全文获取类型
收费全文 | 1166篇 |
免费 | 157篇 |
国内免费 | 138篇 |
专业分类
电工技术 | 35篇 |
综合类 | 134篇 |
化学工业 | 149篇 |
金属工艺 | 7篇 |
机械仪表 | 33篇 |
建筑科学 | 199篇 |
矿业工程 | 96篇 |
能源动力 | 32篇 |
轻工业 | 7篇 |
水利工程 | 203篇 |
石油天然气 | 11篇 |
武器工业 | 2篇 |
无线电 | 53篇 |
一般工业技术 | 167篇 |
冶金工业 | 22篇 |
原子能技术 | 4篇 |
自动化技术 | 307篇 |
出版年
2024年 | 6篇 |
2023年 | 27篇 |
2022年 | 47篇 |
2021年 | 53篇 |
2020年 | 58篇 |
2019年 | 45篇 |
2018年 | 35篇 |
2017年 | 57篇 |
2016年 | 47篇 |
2015年 | 62篇 |
2014年 | 78篇 |
2013年 | 59篇 |
2012年 | 70篇 |
2011年 | 111篇 |
2010年 | 98篇 |
2009年 | 101篇 |
2008年 | 103篇 |
2007年 | 105篇 |
2006年 | 74篇 |
2005年 | 57篇 |
2004年 | 52篇 |
2003年 | 45篇 |
2002年 | 25篇 |
2001年 | 14篇 |
2000年 | 11篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1986年 | 2篇 |
1979年 | 2篇 |
排序方式: 共有1461条查询结果,搜索用时 0 毫秒
51.
推土板切土角对干土壤动态行为影响的离散元模拟 总被引:6,自引:2,他引:4
根据液桥对土壤微观力学结构的影响,在传统离散单元法理论的基础上,建立了土壤颗粒接触非线性力学模型,并对不同切土角推土板前端干土壤的动态行为进行了离散元模拟。准确再现了实验室实验中切土角对板面前端干土壤动态行为影响的定性和定量结果,并通过离散元细观分析从土壤内部土壤颗粒运动合理解释了干土壤宏观形态的变化规律和影响因素。 相似文献
52.
Hongyang Cheng Haruyuki Yamamoto Klaus Thoeni Yang Wu 《Geotextiles and Geomembranes》2017,45(4):361-376
This paper presents a novel analytical solution for geotextile-wrapped soil based on a comprehensive numerical analysis conducted using the discrete element method (DEM). By examining the soil–geotextile interface friction, principal stress distribution, and stress–strain relations of the constituent soil and geotextile in the DEM analysis, a complete picture of the mechanical characterization of geotextile-wrapped soil under uniaxial compression is first provided. With these new insights, key assumptions are verified and developed for the proposed analytical solution. In the DEM analysis, a near-failure state line that predicts stress ratios relative to the maximums at failure with respect to deviatoric strain is uniquely identified; dilation rates are found to be related to stress ratios via a single linear correlation regardless of the tensile stiffness of the geotextile. From these new findings, the assumptions on the stress-state evolution and the stress–dilatancy relation are developed accordingly, and the wrapped granular soil can therefore be modeled as a Mohr–Coulomb elastoplastic solid with evolving stress ratio and dilation rate. The development of the proposed analytical model also demonstrates an innovative approach to take advantage of multiscale insights for the analytical modeling of complex geomaterials. The analytical model is validated with the DEM simulation results of geotextile-wrapped soil under uniaxial compression, considering a wide range of geotextile tensile stiffnesses. To further examine the predictive capacity of the analytical model, the stress–strain response under triaxial compression conditions is solved analytically, taking both different confining pressures and geotextile tensile stiffnesses into account. Good agreement is obtained between the analytical and DEM solutions, which suggests that the key assumptions developed in the uniaxial compression conditions also remain valid for triaxial compression conditions. 相似文献
53.
The discharge behaviour of different port configurations in a HICOM mill is investigated using DEM simulation. The charge in the mill is strongly sheared and circulates rapidly but has a free surface shape that is constant and which rotates with the mill rotation. The horizontal cross-sectional area of the charge decreases with increasing height. Particles within the mill discharge when the rotating charge flows over and is pushed towards the discharge ports. DEM enables the prediction of transient and steady state mass flow rates from each of the individual discharge ports. Twelve discharge ports at different locations in the mill are used here to explore the optimality of the various size and location options and to explore if there is any interaction in the discharge between adjacent ports. This provides information relevant to the operation of this type of mill, guidance for port selection and provides a general demonstration of how DEM can be used to predict transport and discharge behaviour of mills. 相似文献
54.
55.
56.
放顶煤采场顶板运动规律的研究 总被引:8,自引:1,他引:8
利用离散元和有限元数值模拟及力学解析计算,分析了放顶煤采场中上覆岩层运动规律;认为采场上覆岩层运动为分层运动,运动结构为拱-梁结构;拱-梁转换的实现,是以拱顶的失稳升高为条件,在分析了影响顶板运动的主要因素(顶板岩层断裂角、放煤步距、顶板岩层块体尺寸、顶煤厚度)的基础上,认为放煤步距过大(≥2m)会降低放煤率,增大老顶垮落的动压冲击程度。放顶煤工作面与非放顶煤工作面的区别是,采空区充填系数小,顶板岩层运动剧烈,走向方向超前支承应力峰值较大。 相似文献
57.
58.
DEM若干理论问题思考 总被引:3,自引:1,他引:2
对用中误差描述和评价DEM整体精度的DEM随机误差观提出质疑,认为DEM是由带随机误差的原始数据内插而成,DEM误差就应由性质不同的两部分误差组成,即测绘所产生的随机误差和内插所产生的对地表曲面的逼近误差,二者可分别进行质量控制,对于内插误差,应采用定义域内的全部点是否符合最大绝对偏差的一次性否决法进行检验.通过讨论三维地面概念模型和DEM高保真问题等概念,说明DEM误差以随机误差概而论之的实质是漠视了DEM高保真这一质量要求;并结合地图代数研究,论述等高线族和地形结构线族的空间几何对偶关系———后者是前者的广义Voronoi界线,因此,当利用等高线数据生产DEM时,并不存在选择性采样F-S数据的必要. 相似文献
59.
Liqiang Lu Jia Yu Xi Gao Yupeng Xu Mehrdad Shahnam William A. Rogers 《American Institute of Chemical Engineers》2020,66(6):e16969
This article investigated the fluidization of sands and small Geldart A biomass mixtures. The mixture fluidized like Geldart A type particles with a uniform bed expansion regime before bubbling. The video recorded color distance between pure sands and sands–biomass mixtures was used to estimate the sands–biomass mixing. The coarse-grained computational fluid dynamics–discrete element method with a hybrid drag model which couples the Syamlal–O'Brien drag and a filtered drag can capture the mixing while the simulation with Gidaspow drag predicted a segregated bed. The simulations were further validated with experimental measured pressure drops. The time averaged pressure drop equals the weight of the bed material, however, its fluctuation is about three times of the bed material fluctuation. 相似文献
60.