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排序方式: 共有63条查询结果,搜索用时 125 毫秒
1.
稻田节肢动物群落的营养联系   总被引:7,自引:0,他引:7  
根据田间调查和室内饲养观察的资料,研究了稻田节肢动物群落的营养结构及类型。在稻田生态系统中,物种之间由于取食与被取食、寄生与被寄生、捕食与被捕食的营养联系,形成了复杂的食物链和食物网。依据物种在食物网中的位置和功能,可将福州市郊区稻田节肢动物群落的营养结构分为3种类型:1)食物网中尚未发现有重寄生环节;2)食物网中有重寄生环节;3)食物网中有兼寄生环节。为了探讨定量研究生物群落营养联系的可能性,本文运用图论的知识把食物网的结构描述为标向图、集合或邻接矩阵,同时用图论的运算法则解决了各种类型的食物网的合并问题,为研究复杂群落的营养关系提供了一种新方法。  相似文献
2.
景观生态学中生态连接度研究进展   总被引:7,自引:3,他引:4       下载免费PDF全文
富伟  刘世梁  崔保山  张兆苓 《生态学报》2009,29(11):6174-6182
生态连接度对生物迁移扩散、基因流动、干扰扩散等生态过程具有重要作用,是目前景观生态学研究的热点内容.生态连接度是测度景观对于资源斑块间运动的促进或者阻碍作用程度的指标.它主要基于渗透和图论两大理论,通过实验、模型模拟以及指数等量化方法描述区域景观结构和功能的变化,广泛应用在自然景观和城市景观格局优化中,对生物多样性保护以及城市开放空间规划具有重要作用.介绍生态连接度的理论基础、评价方法,应用以及主要结论,并对景观生态学中生态连接度的未来研究方向进行展望,以促进生态连接度研究的进一步发展.  相似文献
3.
Graph models of habitat mosaics   总被引:5,自引:0,他引:5  
Graph theory is a body of mathematics dealing with problems of connectivity, flow, and routing in networks ranging from social groups to computer networks. Recently, network applications have erupted in many fields, and graph models are now being applied in landscape ecology and conservation biology, particularly for applications couched in metapopulation theory. In these applications, graph nodes represent habitat patches or local populations and links indicate functional connections among populations (i.e. via dispersal). Graphs are models of more complicated real systems, and so it is appropriate to review these applications from the perspective of modelling in general. Here we review recent applications of network theory to habitat patches in landscape mosaics. We consider (1) the conceptual model underlying these applications; (2) formalization and implementation of the graph model; (3) model parameterization; (4) model testing, insights, and predictions available through graph analyses; and (5) potential implications for conservation biology and related applications. In general, and for a variety of ecological systems, we find the graph model a remarkably robust framework for applications concerned with habitat connectivity. We close with suggestions for further work on the parameterization and validation of graph models, and point to some promising analytic insights.  相似文献
4.
图论在中国三尖杉属植物区系地理成分划分中的应用   总被引:4,自引:0,他引:4  
本文根据图论中树与生成树的理论,选用中国三尖杉属(Cephalotaxus)8种植物的地理分布资料,采用图论分类法——Prim法,对国产三尖杉属植物地理分布进行定量研究。结果表明,本文应用图论分类法划分植物区系地理成分基本上是成功的,其结果与传统分析基本相符,尤其是采用不对称信息系数构成相异矩阵的方法;此外,本方法还有以下特点:(1)结果直观、简单;(2)能处理非常复杂的植物地理分布问题;(3)能避免因人为主观意识所引起的片面性甚至错误;(4)能准确地反映各类区系地理成分之间及其在地质时期植物地理联系的“亲缘关系”。  相似文献
5.
6.
Isolation by resistance   总被引:2,自引:0,他引:2  
Despite growing interest in the effects of landscape heterogeneity on genetic structuring, few tools are available to incorporate data on landscape composition into population genetic studies. Analyses of isolation by distance have typically either assumed spatial homogeneity for convenience or applied theoretically unjustified distance metrics to compensate for heterogeneity. Here I propose the isolation-by-resistance (IBR) model as an alternative for predicting equilibrium genetic structuring in complex landscapes. The model predicts a positive relationship between genetic differentiation and the resistance distance, a distance metric that exploits precise relationships between random walk times and effective resistances in electronic networks. As a predictor of genetic differentiation, the resistance distance is both more theoretically justified and more robust to spatial heterogeneity than Euclidean or least cost path-based distance measures. Moreover, the metric can be applied with a wide range of data inputs, including coarse-scale range maps, simple maps of habitat and nonhabitat within a species' range, or complex spatial datasets with habitats and barriers of differing qualities. The IBR model thus provides a flexible and efficient tool to account for habitat heterogeneity in studies of isolation by distance, improve understanding of how landscape characteristics affect genetic structuring, and predict genetic and evolutionary consequences of landscape change.  相似文献
7.
中国地方品种鸡的分类研究   总被引:2,自引:0,他引:2  
中国鸡种资源极为丰富,中国历史上形成的许多优良地方品种鸡,对中国养鸡事业发展和世界养鸡业都曾做出过重要贡献。为充分利用我国地方鸡种资源遗传潜力和杂种优势,本文利用图论主成分分类法与系统聚类法根据20项指标研究了中国30个地方品种鸡的分类问题,分类结果比较符合实际,特别是图论主成分分类图直观清楚,生物学含意明确,对中国鸡种资源和基因库的利用有实际参考价值。  相似文献
8.
Circuits and efficiency in incomplete block designs   总被引:1,自引:0,他引:1  
PATERSON  LINDSAY 《Biometrika》1983,70(1):215-225
9.
Fuite J  Vernon SD  Broderick G 《Genomics》2008,92(6):393-399
This work investigates the significance of changes in association patterns linking indicators of neuroendocrine and immune activity in patients with chronic fatigue syndrome (CFS). Gene sets preferentially expressed in specific immune cell isolates were integrated with neuroendocrine data from a large population-based study. Co-expression patterns linking immune cell activity with hypothalamic–pituitary–adrenal (HPA), thyroidal (HPT) and gonadal (HPG) axis status were computed using mutual information criteria. Networks in control and CFS subjects were compared globally in terms of a weighted graph edit distance. Local re-modeling of node connectivity was quantified by node degree and eigenvector centrality measures. Results indicate statistically significant differences between CFS and control networks determined mainly by re-modeling around pituitary and thyroid nodes as well as an emergent immune sub-network. Findings align with known mechanisms of chronic inflammation and support possible immune-mediated loss of thyroid function in CFS exacerbated by blunted HPA axis responsiveness.  相似文献
10.
Direct reciprocity on graphs   总被引:1,自引:0,他引:1  
Direct reciprocity is a mechanism for the evolution of cooperation based on the idea of repeated encounters between the same two individuals. Here we examine direct reciprocity in structured populations, where individuals occupy the vertices of a graph. The edges denote who interacts with whom. The graph represents spatial structure or a social network. For birth-death or pairwise comparison updating, we find that evolutionary stability of direct reciprocity is more restrictive on a graph than in a well-mixed population, but the condition for reciprocators to be advantageous is less restrictive on a graph. For death-birth and imitation updating, in contrast, both conditions are easier to fulfill on a graph. Moreover, for all four update mechanisms, reciprocators can dominate defectors on a graph, which is never possible in a well-mixed population. We also study the effect of an error rate, which increases with the number of links per individual; interacting with more people simultaneously enhances the probability of making mistakes. We provide analytic derivations for all results.  相似文献
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