡胺聚糖链,减少瘢痕,促进损伤的神经纤维再生。  相似文献   
995.
目的 探讨银杏叶提取物对在体缺血冷藏再灌注后肺组织ICAM-1和P选择素基因mRNA表达的影响。方法 新西兰白兔30只。随机分为3组:对照组、LPD组和GBE组.建立兔在体缺血冷藏再灌注模型,对照组左肺不灌注肺保护液,阻断左肺门后直接将左肺下叶载体冷藏于10℃肺保存器内2h,再灌注2h;LPD组左肺门阻断后经肺动脉灌注LPD液,余同对照组;GBE组灌注液为合银杏叶提取物(Ginkgo Biloba Extract,GBE)的LPD液,余同LPD组。分别于左肺门阻断前、缺血2h、再灌注2h取左肺组织,RTPCR技术检测P-选择素和ICAM-1基因mRNA的表达;免疫纽化技术检测P-选择素和ICAM-1基因蛋白质产物量。结果 三组在缺血前及缺血2h再灌注前P—selectin基因mRNA表达量及其蛋白质产物免疫组化评分组间均未有显著性差异。再灌注2h后,GBE组P—selectin基因mRNA表达量厦其蛋白质产物免疫组化评分显著低于LPD组和对照组。,缺血前,所有三组ICAM—1基因mRNA表达量均未有显著性差异,在缺血2h后再难注前及再灌注2h后,ICAM—1基因mRNA表达量及其蛋白质产物免疫组化评分在GBE组均显著低于对照组和LPD组。结论 银杏叶提取物可抑制P—selectin和ICAM—1基因mRNA的表达上调,使肺组织P—selectin和细胞间粘附分子-1蛋白产物减少,从而减轻保存肺的缺血再灌注损伤。银杏叶提取物作为肺保护液添加剂,在进一步研究后可以试用于临床肺移植,为中药提取物的开发应用展示了光明的前景。  相似文献   
996.
NGF在成年猴脑的分布   总被引:1,自引:1,他引:1  
为了解NGF在成年猴脑的分布,采用免疫组化SP法对成年猴脑多个冠状位切片进行免疫组化反应。结果证明,NGF阳性反应神经元主要分布于大脑皮质Ⅲ、V层,小脑Purkinje细胞,海马,齿状回,纹状体,脑干网状结构等处。此外,在黑质、舌下神经核、迷走神经背核、前庭神经核、三叉神经核、疑核、下橄榄核也出现NGF阳性反应。在大脑和脑干还观察到NGF阳性胶质细胞。本实验结果表明,在成年猴脑的多个脑区有NGF表达,提示NGF可能涉及猴脑某些神经元及胶质细胞的生理过程。  相似文献   
997.
目的 探讨^18F-脱氧葡萄糖(FDG)正电子发射型计算机断层显影(PET)脑显像和其他医学影像方法对早期诊断放射性脑损伤的价值,以达到预防、减少脑放射损伤的目的。方法 静脉注射^18F-FDG后行脑显像,获得横断面、冠状面、矢状面断层显像。所有病人均进行CT检查。结果 20例正常人脑PET显像图像可见大脑皮质各叶、基底神经节、丘脑及小脑放射性分布均匀对称。12例完成头颈部恶性肿瘤放疗后有临床症状者均检出不同程度局灶性脑组织葡萄糖代谢下降,显像阳性率100%;其中10例鼻咽癌放疗后PET结果提示放射脑损伤病灶共23处,最常见于颞叶病灶13处、脑干4处、小脑4处以及顶叶2处。2例脑胶质细胞瘤放疗病人,PET结果提示病灶:顶叶2处、颞叶1处、枕叶1处。12例放疗后病人CT检查仅10例提示放射性脑损伤。结论 PET脑显像能准确、早期诊断脑放射损伤,是头颈部恶性肿瘤肿瘤放疗后的非常重要的监测手段。  相似文献   
998.
