全文获取类型
收费全文 | 223827篇 |
免费 | 21885篇 |
国内免费 | 13036篇 |
专业分类
电工技术 | 17625篇 |
技术理论 | 7篇 |
综合类 | 17982篇 |
化学工业 | 32485篇 |
金属工艺 | 13547篇 |
机械仪表 | 15071篇 |
建筑科学 | 18586篇 |
矿业工程 | 7397篇 |
能源动力 | 6655篇 |
轻工业 | 16575篇 |
水利工程 | 5238篇 |
石油天然气 | 12036篇 |
武器工业 | 2500篇 |
无线电 | 26409篇 |
一般工业技术 | 23348篇 |
冶金工业 | 9191篇 |
原子能技术 | 2470篇 |
自动化技术 | 31626篇 |
出版年
2024年 | 1095篇 |
2023年 | 3686篇 |
2022年 | 7183篇 |
2021年 | 9833篇 |
2020年 | 7508篇 |
2019年 | 5839篇 |
2018年 | 6519篇 |
2017年 | 7656篇 |
2016年 | 6606篇 |
2015年 | 9746篇 |
2014年 | 12389篇 |
2013年 | 14430篇 |
2012年 | 16612篇 |
2011年 | 17560篇 |
2010年 | 16126篇 |
2009年 | 15127篇 |
2008年 | 14911篇 |
2007年 | 14042篇 |
2006年 | 13080篇 |
2005年 | 10380篇 |
2004年 | 7301篇 |
2003年 | 6258篇 |
2002年 | 6036篇 |
2001年 | 5311篇 |
2000年 | 4411篇 |
1999年 | 3979篇 |
1998年 | 2829篇 |
1997年 | 2391篇 |
1996年 | 2189篇 |
1995年 | 1841篇 |
1994年 | 1484篇 |
1993年 | 991篇 |
1992年 | 837篇 |
1991年 | 567篇 |
1990年 | 453篇 |
1989年 | 376篇 |
1988年 | 265篇 |
1987年 | 177篇 |
1986年 | 156篇 |
1985年 | 83篇 |
1984年 | 71篇 |
1983年 | 56篇 |
1982年 | 62篇 |
1981年 | 60篇 |
1980年 | 56篇 |
1979年 | 31篇 |
1978年 | 10篇 |
1976年 | 10篇 |
1959年 | 11篇 |
1951年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
J.A. Bakken L. Barone D. Braun M. Caillat C. Dionisi C. Dor H. Elmamouni F. Ferroni G.L. Grazer J.T. He R. Herbiet B. Ille P. Lecomte E. Longo P.F. Loverre Y.S. Lu J.P. Martin U. Micke R.P. Mount P.A. Pirou H.-G. Sander D. Schmitz M. Schneegans D.P. Stickland R.L. Sumner K.L. Tung E. Valente M. Vivargent 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1985,228(2-3):294-302
A calorimeter of 25 bismuth germanate (BGO) crystals equipped with silicon photodiode readout has been tested at the CERN SPS in the energy range 1–50 GeV. The response for electrons has been shown to be linear in this energy range and the rms resolution obtained (
) is approximately 1%, for E > 4 GeV. The electron/pion separation was found to be better than 1:500 in the energy range 1–20 GeV. Data on lateral and longitudinal shower development were compared with the results of a Monte Carlo simulation using the SLAC-EGS program and found to be in good agreement. 相似文献
72.
本文介绍了一个用户接口管理系统NUUIMS的设计和实现.重点叙述了该系统基于规范化目标用户接口模型的设计思想,系统组成及描述方法.文章也讨论了使用NUUIMS设计而成的用户接口的特点. 相似文献
73.
74.
中国铜冶炼企业的竞争趋势及对策建议 总被引:1,自引:0,他引:1
文章分析了我国大型及中小型铜冶炼企业所面临竞争环境,提出了我国铜冶炼企业应采取的对策建议,即:联合进口原料;走大型企业联合之路,组建中国铜业集团;开发利用海外资源;加大国内资源勘探;继续进行技改、挖潜,提高企业竞争力等。 相似文献
75.
A photochromic nanocomposite based on Keggin structure phosphomolybdic acid (PMoA) well dispersed in polyethyleneglycol (PEG) was fabricated. TEM image showed that PMoA nanoparticles with narrow size distribution were finely dispersed in polymer matrix. FT-IR results showed that the Keggin geometry of polyoxometalates was still preserved inside the composites and strong coulombic interaction was built between PMoA and polymer matrix. Under UV irradiation, the film was reduced photochemically to yield a blue species, which was in accordance with a charge-transfer mechanism. 相似文献
76.
77.
Jianxin Wei Mark R Pickering Michael R Frater John F Arnold John A Boman Wenjun Zeng 《IEEE transactions on image processing》2005,14(8):1033-1042
It is well known that tile-boundary artifacts occur in wavelet-based lossy image coding. However, until now, their cause has not been understood well. In this paper, we show that boundary artifacts are an inescapable consequence of the usual methods used to choose tile size and the type of symmetric extension employed in a wavelet-based image decomposition system. This paper presents a novel method for reducing these tile-boundary artifacts. The method employs odd tile sizes (2N + 1 samples) rather than the conventional even tile sizes (2N samples). It is shown that, for the same bit rate, an image compressed using an odd tile length low-pass first (OTLPF) convention has significantly less boundary artifacts than an image compressed using even tile sizes. The OTLPF convention can also be incorporated into the JPEG 2000 image compression algorithm using extensions defined in Part 2 of this standard. 相似文献
78.
BaMgAl10O17∶Eu2 (BAM) was prepared in the microemulsion system and its phase behavior was studied. There exists a small region in the reverse microemulsion system where the dispersed particles are of spherical form. In this way, BAM blue phosphor with good dispersion can be synthesized. The microemulsion phase diagrams of the pseudo-ternary system (Triton X-100/cosurfactant-oil-BAM brine) were first established intuitively by the dilution method. The microstructure of microemulsions was determined through eyeballing, conductance technique, and polar optical microscopy. Its phase behavior is affected by various factors, such as temperature (room temperature, 30, 40 ℃), oil, surfactants, and cosurfactants in microemulsions. According to the phase diagrams, the microemulsion system of Triton X-100/1-hexanol-hexane-BAM brine was chosen to prepare the precursor. The BAM phosphor can be obtained via sintering the precursor at a comparatively low temperature. The phosphors were characterized by XRD and vacuum ultraviolet (VUV) spectra. 相似文献
79.
80.