全文获取类型
收费全文 | 6932篇 |
免费 | 190篇 |
国内免费 | 21篇 |
专业分类
化学 | 4529篇 |
晶体学 | 68篇 |
力学 | 126篇 |
数学 | 749篇 |
物理学 | 1671篇 |
出版年
2023年 | 57篇 |
2022年 | 209篇 |
2021年 | 198篇 |
2020年 | 162篇 |
2019年 | 172篇 |
2018年 | 141篇 |
2017年 | 136篇 |
2016年 | 244篇 |
2015年 | 218篇 |
2014年 | 220篇 |
2013年 | 420篇 |
2012年 | 437篇 |
2011年 | 526篇 |
2010年 | 332篇 |
2009年 | 349篇 |
2008年 | 453篇 |
2007年 | 390篇 |
2006年 | 344篇 |
2005年 | 294篇 |
2004年 | 277篇 |
2003年 | 187篇 |
2002年 | 175篇 |
2001年 | 120篇 |
2000年 | 118篇 |
1999年 | 87篇 |
1998年 | 63篇 |
1997年 | 68篇 |
1996年 | 65篇 |
1995年 | 66篇 |
1994年 | 65篇 |
1993年 | 53篇 |
1992年 | 67篇 |
1991年 | 42篇 |
1990年 | 32篇 |
1989年 | 24篇 |
1988年 | 29篇 |
1987年 | 17篇 |
1986年 | 20篇 |
1985年 | 25篇 |
1984年 | 27篇 |
1983年 | 14篇 |
1982年 | 36篇 |
1981年 | 20篇 |
1980年 | 22篇 |
1979年 | 9篇 |
1978年 | 11篇 |
1977年 | 17篇 |
1976年 | 14篇 |
1975年 | 10篇 |
1974年 | 17篇 |
排序方式: 共有7143条查询结果,搜索用时 15 毫秒
21.
22.
Maria do Carmo Rangel Varela Milton Francisco de Jesus Filho Fernando Galembeck 《Hyperfine Interactions》1994,83(1):159-167
Mössbauer spectroscopy was used to follow the aging of ferrihydrite with different amounts of acetate, to achieve more crystalline products. Mössbauer spectra of fresh samples did not show any magnetic components. After two years aging, the solids presented crystalline fractions. Hematite formation was inhibited as acetate content increased in solids. For an acetate/iron molar ratio equal to 0.63 goethite was formed instead of hematite. X-ray diffraction confirmed these results. This work shows that synthetic samples can be used for elucidating the anti-hematitic effect of organic matter already detected in soils. 相似文献
23.
24.
25.
26.
27.
28.
Eimer GA Gómez Costa MB Pierella LB Anunziata OA 《Journal of colloid and interface science》2003,263(2):400-407
The adsorption of aniline on Na-AlMCM-41 synthesized by us has been characterized by infrared spectroscopy, temperature programmed desorption (TPD), and differential thermal analysis methods. Aniline would be mostly bound to the mesostructure through weak pi interactions. On the mesostructure containing adsorbed water, the co-adsorption of aniline could occur by weak hydrogen bonding through surface water molecules. For water, two possible modes of adsorption have been identified. Different associations between aniline and hydrated and nonhydrated mesostructures have been evaluated in order to favor the posterior in situ polymerization of adsorbed aniline. 相似文献
29.
Maria Merces Marques C. Costa F. Lemos F. Ram?a Ribeiro A. R. Dias 《Reaction Kinetics and Catalysis Letters》1997,62(1):9-15
In this paper we present a kinetic approach to the analysis of steady-state homogeneous Ziegler-Natta polymerization activity
data. The influence of the number of monomeric species that are coordinated to the active site on the apparent rate law is
discussed and the equations are fitted to the experimental results. 相似文献
30.
Santos E Schühle DT Jones H Schmickler W 《Langmuir : the ACS journal of surfaces and colloids》2005,21(14):6406-6421
The nonlinear optical properties of self-assembled monolayers obtained from bonding two different alpha-functionalized terthiophenes (alpha-T3) to (111) silver electrode surfaces have been investigated using second harmonic generation (SHG). The two (alpha-T3) compounds used were functionalized with alkane chains of different lengths (C8 and C4), and each was terminated with a thiol anchoring group. A nitrile group was attached to the terminal thiophene ring of the (alpha-T3) compound with the C4 chain. The orientation of the polarization of the incident beam was changed systematically and gradually between "p" and "s" orientation and the SH signal (isotropic and anisotropic contributions) analyzed in both directions ("P" and "S"). The symmetry of the system was reduced by the presence of the adlayers from C3v to C3. The dependence on the applied potential and the incident wavelength has also been studied. The relative magnitudes and phases of the various second-order tensor elements have been estimated and compared with the values for a bare surface. A resonance process in the (alpha-T3) pi moiety has been investigated, and from this, the effective "band-gap" energies of the organic semiconductor SAMs (i.e., the energy difference between the pi-pi bands) have been estimated. 相似文献