全文获取类型
收费全文 | 688篇 |
免费 | 19篇 |
国内免费 | 5篇 |
专业分类
化学 | 555篇 |
晶体学 | 4篇 |
力学 | 11篇 |
数学 | 72篇 |
物理学 | 70篇 |
出版年
2023年 | 3篇 |
2022年 | 14篇 |
2021年 | 14篇 |
2020年 | 11篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 3篇 |
2016年 | 17篇 |
2015年 | 22篇 |
2014年 | 19篇 |
2013年 | 32篇 |
2012年 | 45篇 |
2011年 | 70篇 |
2010年 | 29篇 |
2009年 | 23篇 |
2008年 | 45篇 |
2007年 | 54篇 |
2006年 | 44篇 |
2005年 | 37篇 |
2004年 | 42篇 |
2003年 | 40篇 |
2002年 | 33篇 |
2001年 | 10篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1998年 | 7篇 |
1997年 | 10篇 |
1996年 | 10篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 1篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1975年 | 2篇 |
1974年 | 2篇 |
排序方式: 共有712条查询结果,搜索用时 0 毫秒
101.
Sylvie Ruette 《Israel Journal of Mathematics》2002,127(1):253-277
We construct aC
rtransformation of the interval (or the torus) which is topologically mixing but has no invariant measure of maximal entropy.
Whereas the assumption ofC
∞ ensures existence of maximal measures for an interval map, it shows we cannot weaken the smoothness assumption. We also compute
the local entropy of the example. 相似文献
102.
Addition of Olah's reagent in benzene or methylene chloride to azirines leads to the formation of difluoroamines or α-fluoroketones. This reaction has been applied to the synthesis of 17 α-fluoropregnenolone. The formation of fluoroketone proceeds via a cationic intermediate. Yield is improved when using a more nucleophilic fluorinating reagent obtained by addition of triethylamine to Olah's reagent. 相似文献
103.
Chaignon P Cortial S Guerineau V Adeline MT Giannotti C Fan G Ouazzani J 《Photochemistry and photobiology》2005,81(6):1539-1543
This work presents the application of an on-line photoreactor to the detection of 3,5-diamino-trifluoromethyl-benzene (3,5-DABTF) in aqueous solutions. When irradiated at 310 nm, this compound is defluorinated to 3,5-diaminobenzoic acid by a nucleophilic substitution of the fluoride by water. Concomitantly, defluorination intermediates polymerize through amide bonds to give dark-colored compounds. We take advantage of the photocatalyzed defluorination and the subsequent decrease in pH to develop an original and specific photoreactor. Continuous recording of pH and temperature in the outlet of the reactor by a dual electrode gives us an opportunity to optimize the system. In the photoreactor, 3,5-DABTF is immediately and totally transformed as attested by the rapid drop of the flowing solution pH from 6.2 to 3.2 and the chromatographic analysis of the outgoing solutions. The detection remains effective from 1 to 1000 parts per million. 相似文献
104.
Magnier S 《The journal of physical chemistry. A》2005,109(24):5411-5414
A theoretical determination of the electronic structure of NaH+ is presented. Potential energy curves and dipole moments have been computed for 48(2)Lambda(+) electronic states (i.e., correlated adiabatically up to Na(6s) + H+) through a model-potential-type method over a wide range of R. Equilibrium distances, transition energies, depths of wells, and/or heights of humps predicted at short and large interatomic separations are reported and compared with available experimental and theoretical values. Variations of the static dipole polarizabilities versus internuclear distance have been determined for the two lowest states. 相似文献
105.
Ali Dirani Fabrice Stehlin Ihab Dika Arnaud Spangenberg Nathan Grumbach Jean‐Louis Gallani Bertrand Donnio Romain Greget Sylvie Begin‐Colin Arnaud Demortire Olivier Soppera 《Macromolecular rapid communications》2011,32(20):1627-1633
DUV interferometric lithography and diblock copolymer self‐organization have successfully been combined to provide a simple and highly collective nanopatterning technique enabling the organization of nanoparticles over several orders of magnitude, from nanometre to millimetre. The nanostructural changes at the surface of the polymer film after thermal annealing have been monitored by AFM and the process parameters optimized for obtaining a long‐range organization of the lamellar domains. In particular, the impact of the annealing conditions and geometric parameters of the substrate patterns have been investigated. The nanopatterns resulting from the lamellar demixion of (PS‐b‐MMA) were used for a controlled deposition of nanoparticles. The affinity of the hydrophobic particles for the PS block was demonstrated, opening new doors towards the preparation of high‐density arrays of nanoparticles with potential applications in data storage.
106.
