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熊子仙 《植物学报》1998,15(3):73-76
本文介绍了Melvill提出的生殖叶学说中的有关生殖叶的概念,雌蕊和雄蕊的起源及同种演化方式。并结合心皮学说进行了讨论。  相似文献   

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均匀度理论   总被引:7,自引:0,他引:7  
根据生态学的格局研究成果,将格局的研究推广到了n维欧氏空间,在任意整数维的欧氏空间建立了均匀度,通过建立“被含”概念,解决了边界问题,并证明n维被合随机格局的被含均匀度定理.  相似文献   

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The study of speciation has become one of the most active areas of evolutionary biology, and substantial progress has been made in documenting and understanding phenomena ranging from sympatric speciation and reinforcement to the evolutionary genetics of postzygotic isolation. This progress has been driven largely by empirical results, and most useful theoretical work has concentrated on making sense of empirical patterns. Given the complexity of speciation, mathematical theory is subordinate to verbal theory and generalizations about data. Nevertheless, mathematical theory can provide a useful classification of verbal theories; can help determine the biological plausibility of verbal theories; can determine whether alternative mechanisms of speciation are consistent with empirical patterns; and can occasionally provide predictions that go beyond empirical generalizations. We discuss recent examples of progress in each of these areas.  相似文献   

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The Cohesion-Tension Theory   总被引:2,自引:0,他引:2  
《The New phytologist》2004,163(3):451-452
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Theory in motion     
Modeling studies are now a significant part of mainstream research in motor control. Novel and classical modeling techniques used in recent work on small and large motor systems illustrate the different roles that models play in furthering our understanding of motor systems. The models presented reveal single neuron short-term memory, unexpected effects of reciprocal inhibition and methods for decoding activity in large populations of neurons.  相似文献   

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A Determination Theory   总被引:1,自引:0,他引:1  
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Theory of mind     
Frith C  Frith U 《Current biology : CB》2005,15(17):R644-R646
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Complex dynamical reaction networks consisting of many components that interact and produce each other are difficult to understand, especially, when new component types may appear and present component types may vanish completely. Inspired by Fontana and Buss (Bull. Math. Biol., 56, 1–64) we outline a theory to deal with such systems. The theory consists of two parts. The first part introduces the concept of a chemical organisation as a closed and self-maintaining set of components. This concept allows to map a complex (reaction) network to the set of organisations, providing a new view on the system’s structure. The second part connects dynamics with the set of organisations, which allows to map a movement of the system in state space to a movement in the set of organisations. The relevancy of our theory is underlined by a theorem that says that given a differential equation describing the chemical dynamics of the network, then every stationary state is an instance of an organisation. For demonstration, the theory is applied to a small model of HIV-immune system interaction by Wodarz and Nowak (Proc. Natl. Acad. USA, 96, 14464–14469) and to a large model of the sugar metabolism of E. Coli by Puchalka and Kierzek (Biophys. J., 86, 1357–1372). In both cases organisations where uncovered, which could be related to functions. Both authors contributed equally.  相似文献   

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It is well known to all those acquainted with D. N. Uznadze's theory of set [ustanovka] (1) that this theory was meant to answer the question of "the character and inner structure of human activity" [11; 79]. But, as A. T. Bochorishvili correctly noted, we do not yet have "clarity in basic concepts. … Soviet psychology cannot yet go so far as to speak of the content of the basic concept of the psychology of set, of the content of set itself" [5: 15]. As a panacea for overcoming these differences of opinion, Bochorishvili proposes that we "widely and actively develop investigations of the theoretical bases of the psychology of set as D. N. Uznadze understood if" (ibid.).  相似文献   

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Recently,there are hesitations in the application scope of the classical Cassie theory and Wenzel theory.In this paper,Molecular Dynamics(MD)simulations are use...  相似文献   

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