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   4723篇
  免费   162篇
  国内免费   79篇
耳鼻咽喉   82篇
儿科学   132篇
妇产科学   53篇
基础医学   1188篇
口腔科学   31篇
临床医学   231篇
内科学   168篇
皮肤病学   16篇
神经病学   1506篇
特种医学   101篇
外科学   285篇
综合类   466篇
预防医学   210篇
眼科学   74篇
药学   246篇
  3篇
中国医学   105篇
肿瘤学   67篇
  2023年   30篇
  2022年   82篇
  2021年   122篇
  2020年   94篇
  2019年   66篇
  2018年   58篇
  2017年   112篇
  2016年   108篇
  2015年   157篇
  2014年   229篇
  2013年   265篇
  2012年   221篇
  2011年   309篇
  2010年   244篇
  2009年   279篇
  2008年   291篇
  2007年   275篇
  2006年   318篇
  2005年   310篇
  2004年   212篇
  2003年   160篇
  2002年   113篇
  2001年   81篇
  2000年   63篇
  1999年   56篇
  1998年   70篇
  1997年   53篇
  1996年   64篇
  1995年   64篇
  1994年   51篇
  1993年   40篇
  1992年   38篇
  1991年   41篇
  1990年   45篇
  1989年   41篇
  1988年   37篇
  1987年   25篇
  1986年   14篇
  1985年   17篇
  1984年   18篇
  1983年   7篇
  1982年   13篇
  1981年   9篇
  1980年   11篇
  1979年   10篇
  1977年   4篇
  1976年   7篇
  1974年   6篇
  1973年   5篇
  1969年   4篇
排序方式: 共有4964条查询结果,搜索用时 31 毫秒
71.
脑立体定向手术戒毒对近期神经心理功能的影响   总被引:1,自引:0,他引:1  
目的:了解脑立体定向手术戒毒对病人智力、记忆等脑功能的影响。方法:采用韦氏成人智力量表(WAIS)、韦氏记忆测验(WMS)、HR—B神经心理成套测验(HR—B)于术前、术后对病人进行检查。结果:①WAIS:知识、相识性、图画填充等分测验以及语言智商、操作智商、总智商术后均有所提高,其中知识、图画填充及总智商有显著性意义(P〈0.05)。②WMS:倒数数字、图片回忆、联想学习、背数等分测验较手术前下降(P〈0.01),触摸测验及记忆商数(MQ)也有下降(P〈0.05)。术后5-6个月对其中19例患者的WMS测验成绩追踪,各分测验成绩及MQ均有改善,尤以数数和记忆商数改善明显(P〈0.01)。③HR—B:脑损伤指数(DQ)手术前后未见明显变化,仅分测验连线A、连线B成绩术后有降低(P〈0.01).而利手敲击成绩较术前有提高(P〈0.01)。结论:于术戒毒未造成患者智力明显下降及脑功能障碍.近期记忆下降可在4~5个月内恢复。  相似文献   
72.
The paper deals with computer simulations of ‘silicon neurons’, which are assemblies of CMOS circuits that generate the equivalents of the ionic currents and of the action potentials of real (biological) neurons. The circuit simulation program SPICE is used to simulate the generation of action potentials by a silicon neuron. Moreover, the equivalent circuits of silicon synapses are described and the behaviours of simple two- and three-neuron networks are analysed. Implications for the areas of neurobiology and formal neural networks are briefly considered.  相似文献   
73.
一个快速稳定的分割系统是研究神经元干细胞变化的基础,为完善此系统,针对多连接边缘模糊的细胞分割提取问题,根据曲线进化原理,我们提出了一种基于水平集方法的改进的几何活动轮廓算法。此算法能自动解决图像的拓扑变化,并能获得更加真实的细胞轮廓边缘。将此方法应用于神经元干细胞的序列图像分割,实验结果证明了此算法的有效性与准确性。  相似文献   
74.
Non-seminomatous germ cell tumours of the testis (NSGCT) form a heterogeneous group of neoplasms. Cell lines derived from NSGCT may provide useful data concerning the biology of neoplasic precursor germ cells, differentiation of tumour stem cells and the relationship between various tissue components of these tumours. Four NSGCT were studied, two mixed tumours composed of teratocarcinoma, yolk sac and trophoblastic elements, and two malignant teratomas with a massive neuroectodermal component, equivalent to primary neuroectodermal tumours (PNET) of the testis. The explanted tumours gave rise to various cell populations, including epitheloid cells, flattened large cells, spindle cells and tear drop cells of neuroblastic type. Ultrastructurally, cultured cells expressed various degrees of neural and muscular differentiation: neurosecretory granules, intermediate filaments of glial nature, and filaments resembling Z-bands. Cultured cells showed the expression of several neural and muscular markers, including neurofilaments, cytokeratin, actin, desmin, neuron-specific enolase, glial fibrillary acidic protein and HNK-1. In addition, three cases expressed HBA-71 antigen and two expressed MyoDI protein. All cases were aneuploid, and an isochromosome 12p, i(12p), was detected in three cases. Myoblastic and neural cells are the predominant tumour cells that grow in vitro, independent of the nature and composition of the primary germ cell tumour. A histogenetic relationship between germ cell tumours and small round cell tumours of childhood is suggested.  相似文献   
75.
