全文获取类型
收费全文 | 55334篇 |
免费 | 5253篇 |
国内免费 | 2667篇 |
专业分类
电工技术 | 3496篇 |
技术理论 | 8篇 |
综合类 | 3627篇 |
化学工业 | 9415篇 |
金属工艺 | 2929篇 |
机械仪表 | 3271篇 |
建筑科学 | 3978篇 |
矿业工程 | 1505篇 |
能源动力 | 1754篇 |
轻工业 | 3489篇 |
水利工程 | 1096篇 |
石油天然气 | 2830篇 |
武器工业 | 646篇 |
无线电 | 6943篇 |
一般工业技术 | 6763篇 |
冶金工业 | 2902篇 |
原子能技术 | 697篇 |
自动化技术 | 7905篇 |
出版年
2024年 | 255篇 |
2023年 | 908篇 |
2022年 | 1800篇 |
2021年 | 2450篇 |
2020年 | 1819篇 |
2019年 | 1521篇 |
2018年 | 1694篇 |
2017年 | 1804篇 |
2016年 | 1623篇 |
2015年 | 2278篇 |
2014年 | 2702篇 |
2013年 | 3431篇 |
2012年 | 3571篇 |
2011年 | 3784篇 |
2010年 | 3323篇 |
2009年 | 3234篇 |
2008年 | 3115篇 |
2007年 | 2949篇 |
2006年 | 2979篇 |
2005年 | 2475篇 |
2004年 | 1856篇 |
2003年 | 1621篇 |
2002年 | 1671篇 |
2001年 | 1530篇 |
2000年 | 1316篇 |
1999年 | 1331篇 |
1998年 | 1162篇 |
1997年 | 989篇 |
1996年 | 799篇 |
1995年 | 670篇 |
1994年 | 495篇 |
1993年 | 429篇 |
1992年 | 329篇 |
1991年 | 266篇 |
1990年 | 183篇 |
1989年 | 179篇 |
1988年 | 144篇 |
1987年 | 86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 0 毫秒
991.
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
992.
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
993.
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
994.
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
995.
996.
997.
基于微机的200Wm核供热堆仿真系统PCNHR1.0的研究 总被引:1,自引:0,他引:1
为了使更多的技术人员形象地了解低温堆供热站的原理 ,在国际原子能机构的支持下 ,清华大学核研院研究开发了基于微机的 2 0 0Mw低温核供热堆仿真系统。它采用两回路、一维漂移流热工水力学模型 ,点中子堆物理以及控制系统模型。能对核供热堆的稳态运行、瞬态过程和事故进行仿真 ,仿真精度接近系统分析结果。在奔腾或以上的微机上 ,WIN DOWS95 /98/NT操作系统下 ,能对过程进行实时仿真 ,而且大多数过程能达到 10倍以上超实时。软件采用VisualC+ + 和FORTRAN混合语言编程 ,运用先进的多线程编程模型、进程通讯和进程控制技术实现了耦合计算和同步控制。 相似文献
998.
By introducing a form of reorder for multidimensional data, we propose a unified fast algo-rithm that jointly employs one-dimensional W transform and multidimensional discrete polynomial trans-form to compute eleven types of multidimensional discrete orthogonal transforms, which contain three types of m-dimensional discrete cosine transforms ( m-D DCTs) ,four types of m-dimensional discrete W transforms ( m-D DWTs) ( m-dimensional Hartley transform as a special case), and four types of generalized discrete Fourier transforms ( m-D GDFTs). For real input, the number of multiplications for all eleven types of the m-D discrete orthogonal transforms needed by the proposed algorithm are only 1/m times that of the commonly used corresponding row-column methods, and for complex input, it is further reduced to 1/(2m) times. The number of additions required is also reduced considerably. Furthermore, the proposed algorithm has a simple computational structure and is also easy to be im-plemented on computer, and th 相似文献
999.
1000.
铁塔CAD中的优化方法研究 总被引:1,自引:0,他引:1
铁塔CAD系统(TowCAD)是已经研制成功的一种用于高压输电铁塔设计分析的工程CAD系统。优化设计是其中的重要组成部分,它涉及到多结构、多工况、多参数等复杂情况,要求多、难度大。为此,本文对满应力优化的数学模型(包括优化目标和函数)、优化迭代方法等进行改进,提出了一种适合输电铁塔优化设计的塔架优化方法。铁塔CAD综合采用塔架优化方法、柔性杆单元理论和数据库无缝嵌入技术进行应力分析和优化设计,较好地满足了优化设计的实际需要。本文的研究工作对于其它复杂桁架结构的优化设计亦有较大的参考价值。 相似文献