全文获取类型
收费全文 | 530篇 |
免费 | 17篇 |
专业分类
化学 | 327篇 |
晶体学 | 4篇 |
力学 | 16篇 |
数学 | 59篇 |
物理学 | 141篇 |
出版年
2024年 | 2篇 |
2023年 | 3篇 |
2022年 | 23篇 |
2021年 | 15篇 |
2020年 | 11篇 |
2019年 | 19篇 |
2018年 | 18篇 |
2017年 | 21篇 |
2016年 | 26篇 |
2015年 | 22篇 |
2014年 | 21篇 |
2013年 | 50篇 |
2012年 | 40篇 |
2011年 | 47篇 |
2010年 | 26篇 |
2009年 | 23篇 |
2008年 | 34篇 |
2007年 | 30篇 |
2006年 | 24篇 |
2005年 | 24篇 |
2004年 | 21篇 |
2003年 | 13篇 |
2002年 | 10篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 6篇 |
1992年 | 2篇 |
1988年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有547条查询结果,搜索用时 0 毫秒
1.
A. B. Drovosekov N. M. Kreines D. I. Kholin V. F. Meshcheryakov M. A. Milyaev L. N. Romashev V. V. Ustinov 《JETP Letters》1998,67(9):727-732
The excitation spectrum in an [Fe/Cr]n multilayer structure with non-collinear magnetic ordering was studied by the ferromagnetic resonance (FMR) method in the
frequency interval 9.5–37 GHz at room temperature. Besides an acoustic branch, several additional modes were observed under
parallel excitation of resonance. The FMR spectrum was calculated analytically in a biquadratic exchange model, neglecting
in-plane anisotropy, for an infinite number of layers in the structure and numerically for a finite number of layers contained
in real samples. It was shown that the observed modes correspond to excitation of standing spin waves with wave vectors perpendicular
to the film plane.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 9, 690–695 (10 May 1998) 相似文献
2.
Andrzej Czopnik Nataly Shitsevalova Alexander Krivchikov Vasyl Pluzhnikov Yuriy Paderno 《Journal of solid state chemistry》2004,177(2):507-514
We have measured heat capacity and thermal expansion of rare earth dodecaborides REB12 (RE=Y, Tb-Tm, Lu). YB12 and LuB12 are diamagnetics whereas the other dodecaborides are ordered antiferromagnetically. The amplitude of the heat capacity discontinuity at the Néel temperature and the shape of the heat capacity variation in the critical region for all these antiferromagnetics are characteristics for amplitude-modulated magnetic structures. In the ordered state TbB12 reveals two first-order phase transitions, most likely due to magnetic structure changes. The heat capacity of ErB12 just below the Néel point shows an anomaly of unclear origin. From the Schottky contribution to the heat capacity we have determined crystal field parameters. They are completely different than that is estimated from Point Charge Model. 相似文献
3.
A new Kohn-Sham formalism is developed for studying the lowest molecular electronic states of given space and spin symmetry whose densities are represented by weighted sums of several reference configurations. Unlike standard spin-density functional theory, the new formalism uses total spin conserving spin-density operators and spin-invariant density matrices so that the method is fully spin-adapted and solves the so-called spin-symmetry dilemma. The formalism permits the use of an arbitrary set of reference (noninteracting) configurations with any number of open shells. It is shown that the requirement of degeneracy of the total noninteracting energies of the reference configurations (or configuration state functions) is equivalent to the stationary condition of the exact energy relative to the weights of the configurations (or configuration state functions). Consequently, at any molecular geometry, the weights can be determined by minimization of the energy, and, for given reference weights, the Kohn-Sham orbitals can be determined. From this viewpoint, the developed theory can be interpreted as an analog of the multiconfiguration self-consistent field approach within density functional theory. 相似文献
4.
