全文获取类型
收费全文 | 22744篇 |
免费 | 3237篇 |
国内免费 | 2206篇 |
专业分类
电工技术 | 1367篇 |
综合类 | 1775篇 |
化学工业 | 1902篇 |
金属工艺 | 622篇 |
机械仪表 | 1551篇 |
建筑科学 | 414篇 |
矿业工程 | 294篇 |
能源动力 | 449篇 |
轻工业 | 1839篇 |
水利工程 | 73篇 |
石油天然气 | 584篇 |
武器工业 | 626篇 |
无线电 | 10190篇 |
一般工业技术 | 2201篇 |
冶金工业 | 373篇 |
原子能技术 | 202篇 |
自动化技术 | 3725篇 |
出版年
2024年 | 72篇 |
2023年 | 368篇 |
2022年 | 570篇 |
2021年 | 688篇 |
2020年 | 827篇 |
2019年 | 712篇 |
2018年 | 748篇 |
2017年 | 922篇 |
2016年 | 1035篇 |
2015年 | 1169篇 |
2014年 | 1591篇 |
2013年 | 1526篇 |
2012年 | 1991篇 |
2011年 | 2022篇 |
2010年 | 1388篇 |
2009年 | 1368篇 |
2008年 | 1445篇 |
2007年 | 1593篇 |
2006年 | 1442篇 |
2005年 | 1077篇 |
2004年 | 894篇 |
2003年 | 787篇 |
2002年 | 604篇 |
2001年 | 563篇 |
2000年 | 486篇 |
1999年 | 378篇 |
1998年 | 347篇 |
1997年 | 268篇 |
1996年 | 251篇 |
1995年 | 203篇 |
1994年 | 194篇 |
1993年 | 148篇 |
1992年 | 129篇 |
1991年 | 112篇 |
1990年 | 80篇 |
1989年 | 46篇 |
1988年 | 18篇 |
1987年 | 22篇 |
1986年 | 16篇 |
1985年 | 11篇 |
1984年 | 19篇 |
1983年 | 16篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1980年 | 5篇 |
1978年 | 2篇 |
1976年 | 3篇 |
1975年 | 5篇 |
1973年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
61.
K. O. Boltar I. D. Burlakov A. M. Filachev E. A. Klimanov V. P. Ponomarenko V. N. Solyakov V. I. Stafeev 《Optical Memory & Neural Networks》2007,16(4):234-247
The recent researches and technological developments of middle and long wavelength infrared HgCdTe photovoltaic detectors
are presented. Structure, topology, design and performance of HgCdTe photodiodes, silicon readout electronics, Focal Plane
Arrays both staring and time delay and integration types, thermal imagers are discussed. Negative differential conductance,
bistability and high frequency oscillations under background infrared radiation in HgCdTe photodiodes are reported. 相似文献
62.
Chun Yang Yin Sharifah Aishah Syed Abdul KadirYing Pei Lim Sharifah Nawirah Syed-AriffinZurinawati Zamzuri 《Fuel Processing Technology》2008
Ash derived from combustion of Malaysian oil palm biomass (empty fruit bunches consisting of fibers) was physically and chemically characterized in order to provide a comprehensive understanding of its specific properties in terms of toxicity, compositions and reusability. Principal analyses conducted include particle size distribution, scanning electron microscopy, elemental dispersive X-ray, elemental analysis, toxicity characteristic leaching procedure (TCLP) as well as thermogravimetric, X-ray diffractometry and Fourier-transform infrared analyses. TCLP result indicated that the oil palm ash (OPA) should not be classified as toxic wastes in terms of heavy metal leachability since leachable copper, cadmium, lead and nickel concentrations were detected below the stipulated leachability limits. It was determined that the OPA contained high amount of potassium as well as presence of silica which implied its suitability to be reused as crude fertilizer or cement replacement material. 相似文献
63.
