全文获取类型
收费全文 | 1201篇 |
免费 | 42篇 |
国内免费 | 3篇 |
专业分类
化学 | 961篇 |
晶体学 | 7篇 |
力学 | 11篇 |
数学 | 82篇 |
物理学 | 185篇 |
出版年
2022年 | 4篇 |
2021年 | 10篇 |
2020年 | 11篇 |
2019年 | 12篇 |
2018年 | 11篇 |
2017年 | 12篇 |
2016年 | 24篇 |
2015年 | 21篇 |
2014年 | 15篇 |
2013年 | 56篇 |
2012年 | 57篇 |
2011年 | 80篇 |
2010年 | 48篇 |
2009年 | 38篇 |
2008年 | 64篇 |
2007年 | 83篇 |
2006年 | 80篇 |
2005年 | 81篇 |
2004年 | 65篇 |
2003年 | 57篇 |
2002年 | 54篇 |
2001年 | 26篇 |
2000年 | 25篇 |
1999年 | 10篇 |
1998年 | 14篇 |
1997年 | 13篇 |
1996年 | 19篇 |
1995年 | 14篇 |
1994年 | 14篇 |
1993年 | 8篇 |
1992年 | 9篇 |
1991年 | 5篇 |
1990年 | 12篇 |
1989年 | 8篇 |
1988年 | 10篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 17篇 |
1984年 | 23篇 |
1982年 | 11篇 |
1981年 | 15篇 |
1980年 | 14篇 |
1979年 | 15篇 |
1978年 | 10篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1975年 | 10篇 |
1974年 | 10篇 |
1973年 | 9篇 |
1964年 | 3篇 |
排序方式: 共有1246条查询结果,搜索用时 15 毫秒
91.
The ligand-ligand redox interaction separated by di-, tri-, and hexanuclear cluster units is discussed in terms of the splitting of the redox waves (DeltaE(L)) and the comproportionation constants (Kcom(L)) of the ligand-based mixed valence state. Although two redox-active monodentate ligands in the mononuclear ruthenium(II) complexes (either cis or trans configurations) do not show appreciable splitting in their reduction waves, interestingly those separated by giant triruthenium and hexarhenium cluster units clearly show splitting. The molecular orbital considerations in the literature suggest that these units possess some pi-type molecular orbitals composed of metal dpi and possibly ligand ppi orbitals. Absence of the redox interactions in oxo-bridged diruthenium(II) and oxo-centered trirhodium(III) complexes where such pi molecular orbitals (including an antibonding one) are fully occupied, indicates the importance of empty pi* orbitals for the ligand redox communication. 相似文献
92.
93.
Highly enantioselective catalytic carbon dioxide incorporation reaction: nickel-catalyzed asymmetric carboxylative cyclization of bis-1,3-dienes 总被引:4,自引:0,他引:4
Takimoto M Nakamura Y Kimura K Mori M 《Journal of the American Chemical Society》2004,126(19):5956-5957
A method for nickel-catalyzed asymmetric carbon dioxide (CO2) incorporation via carbon-carbon bond formation was developed. In the presence of a catalytic amount of Ni(acac)2 and MeO-MOP, various bis-1,3-dienes reacted with CO2 (1 atm) and a diorganozinc reagent (Me2Zn or Ph2Zn) to afford cyclic carboxylic acids in good yields (71-100%) and with high enantioselectivities (90-96% ee). 相似文献
94.
Thermal diffusion forced Rayleigh scattering results on thermal diffusion of poly(ethylene oxide) (PEO) in ethanol/water mixtures are presented. In water-rich solvent mixtures, PEO is found to migrate towards regions of lower temperature. This is typical for polymer solutions and corresponds to a positive Soret coefficient of PEO. In solvent mixtures with low water content, however, the polymer is found to migrate towards higher temperatures, corresponding to a negative Soret coefficient of PEO in ethanol-rich solutions. To our knowledge, this is the first observed sign change of the Soret coefficient of a polymer in solution. We also present a simple lattice model for the polymer solvent system and calculate Soret coefficients with statistical mechanics methods. The calculated values agree qualitatively with the experimental results. 相似文献
95.
Magnetic-field-induced ordering of electrons around vortices is a striking phenomenon recently found in high-T(c) cuprates. To identify its consequence in the quasiparticle dynamics, the magnetic-field (H) dependence of the low-temperature thermal conductivity kappa of La(2-x)SrxCuO4 crystals is studied for a wide doping range. It is found that the behavior of kappa(H) in the subkelvin region changes drastically across optimum doping, and the data for underdoped samples are indicative of unusual magnetic-field-induced localization of quasiparticles; this localization phenomenon is probably responsible for the unusual "insulating normal state" under high magnetic fields. 相似文献
96.
97.
Signal denoising and baseline correction by discrete wavelet transform for microchip capillary electrophoresis 总被引:1,自引:0,他引:1
Signal denoising and baseline correction using discrete wavelet transform (DWT) are described for microchip capillary electrophoresis (MCE). DWT was performed on an electropherogram describing a separation of nine tetramethylrohodamine-5-isothiocyanate labeled amino acids, following MCE with laser-induced fluorescence detection, using Daubechies 5 wavelet at a decomposition level of 6. The denoising efficiency was compared with, and proved to be superior to, other commonly used denoising techniques such as Fourier transform, Savitzky-Golay smoothing and moving average, in terms of noise removal and peak preservation by directly visual inspection. Novel strategies for baseline correction were proposed, with a special interest in baseline drift that frequently occurred in chromatographic and electrophoretic separations. 相似文献
98.
[reaction: see text] The Heck reaction is a more efficient and reliable method than previous ones for introducing a C3 unit at the benzyl position for the synthesis of Beraprost. Especially, trialkylated long-chain amines such as (n-C(8)H(17))(3)N and (n-C(12)H(25))(3)N resulted in good yields. This development will be used for the industrial synthesis of Beraprost. 相似文献
99.
Dynarowicz-L&acedil;tka P Kita K Milart P Dhanabalan A Cavalli A Oliveira ON 《Journal of colloid and interface science》2001,239(1):145-157
A series of 5'-phenyl-m-terphenyl carboxylic acid (PTCA) derivatives with methyl, chloro, and fluoro substituents at both side phenyl rings have been synthesized and characterized as Langmuir monolayers at the air/water interface. A comparative analysis, based on the surface pressure and electric surface potential measurements under a variety of experimental conditions, is complemented with BAM images. Copyright 2001 Academic Press. 相似文献