全文获取类型
| 收费全文 | 3685篇 |
| 免费 | 514篇 |
| 国内免费 | 203篇 |
专业分类
| 电工技术 | 262篇 |
| 综合类 | 554篇 |
| 化学工业 | 201篇 |
| 金属工艺 | 64篇 |
| 机械仪表 | 229篇 |
| 建筑科学 | 113篇 |
| 矿业工程 | 42篇 |
| 能源动力 | 65篇 |
| 轻工业 | 84篇 |
| 水利工程 | 45篇 |
| 石油天然气 | 52篇 |
| 武器工业 | 51篇 |
| 无线电 | 629篇 |
| 一般工业技术 | 501篇 |
| 冶金工业 | 50篇 |
| 原子能技术 | 37篇 |
| 自动化技术 | 1423篇 |
出版年
| 2025年 | 23篇 |
| 2024年 | 70篇 |
| 2023年 | 82篇 |
| 2022年 | 61篇 |
| 2021年 | 100篇 |
| 2020年 | 137篇 |
| 2019年 | 119篇 |
| 2018年 | 138篇 |
| 2017年 | 146篇 |
| 2016年 | 163篇 |
| 2015年 | 143篇 |
| 2014年 | 187篇 |
| 2013年 | 246篇 |
| 2012年 | 314篇 |
| 2011年 | 281篇 |
| 2010年 | 205篇 |
| 2009年 | 223篇 |
| 2008年 | 214篇 |
| 2007年 | 210篇 |
| 2006年 | 169篇 |
| 2005年 | 147篇 |
| 2004年 | 143篇 |
| 2003年 | 119篇 |
| 2002年 | 86篇 |
| 2001年 | 102篇 |
| 2000年 | 76篇 |
| 1999年 | 56篇 |
| 1998年 | 47篇 |
| 1997年 | 40篇 |
| 1996年 | 49篇 |
| 1995年 | 53篇 |
| 1994年 | 47篇 |
| 1993年 | 29篇 |
| 1992年 | 33篇 |
| 1991年 | 21篇 |
| 1990年 | 19篇 |
| 1989年 | 18篇 |
| 1988年 | 9篇 |
| 1987年 | 7篇 |
| 1986年 | 10篇 |
| 1985年 | 5篇 |
| 1984年 | 7篇 |
| 1983年 | 4篇 |
| 1982年 | 6篇 |
| 1981年 | 6篇 |
| 1980年 | 5篇 |
| 1979年 | 5篇 |
| 1977年 | 3篇 |
| 1976年 | 4篇 |
| 1955年 | 5篇 |
排序方式： 共有4402条查询结果，搜索用时 0 毫秒
71.
Deepak K. Gupta Fred van Keulen Matthijs Langelaar 《International journal for numerical methods in engineering》2020,121(3):450-476
Multiresolution topology optimization (MTO) methods involve decoupling of the design and analysis discretizations, such that a high-resolution design can be obtained at relatively low analysis costs. Recent studies have shown that the MTO method can be approximately 3 and 30 times faster than the traditional topology optimization method for two-dimensional (2D) and three-dimensional (3D) problems, respectively. To further exploit the potential of decoupling analysis and design, we propose a dp-adaptive MTO method, which involves locally increasing/decreasing the polynomial degree of the shape functions (p) and the design resolution (d). The adaptive refinement/coarsening is performed using a composite refinement indicator that includes criteria based on analysis error, presence of intermediate densities, as well as the occurrence of design artifacts referred to as QR-patterns. While standard MTO must rely on filtering to suppress QR-patterns, the proposed adaptive method ensures efficiently that these artifacts are suppressed in the final design, without sacrificing the design resolution. The applicability of the dp-adaptive MTO method is demonstrated on several 2D mechanical design problems. For all the cases, significant speedups in computational time are obtained. In particular for design problems involving low material volume fractions, speedups of up to a factor of 10 can be obtained over the conventional MTO method. 相似文献
72.
Tittu Varghese Mathew Jayamanideep Rebbagondla Sundararajan Natarajan 《International journal for numerical methods in engineering》2020,121(19):4329-4346
Nouy and Clement introduced the stochastic extended finite element method to solve linear elasticity problem defined on random domain. The material properties and boundary conditions were assumed to be deterministic. In this work, we extend this framework to account for multiple independent input uncertainties, namely, material, geometry, and external force uncertainties. The stochastic field is represented using the polynomial chaos expansion. The challenge in numerical integration over multidimensional probabilistic space is addressed using the pseudo-spectral Galerkin method. Thereafter, a sensitivity analysis based on Sobol indices using the derived stochastic extended Finite Element Method solution is presented. The efficiency and accuracy of the proposed novel framework against conventional Monte Carlo methods is elucidated in detail for a few one and two dimensional problems. 相似文献
73.
