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目的:考察苍术遗传变异与挥发油变异的关系,揭示苍术挥发油变异的生物学基础。方法:分单株取来源于多个居群的苍术,同株苍术根茎与叶片采用同一编号,根茎用GC—MS分析挥发油变异,叶片采用随机扩增多态性(RAPD)技术分析遗传变异,然后利用方差分析、聚类分析等分析二者的关系。结果:①不论在个体水平还是居群水平,苍术非道地药材与道地药材的差异显著,前者(居群Ⅰ和Ⅱ的亚居群1~5,样品1~36)主要由茅术醇和p-桉叶醇组分;后者(居群Ⅲ的亚居群6、7,样品37—47)主要由苍术酮和苍术素组成,并含有较多茅术醇和p-桉叶醇;②RAPD数据在居群水平的分析显示,苍术居群Ⅱ和Ⅲ聚类后,再与居群Ⅰ聚类。个体水平上,居群Ⅲ的全部11个个体聚为一类,亚居群5的5个个体聚类,其他苍术个体均为按居群或亚居群聚类。结论:不论在居群水平还是个体水平,苍术挥发油变异与遗传变异均呈现出特有的规律性,但二者并不一致,提示除了遗传因子外,环境因子对苍术道地药材的形成具有重要作用。 相似文献
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Rocío L. Cecchini Carlos M. Lorenzetti Ana G. Maguitman Nlida Beatríz Brignole 《Information processing & management》2008,44(6):1863
Systems for searching the Web based on thematic contexts can be built on top of a conventional search engine and benefit from the huge amount of content as well as from the functionality available through the search engine interface. The quality of the material collected by such systems is highly dependant on the vocabulary used to generate the search queries. In this scenario, selecting good query terms can be seen as an optimization problem where the objective function to be optimized is based on the effectiveness of a query to retrieve relevant material. Some characteristics of this optimization problem are: (1) the high-dimensionality of the search space, where candidate solutions are queries and each term corresponds to a different dimension, (2) the existence of acceptable suboptimal solutions, (3) the possibility of finding multiple solutions, and in many cases (4) the quest for novelty. This article describes optimization techniques based on Genetic Algorithms to evolve “good query terms” in the context of a given topic. The proposed techniques place emphasis on searching for novel material that is related to the search context. We discuss the use of a mutation pool to allow the generation of queries with new terms, study the effect of different mutation rates on the exploration of query-space, and discuss the use of a especially developed fitness function that favors the construction of queries containing novel but related terms. 相似文献
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In order to test the hypothesis that genetic influences are moreimportant as a cause of reading disability in girls than in boys,composite reading performance data from identical and fraternal twinpairs were analyzed using both concordance and multiple regressionmethods. The sample included 206 identical (99 male, 107 female), 159same-sex fraternal (90 male, 69 female), and 117 opposite-sex fraternaltwin pairs, in which at least one member of each pair had readingdifficulties. Although the difference between the concordance rates forreading disabilities in female identical and same-sex fraternal twinpairs was somewhat greater (65% for identical twins vs.32% for fraternal twins) than the difference in concordance ratesfor boys (68% vs. 39%), loglinear analysis of thesecategorical data revealed that the interaction between sex, zygosity,and concordance was not significant (p > 0.70). Moreover,the heritability of reading disability(h
2
g) estimated from regression analysisof the reading performance data in males was nearly identical to that infemales (h
2
g = 0.58 and 0.59,respectively; p > 0.90). Thus, results of this studyprovide little or no evidence for the hypothesis of greater geneticinfluence on reading difficulties in girls than in boys. 相似文献
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许多复杂的图像处理需要结合其他的图像处理算法才能实现,因此,主要介绍了计算机图像处理中的图像草稿效果算法,并在该算法的基础上利用VB6.0语言所提供的图像处理功能实现了图像表面的草稿效果。 相似文献
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针对Hopfield网络在求解优化问题中学习效率低,收敛速度慢,容易陷入局部最优等缺点和不足,把遗传算法同Hopfield网络结合起来,形成进化神经网络,对网络权值进行优化,并且通过对算法的讨论,说明该算法的有效性。 相似文献
90.
Genetic and Rare Disease Diagnoses: A Review of Resources for Patients and Health Care Professionals
Rachel F. Fenske 《Medical reference services quarterly》2020,39(3):254-268
Abstract This article reviews genetic and rare disease resources from the National Library of Medicine and National Institutes of Health that assist patients and their families to decipher the complexity of rare and genetically related diseases. Librarians can use these resources to guide those seeking genetic information that encompasses the medical, social, psychological, and financial aspects of living with a rare disease. Physicians and healthcare professionals will find these resources helpful when assisting patients and engaging in genetic research. 相似文献