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野营折叠网壳结构表面定常风场的数值模拟研究 总被引:1,自引:0,他引:1
基于流体动力学基本原理和大气边界层基本理论,运用计算流体动力学软件Fluent6.3对野营折叠网壳结构表面风压分布进行数值模拟技术的基础性研究,对比与风洞试验数据,确定复杂体型结构数值模拟时的计算域尺寸、网格划分方式、网格数量、湍流模型等基本参数设定,得到野营折叠网壳在不同风向角下的表面风压分布及其结构体形系数,同风洞试验结果对比,吻和较好。分析表明风速对结构风荷载体形系数影响较小,而风向角对风荷载体形系数的影响较大;所得结构的体形系数,为类似体型结构的抗风设计提供依据。 相似文献
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Increasing consumption of ultra-processed products from early age has raised growing concerns. In this context, the aims of the present work were: i) to explore the automatic mental associations raised by packages of ultra-processed products among parents of children under 12 months of age, ii) to estimate the valence of the affective reactions elicited by ultra-processed products, and iii) to explore the influence of socio-demographic variables and feeding styles on the valence of parents' associations with ultra-processed products. A total of 419 parents of children under 12 months of age were recruited at 20 health facilities that offer well-child services, selected using probability proportional to size sampling based on the number of births at each institution. Participants were presented with the labels of six ultra-processed products (corn snack, frankfurters, milk dessert, orange juice, wafer cookies, yogurt) and were asked to indicate the first words that came to their mind. The products raised mixed mental associations, which were mainly related to pleasure and health. Responses from the majority of participants (61–82%) evidenced negative associations with corn snacks, frankfurters and wafer cookies, whereas responses from 35 to 45% of the participants suggested a positive affective reaction towards orange juice, milk dessert and yogurt. Likelihood of having a positive affective reaction towards the evaluated ultra-processed products was higher for parents of 1 to 4 months infants, as well as those from low educational level and low socio-economic status. In addition, beliefs about three feeding practices (restriction on diet quality, indulgence in screen use and pressure for finishing) significantly influenced the valence of the associations. Results from the present work suggest the need to implement regulatory measures to reduce positive associations with ultra-processed products among parents and contribute to reduce their consumption among infants. 相似文献
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Elevation datasets (e.g. point clouds) are an essential but often unavailable ingredient for the construction of 3D city models. We investigate in this paper to what extent can 3D city models be generated solely from 2D data without elevation measurements. We show that it is possible to predict the height of buildings from 2D data (their footprints and attributes available in volunteered geoinformation and cadastre), and then extrude their footprints to obtain 3D models suitable for a multitude of applications. The predictions have been carried out with machine learning techniques (random forests) using 10 different attributes and their combinations, which mirror different scenarios of completeness of real-world data. Some of the scenarios resulted in surprisingly good performance (given the circumstances): we have achieved a mean absolute error of 0.8m in the inferred heights, which satisfies the accuracy recommendations of CityGML for LOD1 models and the needs of several GIS analyses. We show that our method can be used in practice to generate 3D city models where there are no elevation data, and to supplement existing datasets with 3D models of newly constructed buildings to facilitate rapid update and maintenance of data. 相似文献
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介绍了太阳能光伏技术的基本原理、系统组成(由太阳能电池板、蓄电池、控制器、逆变器组成)、运行方式(有独立系统、群控系统、并网系统、混合系统、并网混合系统几种运行方式)、太阳能电池板的安装要求等,分析了光伏技术在建筑照明、太阳能水泵、光伏建筑一体化等领域的应用。 相似文献
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对新疆伊犁自治州果子沟斜拉桥Z2#主塔施工中针对主塔进行塔梁异步施工的特点,将施工中的测量监控与测量放样结合起来,从而改进工作流程,提高工作效率,确保主塔施工精度。 相似文献
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采用台架试验方法评估了在改变发动机进口温度、功率及转速条件下,优能120纳米冷却液对油电混动车运行热效率的影响。结果表明:温度由90℃切换至95℃时,发动机的出口温度为108℃,比参比防冻液要高9.29℃,此时平均油耗下降11.85%,最大油耗下降18.1%,发电效率提高0.52%,并且入口温度提高后其增加的油耗量仅占防冻液的20%。热机效率的提高是纳米冷却液提升了气缸工作温度,高沸点与高换热率降低了流体由于汽化产生气阻与热损失,及"发动机高温燃烧→水箱快速散热→发动机高温燃烧"周期性循环热平衡运行机制三者共同作用的结果。试验出现过热停机现象是由于发动机进口温度被恒定至设定值,故流经水箱的纳米流体的快速降温作用无法体现所致。 相似文献
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