全文获取类型
收费全文 | 195336篇 |
免费 | 16291篇 |
国内免费 | 7875篇 |
专业分类
电工技术 | 11227篇 |
技术理论 | 10篇 |
综合类 | 11012篇 |
化学工业 | 31344篇 |
金属工艺 | 11590篇 |
机械仪表 | 12236篇 |
建筑科学 | 12345篇 |
矿业工程 | 4826篇 |
能源动力 | 4522篇 |
轻工业 | 11455篇 |
水利工程 | 3830篇 |
石油天然气 | 10900篇 |
武器工业 | 1384篇 |
无线电 | 21455篇 |
一般工业技术 | 29996篇 |
冶金工业 | 12292篇 |
原子能技术 | 5274篇 |
自动化技术 | 23804篇 |
出版年
2024年 | 1553篇 |
2023年 | 3067篇 |
2022年 | 5763篇 |
2021年 | 7732篇 |
2020年 | 5843篇 |
2019年 | 4936篇 |
2018年 | 6200篇 |
2017年 | 6641篇 |
2016年 | 6089篇 |
2015年 | 6959篇 |
2014年 | 8916篇 |
2013年 | 10675篇 |
2012年 | 11546篇 |
2011年 | 12387篇 |
2010年 | 10722篇 |
2009年 | 10352篇 |
2008年 | 10169篇 |
2007年 | 9569篇 |
2006年 | 8840篇 |
2005年 | 7494篇 |
2004年 | 5710篇 |
2003年 | 5648篇 |
2002年 | 5799篇 |
2001年 | 5231篇 |
2000年 | 4392篇 |
1999年 | 3801篇 |
1998年 | 2954篇 |
1997年 | 2467篇 |
1996年 | 2169篇 |
1995年 | 1899篇 |
1994年 | 1589篇 |
1993年 | 1357篇 |
1992年 | 1292篇 |
1991年 | 1111篇 |
1990年 | 1124篇 |
1989年 | 1046篇 |
1988年 | 930篇 |
1987年 | 858篇 |
1986年 | 772篇 |
1985年 | 724篇 |
1984年 | 709篇 |
1981年 | 675篇 |
1979年 | 740篇 |
1978年 | 777篇 |
1977年 | 739篇 |
1976年 | 755篇 |
1975年 | 713篇 |
1974年 | 719篇 |
1973年 | 723篇 |
1972年 | 705篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Jing Wang Walker D.M. Xiang Lu Majhi A. Kruseman B. Gronthoud G. Villagra L.E. van de Wiel P.J.A. Eichenberger S. 《Design & Test of Computers, IEEE》2007,24(3):226-234
Excessive power supply noise during test can cause overkill. This article discusses two models for supply noise in delay testing and their application to test compaction. The proposed noise models avoid complicated power network analysis, making them much faster than existing power noise analysis tools. can cause performance degradation and 相似文献
62.
63.
64.
Chai-Chin Lin Chih-Ming Chen Jenn-Hwan Tarng Hsueh-Ming Hang Hsiao-Cheng Yu 《Broadcasting, IEEE Transactions on》2002,48(1):38-43
Field tests of the transmission performance of the ATSC DTV system have been conducted in Taiwan. The test results as well as comparisons against the NTSC system performance are reported and analyzed. From the measured results the reception characteristics of the DTV can be deduced and can provide guidelines for television stations to design the transmission system, schedule equipment deployment, plan service coverage areas, and improve the reception quality of the digital signal 相似文献
65.
Yu. Dzyadykevych O. Smiyan 《International Journal of Refractory Metals and Hard Materials》2007,25(5-6):361-366
The results of investigation of initial stage of the tantalum borating as well as the effect of oxygen and hydrogen on it are presented. The scheme of the initial stage of tantalum boron saturation is proposed. 相似文献
66.
V. A. Borodulya Yu. S. Teplitskii Yu. G. Epanov I. I. Markevich 《Journal of Engineering Physics and Thermophysics》1987,53(6):1393-1396
Experimental data was obtained on external heat transfer in infiltrated granular beds of coarse particles. It was determined that calcualtions with the proposed model agree satisfactorily with the experimental results.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 6, pp. 919–923, December, 1988. 相似文献
67.
68.
A method for measuring the characteristics of tunneling and impact ionization in thin-film electroluminescent emitters is suggested. This method makes it possible to find time dependences of the space-charge layer thickness near the anode and the length of the impact ionization region, to determine more exactly the time dependence of the field in the potential barrier at the cathode interface, the maximum depth of the surface states from which electron tunneling occurs, the minimum thickness of the barrier, and the electron tunneling probability, as well as the impact ionization rate for the deep centers related to structural defects of the phosphor layer. 相似文献
69.
O. A. Neucheva A. A. Evstrapov Yu. B. Samsonenko G. E. Cirlin 《Technical Physics Letters》2007,33(11):923-925
We have studied the reflectivity spectra of doped GaAs nanowhiskers (NWs) with various morphologies, which were grown by molecular-beam epitaxy. It is established that the character of the reflectivity spectra of NWs is determined by the shape of nanocrystals. NWs with droplike and pointlike vertices differently interact with electromagnetic radiation. Laser radiation produces a spectraly selective action on the NW array, which leads to a change in the NW height and induces “caking” of their vertices, thus modifying the reflectivity of the sample. This phenomenon can be used for the creation of local microstructures with preset characteristics in large NW arrays. 相似文献
70.
Electromechanical properties of the 0-0-2-2 type composite based on platelike crystals of solid solutions of ferroelectric
relaxors of the Pb(A1/3Nb2/3)O3-PbTiO3 system (A = Zn, Mg) have been studied for the first time. Factors accounting for the record values of some effective parameters
of this composite are considered. The relationship between the components of the elastic compliance tensor of the layered
structures forming the composite and the positions of maxima of the effective hydrostatic parameters is established. 相似文献