全文获取类型
收费全文 | 13434篇 |
免费 | 2198篇 |
国内免费 | 2498篇 |
专业分类
化学 | 10155篇 |
晶体学 | 201篇 |
力学 | 178篇 |
综合类 | 110篇 |
数学 | 59篇 |
物理学 | 4240篇 |
无线电 | 3187篇 |
出版年
2024年 | 33篇 |
2023年 | 217篇 |
2022年 | 307篇 |
2021年 | 491篇 |
2020年 | 593篇 |
2019年 | 513篇 |
2018年 | 447篇 |
2017年 | 570篇 |
2016年 | 669篇 |
2015年 | 643篇 |
2014年 | 720篇 |
2013年 | 1202篇 |
2012年 | 967篇 |
2011年 | 853篇 |
2010年 | 691篇 |
2009年 | 814篇 |
2008年 | 812篇 |
2007年 | 852篇 |
2006年 | 826篇 |
2005年 | 761篇 |
2004年 | 683篇 |
2003年 | 595篇 |
2002年 | 561篇 |
2001年 | 404篇 |
2000年 | 411篇 |
1999年 | 360篇 |
1998年 | 272篇 |
1997年 | 268篇 |
1996年 | 225篇 |
1995年 | 216篇 |
1994年 | 170篇 |
1993年 | 168篇 |
1992年 | 153篇 |
1991年 | 110篇 |
1990年 | 87篇 |
1989年 | 66篇 |
1988年 | 79篇 |
1987年 | 42篇 |
1986年 | 41篇 |
1985年 | 26篇 |
1984年 | 30篇 |
1983年 | 22篇 |
1982年 | 29篇 |
1981年 | 15篇 |
1980年 | 18篇 |
1979年 | 23篇 |
1978年 | 22篇 |
1977年 | 13篇 |
1976年 | 19篇 |
1975年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 437 毫秒
41.
42.
含三正辛胺微胶囊对六价铬的富集 总被引:5,自引:0,他引:5
本文将对六价铬有效的萃取剂TOA(三正辛胺)微胶囊化,制成填充柱型的酸性体系六价铬的富集分离装置。实验结果表明,微胶囊填充柱中每毫升TOA对六价铬的最大萃取容量为158.0g/mL,为纯TOA液相萃取的4.9倍。微胶囊经碱/水洗涤后,可再生使用。 相似文献
43.
J. Hong E. S. Lambers C. R. Abernathy S. J. Pearton R. J. Shul W. S. Hobson 《Journal of Electronic Materials》1998,27(3):132-137
Dry etching of InGaP, AlInP, and AlGaP in inductively coupled plasmas (ICP) is reported as a function of plasma chemistry (BCl3 or Cl2, with additives of Ar, N2, or H2), source power, radio frequency chuck power, and pressure. Smooth anisotropic pattern transfer at peak etch rates of 1000–2000Å·min?1 is obtained at low DC self-biases (?100V dc) and pressures (2 mTorr). The etch mechanism is characterized by a trade-off between supplying sufficient active chloride species to the surface to produce a strong chemical enhancement of the etch rate, and the efficient removal of the chlorinated etch products before a thick selvedge layer is formed. Cl2 produces smooth surfaces over a wider range of conditions than does BCl3. 相似文献
44.
45.
46.
综述了国外离子束刻蚀和沉积系统的研究进展,指出了离子束系统在半导体技术研究,开发和生产中的重要性。 相似文献
47.
低压铝箔交流腐蚀研究 总被引:4,自引:2,他引:2
在30Hz频率下,通过铝箔在HCl+H2SO4+HNO3+H3PO4体系中的交流腐蚀,研究腐蚀液组成中腐蚀主体及缓蚀剂对铝箔腐蚀的作用,探讨腐蚀过程中电源频率、腐蚀液温度、电流密度及腐蚀时间对铝箔腐蚀的影响。腐蚀液组成的配比恰当,有利于比容的提高。在特定的频率下采用合适的腐蚀液温度、适宜的电流密度和腐蚀时间可以提高铝箔的静电容量。 相似文献
48.
Europium (Eu+) ions were confined in a Paul trap and detected by non-destructive method. Storage time of Eu+ ions achieved in vacuum was improved by orders of magnitude employing buffer gas cooling. The experimentally detected signal
was fitted to the ion response signal and the total number of ions trapped was estimated. It is found that the peak signal
amplitude as well as the product of FWHM and the peak signal amplitude is proportional to the total number of trapped ions.
The trapped ion secular frequency was swept at different rates and its effect on the absorption line profile was studied both
experimentally and theoretically. 相似文献
49.
The interactive two-state model of cell membrane ion channels in an electric field is formulated on the Bethe lattice by means
of the exact recursion relations. The probability of channel opening or maximum fractions of open potassium and sodium channels
are obtained by solving a non-linear algebraic equation. Using known parameters for the conventional mean-field theory the
model gives a good agreement with the experiment both at low and high trans-membrane potential values. For intermediate voltages,
the numerical results imply that collective effects are introduced by trans-membrane voltage. 相似文献
50.
The dry etching characteristics of transparent and conductive indium-zinc oxide (IZO) films have been investigated using an inductively coupled high-density plasma. While the Cl2-based plasma mixture showed little enhancement over physical sputtering in a pure argon atmosphere, the CH4/H2/Ar chemistry produced an increase of the IZO etch rate. On the other hand, the surface morphology of IZO films after etching in Ar and Ar/Cl2 discharges is smooth, whereas that after etching in CH4/H2/Ar presents particle-like features resulting from the preferential desorption of In- and O-containing products. Etching in CH4/H2/Ar also produces formation of a Zn-rich surface layer, whose thickness (∼40 nm) is well-above the expected range of incident ions in the material (∼1 nm). Such alteration of the IZO layer after etching in CH4/H2/Ar plasmas is expected to have a significant impact on the transparent electrode properties in optoelectronic device fabrication. 相似文献