O. Gravrand E. De Borniol S. Bisotto L. Mollard G. Destefanis 《Journal of Electronic Materials》2007,36(8):981-987
This paper aims at studying the feasibility of very long infrared wavelength (VLWIR) (12–18 μm) focal plane arrays using n-on-p planar ion-implanted technology. To explore and analyze the feasibility of such VLWIR detectors, a set of four Cd
x
Hg1−x
Te LPE layers with an 18 μ cutoff at 50 K has been processed at Defir (LETI/LIR–Sofradir joint laboratory), using both our “standard” n-on-p process and our improved low dark current process. Several 320 × 256 arrays, 30-μm pitch, have been hybridized on standard Sofradir readout circuits and tested. Small dimension test arrays characterization
is also presented. Measured photonic currents with a 20°C black body suggest an internal quantum efficiency above 50%. Typical
I(V) curves and thermal evolution of the saturation current are discussed, showing that standard photodiodes remain diffusion
limited at low biases for temperatures down to 30 K. Moreover, the dark current gain brought by the improved process is clearly
visible for temperatures higher than 40 K. Noise measurements are also discussed showing that a very large majority of detectors
appeared background limited under usual illumination and biases. In our opinion, such results demonstrate the feasibility
of high-performance complex focal plane arrays in the VLWIR range at medium term. 相似文献
64.
CAO Wei-feng WANG Wen-boBeijing University of Posts Telecommunications Beijing P.R. China 《中国邮电高校学报(英文版)》2005,12(4)
1IntroductionCurrently,smart antenna technology can greatly en-hance system performance and i mprove the system ca-pacity so that it has been considered as a keytechnologyinthe third generation wireless communicationsystems .The researches on channel model , beamforming algo-rithms and receive algorithms have been widely carriedout and a great many of proposition have beensubmittedtothe 3th Generation Project Partner (3GPP) . Fromthe viewpoint of link-level and system-level research,many asp… 相似文献
65.
Lean philosophy: implementation in a forging company 总被引:2,自引:2,他引:0
Ajit Kumar Sahoo N. K. Singh Ravi Shankar M. K. Tiwari 《The International Journal of Advanced Manufacturing Technology》2008,36(5-6):451-462
This research addresses the implementation of lean philosophy in a forging company with a focus on radial forging production
flow lines. Here, the prime motive is to evolve and test several strategies to eliminate waste on the shop floor. In this
research, a systematic approach is suggested for the implementation of lean principles. This paper describes an application
of value stream mapping (VSM). Consequently, the present and future states of value stream maps are constructed to improve
the production process by identifying waste and its sources. Furthermore, Taguchi’s method of design of experiments is pursued
here to minimize the forging defects produced due to imperfect operating conditions. A noticeable reduction in set-up time
and work-in-process (WIP) inventory level is substantiated. Finally, we conclude with a discussion of managerial implications
and the future scope of research. 相似文献
66.
本文分析了相控阵机载预警(AEW)雷达杂波抑制的现有两种辅助通道降维技术(Klemm方法和简化方法)的性能,并提出了一种新的辅助通道方法。新方法的基本思想为:根据待处理距离段内各距离单元杂波能量在波束一多普勒域分布的统计特征自适应地选取辅助通道,使所选辅助通道实时地逼近杂波子空间,从而有效抑制杂波。本文方法不但可以用于非正侧视阵情况,而且误差鲁棒性好。计算机仿真结果证实了其有效性。 相似文献
67.
68.
本文将等效介电常数近似分析方法在应用范围和处理方法上进行了一些改进.发展为双等效介电常数近似分析法,然后用它来分析矩形介质波导阵列.推得两个一维周期的耦合特征方程。如果将Macatili方法应用范围扩展用来研究该波导阵列也会得到同样的结果,它们都能在二维平面上较准确地反应出通带和阻带等主要周期特性。 相似文献
69.
本文介绍红外热象技术在工程热物理研究中某些应用的探索。作为实例,通过热象技术,实验研究了具有水平凸台离散热源的倾斜板的散热,在研究它的自然对流换热部份结合利用激光全息干涉技术。此间着重于分析倾斜角对散热的影响。 相似文献
70.