全文获取类型
收费全文 | 345531篇 |
免费 | 3678篇 |
国内免费 | 1350篇 |
专业分类
电工技术 | 6349篇 |
综合类 | 599篇 |
化学工业 | 48794篇 |
金属工艺 | 17263篇 |
机械仪表 | 13476篇 |
建筑科学 | 7681篇 |
矿业工程 | 2231篇 |
能源动力 | 7615篇 |
轻工业 | 23592篇 |
水利工程 | 4002篇 |
石油天然气 | 7055篇 |
武器工业 | 43篇 |
无线电 | 39750篇 |
一般工业技术 | 73849篇 |
冶金工业 | 56142篇 |
原子能技术 | 8420篇 |
自动化技术 | 33698篇 |
出版年
2021年 | 2161篇 |
2019年 | 2066篇 |
2018年 | 11361篇 |
2017年 | 11914篇 |
2016年 | 8213篇 |
2015年 | 2970篇 |
2014年 | 4443篇 |
2013年 | 12034篇 |
2012年 | 9465篇 |
2011年 | 17411篇 |
2010年 | 14973篇 |
2009年 | 14959篇 |
2008年 | 15146篇 |
2007年 | 17015篇 |
2006年 | 7878篇 |
2005年 | 10569篇 |
2004年 | 9003篇 |
2003年 | 8488篇 |
2002年 | 7332篇 |
2001年 | 6906篇 |
2000年 | 6621篇 |
1999年 | 6793篇 |
1998年 | 16334篇 |
1997年 | 11609篇 |
1996年 | 8937篇 |
1995年 | 6860篇 |
1994年 | 6046篇 |
1993年 | 6087篇 |
1992年 | 4413篇 |
1991年 | 4204篇 |
1990年 | 4074篇 |
1989年 | 4057篇 |
1988年 | 3759篇 |
1987年 | 3388篇 |
1986年 | 3393篇 |
1985年 | 3742篇 |
1984年 | 3460篇 |
1983年 | 3218篇 |
1982年 | 3024篇 |
1981年 | 3038篇 |
1980年 | 3031篇 |
1979年 | 2829篇 |
1978年 | 2869篇 |
1977年 | 3145篇 |
1976年 | 4102篇 |
1975年 | 2417篇 |
1974年 | 2379篇 |
1973年 | 2396篇 |
1972年 | 2018篇 |
1971年 | 1781篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
911.
The effects of a biquadratic exchange and an external magnetic field on the phase states of a twodimensional non-Heisenberg ferromagnet have been studied with allowance for magnetoelastic and magnetodipolar interactions. 相似文献
912.
Carlos Fernandes Agostinho C. Rosa 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2008,12(10):955-979
Mate selection plays a crucial role in both natural and artificial systems. While traditional Evolutionary Algorithms (EA)
usually engage in random mating strategies, that is, mating chance is independent of genotypic or phenotypic distance between
individuals, in natural systems non-random mating is common, which means that somehow this mechanism has been favored during
the evolutionary process. In non-random mating, the individuals mate according to their parenthood or likeness. Previous studies
indicate that negative assortative mating (AM)—also known as dissortative mating—, which is a specific type of non-random mating, may improve EAs performance by maintaining the genetic diversity of the
population at a higher level during the search process. In this paper we present the Variable Dissortative Mating Genetic Algorithm (VDMGA). The algorithm holds a mechanism that varies the GA’s mating restrictions during the run by means of simple rule
based on the number of chromosomes created in each generation and indirectly influenced by the genetic diversity of the population.
