全文获取类型
收费全文 | 12784篇 |
免费 | 963篇 |
国内免费 | 456篇 |
专业分类
电工技术 | 641篇 |
综合类 | 805篇 |
化学工业 | 2172篇 |
金属工艺 | 745篇 |
机械仪表 | 761篇 |
建筑科学 | 1015篇 |
矿业工程 | 353篇 |
能源动力 | 324篇 |
轻工业 | 591篇 |
水利工程 | 190篇 |
石油天然气 | 803篇 |
武器工业 | 73篇 |
无线电 | 1436篇 |
一般工业技术 | 1716篇 |
冶金工业 | 863篇 |
原子能技术 | 119篇 |
自动化技术 | 1596篇 |
出版年
2024年 | 68篇 |
2023年 | 273篇 |
2022年 | 337篇 |
2021年 | 504篇 |
2020年 | 414篇 |
2019年 | 328篇 |
2018年 | 413篇 |
2017年 | 436篇 |
2016年 | 409篇 |
2015年 | 447篇 |
2014年 | 586篇 |
2013年 | 674篇 |
2012年 | 753篇 |
2011年 | 823篇 |
2010年 | 670篇 |
2009年 | 676篇 |
2008年 | 692篇 |
2007年 | 617篇 |
2006年 | 676篇 |
2005年 | 620篇 |
2004年 | 419篇 |
2003年 | 353篇 |
2002年 | 329篇 |
2001年 | 249篇 |
2000年 | 286篇 |
1999年 | 343篇 |
1998年 | 329篇 |
1997年 | 305篇 |
1996年 | 257篇 |
1995年 | 186篇 |
1994年 | 175篇 |
1993年 | 140篇 |
1992年 | 99篇 |
1991年 | 74篇 |
1990年 | 79篇 |
1989年 | 34篇 |
1988年 | 43篇 |
1987年 | 26篇 |
1986年 | 20篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
The present study examines the behavior of a classical charged point particle in near-elliptic orbits about an infinitely massive and oppositely charged nucleus, while acted upon by applied electromagnetic radiation. As recently shown for near-circular orbits, and now extended here to the elliptical case, rather surprising nonlinear dynamical effects are readily produced for this simple system. A broad range of stability-like conditions can be achieved by applying radiation to this classical atom. A perfect balance condition is examined, which requires an infinite number of plane waves representing harmonics of the orbital motion. By applying a scale factor to this radiation, stability-like conditions are produced where periodic variations in semimajor and semiminor axes occur for extended periods of time, before orbital decay eventually takes over due to the effects of radiation reaction. This work is expected to lead to both practical suggestions on experimental ideas involving controlling ionization and stabilization conditions, as well as hopefully aiding in theoretical explorations of stochastic electrodynamics. 相似文献
22.
用正电子湮没研究含砷α黄铜的脱锌机制 总被引:3,自引:0,他引:3
分别测量了含0.00、0.01、0.03、0.05、007、0.10wt%As的68wt%Cu-Zn合金在1%CuCl2水溶液中脱锌后的正电子寿命谱。讨论了黄铜脱锌及砷抑制脱锌的空位体扩散机制。 相似文献
23.
核电在改善空气质量方面具有重要的作用。本文对比了核电与煤电的空气污染物排放系数,根据空气污染物引起的死亡率与人均燃煤发电量的负指数幂关系,评估了中国通过发展核电在改善空气质量方面对居民的健康效益,并对未来的健康效益进行了分析。结果显示,发展核电能够避免的死亡人数在增加。据估算,1995—2018年,中国核电累计可避免约4.7万人因空气污染物死亡,可避免约22.6万人因空气污染物患病。2020—2030年,预计会避免8.3万~9.4万人死亡,避免39.7万~45.1万人患病。 相似文献
24.
During research on different stan- dards for electrical accessories and household electrical appliances it has been suggested that to connect Chinese standards to IEC(International Electrotechnical Commission)standards we should carry out essential innovations based on assimilat- ing according to our own practical conditions.This method is the only way to standardize and at the same time maintain Chinese characteristics. 相似文献
25.
Chunjie Wang Yue Wang Yongliang Cheng Wenzhi Huang Zuhair S. Khan Xizhi Fan Ying Wang Binglin Zou Xueqiang Cao 《Journal of Materials Science》2012,47(10):4392-4399
Rare earth zirconates (Ln2Zr2O7, Ln = La, Nd, Sm, and Gd) with pyrochlore structure were prepared by hydrothermal method with polyethylene glycol as surfactant.
X-ray diffraction, thermogravimetric analysis/differential scanning calorimetry, Fourier transform infrared spectroscopy,
Raman spectroscopy, and field emission scanning electron microscopy were utilized to characterize the phase structure, thermal
decomposition, and morphology of the products. Qualitative analysis indicates that the as-prepared zirconates are pyrochlore-type
structures. The specific surface area, lattice parameter, and average crystallite size of the as-prepared products are closely
related to the ionic radius. The activation energy of crystal growth shows an increasing trend with the decrease in ionic
radii. The sintering behavior of compacted body was also investigated, revealing that the sintering-resistance properties
of Ln2Zr2O7 are descending as the order of La2Zr2O7, Nd2Zr2O7, Sm2Zr2O7, and Gd2Zr2O7. 相似文献
26.
通过实验分析围挡式洁净区的3个特性指标,即:流线平行度、乱流度和下限风速,并指出其应用价值和市场前景。 相似文献
27.
Liu XQ Lu W Shen SC Tan HH Jagadish C Zou J 《Journal of nanoscience and nanotechnology》2001,1(4):389-392
A pseudomorphic Al0.5Ga0.5As/In0.25Ga0.75As/GaAs asymmetric quantum wire (QWR) structure was grown on GaAs V-grooved substrate by low pressure metal organic vapor phase epitaxy. The formation of crescent shaped QWRs at the bottom of the V-grooves was confirmed by both transmission electron microscopy and photoluminescence (PL) spectra. The temperature dependence of PL spectra demonstrated a fast decrease of the sidewall quantum well PL intensity with increasing temperature, which originates from relaxation of carriers from well to wire region. The self-aligned dual implantation technique was successfully used to selectively disable the adjacent quantum structures. Decrease of the PL intensity of QWR at 8 K was observed after selective implantation, which resulted from a decreased number of carriers relaxed from adjacent quantum structures. 相似文献
28.
29.
30.
为满足高精度惯导测试设备的需要,针对我国目前直流伺服系统仍采用IGBT、晶闸管为主功率电路的现状,采用第五代智能功率模块IPM开发了一款新型的直流伺服系统;该系统相对于采用传统功率器件的伺服系统在性能指标与可靠性方面都有极大地提高,电流环带宽达到了1kHz.同时具有很好的电磁兼容性;应用于某高精度惯导测试设备0.001°/s速率检测,速率精度为0.0×10°,速率平稳度为9.2×10-5,结果表明,IPM智能功率模块应用于惯导测试设备中,系统性能稳定,伺服精度高,尤其是在功率密度和抗干扰性能方面表现突出,具有很好的应用前景. 相似文献