全文获取类型
收费全文 | 1646篇 |
免费 | 222篇 |
国内免费 | 332篇 |
专业分类
化学 | 1083篇 |
晶体学 | 27篇 |
力学 | 68篇 |
综合类 | 27篇 |
数学 | 280篇 |
物理学 | 715篇 |
出版年
2024年 | 5篇 |
2023年 | 8篇 |
2022年 | 51篇 |
2021年 | 34篇 |
2020年 | 33篇 |
2019年 | 40篇 |
2018年 | 35篇 |
2017年 | 59篇 |
2016年 | 53篇 |
2015年 | 43篇 |
2014年 | 73篇 |
2013年 | 107篇 |
2012年 | 105篇 |
2011年 | 118篇 |
2010年 | 98篇 |
2009年 | 111篇 |
2008年 | 106篇 |
2007年 | 120篇 |
2006年 | 103篇 |
2005年 | 85篇 |
2004年 | 77篇 |
2003年 | 69篇 |
2002年 | 69篇 |
2001年 | 59篇 |
2000年 | 57篇 |
1999年 | 40篇 |
1998年 | 21篇 |
1997年 | 18篇 |
1996年 | 29篇 |
1995年 | 39篇 |
1994年 | 24篇 |
1993年 | 30篇 |
1992年 | 27篇 |
1991年 | 26篇 |
1990年 | 15篇 |
1989年 | 14篇 |
1988年 | 19篇 |
1987年 | 29篇 |
1986年 | 17篇 |
1985年 | 10篇 |
1984年 | 16篇 |
1981年 | 11篇 |
1980年 | 15篇 |
1979年 | 12篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1975年 | 6篇 |
1972年 | 8篇 |
1966年 | 4篇 |
排序方式: 共有2200条查询结果,搜索用时 8 毫秒
101.
J. G. Santos L. B. Silveira A. C. Oliveira V. K. Garg B. M. Lacava A. C. Tedesco P. C. Morais 《Hyperfine Interactions》2007,175(1-3):71-75
Transmission electron microscopy, X-ray diffraction and Mössbauer spectroscopy were used in the characterization of a nanocomposite containing magnetic nanoparticles dispersed in a glycolic acid-based template. Maghemite nanoparticles were identified as the iron oxide phase dispersed in the polymeric template. From the low-temperature Mössbauer data the amount of the iron-based, non-magnetic material at the nanoparticle surface was estimated as roughly one monolayer in thickness. 相似文献
102.
M.A.G. Soler G.B. Alcantara W.R. Viali J.R.L. Fernandez V.K. Garg P.C. Morais 《Surface science》2007,601(18):3921-3925
In this study γ-Fe2O3 nanoparticle, surface-coated with increasing amount of oleic acid, have been prepared while the stability against particle degradation under laser excitation intensity was investigated. Maghemite nanoparticle was obtained via oxidation of magnetite nanoparticle, the latter synthesized by co-precipitation of Fe (II) and Fe (III) ions in alkaline medium. By varying the experimental conditions of surface-coating maghemite nanoparticles with oleic acid, samples with different grafting coefficient were obtained and investigated using X-ray diffraction and different spectroscopic techniques, namely Raman, Mössbauer, and infrared. The amount of oleic acid adsorbed on the maghemite surface was estimated via the carbon content obtained from elemental analysis. 相似文献
103.
104.
105.
本文研究了催化反应非线性奇摄动边值问题.利用微分不等式理论和方法,得到了问题的解的任意次近似渐近估计. 相似文献
106.
107.
Recent X-ray diffraction studies on α-quartz (SiO2) by Kingmaet al [1], have shown the occurrence of a reversible, crystalline-to-crystalline, phase transition just prior to amorphization
at ≈ 21 GPa. This precursor transition has also been confirmed by our recent molecular dynamics simulation study [2]. In order
to investigate the possibility of a similar behaviour in other isostructural compounds, which also undergo pressure induced
amorphization, α-GeO2 and α-AlPO4 (berlinite form) were studied using energy dispersive X-ray diffraction. In either of these materials, no such phase transition
is detected prior to amorphization. The onset of amorphization and its reversal is found to be time dependent in GeO2. 相似文献
108.
提出了Fe2+-H2O2-亚甲基蓝化学发光新体系并用于阿魏酸钠的测定。实验发现,在酸性介质中,Fe2+-H2O2体系可与亚甲基蓝反应产生极强的化学发光,阿魏酸钠对此化学发光具有显著的抑制作用。据此,结合流动注射技术,建立了阿魏酸钠化学发光分析新方法。研究了影响化学发光强度的因素,化学发光信号的降低值(ΔI)与阿魏酸钠浓度在4.5×10-6~4.5×10-5mol/L范围内呈良好的线性关系,方法的检出限为7.0×10-7mol/L。对4.8×10-6mol/L的阿魏酸钠进行了11次平行测定,其RSD=0.8%,该法已用于片剂中阿魏酸钠含量的测定。 相似文献
109.
110.
P. C. Morais A. C. Oliveira V. K. Garg M. L. Silva E. F. C. Alcântara F. Q. Soares D. Rabelo 《Hyperfine Interactions》2007,177(1-3):51-56
We have used time-differential perturbed angular correlation (PAC) spectroscopy with 181Ta-probes to study the electric field gradient at Zr-sites in synthetic zircon and hafnon between room temperature and 1,200°C. PAC spectra are similar to those obtained from naturally occurring zircons. In particular, a change in slope of the quadrupole coupling vs. temperature is observed in the synthetic zircon at the same temperature as seen in natural zircons from the Mud Tank carbonatite (Australia). The synthetic hafnon data also shows this feature but at somewhat higher temperature. Low-temperature PAC spectra of both synthetic zircon and hafnon have a clearly reduced anisotropy. We believe that the cause for this is a electronic defect, possibly created during the β-decay of the probe parent nucleus. 相似文献