AbstractCryptographic attacks are typically constructed by black-box methods and combinations of simpler properties, for example in [Generalised] Linear Cryptanalysis. In this article, we work with a more recent white-box algebraic-constructive methodology. Polynomial invariant attacks on a block cipher are constructed explicitly through the study of the space of Boolean polynomials which does not have a unique factorisation and solving the so-called Fundamental Equation (FE). Some recent invariant attacks are quite symmetric and exhibit some sort of clear structure, or work only when the Boolean function is degenerate. As a proof of concept, we construct an attack where a highly irregular product of seven polynomials is an invariant for any number of rounds for T-310 under certain conditions on the long term key and for any key and any IV. A key feature of our attack is that it works for any Boolean function which satisfies a specific annihilation property. We evaluate very precisely the probability that our attack works when the Boolean function is chosen uniformly at random. 相似文献
74.
给出了Chebyshev多项式与幂函数互化的系数计算递推公式 ,并由此得到了类似杨辉三角的系数计算和Chebyshev多项式与一般多项式的互化算法 ,进一步得到了多项式精简的算法 . 相似文献
75.
针对磁轴承悬浮力分析比较复杂的问题,提出利用场路结合分析磁轴承悬浮力的方法.基于磁路法推导了径向磁轴承悬浮力的线性化模型,针对具体的磁轴承系统,利用有限元法分析了磁轴承能够满足线性化模型的偏置电流选择范围和磁轴承转子偏移范围,通过最小二乘法修正了线性化模型的电流刚度系数和位移刚度系数,并对超出线性化模型范围的悬浮力进行... 相似文献
76.
以牛顿法为基础,提出了一种拟牛顿法的逆布雷顿秩1的方法来计算配电网络的潮流,该方法减少了每步迭代的计算量和计算时间。与经典的保留二阶项配电网络潮流算法相比,拟牛顿法计算速度快,且能很快收敛,IEEE33节点、145节点的配电系统算例,验证了所提方法的有效性。 相似文献
77.
本文对特征多项式方程的稳定性,提出了基于辗转相除的连分式稳定判据,原理清晰,证明容易。它还能在特征多项式方程缺项和不稳定的情况下,指出正根的个数。也推导了它和劳斯判据、古尔维茨判据之间的关系式,并且对米哈伊洛夫判据曲线进行了改良。 相似文献
78.
在未来多能互补、综合能源系统的背景下,传统配电网和配气网独立调度运行的模式已经不能满足多种能源互补的运行要求。为此,该文提出气电综合能源配网系统最优潮流的凸优化方法,即利用二阶锥规划方法对配电网潮流方程约束进行处理,并提出运用增强二阶锥规划与泰勒级数展开相结合的方法对天然气潮流方程约束进行处理,进而将非线性的气电综合能源配网系统优化调度问题转化为混合整数二阶锥规划模型,为气电综合能源配网的气/电协调优化运行和规划设计提供支撑。同时在配网系统中引入气电联合需求响应来提高系统调度的可控性和灵活性,从而更好的消纳新能源,以达到配网系统的优化运行。仿真结果表明,运用增强二阶锥规划与泰勒级数展开相结合的方法能更好提高配气网的二阶锥松弛精度,且考虑气电联合需求响应能够提高综合能源配网系统运行的经济性和新能源的消纳能力。 相似文献
79.
《Displays》2016
In this paper, we introduce an efficient demosaicking method based on Taylor series and adaptive direction selection using adaptive weight. Taylor series is used to approximate the to-be-interpolated value using values of neighbor pixels in four directions. Instead of estimating the edge orientations via limited candidate directions as conventional demosaicking methods, we propose an adaptive direction and weight selection based demosaicking method to achieve high efficiency. The weight is used to evaluate the similarity among the neighbor pixels. Experimental results indicate that the proposed method outperforms existing approaches in both objective and subjective performance. 相似文献
80.
Financial time series prediction is regarded as one of the most challenging job because of its inherent complexity, and the hybrid forecasting model incorporating autoregressive integrated moving average and support vector machine (SVM) has been implemented widely to deal with the both linear and nonlinear patterns in time series data. However, the SVM model does not take into consideration the time correlation knowledge between different data points in time series, which impacts the learning efficiency of the SVM in real application. To overcome this restriction, this paper proposes the Taylor Expansion Forecasting model as an alternative to the SVM and develops a novel hybrid methodology via combining autoregressive integrated moving average and Taylor Expansion Forecasting to exploit the comprehensive forecasting capacity to the financial time series data with noise. Both theoretical proof and empirical results obtained on several commodity future prices demonstrate that the proposed hybrid model improves greatly the forecasting accuracy. 相似文献