全文获取类型
收费全文 | 16801篇 |
免费 | 1489篇 |
国内免费 | 746篇 |
专业分类
电工技术 | 2342篇 |
综合类 | 1201篇 |
化学工业 | 651篇 |
金属工艺 | 693篇 |
机械仪表 | 1834篇 |
建筑科学 | 790篇 |
矿业工程 | 465篇 |
能源动力 | 372篇 |
轻工业 | 332篇 |
水利工程 | 235篇 |
石油天然气 | 261篇 |
武器工业 | 143篇 |
无线电 | 4153篇 |
一般工业技术 | 1092篇 |
冶金工业 | 371篇 |
原子能技术 | 454篇 |
自动化技术 | 3647篇 |
出版年
2024年 | 35篇 |
2023年 | 145篇 |
2022年 | 250篇 |
2021年 | 289篇 |
2020年 | 356篇 |
2019年 | 254篇 |
2018年 | 309篇 |
2017年 | 448篇 |
2016年 | 501篇 |
2015年 | 599篇 |
2014年 | 977篇 |
2013年 | 963篇 |
2012年 | 1310篇 |
2011年 | 1609篇 |
2010年 | 1156篇 |
2009年 | 1087篇 |
2008年 | 1109篇 |
2007年 | 1233篇 |
2006年 | 1150篇 |
2005年 | 946篇 |
2004年 | 785篇 |
2003年 | 616篇 |
2002年 | 496篇 |
2001年 | 366篇 |
2000年 | 307篇 |
1999年 | 261篇 |
1998年 | 225篇 |
1997年 | 216篇 |
1996年 | 190篇 |
1995年 | 148篇 |
1994年 | 161篇 |
1993年 | 103篇 |
1992年 | 91篇 |
1991年 | 75篇 |
1990年 | 51篇 |
1989年 | 53篇 |
1988年 | 41篇 |
1987年 | 28篇 |
1986年 | 23篇 |
1985年 | 13篇 |
1984年 | 20篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1960年 | 2篇 |
1955年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
利用线阵CCD实现宽波段、大视场短脉冲激光波长的远场测量 总被引:5,自引:1,他引:4
介绍了一种利用线阵CCD实现宽波段、大视场脉冲激光波长及方向远场测量的原理和实验装置;对强烈背景下激光信号的提取与处理方法进行了理论分析和实验研究,给出了系统信噪比与探测器件工作频率的理论公式;最后简要介绍了远场实验和测试结果 相似文献
83.
T.A. Wyatt 《Journal of Wind Engineering & Industrial Aerodynamics》2004,92(5):359-374
The classical spectral analysis of structural response to a gusty wind is applied to the prediction of fatigue damage as expressed by the rate of accumulation of Miner's quotient, using the rainflow algorithm to establish stress-range cycle counts. A general solution in chart form is given for the effect of the broad-band (quasi-static) part of the response spectrum, together with an algebraic formulation for its combination with the effect of narrow-band (quasi-resonant) response.A procedure for integration of the long-term expectation of Miner's quotient is indicated. It is concluded that quasi-static response alone is unlikely to pose a serious fatigue problem. With generally anticipated levels of dynamic response, fatigue damage is greatly increased, but can be controlled at acceptable levels by care to avoid features especially sensitive to fatigue. 相似文献
84.
MuShanxiang JiXiaoli LiMing LiXingguo 《电子科学学刊(英文版)》2003,20(6):407-413
Linear Modulated Frequency (LMF) Costas Stepped Frequency Radar (SFR) signal is introduced. Its ambiguity function is derived and analyzed in detail and its feasibility is validated in theory. The scheme of the proposed signal processing is also presented. The results of theoretic analysis and simulation show that, by using the proposed signal and increasing the bandwidth of the total stepped frequency, the ambiguity sidelobe is well suppressed and the range-velocity coupling in the stepped frequency radar is also greatly weakened. 相似文献
85.
东安石灰石矿爆破降震新技术 总被引:1,自引:0,他引:1
本文介绍了湘钢东安石灰石矿和长沙矿冶研究院合作进行降震技术试验研究的结果.异步分区起爆综合降震技术既可显著降震,由于振动频率提高,降低了周围民房的地震效应,减轻了房屋的摆动程度. 相似文献
86.
87.
Service Load Effective Compression Flange Width in Fiber Reinforced Polymer Deck Systems Acting Compositely with Steel Stringers 总被引:1,自引:0,他引:1
This paper reports on the field study of a steel stringer-fiber reinforced polymer (FRP) deck composite bridge in Pennsylvania. The objective of the study is to assess the effective compression flange width in the FRP deck and floor systems when they act compositely with underlying steel girders at service conditions. The research results reported herein support the notion of employing a design approach, for both interior and exterior girders of a composite floor system, that is philosophically consistent with current practice related to steel girders acting compositely with concrete decking. It appears from the results presented herein that FRP decks and floors acting compositely with underlying steel girders exhibit an effective width that is close to the actual girder spacing for interior beams, and approximately one-half this value for exterior beams. 相似文献
88.
Seong Hyuk Lee Junghee Lee Kwan-Gu Kang Joon Sik Lee 《Journal of Mechanical Science and Technology》2006,20(8):1292-1301
This article investigates numerically the carrier-phonon interactions in thin gallium arsenide (GaAs) film structures irradiated
by subpicosecond laser pulses to figure out the role of several recombination processes on the energy transport during laser
pulses and to examine the effects of laser fluences and pulses on non-equilibrium energy transfer characteristics in thin
film structures. The self-consistent hydrodynamic equations derived from the Boltzmann transport equations are established
for carriers and two different types of phonons, i.e., acoustic phonons and longitudinal optical (LO) phonons. From the results,
it is found that the two-peak structure of carrier temperatures depends mainly on the pulse durations, laser fluences, and
nonradiative recombination processes, two different phonons are in nonequilibrium state within such lagging times, and this
lagging effect can be neglected for longer pulses. Finally, at the initial stage of laser irradiation, SRH recombination rates
increases sufficiently because the abrupt increase in carrier number density no longer permits Auger recombination to be activated.
For thin GaAs film structures, it is thus seen that Auger recombination is negligible even at high temperature during laser
irradiation. 相似文献
89.
A stochastic model is proposed for a basic mechanism in the formation of uncertainties in physical quantity measurements.
__________
Translated from Izmeritel'naya Tekhnika, No. 1, pp. 12–17, January, 2006. 相似文献
90.
本文提出了一种适合于特殊环境使用的光纤局域网的拓扑结构——类星型结构。这种结构解决了多通道的同时传输问题。此外,文中还对 OLAN 网的层次划分和各层的协议进行了分析和讨论。 相似文献