全文获取类型
收费全文 | 6032篇 |
免费 | 186篇 |
国内免费 | 15篇 |
专业分类
电工技术 | 337篇 |
综合类 | 17篇 |
化学工业 | 1493篇 |
金属工艺 | 166篇 |
机械仪表 | 121篇 |
建筑科学 | 114篇 |
矿业工程 | 2篇 |
能源动力 | 254篇 |
轻工业 | 529篇 |
水利工程 | 8篇 |
石油天然气 | 6篇 |
无线电 | 533篇 |
一般工业技术 | 1048篇 |
冶金工业 | 1003篇 |
原子能技术 | 119篇 |
自动化技术 | 483篇 |
出版年
2023年 | 36篇 |
2022年 | 67篇 |
2021年 | 112篇 |
2020年 | 54篇 |
2019年 | 64篇 |
2018年 | 94篇 |
2017年 | 83篇 |
2016年 | 101篇 |
2015年 | 85篇 |
2014年 | 163篇 |
2013年 | 342篇 |
2012年 | 243篇 |
2011年 | 332篇 |
2010年 | 249篇 |
2009年 | 277篇 |
2008年 | 299篇 |
2007年 | 253篇 |
2006年 | 221篇 |
2005年 | 228篇 |
2004年 | 184篇 |
2003年 | 190篇 |
2002年 | 172篇 |
2001年 | 141篇 |
2000年 | 118篇 |
1999年 | 124篇 |
1998年 | 401篇 |
1997年 | 247篇 |
1996年 | 171篇 |
1995年 | 127篇 |
1994年 | 138篇 |
1993年 | 112篇 |
1992年 | 62篇 |
1991年 | 56篇 |
1990年 | 48篇 |
1989年 | 67篇 |
1988年 | 46篇 |
1987年 | 39篇 |
1986年 | 39篇 |
1985年 | 42篇 |
1984年 | 38篇 |
1983年 | 48篇 |
1982年 | 33篇 |
1981年 | 34篇 |
1980年 | 26篇 |
1979年 | 29篇 |
1978年 | 32篇 |
1977年 | 36篇 |
1976年 | 56篇 |
1975年 | 15篇 |
1974年 | 16篇 |
排序方式: 共有6233条查询结果,搜索用时 10 毫秒
51.
Circularly polarised printed antenna fed by coplanar waveguide 总被引:1,自引:0,他引:1
A new structure of the circularly polarised printed antenna fed by coplanar waveguide (CPW) is proposed. FDTD analysis predicts the radiation of the circularly polarised wave from the antenna. The validity of this analysis is established by comparing with experimental results 相似文献
52.
Makoto Ishiguro Katsufumi Ohmuro Yukito Saitoh Yuuta Takahashi Jun Watanabe Tsutomu Arai Yoji Ito Keiji Mihayashi 《Journal of the Society for Information Display》2012,20(11):598-603
We have successfully developed a quarter‐wave retardation film (QWF) for wide viewing angle 3D liquid crystal displays (3D‐LCDs) that provides high luminance, low crosstalk, low color change, and low head‐tilt‐angle dependency. It was found that the out‐of‐plane retardation (Rth) of the QWF in the LCD needs to be close to 0 nm in order to improve the 3D display properties at an off‐axis position and that the in‐plane retardation (Re) needs to be adjusted from 120 to 130 nm to achieve low color change with head tilting. We adopted a coating process for making our QWF because of its potential for retardation control. 3D‐LCDs with this QWF whose Rth was nearly zero had high performance and allowed off‐axis other than on‐axis. 相似文献
53.
Crystallization of potassium titanate from the amorphous phase 总被引:1,自引:0,他引:1
Tadashi Endo Hiroyuki Nagayama Tsugio Sato Masahiko Shimada 《Journal of Materials Science》1988,23(2):694-698
By using amorphous potassium titanates as the starting materials, a sintered body of K2Ti4O9 or K2Ti6O13 with porous and fibrous textures was prepared. K2Ti2O5 and a new phase, K6Ti4O11 were synthesized by the thermal reaction of KNO3 with TiO2 at 1000° C for 10 to 20 h. On leaching in water to expel excess of potassium ions, both phases became amorphous. After mixing and moulding these amorphous materials in the desired proportion, a sintered body containing fibrous crystals of K2Ti4O9 was readily fabricated by heating at 1000° C for 12 h. When 5 wt % B2O3 was added to the amorphous phases, single phase K2Ti6O13, with a fibrous texture grew well on heating at 1000° C for 12 h. Addition of PVA polymer to the amorphous phases was responsible for controlling the porosity of the sintered body, e.g. about 52% theoretical density at 20 wt% PVA polymer. The optimum conditions for preparing the amorphous phases were systematically examined and the effect of the chemical reaction environments, such as different crucible materials on the calcination of KNO3 and TiO2 were also discussed. 相似文献
54.
