全文获取类型
收费全文 | 5265篇 |
免费 | 785篇 |
国内免费 | 652篇 |
专业分类
电工技术 | 444篇 |
综合类 | 447篇 |
化学工业 | 166篇 |
金属工艺 | 49篇 |
机械仪表 | 244篇 |
建筑科学 | 161篇 |
矿业工程 | 53篇 |
能源动力 | 130篇 |
轻工业 | 55篇 |
水利工程 | 294篇 |
石油天然气 | 24篇 |
武器工业 | 29篇 |
无线电 | 501篇 |
一般工业技术 | 430篇 |
冶金工业 | 378篇 |
原子能技术 | 14篇 |
自动化技术 | 3283篇 |
出版年
2024年 | 50篇 |
2023年 | 145篇 |
2022年 | 200篇 |
2021年 | 219篇 |
2020年 | 219篇 |
2019年 | 208篇 |
2018年 | 178篇 |
2017年 | 219篇 |
2016年 | 253篇 |
2015年 | 233篇 |
2014年 | 298篇 |
2013年 | 361篇 |
2012年 | 316篇 |
2011年 | 352篇 |
2010年 | 289篇 |
2009年 | 323篇 |
2008年 | 318篇 |
2007年 | 324篇 |
2006年 | 331篇 |
2005年 | 295篇 |
2004年 | 262篇 |
2003年 | 229篇 |
2002年 | 205篇 |
2001年 | 136篇 |
2000年 | 133篇 |
1999年 | 103篇 |
1998年 | 95篇 |
1997年 | 70篇 |
1996年 | 68篇 |
1995年 | 49篇 |
1994年 | 36篇 |
1993年 | 37篇 |
1992年 | 20篇 |
1991年 | 28篇 |
1990年 | 19篇 |
1989年 | 18篇 |
1988年 | 8篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 8篇 |
1984年 | 9篇 |
1983年 | 3篇 |
1982年 | 7篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1965年 | 2篇 |
1964年 | 2篇 |
1963年 | 2篇 |
1960年 | 2篇 |
1956年 | 1篇 |
排序方式: 共有6702条查询结果,搜索用时 31 毫秒
11.
讨论了输出终端带不等式约束情形的多输入多输出系统,说明了这些约束可以通过修改输入柔化系数而使其得以满足,在柔化系数的选择范围确定过程中,为了避免矩阵求逆,采用利用已知数据辨识参数的方法来确定柔化系数,从而使得问题简化。降低了计算量且加快了收敛速度。 相似文献
12.
Thirty patients who had undergone either a right or left unilateral temporal lobectomy (14 RTL; 16 LTL) and 16 control participants were tested on a computerized human analogue of the Morris Water Maze. The procedure was designed to compare allocentric and egocentric spatial memory. In the allocentric condition, participants searched for a target location on the screen, guided by object cues. Between trials, participants had to walk around the screen, which disrupted egocentric memory representation. In the egocentric condition, participants remained in the same position, but the object cues were shifted between searches to prevent them from using allocentric memory. Only the RTL group was impaired on the allocentric condition, and neither the LTL nor RTL group was impaired on additional tests of spatial working memory or spatial manipulation. The results support the notion that the right anterior temporal lobe stores long-term allocentric spatial memories. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
13.
Wesley W. Chu Ph.D. Ion T. leong Ph.D. Ricky K. Taira Ph.D. 《The VLDB Journal The International Journal on Very Large Data Bases》1994,3(4):445-477
We introduce a semantic data model to capture the hierarchical, spatial, temporal, and evolutionary semantics of images in pictorial databases. This model mimics the user's conceptual view of the image content, providing the framework and guidelines for preprocessing to extract image features. Based on the model constructs, a spatial evolutionary query language (SEQL), which provides direct image object manipulation capabilities, is presented. With semantic information captured in the model, spatial evolutionary queries are answered efficiently. Using an object-oriented platform, a prototype medical-image management system was implemented at UCLA to demonstrate the feasibility of the proposed approach. 相似文献
14.
