全文获取类型
收费全文 | 1020篇 |
免费 | 52篇 |
专业分类
化学 | 647篇 |
晶体学 | 4篇 |
力学 | 27篇 |
数学 | 158篇 |
物理学 | 236篇 |
出版年
2023年 | 4篇 |
2022年 | 12篇 |
2021年 | 61篇 |
2020年 | 17篇 |
2019年 | 28篇 |
2018年 | 22篇 |
2017年 | 19篇 |
2016年 | 80篇 |
2015年 | 49篇 |
2014年 | 55篇 |
2013年 | 107篇 |
2012年 | 58篇 |
2011年 | 57篇 |
2010年 | 46篇 |
2009年 | 51篇 |
2008年 | 49篇 |
2007年 | 26篇 |
2006年 | 41篇 |
2005年 | 19篇 |
2004年 | 23篇 |
2003年 | 11篇 |
2002年 | 10篇 |
2001年 | 7篇 |
2000年 | 9篇 |
1999年 | 9篇 |
1998年 | 3篇 |
1997年 | 10篇 |
1996年 | 5篇 |
1995年 | 8篇 |
1994年 | 5篇 |
1992年 | 3篇 |
1991年 | 9篇 |
1990年 | 7篇 |
1989年 | 9篇 |
1988年 | 3篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 13篇 |
1984年 | 20篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 9篇 |
1977年 | 10篇 |
1975年 | 9篇 |
1974年 | 6篇 |
1973年 | 4篇 |
1972年 | 5篇 |
排序方式: 共有1072条查询结果,搜索用时 312 毫秒
111.
In the present paper, we obtain new results on universality as applications of hybrid universality and almost-periodicity in its half-plane of absolute convergence. By using these, we show the universality for Euler products of Igusa type, Euler-Zagier multiple zeta-functions and Tornheim-Hurwitz type of double zeta-functions. 相似文献
112.
Zbigniew Pucha?a Piotr Gawron ?ukasz Skowronek Karol ?yczkowski 《Linear algebra and its applications》2011,434(1):327-342
We study operators acting on a tensor product Hilbert space and investigate their product numerical range, product numerical radius and separable numerical range. Concrete bounds for the product numerical range for Hermitian operators are derived. Product numerical range of a non-Hermitian operator forms a subset of the standard numerical range containing the barycenter of the spectrum. While the latter set is convex, the product range needs not to be convex nor simply connected. The product numerical range of a tensor product is equal to the Minkowski product of numerical ranges of individual factors. 相似文献
113.
Albrecht Ł Jiang H Jørgensen KA 《Angewandte Chemie (International ed. in English)》2011,50(37):8492-8509
Asymmetric organocatalysis has been successfully incorporated in many multistep one-pot sequences to provide simple access to structurally complex target molecules in a highly stereoselective fashion. The key feature behind this success is the ability of organocatalyzed reactions to proceed efficiently in the presence of large amounts of spectator reagents. Additionally, owing to their organic nature and substoichiometric presence, organocatalysts are also expected to become innocent bystanders in subsequent transformations. In this Minireview, an easy-to-use classification and nomenclatural system that is capable of systematically and informatively describing each one-pot reaction is introduced, and selected important contributions within the field of organocatalytic one-pot reactions are reviewed according to this new system. Finally, future developments and perspectives in the field are discussed. 相似文献
114.
Dr. Iwona Olejniczak Dr. Andrzej Łapiński Prof. Roman Świetlik Dr. Jean Olivier Dr. Stéphane Golhen Dr. Lahcène Ouahab 《Chemphyschem》2011,12(11):2124-2130
The room‐temperature infrared and Raman spectra of a series of four isostructural polymeric salts of 2,3,6,7‐tetrakis(2‐cyanoethylthio)‐tetrathiafulvalene (TCE‐TTF) with paramagnetic (CoII, MnII) and diamagnetic (ZnII, CdII) ions, together with BF4? or ClO4? anions are reported. Infrared and Raman‐active modes are identified and assigned based on theoretical calculations for neutral and ionized TCE‐TTF using density functional theory (DFT) methods. It is confirmed that the TCE‐TTF molecules in all the materials investigated are fully ionized and interact in the crystal structure through cyanoethylthio groups. The vibrational modes related to the C?C stretching vibrations of TCE‐TTF are analyzed assuming the occurrence of electron–molecular vibration coupling (EMV). The presence of the antisymmetric C?C dimeric mode provides evidence that charge transfer takes place between TCE‐TTF molecules belonging to neighboring polymeric networks. 相似文献
115.