Localized in vivo 1H magnetic resonance spectroscopy (MRS) was used to investigate metabolite levels in the brain of adult Zucker Diabetic Fatty (ZDF) rats, an animal model for type 2 diabetes mellitus. This study focussed on the hippocampus, assumed to be one of the main brain areas affected by this disease. Together with an almost 5-fold increase in blood glucose concentration measured by glucose oxidation, significant increases were found in the hippocampal concentrations of glucose (4.93 vs 1.66 mM p < 0.001), myo-inositol (6.52 vs 4.30 mM; p < 0.05), and total creatine (12.71 vs 10.50 mM; p < 0.05) in ZDF rats (n = 5) compared with littermates (n = 5). Although no obvious alterations were detected in the hippocampal levels of other metabolites, including NAA + NAAG and choline-containing compounds in the ZDF rats, the increase in Glc and Ins levels is in line with elevated brain tissue contents of these metabolites in patients with diabetes mellitus.  相似文献   
999.
Cortical spreading depression (CSD) and peri‐infarct depolarisation (PID) are related phenomena that have been associated with the human clinical syndromes of migraine (CSD), head injury and stroke (PID). Nevertheless the existence of CSD in man remains controversial, despite the detection of this phenomenon in the brains of most, if not all, other animal species investigated. This failure to unambiguously detect CSD clinically may be at least partly due to the anatomically complex, gyrencephalic structure of the human brain. This study was designed to establish conditions for the study of CSD in the brain of a gyrencephalic species using the noninvasive technique of magnetic resonance imaging (MRI). The 3‐dimensional (3D) gyrencephalic anatomy of the cat brain was examined to determine the imaging conditions necessary to detect CSD events. Orthogonal transverse, sagittal and horizontal T1‐weighted image slices showed that the marginal and suprasylvian gyri were the most appropriate cortical structures to study CSD. This was in view of (1) their simple geometry: (2) their lengthy extent of grey matter orientated rostrocaudally in the cortex: (3) their separation by a sulcus across which CSD spread could be studied and (4) the discontinuity in the grey matter in these regions between the right and left hemispheres dorsal to the corpus callosum. The structure suggested by the T1‐weighted images was corroborated by systematic diffusion tensor imaging to map the fractional anisotropy and diffusion trace. Thus a single horizontal image plane could visualise the neighbouring suprasylvian and marginal gyri of both cerebral hemispheres, whereas its complex shape and position ruled out the ectosylvian gyrus for CSD studies. With the horizontal imaging plane, CSD events were reproducibly detected by animating successive diffusion‐weighted MR images following local KCl stimulation of the cortical surface. In single image frames, CSD detection and characterisation required image subtraction or statistical mapping methods that, nevertheless, yielded concordant results. In repeat experiments, CSD events were qualitatively similar in appearance whether elicited by sustained or transient KCl applications. Our experimental approach thus successfully describes cat brain anatomy in vivo, and elucidates the necessary conditions for the application of MRI methods to detect CSD propagation.  相似文献   
1000.
目的: 观察葛根素对大鼠局灶性脑缺血再灌注损伤后炎症反应的抑制作用并探讨其作用机制。方法: 采用大鼠大脑中动脉内栓线阻断法(MCAO)复制大鼠脑缺血再灌注损伤模型,于缺血开始及再灌注即刻由尾静脉注射葛根素18 mg·kg-1,缺血 2 h 再灌注 24 h 后取缺血侧脑组织,HE染色观察海马存活锥体细胞数,比色法测定脑组织MPO活性观察脑组织中性粒细胞浸润程度,Western blotting及RT-PCR法测定脑组织中ICAM-1 蛋白及mRNA表达情况及NF-κB p65亚基核转位情况。结果: 葛根素组缺血侧脑组织海马存活锥体细胞数明显高于缺血再灌注损伤组(P<0.01), MPO活性明显低于缺血再灌注损伤组(P<0.01),ICAM-1 蛋白及mRNA表达较缺血再灌注损伤组明显减少(P<0.01),NF-κB p65蛋白亚基核转位明显少于缺血再灌注损伤组(P<0.01)。结论: 葛根素可减轻大鼠脑缺血再灌注损伤后炎症反应,这可能是其发挥脑保护作用的机制之一。  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