基于MATLAB在化工优化设计中的应用 总被引:2,自引:0,他引:2
结合化工优化计算的实例,着重介绍如何应用MATLAB7.0提供的优化工具箱来对线性规划及非线性规划模型进行求解。 相似文献
15.
Non-pinched, minimum energy solutions are important class of distillation designs that offer the potential advantage of a better trade-off between capital investment and operating costs. In this paper, two important tasks associated with non-pinched distillation designs are studied. Thus the novel contributions of this work to the literature are
- (1) A comprehensive methodology for finding non-pinched minimum energy designs.
- (2) Understanding of the reasons for the existence of non-pinched distillation designs.
16.
H. Ji J. E. Dolbow 《International journal for numerical methods in engineering》2004,61(14):2508-2535
We consider a problem stemming from recent models of phase transitions in stimulus‐responsive hydrogels, wherein a sharp interface separates swelled and collapsed phases. Extended finite element methods that approximate the local solution with an enriched basis such that the mesh need not explicitly ‘fit’ the interface geometry are emphasized. Attention is focused on the weak enforcement of the normal configurational force balance and various options for evaluating the jump in the normal component of the solute flux at the interface. We show that as the reciprocal interfacial mobility vanishes, it plays the role of a penalty parameter enforcing a pure Dirichlet constraint, eventually triggering oscillations in the interfacial velocity. We also examine alternative formulations employing a Lagrange multiplier to enforce this constraint. It is shown that the most convenient choice of basis for the Lagrange multiplier results in oscillations in the multiplier field and a decrease in accuracy and rate of convergence in local error norms, suggesting a lack of stability in the discrete formulation. Under such conditions, neither the direct evaluation of the gradient of the approximation at the phase interface nor the interpretation of the Lagrange multiplier field provide a robust means to obtain the jump in the normal component of solute flux. Fortunately, the adaptation and use of local, domain‐integral methodologies considerably improves the flux evaluations. Several example problems are presented to compare and contrast the various techniques and methods. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
17.
Seth Green George Turkiyyah 《International journal for numerical methods in engineering》2004,61(3):380-405
We present a new method for enforcing boundary conditions within subdivision finite element simulations of thin shells. The proposed framework is demonstrated to be second-order accurate with respect to increasing refinement in the displacement and energy norm for simply supported, clamped, free and symmetric boundary conditions. Second-order accuracy on the boundary is consistent with the accuracy of subdivision-based approaches for the interior of a body. Our proposed framework is applicable to both triangular and quadrilateral refinement schemes, and does not impose any topological requirements upon the underlying subdivision control mesh. Several examples from an obstacle course of benchmark problems are used to demonstrate the convergence of the scheme. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
18.
We study low-frequency vibrations of a vibroprotective system of solid bodies formed by a roller damper and a moving load-carrying body under the action of external harmonic excitations. The dynamic equations of combined motion of the working body of the damper over the hinged roller without sliding and the load-carrying body are deduced and numerically analyzed. A new procedure is proposed for the evaluation of the optimal parameters of adjustment of roller dampers in nonlinear systems. 相似文献
19.
20.
Drew Michael R.; Yang Cynthia; Ohyama Tatsuya; Balsam Peter D. 《Canadian Metallurgical Quarterly》2004,30(3):163
Three experiments investigated the effects of varying the conditioned stimulus (CS) duration between training and extinction. Ring doves (Streptopelia risoria) were autoshaped on a fixed CS-unconditioned stimulus (US) interval and extinguished with CS presentations that were longer, shorter, or the same as the training duration. During a subsequent test session, the training CS duration was reintroduced. Results suggest that the cessation of responding during an extinction session is controlled by generalization of excitation between the training and extinction CSs and by the number of nonreinforced CS presentations. Transfer of extinction to the training CS is controlled by the similarity between the extinction and training CSs. Extinction learning is temporally specific. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献