全文获取类型
收费全文 | 55531篇 |
免费 | 5285篇 |
国内免费 | 2668篇 |
专业分类
电工技术 | 3507篇 |
技术理论 | 8篇 |
综合类 | 3650篇 |
化学工业 | 9445篇 |
金属工艺 | 2945篇 |
机械仪表 | 3288篇 |
建筑科学 | 3991篇 |
矿业工程 | 1522篇 |
能源动力 | 1766篇 |
轻工业 | 3501篇 |
水利工程 | 1097篇 |
石油天然气 | 2863篇 |
武器工业 | 651篇 |
无线电 | 6958篇 |
一般工业技术 | 6784篇 |
冶金工业 | 2923篇 |
原子能技术 | 699篇 |
自动化技术 | 7886篇 |
出版年
2024年 | 260篇 |
2023年 | 920篇 |
2022年 | 1813篇 |
2021年 | 2467篇 |
2020年 | 1835篇 |
2019年 | 1532篇 |
2018年 | 1703篇 |
2017年 | 1817篇 |
2016年 | 1633篇 |
2015年 | 2286篇 |
2014年 | 2717篇 |
2013年 | 3438篇 |
2012年 | 3576篇 |
2011年 | 3806篇 |
2010年 | 3332篇 |
2009年 | 3236篇 |
2008年 | 3110篇 |
2007年 | 2952篇 |
2006年 | 2983篇 |
2005年 | 2481篇 |
2004年 | 1856篇 |
2003年 | 1624篇 |
2002年 | 1678篇 |
2001年 | 1537篇 |
2000年 | 1326篇 |
1999年 | 1335篇 |
1998年 | 1160篇 |
1997年 | 992篇 |
1996年 | 805篇 |
1995年 | 671篇 |
1994年 | 496篇 |
1993年 | 429篇 |
1992年 | 330篇 |
1991年 | 267篇 |
1990年 | 186篇 |
1989年 | 180篇 |
1988年 | 144篇 |
1987年 | 88篇 |
1986年 | 88篇 |
1985年 | 77篇 |
1984年 | 33篇 |
1983年 | 27篇 |
1982年 | 37篇 |
1981年 | 34篇 |
1980年 | 23篇 |
1979年 | 21篇 |
1977年 | 16篇 |
1976年 | 19篇 |
1974年 | 13篇 |
1973年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
数据集中的冗余属性会降低数据采掘结果的解释能力及精度。该文介绍了在非项目集类型的数据集中采掘聚类关联规则的基本原理,并利用RoughSet理论对属性间的归纳依赖关系进行了分析,提出了一个在数据集中发现没有冗余属性的最小归纳依赖关系的算法,使采掘出的关联规则的精度及解释能力都达到令人满意的水平。 相似文献
992.
A new approach for the solution of singular optima in truss topology optimization with stress and local buckling constraints 总被引:3,自引:1,他引:2
The present paper investigates problems of truss topology optimization under local buckling constraints. A new approach for
the solution of singular problems caused by stress and local buckling constraints is proposed. At first, a second order smooth-extended
technique is used to make the disjoint feasible domains connect, then the so-called ε-relaxed method is applied to eliminate
the singular optima from problem formulation. By means of this approach, the singular optimum of the original problem caused
by stress and local buckling constraints can be searched approximately by employing the algorithms developed for sizing optimization
problems with high accuracy. Therefore, the numerical problem resulting from stress and local buckling constraints can be
solved in an elegant way. The applications of the proposed approach and its effectiveness are illustrated with several numerical
examples.
Received May 2, 2000 相似文献
993.
对机器人工作空间的求解方法进行对比研究。针对大型喷浆机器人的具体特点 ,使用蒙特卡洛法分析其工作空间 ,取得了良好的效果。 相似文献
994.
995.
We first present a modified Hopfield network, the clipped Hopfield network, with synaptic weights assigned to three values {-1,0,+1}. We give the necessary conditions under which a set of 2n binary vectors can be stored as stable points of the network. We show that in the parallel updating mode, for most of the state vectors, the network will always converge to these 2n stable points. We further demonstrate that these 2n stable points can be divided into two groups, the alpha group and the beta group, each with n stable points. It is shown that the basins of attraction of the stable points in the alpha group are evenly distributed, and the basins of attraction of the stable points in the beta group are also evenly distributed. By ways of application, we show that this class of Hopfield network can be used to build a cryptographically secure keystream generator. 相似文献
996.
A hermetic package based on localized aluminum/silicon-to-glass bonding has been successfully demonstrated. Less than 0.2 MPa contact pressure with 46 mA current input for two parallel 3.5-μm-wide polysilicon on-chip microheaters can raise the temperature of the bonding region to 700°C bonding temperature and achieve a strong and reliable bond in 7.5 min. The formation of aluminum oxide with silicon precipitate composite layer is believed to be the source of the strong bond. Accelerated testing in an autoclave shows some packages survive more than 450 h under 3 atm, 100% RH and 128°C. Premature failure has been attributed to some unbonded regions on the failed samples. The bonding yield and reliability have been improved by increasing bonding time and applied pressure 相似文献
997.
The features of two important application scenarios, supporting mobile switches with fixed end users and mobile switches with mobile users, are dramatically different from those of the traditional wired network structure. To exploit mobile switches, the location and configuration management of mobile switches is essential to handle the mobility and topology change of the wireless/mobile ATM network. In this paper we address the location management and configuration problems of mobile switches in an ATM network. We investigate several aspects of the location management problem including architecture to support switch mobility, mobile switch tracking, and mobile switch locating. We propose an approach that is based on the Private Network-Network Interface (PNNI) protocol. We extend the PNNI protocol to enable it to handle mobile switches. Moreover, we develop analytical models to determine the tracking and locating costs for mobile switches under the proposed scheme. The models illustrate the relation between total cost (tracking cost + locating cost) and peer group size. The models can be used to derive the optimal configuration for an ATM network with mobile switches. 相似文献
998.
The impact of delay defects on these functionally untestable paths on overall circuit performance involves identification of such paths determining the achievable path delay fault coverage and reducing the subsequent test generation effort. The experimental results for two microprocessors (Parwan and DLX) indicate that a significant percentage of structurally testable paths are functionally untestable 相似文献
999.
1000.