Łukasz Kosiński 《Journal of Geometric Analysis》2011,21(4):902-919
We give a characterization of non-hyperbolic pseudoconvex Reinhardt domains in ℂ2 for which the answer to the Serre problem is positive. Moreover, all non-hyperbolic pseudoconvex Reinhardt domains in ℂ2 with non-compact automorphism group are explicitly described. 相似文献
116.
Martowicz Adam Kantor Sławomir Pieczonka Łukasz Bryła Jakub Roemer Jakub 《Meccanica》2021,56(4):841-854
Meccanica - The work is devoted to the numerical aspects of the modeling tool elaborated to simulate the phenomenon of solid phase transformation in shape memory alloys. Particularly, a nonlocal... 相似文献
117.
KATARZYNA BUCIOR ANDRZEJ PATRYKIEJEW OREST PIZIO STEFAN SOKOŁOWSKI ZOFIA SOKOŁOWSKA 《Molecular physics》2013,111(6):721-731
We investigate the fluid—fluid demixing transitions in the case of adsorption of so-called symmetric binary mixtures in slit-like pores at temperatures higher than the bulk gas—liquid critical temperature. The aim of the study is to determine how the demixing of such mixtures in the pores depends on the bulk phase composition and on the parameters characterizing the pore. The calculations have been carried out by means of a density functional theory. In the case of an equimolar bulk mixture, the demixing transition inside the pore occurs only when the adsorption potentials of both species are identical. The occurrence of this transition is manifested by a cusp in the adsorption isotherm. For nonequimolar bulk phase compositions, the transition can also take place if the adsorption energies of both components are different. However, the difference in the adsorption energies should be small enough, otherwise a continuous demixing takes place. For non-equimolar compositions two branches of the grand canonical potential intersect, whereas for equimolar bulk composition they meet tangentially. We have determined phase behaviour for several model systems. 相似文献
118.
We report on studies of changes in the emission spectra (excited at 808 nm) of the Yb-doped Ca4NdO(BO3)3 single crystals due to the photothermal effects caused by the pulsed Nd:YAG laser. Increase of the sample's surface temperature after laser treatment leads to significant enhancement of the 1040 to 1060 nm emission (ascribed to the Nd3+ 4F3/2 → 4I9/2, 4I11/2 transitions) and simultaneous decrease of the 975 to 1050 nm emission (corresponding to the Yb3+ 2F5/2 → 2F7/2 transition). We explain such an increase of the Nd3+ luminescence by thermally activated Yb3+ → Nd3+ energy transfer. 相似文献
119.
Abstract With comparable molar quantities, chromotropic acid reacts with compounds containing aldehyde groups -CHO e.g. with formadehyde or glyoxylic acid to form cyclic compounds with rings containing four chromotropic acid fragments — cyclotetrachromotropylene derivatives. The cyclic compounds, due to the presence of a cavity in the molecule, can play the part of host and complex smaller molecules, which has been confirmed on the basis of triethylamine by the 1H-NMR measurements. Using spectrophotometric method the stability constant of 1:1 complex formed between Ti(IV) and cyclic compound chromotropic acid with formaldehyde has been determined - K = (9,0 ± 0,1) 104. 相似文献
120.
Małgorzata Norek Grzegorz Łuka Marek Godlewski Tomasz Płociński Marta Michalska-Domańska Wojciech J. Stępniowski 《Applied Physics A: Materials Science & Processing》2013,111(1):265-271
Luminescent properties of ZnO nanorods covered with Ag nanoparticles are examined. Nanorods were synthesized on AAO templates using Atomic Layer Deposition (ALD) technique. Two types of the samples were prepared with different arrangement of ZnO nanorods and doping conditions. Nanorods of the second type were codoped with Al, to stimulate defect-related emissions. The ZnO material fills heterogeneously the interior of the AAO nanopores and has hexagonal, wurtzite structure. Both types of structures exhibit a broad defect-related emission at about 440 nm, most probably related to recombination at zinc interstitial (Zni) defects. This emission in samples with a random distribution of ZnO:Al nanorods and finer Ag nanoparticles is enhanced by factor of ~2.5 upon Ag deposition. The so-obtained material is interesting from the point of view of its application in blue range emitting diodes. 相似文献