全文获取类型
收费全文 | 263609篇 |
免费 | 18665篇 |
国内免费 | 9624篇 |
专业分类
电工技术 | 13665篇 |
技术理论 | 20篇 |
综合类 | 14570篇 |
化学工业 | 44165篇 |
金属工艺 | 14924篇 |
机械仪表 | 15858篇 |
建筑科学 | 17689篇 |
矿业工程 | 6295篇 |
能源动力 | 6322篇 |
轻工业 | 15718篇 |
水利工程 | 4840篇 |
石油天然气 | 14547篇 |
武器工业 | 1644篇 |
无线电 | 28572篇 |
一般工业技术 | 38706篇 |
冶金工业 | 16304篇 |
原子能技术 | 5820篇 |
自动化技术 | 32239篇 |
出版年
2024年 | 1066篇 |
2023年 | 3671篇 |
2022年 | 7069篇 |
2021年 | 9483篇 |
2020年 | 7163篇 |
2019年 | 6133篇 |
2018年 | 7507篇 |
2017年 | 8307篇 |
2016年 | 7697篇 |
2015年 | 8916篇 |
2014年 | 11834篇 |
2013年 | 14632篇 |
2012年 | 15459篇 |
2011年 | 16557篇 |
2010年 | 14405篇 |
2009年 | 14013篇 |
2008年 | 13703篇 |
2007年 | 13101篇 |
2006年 | 12704篇 |
2005年 | 10958篇 |
2004年 | 8059篇 |
2003年 | 7602篇 |
2002年 | 7385篇 |
2001年 | 6710篇 |
2000年 | 6292篇 |
1999年 | 6075篇 |
1998年 | 5115篇 |
1997年 | 4171篇 |
1996年 | 3808篇 |
1995年 | 3245篇 |
1994年 | 2742篇 |
1993年 | 2161篇 |
1992年 | 1905篇 |
1991年 | 1635篇 |
1990年 | 1520篇 |
1989年 | 1388篇 |
1988年 | 1226篇 |
1987年 | 1024篇 |
1986年 | 938篇 |
1985年 | 844篇 |
1984年 | 808篇 |
1982年 | 724篇 |
1981年 | 725篇 |
1979年 | 772篇 |
1978年 | 793篇 |
1977年 | 776篇 |
1976年 | 778篇 |
1975年 | 729篇 |
1974年 | 730篇 |
1973年 | 735篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
32.
In this paper, the moving least-squares differential quadrature (MLSDQ) method is employed for free vibration of thick antisymmetric laminates based on the first-order shear deformation theory. The generalized displacements of the laminates are independently approximated with the centered moving least-squares (MLS) technique within each domain of influence. The MLS nodal shape functions and their partial derivatives are computed quickly through back-substitutions after only one LU decomposition. Subsequently, the weighting coefficients in the MLSDQ discretization are determined with the nodal partial derivatives of the MLS shape functions. The MLSDQ method combines the merits of both the differential quadrature and meshless methods which can be conveniently applied to complex domains and irregular discretizations without loss of implementation efficiency and numerical accuracy. The natural frequencies of the laminates with various edge conditions, ply angles, and shapes are calculated and compared with the existing solutions to study the numerical accuracy and stability of the MLSDQ method. Effects of support size, order of completeness of basis functions, and node irregularity on the numerical accuracy are investigated in detail. 相似文献
33.
The microstructure evolution in nonstoichiometric titanium carbide is studied during high-temperature deformation at high strain rates and low strains (shock compression) and at slow strain rates and high strains (superplastic regime). The results demonstrate that high-temperature deformation in a broad range of strain rates offers a means of controlling the microstructure of titanium carbide. By varying deformation conditions, one can obtain materials differing in microstructure and chemical composition, in particular, with equilibrium and nonequilibrium microstructures. Accordingly, the physicochemical properties of such materials also differ. 相似文献
34.
Whispering-gallery-like modes in square resonators 总被引:1,自引:0,他引:1
Wei-Hua Guo Yong-Zhen Huang Qiao-Yin Lu Li-Juan Yu 《Quantum Electronics, IEEE Journal of》2003,39(9):1106-1110
The mode frequencies and field distributions of whispering-gallery (WG)-like modes of square resonators are obtained analytically, which agree very well with the numerical results calculated by the FDTD technique and Pade approximation method. In the analysis, a perfect electric wall for the transverse magnetic mode or perfect magnetic wall for the transverse electric mode is assumed at the diagonals of the square resonators, which not only provides the transverse mode confinement, but also requires the longitudinal mode number to be an even integer. The WG-like modes of square resonators are nondegenerate modes with high-quality factors, which make them suitable for fabricating single-mode low-threshold semiconductor microcavity lasers. 相似文献
35.
Shi-Jin Ding Hang Hu Lim H.F. Kim S.J. Yu X.F. Chunxiang Zhu Li M.F. Byung Jin Cho Chan D.S.H. Rustagi S.C. Yu M.B. Chin A. Dim-Lee Kwong 《Electron Device Letters, IEEE》2003,24(12):730-732
For the first time, we successfully fabricated and demonstrated high performance metal-insulator-metal (MIM) capacitors with HfO/sub 2/-Al/sub 2/O/sub 3/ laminate dielectric using atomic layer deposition (ALD) technique. Our data indicates that the laminate MIM capacitor can provide high capacitance density of 12.8 fF//spl mu/m/sup 2/ from 10 kHz up to 20 GHz, very low leakage current of 3.2 /spl times/ 10/sup -8/ A/cm/sup 2/ at 3.3 V, small linear voltage coefficient of capacitance of 240 ppm/V together with quadratic one of 1830 ppm/V/sup 2/, temperature coefficient of capacitance of 182 ppm//spl deg/C, and high breakdown field of /spl sim/6 MV/cm as well as promising reliability. As a result, the HfO/sub 2/-Al/sub 2/O/sub 3/ laminate is a very promising candidate for next generation MIM capacitor for radio frequency and mixed signal integrated circuit applications. 相似文献
36.
MAX3100在80C196串口扩展中的应用 总被引:1,自引:0,他引:1
介绍采用新型的UART器件MAX3100为Intel单片机80C196扩展串口,给出了硬件设计和软件编程,并对关键技术进行了说明。 相似文献
37.
38.
近两年.IP电话又叫网络电话的发展受到全球的关注。随着宽带接入的发展,基于宽带接入提供的网络电话具有了更大的生命力。从宽带电话的经营模式出发,探究这类业务的出现时现有话音业务市场的影响,进而分析这类业务的发展前景。 相似文献
39.
从稳态到动态的空气调节 总被引:1,自引:0,他引:1
分析传统空调所提供的稳态参数微气候环境不一定能达到人的舒适和健康的要求,提出符合人本身生理习惯的空调送风方式应该是动态空气调节.认为个人可调节和适宜的环境渐变能同时保证舒适和健康两方面需要. 相似文献
40.