全文获取类型
收费全文 | 613篇 |
免费 | 120篇 |
国内免费 | 57篇 |
学科分类
工业技术 | 790篇 |
出版年
2023年 | 3篇 |
2022年 | 5篇 |
2021年 | 11篇 |
2020年 | 21篇 |
2019年 | 30篇 |
2018年 | 24篇 |
2017年 | 43篇 |
2016年 | 35篇 |
2015年 | 41篇 |
2014年 | 47篇 |
2013年 | 35篇 |
2012年 | 37篇 |
2011年 | 41篇 |
2010年 | 36篇 |
2009年 | 31篇 |
2008年 | 28篇 |
2007年 | 31篇 |
2006年 | 33篇 |
2005年 | 20篇 |
2004年 | 25篇 |
2003年 | 33篇 |
2002年 | 38篇 |
2001年 | 44篇 |
2000年 | 27篇 |
1999年 | 22篇 |
1998年 | 20篇 |
1997年 | 12篇 |
1996年 | 9篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
排序方式: 共有790条查询结果,搜索用时 15 毫秒
51.
本文构造了一类具有任意阶奇异性的平面和空间等参数和亚参数单元,并证明了在单元内部和边界上具有相同的奇异性且在缺口或裂缝尖端总应变能处处有界。此外,文中还讨论了它们在线弹性V型口和幂硬化材料裂缝等问题中的应用。 相似文献
52.
一种十字丝中心坐标检测方法 总被引:1,自引:0,他引:1
数字图像中十字丝中心位置的检测方法较多,十字丝模板匹配和边缘检测等算法存在运算量大、实时性不强等问题.提出十字丝中心综合检测方法,该方法计算量小,主要运用图像分块、十字中心查找、灰度阈值、逻辑排除、十字模板匹配等技术.讨论不同方法的应用条件、提供具体参数并分析实验结果.实际运行情况表明,十字丝坐标综合检测方法有效可行. 相似文献
53.
54.
55.
偏轴钻具组合防斜打快的强度分析 总被引:14,自引:0,他引:14
针对偏轴防斜打快技术中所用的钻具组合的受力状态复杂,对整个钻柱系统的安全性有较大影响的问题,考虑安全、有效的钻井施工特别需要对偏轴接头及接头附近的钻铤强度进行分析,找出钻具组合的危险点,以便于校核钻具组合的强度和改进偏轴钻具组合的结构设计的实际.以下部钻柱为研究对象,将钻头以上部分分成多个梁单元,进行结构离散,建立力学模型,采用有限元分析方法,进行偏轴接头强度分析.研究表明,偏轴钻具防斜钻具组合的最大复合应力发生在偏轴接头与下部钻铤的结合部位,主要由弯曲载荷和轴向力产生.在应力最危险部位,应特别注意钻具的强度安全问题. 相似文献
56.
Maria Carmen Falvo Richard BartoniGennaro Maranzano 《Electric Power Systems Research》2011,81(12):2127-2138
The energy consumptions growth, the upward interest for environmental sustainability and the technological evolution carry to the necessity to review the planning criteria of urban mobility systems in large cities and metropolitan areas. With this aim, new studies and projects are in progress, especially dealing with the power systems for metro-transit lines and surface electric vehicles. In this framework, the authors perform a study that, from an overview about the main energy management issues connected to the city transport, provides an innovative proposal for the design of sustainable urban mobility system: the integration of the metro-lines with surface plug-in electric vehicles. The present paper includes the energy analysis results, obtained by an application on a real case study of an home-made simulation software, describes the proposal in terms of power systems architecture and business models, pointing out the potential advantages that its implementation could give in terms of energy saving, environmental sustainability and reduced economic impact, as a result of the maximum exploitation of existing electric power plant. 相似文献
57.
螺旋理论以其几何概念清楚,物理意义明确,表达形式简单等优势,常被用于分析机构的自由度。按照传统的G-K(Grubler-Kutzbach)公式,能较容易地计算出串联机构的自由度,而对于一些特殊机构,尤其是含有闭环子链的复杂并联机构,往往无法便捷、正确地求解其自由度。为解决以上问题,以一种拓扑结构为[3-R(4S)1-RUPU]+R型的Delta并联机器人为研究对象,对其4S闭环子链进行了等效运动副螺旋系的求解,并判别了机构的局部自由度以及公共约束;利用修正的G-K公式,分别对原机构和等效后的机构进行了自由度的验证。结果表明:两种情形下的自由度数均为4,且自由度的性质为3平移1旋转,与实际设计相符。 相似文献
58.
59.
The present paper contributes in the discussion of heterogeneous gas/metal reactions by discussing the influence of the dew point (dp) during intercritical annealing on the sub‐surface constitution. Annealing trials with different Advanced High Strength Steels (AHSS) were carried out and the element distribution within the sub‐surface was analysed by glow discharge optical emission spectrometer (GD‐OES). For modelling purpose the gained element distribution data were adjusted in a way that the selective oxidation products were considered within the sub‐surface element profiles. Several transformation temperatures along the depth profiles according to the adjusted GD‐OES data have been computed for the dp ?30 °C and +5 °C. In all cases the according models have been implemented in Matlab. The thermodynamic data have been obtained via the Matlab‐ThermoCalc interface. Empirical equations have been applied for the determination of the bainite and martensite start temperatures. It is shown that the sub‐surface constitution and the transformation temperature differ significantly. In most cases the change of the transformation temperature within the surface and sub‐surface reaches up to 100 °C compared to the bulk. For a Dual‐Phase (DP) Steel with C(0.15%)Mn(1.7%)Al(1.7%)Cr(0.5%), the change of the A<sub>e1sub>‐temperature is with 300 °C significantly higher. However one has to keep in mind that the 2‐phase composition can not be assumed to be constant during intercritical annealing. It is therefore concluded that for the purpose of simulating the selective oxidation processes during intercritical annealing of AHSS the continuous change of the sub‐surface constitution must be incorporated in the future work. 相似文献
60.
We present a sub‐structuring method for the coupling between a large elastic structure, and a stratified soil half‐space exhibiting random heterogeneities over a bounded domain and impinged by incident waves. Both media are also weakly dissipative. The concept of interfaces classically used in sub‐structuring methods is extended to ‘volume interfaces’ in the proposed approach. The random dimension of the stochastic fields modelling the heterogeneities in the soil is reduced by introducing a Karhunen–Loéve expansion of these stochastic fields. The coupled overall problem is solved by Monte‐Carlo simulation techniques. A realistic example of a large industrial structure interacting with an uncertain stratified soil medium under earthquake is finally presented. This case study and others validate the presented methodology and its ability to handle complex mechanical systems. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献