全文获取类型
收费全文 | 3509篇 |
免费 | 85篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 184篇 |
综合类 | 9篇 |
化学工业 | 621篇 |
金属工艺 | 101篇 |
机械仪表 | 118篇 |
建筑科学 | 82篇 |
能源动力 | 83篇 |
轻工业 | 298篇 |
水利工程 | 9篇 |
无线电 | 345篇 |
一般工业技术 | 632篇 |
冶金工业 | 857篇 |
原子能技术 | 83篇 |
自动化技术 | 175篇 |
出版年
2023年 | 13篇 |
2022年 | 33篇 |
2021年 | 56篇 |
2020年 | 18篇 |
2019年 | 34篇 |
2018年 | 47篇 |
2017年 | 31篇 |
2016年 | 45篇 |
2015年 | 43篇 |
2014年 | 81篇 |
2013年 | 142篇 |
2012年 | 101篇 |
2011年 | 151篇 |
2010年 | 98篇 |
2009年 | 145篇 |
2008年 | 122篇 |
2007年 | 127篇 |
2006年 | 105篇 |
2005年 | 105篇 |
2004年 | 88篇 |
2003年 | 104篇 |
2002年 | 86篇 |
2001年 | 86篇 |
2000年 | 67篇 |
1999年 | 106篇 |
1998年 | 345篇 |
1997年 | 221篇 |
1996年 | 160篇 |
1995年 | 91篇 |
1994年 | 90篇 |
1993年 | 69篇 |
1992年 | 34篇 |
1991年 | 52篇 |
1990年 | 50篇 |
1989年 | 40篇 |
1988年 | 46篇 |
1987年 | 33篇 |
1986年 | 37篇 |
1985年 | 39篇 |
1984年 | 25篇 |
1983年 | 18篇 |
1982年 | 23篇 |
1981年 | 21篇 |
1980年 | 20篇 |
1979年 | 12篇 |
1978年 | 17篇 |
1977年 | 20篇 |
1976年 | 41篇 |
1975年 | 10篇 |
1974年 | 12篇 |
排序方式: 共有3597条查询结果,搜索用时 15 毫秒
1.
2.
3.
Yamaoka M. Shinozaki Y. Maeda N. Shimazaki Y. Kato K. Shimada S. Yanagisawa K. Osada K. 《Solid-State Circuits, IEEE Journal of》2005,40(1):186-194
An on-chip 1-Mb SRAM suitable for embedding in the application processor used in mobile cellular phones was developed. This SRAM supports three operating modes - high-speed active mode, low-leakage low-speed active mode, and standby mode - and uses a subdivisional power-line control (SPC) scheme. The combination of three operating modes and the SPC scheme realizes low-power operation under actual usage conditions. It operates at 300 MHz, with leakage of 25 /spl mu/A/Mb in standby mode, and 50 /spl mu/A/Mb at the low-leakage active mode. This SRAM also uses a self-bias write scheme that decreases of minimum operating voltage by about 100 mV. 相似文献
4.
5.
A new configuration based on the polarization-mismatching scheme with time delay for efficient frequency tripling conversion is proposed in this paper. The calculated results showed that the requirement for the efficient frequency tripling conversion of a 1-ps laser pulse is not only the optimization of peak intensity of the second-harmonic pulse, but also the optimization of the pulse duration ratio and temporal difference between the o-polarization second-harmonic pulse and the e-polarization first-harmonic pulse due to group-velocity mismatch among the interacting pulses. With the proposed scheme the group velocity mismatch can be compensated. Overall energy conversion efficiency increases from 55% to 75% under the optimized conditions at the intensity of 6 GW/cm2. The temporal shape of the third-harmonic pulse with 1 ps pulse duration has no subpulses. The optimization of the efficient frequency tripling conversion for intensities of over 75 GW/cm2 is also described. The results showed that the maximum tripling energy conversion efficiency is close to 80% with the optimized doubler and tripler 相似文献
6.
H. Nakamura M. Yoshinaga S. Nagashima A. Kato 《Journal of the European Ceramic Society》1996,16(12):1329-1335
Alumina-hydrate-coated SiC particles were prepared via a homogeneous precipitation method using urea, and the conditions for uniform coating and less coalescence of the particles were investigated. Coalescence of coated particles could be said to occur by collision and agglomeration followed by deposition of alumina hydrate on the agglomerated particles. Coalescence of coated particles was suppressed by use of low reaction temperature, low concentration of aluminium sulfate, high concentration of urea, intensive stirring, and a flow reactor. 相似文献
7.
8.
A new mathematical model for study of an interface crack between two dissimilar elastic half planes is proposed. A process zone is formed along the interface between the physical crack and the continuous part. Both the crack opening (and sliding) displacement with a smooth shape and the finite magnitude of stress concentration appear in this zone. The analytical model is expressed by closed elastic solutions using complex variables, but with no oscillations at the crack tip. 相似文献
9.
Ponds following anaerobic reactors, such as Upflow Anaerobic Sludge Blanket (UASB) reactors, have been termed polishing ponds in the literature. The present paper analyses the removal of E. coli and helminth eggs in five UASB-polishing pond systems in Brazil. Since there were ponds in series, the total number of ponds was 10. The ponds had average retention times varying from 2 to 21 days, and depths ranging from 0.40 to 2.00 m. The shallow ponds in series, even with low retention times, were able to produce effluents complying with the coliform WHO guidelines for unrestricted irrigation (< or = 1000 MPN/100 ml). An equation for the coliform decay coefficient was proposed: Kb (dispersed flow) = 0.710H(-0955) (20 degrees C). The equation highlights the inverse relationship between the pond depth and the decay coefficient. All polishing pond systems were able to produce effluents with helminth eggs concentrations predominantly equal to zero, and satisfying the WHO guidelines for unrestricted and restricted irrigation (< or = 1 egg/L, arithmetic mean). The approximate range of helminth eggs removal efficiency was predicted satisfactorily. 相似文献
10.
Tests and theoretical analysis on the maximum strength of high strength bolted tension flanges joining square hollow section members have been carried out. Yield line theory has been applied in a similar way to that presented in a previous paper. Correlation between test results and theoretical predictions is quite satisfactory. Based on this study, a simple design formula has been proposed. 相似文献