55.
新型陶瓷与熔融盐复合蓄热材料优化组合的数值模拟 总被引:12,自引:0,他引:12
将高温熔融盐相变蓄热材料和陶瓷固相蓄热材料进行复合 ,成功地研制成了能快速吸热和放热且蓄热密度高、蓄热量大的新型复合蓄热材料。分别以Al2 O3 ,MgO ,SiC为代表的陶瓷材料与 6 0LiF 40NaF ,5 0LiF 5 0KF ,6 0 .1NaCl 39.9MgCl2 ,LiH等为代表的 10余种高温熔融盐材料为复合研究对象 ,对复合蓄热材料的蓄热密度等与温度、复合材料中熔融盐的含量、材料种类间的关系进行了数值模拟研究 ,得到了对复合材料的优化设计具有指导意义的结论 相似文献
56.
57.
Tsuyoshi Nakai Kiyofumi Yamada Hiroyuki Mizoguchi 《International journal of molecular sciences》2021,22(11)
Alzheimer’s disease (AD) is an age-related and progressive neurodegenerative disorder. It is widely accepted that AD is mainly caused by the accumulation of extracellular amyloid β (Aβ) and intracellular neurofibrillary tau tangles. Aβ begins to accumulate years before the onset of cognitive impairment, suggesting that the benefit of currently available interventions would be greater if they were initiated in the early phases of AD. To understand the mechanisms of AD pathogenesis, various transgenic mouse models with an accelerated accumulation of Aβ and tau tangles have been developed. However, none of these models exhibit all pathologies present in human AD. To overcome these undesirable phenotypes, APP knock-in mice, which were presented with touchscreen-based tasks, were developed to better evaluate the efficacy of candidate therapeutics in mouse models of early-stage AD. This review assesses several AD mouse models from the aspect of biomarkers and cognitive impairment and discusses their potential as tools to provide novel AD therapeutic approaches. 相似文献
58.
Hiroyuki?Y.?SuzukiEmail author Hidenori?Kuroki 《Metals and Materials International》2004,10(2):185-191
A new compacting method for powder materials is presented. High-Speed Centrifugal Compaction Process (HCP) utilizes centrifugal
force of about 10,000 g for the compaction. HCP is suitable for net shape compaction of fine sub-micron and nano-powders.
HCP possesses a unique compacting mechanism that is different from other colloidal processes including Pressure Casting (PC),
and has a number of useful characteristics. HCP has a higher compacting speed than PC, wide applicability for net shape formation,
as well as a defect removing function. Because of homogeneous and flawless green microstructure, HCP alumina shows superior
sinterability and higher strength and hardness than most of other aluminas.
This article is based on a presentation made in the symposium “The 3rd KIM-JIM Joint Symposium on Advanced Powder Materials“,
held at Korea University, Seoul, Korea, October 26–27, 2001 under auspices of The Korean Institute of Metals and Materials
and The Japan Institute of Metals. 相似文献
59.
Hydrogenation of four bituminous coals impregnated with 5 wt% of either mixtures of ZnCl2-MCln (CuCl, CrCl3 and MoCl5) systems or ZnCl2 was carried out using a batch autoclave system at 400° for 3 h at 9.8 MPa of initial hydrogen pressure. The ZnCl2-MoCl5 system showed the highest yield of the hexane-soluble (HS) fraction compared with the other systems irrespective of the coal used. The difference between the yields of HS fractions using the ZnCl2-MoCl5 and other systems was most marked for coals of fairly low volatile matter content, though the conversion was relatively low (47–66%), whilst for coals of high volatile matter content HS yields with the binary melt systems were high (86–91% conversion). Elemental analyses of the HS fractions indicated that the ZnCl2-MoCl5 system is most favourable in decreasing the average molecular weight and the heteroatom content of HS, this characteristic trend being confirmed also with five HS fractions separated by Chromatographic techniques. Both elemental analyses and molecular weights of asphaltene (benzene-soluble materials, BS) indicated that the ZnCl2-MoCl5 system is also most effective in cracking coal structure. 相似文献
60.
Koki Murano Tomoyoshi Shimobaba Atsushi Sugiyama Naoki Takada Takashi Kakue Minoru Oikawa Tomoyoshi Ito 《Computer Physics Communications》2014
We report fast computation of computer-generated holograms (CGHs) using Xeon Phi coprocessors, which have massively x86-based processors on one chip, recently released by Intel. CGHs can generate arbitrary light wavefronts, and therefore, are promising technology for many applications: for example, three-dimensional displays, diffractive optical elements, and the generation of arbitrary beams. CGHs incur enormous computational cost. In this paper, we describe the implementations of several CGH generating algorithms on the Xeon Phi, and the comparisons in terms of the performance and the ease of programming between the Xeon Phi, a CPU and graphics processing unit (GPU). 相似文献