全文获取类型
收费全文 | 387473篇 |
免费 | 40270篇 |
国内免费 | 23795篇 |
专业分类
电工技术 | 48355篇 |
技术理论 | 24篇 |
综合类 | 39957篇 |
化学工业 | 36857篇 |
金属工艺 | 12569篇 |
机械仪表 | 28450篇 |
建筑科学 | 28165篇 |
矿业工程 | 13196篇 |
能源动力 | 10968篇 |
轻工业 | 17902篇 |
水利工程 | 9032篇 |
石油天然气 | 13280篇 |
武器工业 | 5603篇 |
无线电 | 50024篇 |
一般工业技术 | 27548篇 |
冶金工业 | 12306篇 |
原子能技术 | 3960篇 |
自动化技术 | 93342篇 |
出版年
2024年 | 1774篇 |
2023年 | 5211篇 |
2022年 | 11013篇 |
2021年 | 12618篇 |
2020年 | 11357篇 |
2019年 | 9100篇 |
2018年 | 8790篇 |
2017年 | 11893篇 |
2016年 | 14106篇 |
2015年 | 15854篇 |
2014年 | 25684篇 |
2013年 | 23228篇 |
2012年 | 28265篇 |
2011年 | 28250篇 |
2010年 | 21686篇 |
2009年 | 22129篇 |
2008年 | 22536篇 |
2007年 | 28998篇 |
2006年 | 26515篇 |
2005年 | 23002篇 |
2004年 | 17685篇 |
2003年 | 16059篇 |
2002年 | 12228篇 |
2001年 | 10054篇 |
2000年 | 8609篇 |
1999年 | 6809篇 |
1998年 | 5103篇 |
1997年 | 4230篇 |
1996年 | 3661篇 |
1995年 | 3029篇 |
1994年 | 2535篇 |
1993年 | 1826篇 |
1992年 | 1515篇 |
1991年 | 1189篇 |
1990年 | 952篇 |
1989年 | 757篇 |
1988年 | 560篇 |
1987年 | 364篇 |
1986年 | 274篇 |
1985年 | 300篇 |
1984年 | 268篇 |
1983年 | 217篇 |
1982年 | 213篇 |
1981年 | 159篇 |
1980年 | 163篇 |
1979年 | 107篇 |
1978年 | 78篇 |
1977年 | 62篇 |
1962年 | 71篇 |
1959年 | 50篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
扩声系统在体育馆中的典型应用 总被引:1,自引:1,他引:0
针对体育馆举办不同类型的大型活动,分别对扩声系统的音质及扩声特点提出要求,以人声和乐器声的频率特性为依据,阐述了调音师在不同场合中对于不同的扩声对象按所要达到的扩声效果应采取的调控方法。 相似文献
102.
103.
104.
Javier Ramírez Antonio García Uwe Meyer-Bäse Fred Taylor Antonio Lloris 《The Journal of VLSI Signal Processing》2003,33(1-2):171-190
Currently there are design barriers inhibiting the implementation of high-precision digital signal processing (DSP) objects with field programmable logic (FPL) devices. This paper explores overcoming these barriers by fusing together the popular distributed arithmetic (DA) method with the residue number system (RNS) for use in FPL-centric designs. The new design paradigm is studied in the context of a high-performance filter bank and a discrete wavelet transform (DWT). The proposed design paradigm is facilitated by a new RNS accumulator structure based on a carry save adder (CSA). The reported methodology also introduces a polyphase filter structure that results in a reduced look-up table (LUT) budget. The 2C-DA and RNS-DA are compared, in the context of a FPL implementation strategy, using a discrete wavelet transform (DWT) filter bank as a common design theme. The results show that the RNS-DA, compared to a traditional 2C-DA design, enjoys a performance advantage that increases with precision (wordlength). 相似文献
105.
L. Sheeney‐Haj‐Ichia S. Pogorelova Y. Gofer I. Willner 《Advanced functional materials》2004,14(5):416-424
Three different configurations of Au‐nanoparticle/CdS‐nanoparticle arrays are organized on Au/quartz electrodes for enhanced photocurrent generation. In one configuration, Au‐nanoparticles are covalently linked to the electrode and the CdS‐nanoparticles are covalently linked to the bare Au‐nanoparticle assembly. The resulting photocurrent, φ = 7.5 %, is ca. 9‐fold higher than the photocurrent originating from a CdS‐nanoparticle layer that lacks the Au‐nanoparticles, φ = 0.8 %. The enhanced photocurrent in the Au/CdS nanoparticle array is attributed to effective charge separation of the electron–hole pair by the injection of conduction‐band electrons from the CdS‐ to the Au‐nanoparticles. Two other configurations involving electrostatically stabilized bipyridinium‐crosslinked Au/CdS or CdS/Au nanoparticle arrays were assembled on the Au/quartz crystal. The photocurrent quantum yields in the two systems are φ = 10 % and φ = 5 %, respectively. The photocurrents in control systems that include electrostatically bridged Au/CdS or CdS/Au nanoparticles by oligocationic units that lack electron‐acceptor units are substantially lower than the values observed in the analogous bipyridinium‐bridged systems. The enhanced photocurrents in the bipyridinium‐crosslinked systems is attributed to the stepwise electron transfer of conduction‐band electrons to the Au‐nanoparticles by the bipyridinium relay bridge, a process that stabilizes the electron–hole pair against recombination and leads to effective charge separation. 相似文献
106.
介绍了医用红宝石激光器触摸屏控制系统的基本结构,分析了医用红宝石激光器中主要电磁干扰(EMI)的产生机制,提出了具体的电磁兼容(EMC)技术措施并得到实验验证。 相似文献
107.
对海底输油管道内智能引导装置研究的必要性进行了分析;介绍了国内外在该领域的技术发展状况。针对智能引导装置的作业对象和环境,提出了技术要求和指标,对智能引导装置进行了总体设计,分析了其作业机理,建立了力学模型并进行了计算。对智能引导装置的控制系统进行了设计,提出了设计过程中应注意的问题。所研制的管内轮式智能引导装置具有质量轻、输出牵引力大、体积小、结构紧凑等特点,对较小管内空间类似系统的设计有一定参考价值。 相似文献
108.
数字电视的条件接收系统 总被引:1,自引:0,他引:1
数字电视的兴起使人们能够欣赏到高质量的电视节目,伴随数字电视的成熟,条件接收系统(CAS)得到很好的发展。主要介绍数字电视条件接收系统相关技术的发展、基本功能、安全机制、工作原理及其安全性要求。 相似文献
109.
110.
Finite element piezothermoelasticity analysis and the active control of FGM plates with integrated piezoelectric sensors and actuators 总被引:3,自引:0,他引:3
An efficient finite element model is presented for the static and dynamic piezothermoelastic analysis and control of FGM
plates under temperature gradient environments using integrated piezoelectric sensor/actuator layers. The properties of an FGM plate are functionally graded in the thickness
direction according to a volume fraction power law distribution. A constant displacement-cum-velocity feedback control algorithm that couples the direct and inverse piezoelectric effects is applied to provide active feedback
control of the integrated FGM plate in a closed loop system. Numerical results for the static and dynamic control are presented
for the FGM plate, which consists of zirconia and aluminum. The effects of the constituent volume fractions and the influence
of feedback control gain on the static and dynamic responses of the FGM plates are examined.
Received: 13 March 2002 / Accepted: 5 March 2003
The work described in this paper was supported by a grant awarded by the Research Grants Council of the Hong Kong Special
Administrative Region, China (Project No. CityU 1024/01E). 相似文献