Bailey PJ Dick CM Fabre S Parsons S Yellowlees LJ 《Dalton transactions (Cambridge, England : 2003)》2006,(13):1602-1610
Treatment of dimethylmagnesium with the alpha-diimine ligands Ar'N=C(R)C(R)=NAr' [R = naphth-1,8-diyl (1), H (2), CH3 (3); Ar' = 2,6-diisopropylphenyl] in diethyl ether provides the neutral methyl-bridged dimeric complexes [(alpha-diimine-.)Mg+(mu-CH3)]2 via single electron transfer (SET) to the coordinated diimine and elimination of a methyl radical. These biradical species have been characterised by EPR spectroscopy and, for the ligand , X-ray crystallography. In the presence of THF the reaction of ligand proceeds to the diamagnetic [(ene-1,2-diamide)Mg(THF)3] complex in which the diimine ligand has been doubly reduced to an ene-diamide by two successive SET processes. Comparison of the structural data for the free ligand with that obtained for the alpha-diimine radical anion and ene-diamide complexes shows the expected increases in C-N, and decreases in C-C, bond lengths within the N-C-C-N unit consistent with the progressive reduction of the ligand. In the case of ligand , reaction at low temperature provides the complex [Mg(mu2-Me){Ar'NC(Me)2C(Me)NAr'}]2 in which methyl transfer to a ligand imine carbon atom has occurred. This species has also been structurally characterised. This contrasts with the formation of the radical species at room temperature, and indicates the involvement of an intermediate in which the radical products of the SET process are held in close proximity by the solvent cage. Two competing processes of methyl radical escape and methyl transfer to the ligand account for the formation of the observed products at different temperatures. 相似文献
107.
The aim of this article is twofold. On the one hand, we study the well-posedness of the Lamé system ${-\mu\Delta-\mu'\nabla{\rm div} }The aim of this article is twofold. On the one hand, we study the well-posedness of the Lamé system -mD-m¢?div{-\mu\Delta-\mu'\nabla{\rm div} } in L
q
(Ω), where Ω is an open subset of
\mathbbRn{{\mathbb{R}}^n} satisfying mild regularity assumptions and the Lamé moduli μ, μ′ are such that μ > 0 and μ + μ′ > 0. On the other hand, we prove the analyticity of the semigroup generated by the Lamé operator as well as the maximal
regularity property for the time-dependent Lamé system equipped with a homogeneous Dirichlet boundary condition based on off-diagonal
estimates. 相似文献
108.
Sylvie Monniaux 《Archiv der Mathematik》1997,68(5):407-417
We give a new proof of a perturbation result due to J. Prüss and H. Sohr [11]: if an operator A has bounded imaginary powers, then so does A+w (w ≧ 0). Instead of Mellin transform on which the proof in [11] is based, we use the functional calculus for sectorial operators
developed in particular by A. McIntosh ([8], [3] and [1]). It turns out that our method gives a more general result than the
one used in [11]. 相似文献
109.
Lafolet F Chardon-Noblat S Duboc C Deronzier A Pruchnik FP Rak M 《Dalton transactions (Cambridge, England : 2003)》2008,(16):2149-2156
An original electrochemical synthesis of {[Rh4(mu-OOCCH3)4(phen)4]2+}n (1) molecular wire films from a solution of binuclear bridged Rh complexes [Rh2(mu-OOCCH3)2(phen)2(X)2](Y)2 (X = H2O, Y = BF4(-) (2a) and X = CH3CN, Y = BF4(-) (2b)) in MeCN electrolyte is reported. UV-vis spectroscopy and quartz crystal microbalance electrochemical coupled techniques have been used to demonstrate the electrosynthesis process. The resulting polymetallic compound has been characterized on the basis of its physicochemical properties, which have been compared with those of a chemically synthesized sample. Furthermore, according to EPR, 1H NMR and electrochemical behaviour, the mechanism of the oxidation of this polymetallic wire, containing mixed valent rhodium centers and alternatively acetate bridged Rh-Rh bonds, has been investigated in detail. 相似文献
110.
Morla A Poirier F Pons S Beaulieu C Charrier JP Ataman-Onal Y Gléhen O Jolivet M Choquet-Kastylevsky G 《Electrophoresis》2008,29(20):4158-4168
Proteomic approaches including high-resolution 2-DE are providing the tools needed to discover disease-associated biomarkers in complex biological samples. Although 2-DE is an extremely powerful approach to analyze the proteome, the separation of proteins with extreme molecular masses still remains an issue requiring improvement. Because high molecular mass (HMM) proteins larger than 150 kDa have already been observed to be differentially expressed in several pathologies such as cancer, we developed an original strategy to analyze this part of the proteome that is not easily separated by 2-DE in polyacrylamide gels. This strategy is based on the 2-DE separation of cyanogen bromide (CNBr) fragments of purified HMM protein fractions, and combines techniques including SEC fractionation, TCA precipitation, CNBr cleavage, 2-DE and MS analysis. The method was first tested on a model protein, the BSA. Preliminary results obtained using colonic tissues led to the identification of six HMM proteins with M(r) comprised between 163 and 533 kDa in their reduced state. These results demonstrated that our CNBr/2-DE approach should provide a powerful tool for identification of new biomarkers larger than 150 kDa. 相似文献