全文获取类型
收费全文 | 63745篇 |
免费 | 7134篇 |
国内免费 | 5016篇 |
专业分类
电工技术 | 5159篇 |
技术理论 | 1篇 |
综合类 | 6488篇 |
化学工业 | 8296篇 |
金属工艺 | 4344篇 |
机械仪表 | 4143篇 |
建筑科学 | 5283篇 |
矿业工程 | 2276篇 |
能源动力 | 1572篇 |
轻工业 | 6921篇 |
水利工程 | 2188篇 |
石油天然气 | 2489篇 |
武器工业 | 803篇 |
无线电 | 6883篇 |
一般工业技术 | 6353篇 |
冶金工业 | 2641篇 |
原子能技术 | 1032篇 |
自动化技术 | 9023篇 |
出版年
2024年 | 494篇 |
2023年 | 1372篇 |
2022年 | 2856篇 |
2021年 | 3570篇 |
2020年 | 2557篇 |
2019年 | 1917篇 |
2018年 | 1993篇 |
2017年 | 2340篇 |
2016年 | 1918篇 |
2015年 | 2939篇 |
2014年 | 3715篇 |
2013年 | 4226篇 |
2012年 | 4910篇 |
2011年 | 4986篇 |
2010年 | 4611篇 |
2009年 | 4438篇 |
2008年 | 4506篇 |
2007年 | 4371篇 |
2006年 | 3758篇 |
2005年 | 3122篇 |
2004年 | 2316篇 |
2003年 | 1714篇 |
2002年 | 1799篇 |
2001年 | 1673篇 |
2000年 | 1210篇 |
1999年 | 672篇 |
1998年 | 410篇 |
1997年 | 283篇 |
1996年 | 229篇 |
1995年 | 186篇 |
1994年 | 170篇 |
1993年 | 113篇 |
1992年 | 100篇 |
1991年 | 79篇 |
1990年 | 61篇 |
1989年 | 58篇 |
1988年 | 30篇 |
1987年 | 26篇 |
1986年 | 30篇 |
1985年 | 16篇 |
1984年 | 11篇 |
1983年 | 11篇 |
1982年 | 13篇 |
1981年 | 19篇 |
1980年 | 23篇 |
1979年 | 13篇 |
1976年 | 4篇 |
1970年 | 4篇 |
1959年 | 9篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
介绍一个汉字点阵屏幕显示电路的组成、工作原理及其实现.着重介绍了PLX9052的ISA接口模式配置、WDM驱动程序地址重定位以及与应用程序的通信的原理及方法.最后给出汉字屏幕显示效果图. 相似文献
2.
采用反相悬浮聚合法合成高吸水性树脂.将丙烯酸(单体,水相)用氢氧化钠部分中和,然后与环己烷(溶剂,油相)共混,用水溶性的过硫酸钾做引发剂,N,N-亚甲基双丙烯酰胺做交联剂,在一定的反应温度和时间下,得到聚丙烯酸钠高吸水性树脂. 相似文献
3.
Yue Rong Yingbo Hua Swami A. Swindlehurst A.L. 《Signal Processing, IEEE Transactions on》2008,56(2):686-701
A space-time optimal power schedule for multiple distributed multiple-input multiple-output (MIMO) links without the knowledge of the instantaneous channel state information (CSI) at the transmitting nodes is proposed. A readily computable expression for the ergodic sum capacity of the MIMO links is derived. Based on this expression, which is a non-convex function of power allocation vectors, a projected gradient algorithm is developed to optimize the power allocation. For a symmetric set of MIMO links with independent identically distributed channels, it is observed that the space-time optimal power schedule reduces to a uniform isotropic power schedule when nominal interference is low, or to an orthogonal isotropic power schedule when nominal interference is high. Furthermore, the transition region between the latter two schedules is seen to be very sharp in terms of nominal interference-to-noise ratio (INR). For MIMO links with correlated channels, the corresponding space-time optimal power schedule is developed based on the knowledge of the channel correlation matrices. It is shown that the channel correlation has a great impact on the ergodic capacity and the optimality of different power scheduling approaches. 相似文献
4.
