全文获取类型
收费全文 | 19047篇 |
免费 | 1722篇 |
国内免费 | 1262篇 |
学科分类
工业技术 | 22031篇 |
出版年
2024年 | 39篇 |
2023年 | 164篇 |
2022年 | 285篇 |
2021年 | 306篇 |
2020年 | 400篇 |
2019年 | 467篇 |
2018年 | 484篇 |
2017年 | 521篇 |
2016年 | 569篇 |
2015年 | 534篇 |
2014年 | 849篇 |
2013年 | 1223篇 |
2012年 | 1277篇 |
2011年 | 1283篇 |
2010年 | 1035篇 |
2009年 | 1029篇 |
2008年 | 1069篇 |
2007年 | 1188篇 |
2006年 | 1122篇 |
2005年 | 953篇 |
2004年 | 849篇 |
2003年 | 780篇 |
2002年 | 675篇 |
2001年 | 541篇 |
2000年 | 541篇 |
1999年 | 541篇 |
1998年 | 467篇 |
1997年 | 427篇 |
1996年 | 397篇 |
1995年 | 384篇 |
1994年 | 304篇 |
1993年 | 260篇 |
1992年 | 229篇 |
1991年 | 205篇 |
1990年 | 165篇 |
1989年 | 136篇 |
1988年 | 104篇 |
1987年 | 57篇 |
1986年 | 43篇 |
1985年 | 34篇 |
1984年 | 25篇 |
1983年 | 12篇 |
1982年 | 15篇 |
1981年 | 17篇 |
1980年 | 3篇 |
1979年 | 8篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1959年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 27 毫秒
991.
《International journal for numerical methods in engineering》2018,115(7):791-824
A new solution approach, based on Tikhonov regularization on the Fredholm integral equations of the first kind, is proposed to find the approximate solutions of the strain softening problems. In this approach, the consistency condition is regularized with the Tikhonov stabilizers along with a regularization parameter, and the internal variable increments are solved from the resulting Euler's equations. It is shown that, as the regularization parameter is increased, the solutions converge to a unique one. A nonlocal yield condition and a nonlocal return mapping algorithm are proposed to carry out the integration of constitutive equations in the time and spatial domains. A global plastic dissipation principle is proposed to relax the classical local plastic dissipation postulate. Numerical examples show that the proposed approach leads to objective, mesh‐independent solutions of the softening‐induced localization problems. A comparison of the results from the proposed approach with those from the gradient‐dependent plasticity model shows that the two models give close solutions. 相似文献
992.
E. Nahvifard 《Journal of Modern Optics》2020,67(6):475-480
ABSTRACTIn this paper, we study detection of the state non-classicality for a quantum harmonic oscillator by a qubit in the presence of dissipation effects. We show that dissipation can enhance the effectiveness of the method in case of using the corrected form of the related nonclassicality witness. Such an improvement is attributed to the fact that dissipation leads to probing a surface, instead of a curve, of the complex plane for non-classicality condition on normally-ordered characteristic function. 相似文献
993.
In this paper, we develop an image pixel based histogram equalization model for image contrast enhancement. The approach is to propose a variational model containing an energy functional to adjust the pixel values of an input image directly so that the resulting histogram can be redistributed to be uniform. This idea is different from existing histogram equalization algorithms where a histogram based on the input image is constructed, a mapping is determined to output a uniform histogram and then the pixel values of the input image are adjusted based on the mapping. In the variational model, a mean brightness term is incorporated to preserve the brightness of the input image, and a geometry constraint can also be added to keep the geometry structure of the input image. Theoretically, the existence of the minimizer of the proposed model, and the convergence of the proposed algorithm are given. Experimental results are reported to demonstrate that the performance of the proposed model are competitive with the other testing histogram equalization methods for several testing images. 相似文献
994.
Juan Zhang 《Asian journal of control》2014,16(1):284-291
In this paper, applying majorization inequalities, new upper and lower bounds for summation of eigenvalues (including the trace) of the solution of the continuous algebraic Riccati equation are presented. Corresponding numerical examples illustrate that our new bounds extend some of the recent results. 相似文献
995.
996.
采用非线性回归方程计算方法,结合实际生产的齿轮钢淬透性数据对数学模型进行修正。在此基础上,开发了齿轮钢淬透性的计算预报平台,实现根据成分和预设的晶粒度级别预报任意端淬距离的淬透性值。模型预测精度高于传统的多元线性回归方法。 相似文献
997.
Market competition requires that organisations excel at both operational performance and innovation. Though process orientation is intended to benefit operations in general, the impact of specific elements remains unclear. The purpose of this study is to identify the specific organisational design components of process orientation that simultaneously influence operational performance and innovation. We survey employees in the financial services sector (N = 1069) regarding the influence of six process-oriented organisation design components on operational performance and innovation using PLS-SEM. The results indicate that organisational structure and process improvement encourage both operational performance and innovation. Personal autonomy is partially beneficial, while the others have no joint influence on operational performance and innovation. This study is first in providing evidence regarding the influence of a broad variety of organisational design components of process orientation on operational performance and innovation. The study contributes to theory on how process orientation improves operational performance and innovation. The findings can serve as a guideline for managers and organisations as to which organisational design components should be implemented to improve operations. 相似文献
998.
田国瑞 《湖南工业职业技术学院学报》2014,(2):20-21
以往对弦的横振动方程进行推导时,一般取其近似值,即很小。本文对角不是很小的情形推导出弦的横振动方程,从而更接近于实际。 相似文献
999.
The sensitivity of the optimal response of a linear system with quadratic performance index to changes in the weighting factors in the performance index is determined. This necessitates finding the sensitivity of the feedback gain matrix K to changes in the weighting factors. It is shown that the sensitivities of K can be obtained as the solution of a set of linear matrix differential equations. Further, for time-invariant systems and an infinite time interval, it is seen that the sensitivities of K are found more simply by solving a set of linear algebraic matrix equations. 相似文献
1000.
《Journal of Process Control》2014,24(1):72-81
In this paper, a new model-order reduction (MOR) approach is presented for reducing large-scale differential-algebraic equation (DAE) systems with higher index. This approach is based upon the balanced truncation, single-point, and multi-point MOR methods. We decompose the DAE system into an ordinary differential equation (ODE) subsystem and a DAE subsystem. The DAE subsystem has the same index as the original DAE system. Then, the balanced truncation method is applied to the ODE subsystem. Both single-point and multi-point methods are used to reduce the DAE subsystem. In generally, the multi-point method can perform better than the single-point method across a wide-range of frequencies. Some numerical examples demonstrate the effectiveness of our approach. 相似文献