全文获取类型
收费全文 | 10931篇 |
免费 | 224篇 |
国内免费 | 319篇 |
专业分类
电工技术 | 383篇 |
综合类 | 213篇 |
化学工业 | 1332篇 |
金属工艺 | 419篇 |
机械仪表 | 742篇 |
建筑科学 | 67篇 |
矿业工程 | 31篇 |
能源动力 | 455篇 |
轻工业 | 92篇 |
水利工程 | 17篇 |
石油天然气 | 14篇 |
武器工业 | 44篇 |
无线电 | 2836篇 |
一般工业技术 | 3262篇 |
冶金工业 | 68篇 |
原子能技术 | 137篇 |
自动化技术 | 1362篇 |
出版年
2024年 | 4篇 |
2023年 | 105篇 |
2022年 | 163篇 |
2021年 | 183篇 |
2020年 | 164篇 |
2019年 | 168篇 |
2018年 | 162篇 |
2017年 | 242篇 |
2016年 | 291篇 |
2015年 | 277篇 |
2014年 | 556篇 |
2013年 | 476篇 |
2012年 | 508篇 |
2011年 | 1010篇 |
2010年 | 570篇 |
2009年 | 668篇 |
2008年 | 672篇 |
2007年 | 569篇 |
2006年 | 592篇 |
2005年 | 449篇 |
2004年 | 404篇 |
2003年 | 385篇 |
2002年 | 365篇 |
2001年 | 234篇 |
2000年 | 250篇 |
1999年 | 300篇 |
1998年 | 273篇 |
1997年 | 261篇 |
1996年 | 273篇 |
1995年 | 165篇 |
1994年 | 164篇 |
1993年 | 102篇 |
1992年 | 103篇 |
1991年 | 95篇 |
1990年 | 73篇 |
1989年 | 78篇 |
1988年 | 44篇 |
1987年 | 9篇 |
1986年 | 12篇 |
1985年 | 3篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 10篇 |
1980年 | 4篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 5篇 |
1974年 | 2篇 |
1973年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
介绍了激光起爆与点火系统中光纤连接器的原理、种类、技术特性及损耗,并对激光起爆与点火系统中光纤连接器的研制动向进行了概括,最后得出一些结论。 相似文献
22.
Michael Fox Richard Hastings Scott Lovald Juan Heinrich 《Journal of Failure Analysis and Prevention》2007,7(3):165-174
A failure analysis case study is presented for a two-piece aerosol containing tetrafluoroethane, commonly referred to as Refrigerant
134a. A gentleman was preparing to recharge the air conditioning system of an automobile when the bottom exploded off the
aerosol container, propelling the body of the aerosol container like a rocket, which hit the man in the eye and blinded him
in that eye. The aerosol was never connected to the air conditioner, therefore backpressure from the air conditioner (AC)
compressor was ruled out as a cause for the explosion. The objective of the study was to determine why the aerosol exploded.
Several recently developed test methods were used, including two types of heat-to-burst tests and a puncture chamber to measure
the pressure-versus-temperature behavior of aerosols. More common test methods were also used, such as water bath pressure
tests, hydro pressure burst tests, pneumatic pressure burst tests, hardness measurements, weight measurements, metallography,
scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and an accident scenario recreation. A semi-empirical
correlation between the hardness and weights of the container bottoms was used to determine the explosion temperature and/or
pressure. This semi-empirical correlation agrees in principle with an analysis of the explosion pressures using finite-element
analysis (FEA). The root cause for the explosion was determined to be a lack of strength of the bottom of the two-piece aerosol
coupled with heating the aerosol to temperatures significantly above room temperature. 相似文献
23.
The influence of the substrate nature on the structure and morphology of ITO thin films grown by thermal evaporation in vacuum is investigated. The as-prepared metal films with Sn/In molar ratio of 0.1 were subsequently annealed for 2 h at 723 K in air (to obtain tin doped indium oxide), then annealed in vacuum at 523 K, followed by UV irradiation (to reduce the electrical resistivity). Irrespective of substrate nature, XRD data evidence a (222) preferential orientation in films. Substrate nature, annealing in vacuum and UV irradiation influence the structure, morphology, optical, electrical and surface wetting properties of the films' surface. 相似文献
24.
András Ványolos Balázs Dóra Attila Virosztek 《Journal of Superconductivity and Novel Magnetism》2007,20(7-8):643-645
We report of a theoretical study on quasi-one dimensional unconventional charge density wave (UCDW) driven by electron–phonon
interaction. Within mean field theory, we find that the wavevector dependence of the coupling leads to a momentum dependent
single particle gap on the Fermi surface. The presence of small energy single particle excitations around the gap nodes significantly
changes the optical conductivity compared to the conventional CDW result. In addition to that, the collective phase excitation
arising from fluctuation of the order parameter leads to further qualitative changes of the conductivity and results in an
effective mass that is nonmonotonic in temperature.
相似文献
25.
中国光纤通信技术的研究、应用和发展 总被引:1,自引:0,他引:1
主要从光纤光缆、光器件与组件、光传输设备与系统、光网络建设等方面论述光纤通信技术在我国的研究、应用发展历程,并对我国光纤通信技术的未来发展进行展望。 相似文献
26.
M. Liu Q. Fang G. He L.Q. Zhu S.S. Pan L.D. Zhang 《Materials Science in Semiconductor Processing》2006,9(6):876
High-k HfOxNy thin films have been grown by radio frequency (rf) reactive sputtering of metal Hf target in N2/Ar/O2 ambient at different substrate temperatures. The chemical compositions of the films have been investigated as a function of substrate temperature by X-ray photoelectron spectroscopy (XPS). XPS measurements showed that nitrogen concentration increases with an increase in substrate temperature. Room-temperature spectroscopic ellipsometry (SE) with photon energy 0.75–6.5 eV was used to investigate the optical properties of the films. SE results demonstrated that refractive index n increases with an increase in substrate temperature. Based on TL parameters which were obtained from the best fit results used in a simulation of the measured spectra, meanwhile, we conclude that the energy band gap (Eg) decreases with an increase in substrate temperature. 相似文献
27.
光纤接入一直是多年来人们不断追求的梦想和探索的技术方向,但由于成本、技术、需求等方面的障碍,至今还没有得到大规模推广与发展。然而,这种局面最近有了很大的改观,出现可迅速发展的势头。主要是因为一些国家政策的扶持、运营商竞争的需要、对收入的追求,以及设备本身价格的下降,光纤接入技术由于各种原因,至今尚未在全球广泛应用,但在日本、美国、瑞典和意大利等国都获得了较多的应用。在中国,光纤接入也有了良好的开端,将在大城市广泛应用,并逐渐推广到全国。 相似文献
28.
29.
介绍了计算机光学零件图自动绘制软件系统的功能,给出了用该软件完成的光学零件图图样,对程序设计过程中的难点及处理方法也进行了详细阐述。 相似文献
30.
This paper presents the problems in the implementation of multipoint connections at switching level using the example of an ATM switching network. By choosing the proper routeing mechanism and the appropriate architecture of the switching element, a switching network can gradually be adapted to an increasing share of multipoint traffic. The first section describes the problems with the handling of multipoint connections within a multiple stage connection oriented switching network. In particular this refers to the routeing of the cells through the switching network. Several alternatives on this issue are discussed. Both, the selected approach based on a differentiated self-routeing mechanism and the corresponding cell format are introduced. In the second part of this article several switch architectures are compared in respect of their multipoint capability. It is demonstrated that at present the most promising solution are switching elements based on the principle of central buffering. A single chip solution using this concept is employed in the presented switching network. 相似文献