Analysis and synthesis of on-chip spiral inductors 总被引:3,自引:0,他引:3
This paper presents a physically based compact model for estimating high-frequency performance of spiral inductors. The model accurately accounts for skin and proximity effects in the metal conductors as well as eddy current losses in the substrate. The model shows excellent agreement with measured data mostly within 10% across a variety of inductor geometries and substrate dopings up to 20 GHz. A web-based spiral inductor synthesis and analysis tool COILS, which makes use of the compact models, is presented. An optimization algorithm using binary searches speeds up the synthesis of inductor designs. 相似文献
5.
Yi‐Hung Chen Ching‐Yuan Chang Wei‐Ling Su Chun‐Yu Chiu Yue‐Hwa Yu Pen‐Chi Chiang Chiung‐Fen Chang Je‐Lueng Shie Chyow‐San Chiou Sally IM Chiang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(1):68-75
This study investigates the ozonation of CI Reactive Black 5 (RB5) by using the rotating packed bed (RPB) and completely stirred tank reactor (CSTR) as ozone contactors. The RPB, which provides high gravitational force by adjusting the rotational speed, was employed as a novel ozone contactor. The same ozone dosage was separately introduced into either the RPB or the CSTR for the investigation, while the experimental solution was continuously circulated within the apparatus consisting of the RPB and CSTR. The decolorization and mineralization efficiencies of RB5 in the course of ozonation are compared for these two methods. Moreover, the dissolved and off‐gas ozone concentrations were simultaneously monitored for the further analysis. As a result, the ozone mass transfer rate per unit volume of the RPB was significantly higher because of its higher mass transfer coefficient and gas–liquid concentration driving force. Furthermore, ozonation kinetics was found to be independent of the gravitational magnitude of an ozone gas–liquid contactor. Therefore, the results suggest employing RPBs as ozone‐contacting devices with the advantage of volume reduction. The experimental results, which can be used for further modeling of the ozonation process in the RPB, also show the requirement of correct design for the RPB. Consequently, the present study is useful for the understanding of practical application of RPBs. Copyright © 2004 Society of Chemical Industry 相似文献
6.
Matlab在“计算机辅助电路分析”中的应用 总被引:2,自引:1,他引:1
"计算机辅助电路分析"课程,是通过计算机仿真实验来训练学生分析和解决电路问题的能力.实践证明,将Matlab软件,特别是其中的Simulink仿真模块作为电路分析工具,引入到计算机辅助电路分析课程教学中,收到了良好的教学效果.本文以二阶电路阶跃响应问题的求解为例,介绍了辅以Matlab的五种求解方法,并对这五种方法的特点进行了比较,说明了Matlab在电路分析方面的优越性. 相似文献
7.
电信服务营销渠道转型的必要性 总被引:5,自引:0,他引:5
分析了电信企业服务营销渠道的特点、旧有的服务营销渠道模式和存在的问题以及今后电信业和市场等方面发展的新需求,对电信服务营销渠道转型的必要性进行了探讨和研究,同时提供了一个可供参考的服务营销渠道价值评估体系架构,从量化服务营销渠道对电信企业贡献价值的角度论述了服务营销渠道转型的必要性。 相似文献
8.
从印刷技术的发展看印刷业的重新定位 总被引:1,自引:1,他引:0
近20年以来的技术革命使印刷业发生了脱胎换骨的变化,曾经被认为是技术含量低、员工文化素质低、劳动密集型的印刷业已今非昔比。世界上最先进的电子技术、激光技术、计算机技术及网络技术在印刷领域广泛地应用与发展,改变了人们对印刷的传统思维和行为。在信息时代的今天。印刷业已经成为信息社会的先行行业。在新的形势下,印刷业的经营既离不开生产又离不开增值服务,全面解决方案的推行使印刷业的外延扩大到了第三产业。 相似文献
9.
An observer-based robust adaptive nonlinear position and speed tracking controller is developed for a permanent magnet synchronous motor with initial rotor angle uncertainty. The unknown initial rotor position is treated as a constant motor parameter in the development of the controller. An incremental encoder, which provides relative position variation of the rotor, is used along with stator current signals to achieve stable control. However, the controller does not require the knowledge of motor parameters and it only assumes friction, external disturbances, and model uncertainties are bounded. By using state observers, the measurement of acceleration and load torque, which is required usually in the nonlinear controller design with high tracking performance, is avoided. The stability of the control system and tracking convergence are guaranteed using Lyapunov theory. Finally, the stability and efficacy of the proposed drive system are verified by experimental results. 相似文献
10.