Alfaya RV Fujiwara ST Gushikem Y Kholin YV 《Journal of colloid and interface science》2004,269(1):32-36
3-n-propylpyridiniumsilsesquioxane chloride polymer, abbreviated as SiPy+Cl-, was used to coat a porous silica gel, SiO2, surface to form the chemically modified solid SiO2/SiPy+Cl-. The resulting polymer film was well adhered to the surface and presented an ion exchange capacity of 0.74 mmol g(-1). Metal halides, MClz [M=Fe(III), Cu(II), and Zn(II)], were adsorbed by the modified solid from ethanol solutions as neutral species by forming the surface anionic complexes described by the equation: mSiO2/SiPy+Cl-+ MClz <=> (SiO2/SiPy+)m[MCl(z+m)]m-, where the [MCl(z+m)]m- species adsorbed on the surface are FeCl4-, ZnCl4(2-), and CuCl4(2-). Accurate estimates of the specific sorption capacities and the heterogeneous stability constants of the immobilized metal complexes were determined with the aid of computational procedures. 相似文献
5.
Protolytic and associative equilibria in aqueous solutions of rhodamine B were studied. The curves of potentiometric titration with NaOH solution of the dye hydrochloride within the 5 ×10-4-3 ×10-2 M range and at an ionic strength of 0.1 M (NaCl or KCl) were treated by chemometric methods of successive modification of the equilibrium system models with regard to spectrophotometric data. The most probable value of the equilibrium constants of the reaction iH+ + jR H
i
R
j
i+ were determined. 相似文献
6.
7.
8.
An O-methylated analog of protonated phenazine-di-N-oxide radical anion abstracts hydrogen from primary and secondary alcohols
in a slow (k
1 < 500 M−1 s−1) bimolecular reaction. No kinetic evidence has been found for the unimolecular release of free methoxyl radicals through
the homolytic N-OMe bond cleavage in these species. DFT calculations at the UB3LYP 6-31G(d) level indicate that protonated
and O-alkylated radical anions of pyrazine, quinoxaline and phenazine di-N-oxides are close analogues of aromatic nitroxyl
radicals with the highest spin density localized on the oxygen and nitrogen of the nitrone moiety. 相似文献
9.
Capillary electrophoretic approach to screen for enzyme inhibitors in natural extracts 总被引:2,自引:0,他引:2
This paper demonstrates development of electrophoretically mediated micro analysis (EMMA), for screening protein tyrosine phosphatase (PTP) inhibitors in natural extracts. It is demonstrated that capillary electrophoresis (CE) separation of the substrate and the product allows for using the assay in an on-column format to monitor the reaction without typically used fluorogenic substrates. Michaelis-Menten kinetics parameters calculated based on the EMMA results (Km = 1.2-1.5 microM) were in a good agreement (Km = 1.0-1.5 microM) obtained using an off-line CE functional assay (CE FA). EMMA of PTP titrated with different concentrations of ligand demonstrated the peak-shift phenomenon normally seen in affinity capillary electrophoresis. This feature of EMMA gives an indication of the binding affinity of the ligand in addition to its functional activity, providing another dimension in characterization of the protein-inhibitor interaction. It was demonstrated that simultaneous screening of the primary PTP target and a secondary, counter target (PTP-C) using the EMMA format can be used to prioritize hits based on their specificity. 相似文献
10.
Timoshenko VM Bouillon JP Chernega AN Shermolovich YG Portella C 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(18):4324-4329
The ethyl ester of beta-bromoperfluorodithiocrotonic acid reacts with dimethyl acetylenedicarboxylate to give 1,4-difluoro-2,3-bis(trifluoromethyl)-but-2-ene-1,4-diylidene-2,2'-bis(4',5'-dicarbomethoxy-1',3'-dithiole) (4), a new type of vinylogue of tetrathiafulvalene. The thermal transformations of this compound lead, depending on the temperature, to the formation of the cyclization products: 11,14-difluoro-2,3,8,9-tetra(carbomethoxy)-12,13-bis(trifluoromethyl)-1,4,7,10-tetrathiadispiro[4.0.4.4]tetradeca-2,8,11,13-tetraene (8) or 5,8-difluoro-6,7-bis(trifluoromethyl)-2,3-bis(carboxymethyl)-1,4-benzodithiine (11). 相似文献