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51.
染色体自动分析一直是医学图象处理领域研究的热点,其关键技术之一是染色体中轴的提取,中轴提取一般采用细化去枝、端点延伸的方法,但是对于一些染色体尤其是比较短小的21号,22号及y染色体,采用上述方法提取的中轴效果不太好,为此,作者提出一种新方法用于优化中轴提取,对长染色体,利用其端部的形状特征优化中轴延伸;而对短染色体,则充分利用短染色体的形状特征和内部带纹信息,由方向链码确定宏观走向,以带纹相对于中轴的方差最小为判据来确定中轴,该方法较好地解决了中轴检测这一难题。 相似文献
52.
一类富足半群的嵌入定理 总被引:2,自引:0,他引:2
陈建飞 《兰州大学学报(自然科学版)》1998,34(3):10-14
主要目的是给出满足正则性条件且含Q-适当断面的富足半群的嵌入定理.第一节列出文中要用到的有关富足半群与适当断面的一些基本结论,与逆断面的情形类似,给出了集合Ι和Λ的定义.第二节给出了含适当断面的富足半群的若干性质,例如,每个含Q-适当断面的富足半群是局部适当半群;若S°是S的Q-适当断面,则对任何x∈RegS,恒有|V(x)∩S°|=1,这一性质表明富足半群中的Q-适当断面是正则半群中Q-逆断面的推广.利用这些性质得到了主要结果:富足半群S满足正则性条件且含有Q-适当断面当且仅当S可作为理想嵌入到一个满足正则性条件的局部适当半群T中,且T含有幂等元u,使对任何f∈E(S),恒有fuR*fL*uf.作为上述结论的一个特殊情形,证明了富足半群满足正则性条件且含有可乘适当断面当且仅当它可嵌入到一个满足正则性条件且含有中心正规幂等元的局部适当半群中. 相似文献
53.
陈岩 《哈尔滨师范大学自然科学学报》1997,13(3):92-97
以大白鼠为实验材料,利用Biocytin作为示踪素,在Vitro水平上采用细胞内注入的方法,揭示其听觉皮层锥体神经元的形态学特性。 相似文献
54.
伊保林 《青海师范大学学报(自然科学版)》1994,(4):1-3
本文给出了右正则中间等元的概念,并且由含右正则中间幂等元u的幂等元生成正则半群E和右逆半群S,构造出正则半群W,它含有右正则中间幂等元,而且使与同构,右逆半群与S同构,完成了对有右正则中间幂等元的这类正则半群的刻划,对称地研究有左正则中间幂等的正则半群,从而作为推论可以得到Blyth,T.S和R.B.Mcfadden[1]的结果。 相似文献
55.
The present study aims to investigate the neural correlates underlying humans’ sensitivity to valence differences in negative stimuli. Event-related potentials (ERPs) for highly negative (HN), moderately negative (MN), and Neutral pictures were recorded while subjects perform a standard/deviant categorization task, irrespective of the emotional valence of the deviants. The results show more negative ERP deflections during HN condition than during MN condition at each 50 ms interval from 350 to 650 ms after stimulus onset (at P3 and slow negative wave (SNW) components). Moreover, emotional effect was also observed for MN stimuli at P3 component (350—450 ms interval). Dipole analyses on the HN-MN difference wave during 350—450 ms interval (P3 component) and that during 450—650 ms interval (SNW component) were both localized to the right medial temporal lobe. Thus, the present study confirmed the human sensitivity to valence variations in emotionally negative stimuli, and further showed that the right medial temporal lobe, in particular, the right hippocampus/amygdala complex, may be the critical neural substrates underlying humans’ differential sensitivity to emotionally negative stimuli of varying valences. 相似文献
56.
Electrophysiological studies have utilized event-related brain potentials (ERPs) to investigate neural processes related to the evaluation of the outcome of behavioral performance or to the evaluation of external feedback. The feedback-related negativity (FRN) in brain potentials has been shown to be sensitive to information indicating monetary loss or negative feedback. Since monetary loss usually indicates both the consequence of previous performance and the reward value of stimuli, it is controversial whether the FRN reflects the cognitive process of error detection per se and/or the motivational/affective process related to the subjective evaluation of the error. This study manipulated the motivational/affective significance of negative feedback by penalizing errors in a context-dependent way in a line judgment task. Participants could lose more money in the loss incentive condition or win less money in the win incentive condition if their subsequent judgment of line segments was less accurate, whereas they could receive performance feedback but without monetary incentive in the neutral condition. Results showed that the size of the FRN effect as well as the size of the P300 effect, as assessed by comparing brain responses to the error trials with the responses to the correct trials, increased linearly over the loss, neutral, and win conditions, suggesting that the FRN is sensitive to the motivational/affective evaluation of the performance outcome. 相似文献
57.
脑对双耳听觉信息整合的神经机制 总被引:1,自引:0,他引:1
综述近60 a来有关脑对双耳听觉信息整合的神经机制的研究进展.首先介绍了脑处理双耳信息的神经解剖学基础,双耳神经元的分类及其生理特性,以及双耳神经元在听觉系统的拓扑学分布研究;然后对脑处理双耳听觉信息研究的热点领域进行了重点探讨,综述了上橄榄复合体、下丘和听皮层双耳神经元对双耳时间差和双耳强度差的编码方式,以及脑通过对这些参数的编码来分析声源方位的神经生理学研究进展;最后对该领域未来研究方向作展望. 相似文献
58.
提出了一种基于叶点识别的中轴生成新算法,该算法对于具有复杂几何形状的物体的变化有着普遍的适应性,通过分析中轴与结构奇异性之间的关系,作者提出了基于中轴的自适应有限元模糊控制的思想。 相似文献
59.
60.
Kang Cheng 《自然科学进展(英文版)》2007,17(13):19-23
Among the many neuroimaging tools available for studying human brain functions, functional magnetic resonance imaging (fMRI) is the most widely used today. One advantage of fMRI over other imaging techniques is its relatively high spatial resolution. High-resolution fMRI, with its superb signal-to-noise ratio and improved tissue-vessel specificity, has strengthened the capability of fMRI and allowed mapping of fine cortical architectures in the human brain. In this review, I will first explain the factors limiting the spatial specificity of the blood oxygenation level-dependent (BOLD) effect, based on which most of fMRI experiments are conducted, and the measures dealing with these factors, and then briefly introduce several high-resolution (sub-millimeter) studies on the functional organization of human primary visual cortex (V1), including mapping of ocular dominance columns, mapping of temporal frequency dependent domains and direct demonstration of tuning to stimulus orientation. 相似文献