全文获取类型
收费全文 | 1232篇 |
免费 | 329篇 |
国内免费 | 66篇 |
专业分类
化学 | 711篇 |
晶体学 | 2篇 |
力学 | 115篇 |
综合类 | 10篇 |
数学 | 29篇 |
物理学 | 760篇 |
出版年
2023年 | 10篇 |
2022年 | 23篇 |
2021年 | 39篇 |
2020年 | 27篇 |
2019年 | 32篇 |
2018年 | 32篇 |
2017年 | 37篇 |
2016年 | 64篇 |
2015年 | 65篇 |
2014年 | 70篇 |
2013年 | 128篇 |
2012年 | 124篇 |
2011年 | 99篇 |
2010年 | 74篇 |
2009年 | 86篇 |
2008年 | 81篇 |
2007年 | 81篇 |
2006年 | 78篇 |
2005年 | 82篇 |
2004年 | 66篇 |
2003年 | 52篇 |
2002年 | 43篇 |
2001年 | 38篇 |
2000年 | 38篇 |
1999年 | 17篇 |
1998年 | 22篇 |
1997年 | 15篇 |
1996年 | 10篇 |
1995年 | 14篇 |
1994年 | 14篇 |
1993年 | 6篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 10篇 |
1989年 | 4篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
排序方式: 共有1627条查询结果,搜索用时 31 毫秒
1.
By use of the 2-m Mcmath-Pierce telescope at Kitt Peak, the high-quality spectra of a plage with moderate brightness near the center of solar disk were obtained. The data include seven spectral lines, which are Hα, Hβ, CaII H and K lines and the infrared triplet. With the consideration of fine structures of solar plages, a two-component atmospheric model is constructed by keeping the cool component to be the quiet atmosphere. Three cases of the hot component are given for different filling factors where the temperature and density distribution are adjusted in order to reproduce the seven observed spectral profiles. We also briefly discuss the influence of the column density at the base of the corona, m0, and the macro-turbulent velocity on the required filling factor and computed profiles. The two-component model is compared with precious one-component semi-empirical models. The limitation of the model is pointed out and further improvement is indicated. 相似文献
2.
3.
4.
E.M. Rabinovich D.W. Johnson Jr. A. Mishkevich E.A. Chandross J. Thomson Jr. 《Journal of Sol-Gel Science and Technology》2003,28(1):19-29
Particulate sol-gel technology uses larger particles than that of alkoxide-derived gels and provides larger pore sizes in the gelled object. This allows relatively rapid drying and fabrication of large rods or tubular shapes. However, the formation of more complex or flat shapes, which require extensive surface contact with a mold, is more difficult. The shrinkage during drying, with the significantly greater stress of surface friction due to adhesion, frequently leads to cracking.We have demonstrated a solution to this problem by floating the gel on the surface of a dense liquid. Dry silica panels up to 28 × 40 × 0.7 cm3 were prepared in this way. The use of patterning molds allowed the fabrication of more sophisticated shapes. These bodies were sintered to transparent vitreous silica articles of near net dimensions. 相似文献
5.
Results from Super-Kamiokande-I’s entire 1496 live days of solar neutrino data are presented, including the absolute flux,
energy spectrum, zenith angle (day/night) and seasonal variation. The possibility of MSW and vacuum oscillations is discussed
in light of these results. Results from the first 1289 days of Super-K-I’s atmospheric neutrino analysis are also presented,
including the evidence for νμ →ν
τ oscillations, against νμ → νsterile oscillations, and the current limits on proton decay. Finally, results based on 56 × 1019 protons on target are given for the K2K long-baseline neutrino oscillation experiment. 相似文献
6.
工业污染排放中气──固两相流的光学测量 总被引:1,自引:0,他引:1
烟尘及各种工业性粉尘排放是典型的气-固两相系.迄今为止,国内外尚缺少有效的监测其排放的手段.本文基于光的散时原理,提出了一种非接触的光学方法,能对上述固体颗粒物的污染排放浓度及粒径大小进行实时、在线的监测。计算机模拟和实验研究表明,该方法具有广阔的工业应用前景。 相似文献
7.
采用常压金属有机物化学气相沉积技术(AP-MOCVD),以二乙基锌(DEZn)为Zn源,去离子水(H2O)为氧源,N2作载气,在外延ZnO薄膜的反应气氛中通入少量氢气,在c-Al2O3衬底上生长出了ZnO∶H薄膜。用X射线双晶衍射和光致发光谱对ZnO∶H薄膜的结晶性能和光学性质进行表征。结果表明,ZnO∶H薄膜(002)和(102)面的Ω扫描半峰全宽分别为46.1 mrad和81.4 mrad,表明该薄膜具有良好的结晶性能;室温下,ZnO∶H薄膜具有较强的紫外光发射(380 nm),在低温10 K光致发光谱中观测到位于3.3630 eV处与氢相关的中性施主束缚激子峰(I4)及其位于3.331 eV处的双电子卫星峰(TES)。采用退火的方法,通过观测I4峰的强度变化,研究了氢在ZnO∶H薄膜中的热稳定性。发现随着退火温度的升高,I4峰的强度逐渐减弱,表明在高温下退火,氢会从ZnO薄膜中逸出。 相似文献
8.
9.
10.