全文获取类型
收费全文 | 1190篇 |
免费 | 56篇 |
国内免费 | 6篇 |
专业分类
化学 | 900篇 |
晶体学 | 11篇 |
力学 | 13篇 |
数学 | 121篇 |
物理学 | 207篇 |
出版年
2023年 | 8篇 |
2022年 | 14篇 |
2021年 | 36篇 |
2020年 | 39篇 |
2019年 | 48篇 |
2018年 | 50篇 |
2017年 | 32篇 |
2016年 | 60篇 |
2015年 | 37篇 |
2014年 | 45篇 |
2013年 | 82篇 |
2012年 | 99篇 |
2011年 | 112篇 |
2010年 | 50篇 |
2009年 | 49篇 |
2008年 | 71篇 |
2007年 | 60篇 |
2006年 | 73篇 |
2005年 | 66篇 |
2004年 | 39篇 |
2003年 | 26篇 |
2002年 | 16篇 |
2001年 | 9篇 |
2000年 | 6篇 |
1999年 | 10篇 |
1998年 | 6篇 |
1997年 | 7篇 |
1996年 | 8篇 |
1995年 | 3篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1988年 | 3篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1972年 | 5篇 |
1971年 | 4篇 |
1970年 | 3篇 |
1966年 | 2篇 |
排序方式: 共有1252条查询结果,搜索用时 31 毫秒
61.
62.
Dmitry A. Gruzdev Galina L. Levit Victor P. Krasnov Evgeny N. Chulakov Liliya Sh. Sadretdinova Aleksandr N. Grishakov Marina A. Ezhikova Mikhail I. Kodess Valery N. Charushin 《Tetrahedron: Asymmetry》2010,21(8):936-942
A comparative study of the kinetic resolution of racemic 2-methyl-1,2,3,4-tetrahydroquinoline and 2,3-dihydro-3-methyl-4H-1,4-benzoxazine using N-phthaloyl-(S)-amino acyl chlorides as chiral acylating agents is described. Temperature and solvent effects on the stereochemical features have been examined. It has been found that N-phthaloyl-(S)-phenylalanyl and N-phthaloyl-(S)-2-phenylglycyl chlorides bearing aromatic substituents close to the stereogenic centre are more stereoselective acylating agents than N-phthaloyl-(S)-alanyl chloride. For the preparative kinetic resolution of racemic amines N-phthaloyl-(S)-phenylalanyl chloride proved to be the most appropriate chiral acylating agent. 相似文献
63.
64.
A. A. Zolotukhin M. P. Bubnov V. K. Cherkasov G. A. Abakumov 《Russian Journal of Coordination Chemistry》2018,44(4):272-283
The key regularities of redox isomerism of six-coordinate bis-semiquinonato cobalt complexes in the crystalline phase are considered. The factors determining the temperature of transition between the redox isomers of various cobalt complexes (mononuclear and binuclear complexes, coordination polymers) were described. The transition parameters were shown to depend not only on the electronic and spatial structure of the ligands in a particular complex, but also on the crystal structure of the complex and intermolecular interactions in the lattice. 相似文献
65.
66.
We give lower bounds for the numbers of real solutions in problems appearing in Schubert calculus in the Grassmannian \({\mathop{\rm Gr}(n,d)}\) related to osculating flags. It is known that such solutions are related to Bethe vectors in the Gaudin model associated to \({\mathop{\rm gl}_n}\). The Gaudin Hamiltonians are self-adjoint with respect to a non-degenerate indefinite Hermitian form. Our bound comes from the computation of the signature of that form. 相似文献
67.
68.
Evgeny Pozhidaev Sofia Torgova Maxim Minchenko Cesar Augusto Refosco Yednak Elio Miraldi 《Liquid crystals》2013,40(8):1067-1081
A chiral ferroelectric smectic C* liquid crystal (FLC) with the helix pitch p 0?=?330 nm was developed to avoid any scattering of visible light when the helix is not unwound over a certain limit. Planar cells with different FLC layer thickness (16 and 44 μm) have been assembled with helix axis parallel to the glass plates and aligned along the rubbing direction. The ellipticity of the light passing through the cells vs. the electric field was investigated, and a method for evaluating the electrically controlled birefringence via ellipticity measurements has been established. We have found that the FLC cell is an optical retardation layer driven by the electric field, the effective birefringence being proportional to the square electric field. The physical origin of the electrically controlled phase shift of the light passing through the FLC layer has been analysed. 相似文献
69.
Natalya N. Smirnova Tatiana G. Kulagina Larisa A. Smirnova Alla E. Mochalova Lyudmila Ya. Tsvetkova Ya. S. Samosudova Maksim B. Kiseliov Evgeny V. Sevast’yanov 《Journal of Thermal Analysis and Calorimetry》2013,112(3):1447-1452
For the first time, the heat capacity $ C_{\text{p}}^{^\circ } $ of poly(2-ethylhexyl acrylate) has been studied in an adiabatic vacuum calorimeter between 7 and 350 K, the standard thermodynamic functions: heat capacity $ C_{\text{p}}^{^\circ } $ (T), enthalpy H°(T) ? H°(0), entropy S°(T) ? S°(0), Gibbs function G°(T) ? H°(0) have been calculated from T → 0 to 350 K. The energy of combustion Δc U of the compound under study has been measured in a calorimeter with a stationary bomb and an isothermal shell. The standard enthalpy of combustion Δc H° and thermodynamic parameters of formation—enthalpy Δf H°, entropy Δf S°, Gibbs function Δf G°—at T = 298.15 K have been calculated. The results have been used to calculate the thermodynamic characteristics of 2-ethylhexyl acrylate bulk polymerization into poly(2-ethylhexyl acrylate) over the range from T → 0 to 350 K. 相似文献
70.
Evgeny V. Shchegol'kov Anna E. Ivanova Yanina V. Burgart Viktor I. Saloutin 《Journal of heterocyclic chemistry》2013,50(Z1):E80-E86
Azo coupling of 1,3‐dicarbonyl compounds with tetrazolyl‐5‐diazonium chloride is used to develop a convenient one‐step procedure for the synthesis of 4,7‐dihydrotetrazolo[5,1‐c][1,2,4]triazines. In contrast to nonfluorinated analogs, 7‐hydroxy‐7‐polyfluoroalkyl‐4,7‐dihydrotetrazolo[5,1‐c][1,2,4]triazines undergo a ring‐chain isomerism resulting from the cleavage at the C7―N7a bond. A distinctive feature of nonfluorinated 4,7‐dihydrotetrazolo[5,1‐c][1,2,4]triazines is the possibility to dehydration, which is accompanied by an azide rearrangement due to the tetrazole ring cleavage with the formation of tetrazolo[1,5‐b][1,2,4]triazines. 相似文献