We compare VDMGA not only with traditional Genetic Algorithms (GA) but also with two preceding non-random mating EAs: the
CHC algorithm and the negative Assortative Mating Genetic Algorithm (nAMGA). We intend to study the effects of the different methods in the performance of GAs and verify the reliability of
the proposed algorithm when facing an heterogeneous set of landscapes. In addition, we include the positive Assortative Mating Genetic Algorithm (pAMGA) in the experiments in order test both negative and positive AM mechanisms, and try to understand if and when negative
AM (or DM) speeds up the search process or enables the GAs to escape local optima traps. For these purposes, an extensive
set of optimization test problems was chosen to cover a variety of search landscapes with different characteristics. Our results
confirm that negative AM is effective in leading EAs out of local optima traps, and show that the proposed VDMGA is at least
as efficient as nAMGA when applied to the range of our problems, being more efficient in very hard functions were traditional
GAs usually fail to escape local optima. Also, scalability tests have been made that show VDMGA ability to decrease optimal
population size, thus reducing the amount of evaluations needed to attain global optima. We like to stress that only two parameters
need to be hand-tuned in VDMGA, thus reducing the tuning effort present in traditional GAs and nAMGA. 相似文献
913.
In this paper, we analyze in some detail the manifold-mapping optimization technique introduced recently [Echeverría and Hemker in space mapping and defect correction. Comput Methods Appl Math 5(2): 107—136, 2005]. Manifold mapping aims at accelerating optimal design procedures that otherwise require many evaluations of time-expensive cost functions. We give a proof of convergence for the manifold-mapping iteration. By means of two simple optimization problems we illustrate the convergence results derived. Finally, the performances of several variants of the method are compared for some design problems from electromagnetics. 相似文献
914.
Stevens M. Williams P.D. Peterson G.L. Kurkowski S.H. 《Computational Intelligence Magazine, IEEE》2008,3(2):65-68
This research supports the hypothesis that the Trust Vector model can be modified to fit the CyberCraft Initiative, and that there are limits to the utility of historical data. This research proposed some modifications and expansions to the Trust Model Vector, and identified areas for future research. 相似文献
915.
916.
John P. kotter 《IT时代周刊》2007,(24):76-77
在拥有了多年大权在握、呼风唤雨的经历之后。相当一部分企业领导人很难从容地放弃权力。这时。董事会必须采取行动,不仅要帮助退休领导人选择和培养好接班人。更要积极参与管理层交接班的全过程。 相似文献
917.
Amnon H. Eden 《Minds and Machines》2007,17(1):121-123
918.
Entrainment and musicality in the human system interface 总被引:1,自引:1,他引:0
Satinder P. Gill 《AI & Society》2007,21(4):567-605
What constitutes our human capacity to engage and be in the same frame of mind as another human? How do we come to share a sense of what ‘looks good’ and what ‘makes sense’? How do we handle differences and come to coexist with them? How do we come to feel that we understand what someone else is experiencing? How are we able to walk in silence with someone familiar and be sharing a peaceful space? All of these aspects are part of human ‘interaction’. In designing interactive technologies designers have endeavoured to explicate, analyse and simulate, our capacity for social adaptation. Their motivations are mixed and include the desires to improve efficiency, improve consumption, to connect people, to make it easier for people to work together, to improve education and learning. In these endeavours to explicate, analyse and simulate, there is a fundamental human capacity that is beyond technology and that facilitates these aspects of being, feeling and thinking with others. That capacity, we suggest, is human entrainment. This is our ability to coordinate the timing of our behaviours and rhythmically synchronise our attentional resources. Expressed within the movements of our bodies and voices, it has a quality that is akin to music. In this paper, disparate domains of research such as pragmatics, social psychology, behaviourism, cognitive science, computational linguistics, gesture, are brought together, and considered in light of the developments in interactive technology, in order to shape a conceptual framework for understanding entrainment in everyday human interaction. 相似文献
919.
Yu. P. Nikolaev 《Automation and Remote Control》2004,65(12):1904-1914
The D-decomposition of a two-dimensional plane of arbitrary coefficients of a discrete characteristic polynomial is studied. The geometry of the boundary curve is analyzed and its common properties with a linear discrete system of any order are described. Example are given. 相似文献
920.
V. P. Shmerko 《Automation and Remote Control》2004,65(6):893-912
Theoretical results due to V. Malyugin on linearization of arithmetical models of logical functions are interpreted and refined from the viewpoint of modern techniques of logical design of integral circuits and nearest neighbor technologies. 相似文献