全文获取类型
收费全文 | 43843篇 |
免费 | 5438篇 |
国内免费 | 3666篇 |
专业分类
电工技术 | 4853篇 |
技术理论 | 1篇 |
综合类 | 5415篇 |
化学工业 | 3269篇 |
金属工艺 | 1075篇 |
机械仪表 | 3438篇 |
建筑科学 | 2256篇 |
矿业工程 | 903篇 |
能源动力 | 1197篇 |
轻工业 | 1989篇 |
水利工程 | 896篇 |
石油天然气 | 1953篇 |
武器工业 | 614篇 |
无线电 | 4033篇 |
一般工业技术 | 3623篇 |
冶金工业 | 960篇 |
原子能技术 | 239篇 |
自动化技术 | 16233篇 |
出版年
2024年 | 213篇 |
2023年 | 532篇 |
2022年 | 1138篇 |
2021年 | 1252篇 |
2020年 | 1319篇 |
2019年 | 1145篇 |
2018年 | 1048篇 |
2017年 | 1334篇 |
2016年 | 1545篇 |
2015年 | 1802篇 |
2014年 | 2565篇 |
2013年 | 2859篇 |
2012年 | 3181篇 |
2011年 | 3451篇 |
2010年 | 2641篇 |
2009年 | 2987篇 |
2008年 | 3054篇 |
2007年 | 3419篇 |
2006年 | 3008篇 |
2005年 | 2477篇 |
2004年 | 2123篇 |
2003年 | 1775篇 |
2002年 | 1530篇 |
2001年 | 1197篇 |
2000年 | 1069篇 |
1999年 | 759篇 |
1998年 | 635篇 |
1997年 | 557篇 |
1996年 | 409篇 |
1995年 | 331篇 |
1994年 | 289篇 |
1993年 | 221篇 |
1992年 | 209篇 |
1991年 | 131篇 |
1990年 | 108篇 |
1989年 | 111篇 |
1988年 | 97篇 |
1987年 | 55篇 |
1986年 | 45篇 |
1985年 | 53篇 |
1984年 | 64篇 |
1983年 | 46篇 |
1982年 | 31篇 |
1981年 | 25篇 |
1980年 | 23篇 |
1979年 | 17篇 |
1978年 | 8篇 |
1977年 | 13篇 |
1976年 | 12篇 |
1975年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
81.
82.
Magnus Fredriksson Niels Saabye Ottosen 《International journal for numerical methods in engineering》2004,61(11):1809-1834
An accurate and variationally consistent 4‐node quadrilateral element is introduced where high coarse mesh accuracy and low mesh distortion sensitivity are characteristic qualities, even when incompressibility is approached for plane strain. One‐point quadrature integration procedure is adopted and a new improved stabilization technique is developed. Orthogonality conditions are utilized so that the patch test is satisfied for arbitrary quadrilaterals. Several numerical examples including a convergence rate study are presented which confirm the excellent performance of this element. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
83.
Doratha E Drake 《Information Processing Letters》2003,85(4):211-213
We present a linear time approximation algorithm with a performance ratio of 1/2 for finding a maximum weight matching in an arbitrary graph. Such a result is already known and is due to Preis [STACS'99, Lecture Notes in Comput. Sci., Vol. 1563, 1999, pp. 259-269]. Our algorithm uses a new approach which is much simpler than the one given by Preis and needs no amortized analysis for its running time. 相似文献
84.
Artem Sokolov Darrell Whitley Andre’ da Motta Salles Barreto 《Genetic Programming and Evolvable Machines》2007,8(3):221-237
This paper evaluates different forms of rank-based selection that are used with genetic algorithms and genetic programming.
Many types of rank based selection have exactly the same expected value in terms of the sampling rate allocated to each member
of the population. However, the variance associated with that sampling rate can vary depending on how selection is implemented.
We examine two forms of tournament selection and compare these to linear rank-based selection using an explicit formula. Because
selective pressure has a direct impact on population diversity, we also examine the interaction between selective pressure
and different mutation strategies. 相似文献
85.
由于在机器人导航等领域新的图像装置不符合透视规则,无法运用传统的透视位置估计方法,采用吴氏零点分解方法,给出非透视3点问题的解析解.利用新图像装置的几何条件,建立了非透视3点方程系统. 相似文献
86.
根据双点后方交会的图形特点和已知条件,列出了方程组,推导出了双点后方交会直接计算座标的简便公式,同时求出了精度计算公式,以供测量人员参考 相似文献
87.
The paper presents a neural network model of the touch sensitivity circuit of the nematode Caenorhabditis elegans. We describe a serie of simulations in which neural networks are trained, using a genetic algorithm, to reproduce the habituation of the nematode's touch sensitive behavior. A lesion study of the network allows to make a direct comparison between the fine functioning of the model and the data collected in real organisms. The model accords well with the known neurobiological data and it suggests some hypotheses about the functioning of the neural circuit and of single neurons. 相似文献
88.
The problem of determining the maximum mean response level crossing rate of a linear system driven by a partially specified Gaussian load process has been considered. The partial specification of the load is given only in terms of its total average energy. The critical input power spectral (PSD) function, which maximizes the mean response level crossing rate, is obtained. The critical input PSD turns out to be highly narrow-banded which fails to capture the erratic nature of the excitation. Consequently, the trade-off curve between the maximum mean response level crossing rate and the maximum disorder in the input process, quantified in terms of its entropy rate, has been generated. The method of Pareto optimization is used to tackle the conflicting objectives of the simultaneous maximization of the mean response level crossing rate and the input entropy rate. The non-linear multi-objective optimization has been carried out using a recently developed multi-criteria genetic algorithm scheme. Illustrative example of determining the critical input of an axially vibrating rod, excited by a partially specified stationary Gaussian load process, has been considered. 相似文献
89.
周培德 《计算机辅助设计与图形学学报》2002,14(3):287-288
周培协三角剖分是否能得到最小权三角剖分,周培德在《周培德三角部分不是最小权三角剖分》一文撰写之前已有新的结论,本文还指出《周培德三角剖分不是最小权三角剖分》一文所举反例不成立。 相似文献
90.