音猬因子的功能受体斑片在培养神经干细胞中的表达   总被引:1,自引:0,他引:1  
许汉鹏  胡沛臻  苟琳  张萍  鞠躬 《解剖学报》2002,33(6):561-565
目的 观察在培养的神经干细胞内是否有发育调控分子———音猬因子 (sonichedgehog)功能受体———斑片 (patched)表达。 方法 神经干细胞克隆在体外培养传代后 ,用patched的特异性引物对培养的神经干细胞进行RT PCR分析 ,PCR产物经克隆测序后 ,用地高辛标记克隆的探针 ,对神经干细胞进行原位杂交分析。 结果 神经干细胞克隆内大量的细胞均可表达sonichedgehog的功能受体patched ,patched阳性细胞间未见明显差别 ,克隆边缘与中央的patched分布也未见明显差别。 结论 sonichedgehog信号传导路可能在神经干细胞的增殖与分化过程中起重要作用。  相似文献   
76.
Several evidences suggest that the posterodorsal medial amygdala (MePD) can be a relevant part of the rat neural circuitry for the regulation of hypothalamic neuroendocrine secretion and for ontogenetically different behavioral displays. The dendritic spine density of Golgi-impregnated neurons from the MePD was evaluated in young rats following acute or chronic restraint stress and in aged animals (24 months old). Compared to the control group, a single 1 h restraint stress session promoted a decreased spine density (p < 0.01) whereas a single 6 h restraint stress session or daily 6-h restraint sessions for 28 consecutive days did not lead to the same effect (p > 0.05). Aged rats showed no difference in this dendritic spine parameter when compared to young adults (p > 0.05). These results indicate that short-term stress (1 h) can affect MePD dendritic spines and that neural plasticity is involved with adaptive responses onwards in restrained rats. On the other hand, brain structural modifications related with ageing appear not to influence the number of certain postsynaptic sites in the MePD of rats.  相似文献   
77.
Perceptual Speed and IQ Are Associated Through Common Genetic Factors   总被引:1,自引:0,他引:1  
Individual differences in inspection time explain about 20% of IQ test variance. To determine whether the association between inspection time and IQ is mediated by common genes or by a common environmental factor, inspection time and IQ were assessed in an extended twin design. Data from 688 participants from 271 families were collected as part of a large ongoing project on the genetics of adult brain function and cognition. The sample consisted of a young adult cohort (mean age 26.2 years) and an older adult cohort (mean age 50.4 years). IQ was assessed with the Dutch version of the WAIS-3R. Inspection time was measured in the so-called -paradigm, in which a subject is asked to decide which leg of the -figure is longest at varying display times of the -figure. The number of correct inspections per second (i.e., the reciprocal of inspection time) was used to index perceptual speed. For Verbal IQ and Performance IQ, heritabilities were 85% and 69%, respectively. For perceptual speed, 46% of the total variance was explained by genetic variance. No differences in heritability estimates across age cohorts or sexes were found. Across the whole sample, a significant phenotypic correlation was found between perceptual speed and Verbal IQ (0.19) and between perceptual speed and Performance IQ (0.27). These correlations were entirely due to a common genetic factor that accounted for 10% of the genetic variance in verbal IQ and for 22% of the genetic variance in performance IQ. This factor is hypothesized to reflect the influence of genetic factors that determine axonal myelination in the central nervous system.  相似文献   
78.
目的 探讨切割穹窿海马伞及脑室给予神经生长因子(NGF)后,对大鼠海马自体神经干细胞增殖和分化为神经元的影响.方法 12只SD大鼠,随机分成给药组和对照组,每组6只,切割右侧穹窿海马伞,两组切割后即时及第2d、4d向侧脑室分别注射NGF和人工脑脊液, 并在术后第3~7d每日腹腔注射2次BrdU.于术后28d灌注取脑、冷冻切片,行BrdU/NF-200免疫荧光双标检测.结果 海马齿状回内BrdU阳性细胞数,给药组和对照组切割侧明显多于正常侧,给药组切割侧和正常侧分别多于对照组切割侧和正常侧;海马齿状回内的BrdU/NF-200双标神经元数,给药组切割侧最多,给药组正常侧和对照组切割侧较少,而对照组正常侧则无.结论 切割穹窿海马伞后,可致大鼠海马齿状回自体神经干细胞增殖加快并向神经元分化,脑室施加 NGF可促进其增殖和分化.  相似文献   
79.
一种EEG信号盲分离和分类的神经网络方法   总被引:2,自引:1,他引:2  
提出一种采用多神经网络处理脑电(EEG)信号的方法。首先,对混有噪声的脑电信号给出一种盲分离的自适应神经算法。通过寻求采样时间序列线性组合的kurtosis系数的局部极值,得出该算法的模型和步骤。在盲分离的基础上,对分离出的估计信号进一步利用Kohonen网络进行分类。将该算法用于300个EEG样本处理,并给出处理结果。  相似文献   
80.
It is well known that prolonged exposure to morphine results in tolerance to morphine-induced antinociception. In the present study, we found that mice that were tolerant to morphine-induced antinociception exhibited an increase in immunoreactivity for the neural cell adhesion molecule in the dorsal horn of the spinal cord, which was highly overlapped with immunoreactivity for the increased metabotropic glutamate receptor 5 induced by morphine. These findings support the idea that repeated stimulation of μ-opioid receptors increases the expression of neural cell adhesion molecule and metabotropic glutamate receptor 5. This phenomenon leads to the enhanced excitatory synaptic transmission in the dorsal horn of the spinal cord, and in turn suppresses the morphine-induced antinociception.  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