全文获取类型
收费全文 | 3429篇 |
免费 | 68篇 |
国内免费 | 8篇 |
专业分类
化学 | 2500篇 |
晶体学 | 24篇 |
力学 | 91篇 |
数学 | 466篇 |
物理学 | 424篇 |
出版年
2021年 | 25篇 |
2020年 | 27篇 |
2019年 | 32篇 |
2018年 | 27篇 |
2017年 | 20篇 |
2016年 | 53篇 |
2015年 | 55篇 |
2014年 | 62篇 |
2013年 | 197篇 |
2012年 | 111篇 |
2011年 | 152篇 |
2010年 | 117篇 |
2009年 | 106篇 |
2008年 | 145篇 |
2007年 | 155篇 |
2006年 | 141篇 |
2005年 | 147篇 |
2004年 | 134篇 |
2003年 | 154篇 |
2002年 | 148篇 |
2001年 | 55篇 |
2000年 | 50篇 |
1999年 | 42篇 |
1998年 | 28篇 |
1997年 | 34篇 |
1996年 | 50篇 |
1995年 | 32篇 |
1994年 | 39篇 |
1993年 | 38篇 |
1992年 | 29篇 |
1991年 | 49篇 |
1990年 | 30篇 |
1989年 | 38篇 |
1988年 | 32篇 |
1987年 | 26篇 |
1986年 | 27篇 |
1985年 | 81篇 |
1984年 | 48篇 |
1983年 | 34篇 |
1982年 | 61篇 |
1981年 | 70篇 |
1980年 | 86篇 |
1979年 | 58篇 |
1978年 | 64篇 |
1977年 | 81篇 |
1976年 | 59篇 |
1975年 | 49篇 |
1974年 | 42篇 |
1973年 | 43篇 |
1972年 | 24篇 |
排序方式: 共有3505条查询结果,搜索用时 0 毫秒
81.
Gérald Perron Lorraine Couture Jacques E. Desnoyers 《Journal of solution chemistry》1992,21(5):433-443
Liquid systems which have strong non-idealities, as seen from their thermodynamic properties, often show evidence of these interactions in the solid-liquid phase diagrams. This suggests that some of the structures present in the solid state can persist in the solution state, on a time average, up to temperatures much higher than the melting point. Volumes and heat capacities of typical systems were either taken from the literature or measured to illustrate this correlation with the phase diagrams. With mixtures of aprotic solvents which show nearly-ideal simple eutectic phase diagrams, the properties of the solutions are also nearly ideal. Examples of systems investigated which show strong non-idealities are ionic surfactant solutions, alcohol-water mixtures, chloroform-triethylamine mixtures and lithium salts in aprotic solvents.Paper written in the honor of Loren Hepler on the occasion of his retirement. 相似文献
82.
Jacques Dubac Pierre Mazerolles Pierre Fagoaga 《Journal of organometallic chemistry》1977,139(3):271-277
The reaction of organomagnesium organolithium compounds (alkyl, aryl, allyl and benzyl derivatives) with 1,2-dimethyl-1-alkoxy-l-silacyclobutanes proceeds with retention of configuration at the silicon atom. Stereochemical results are discussed in terms of the SN2Si mechanism. The proposed configurations are supported by 1H and 13C NMR data. 相似文献
83.
Jacques Barrau Marsan Bouchaut Hlne Lavayssiere Gabriel Dousse Jacques Satg 《Helvetica chimica acta》1979,62(1):152-154
Complexed dialkylgermylenes R2GeNR3 or R2GePy react with oxiranes or thiirane and lead to dialkylgermanone and germathione via germaoxetanes or germathiacyclobutane. The formation of germadioxolanes or germadithiolane finally observed arises from condensation of dialkylgermanone (or germathione) on oxiranes (or thiirane). 相似文献
84.
Laurent Griffe Dr. Mary Poupot Dr. Patrice Marchand Dr. Alexandrine Maraval Dr. Cédric‐Olivier Turrin Dr. Olivier Rolland Pascal Métivier Dr. Gérard Bacquet Dr. Jean‐Jacques Fournié Dr. Anne‐Marie Caminade Dr. Rémy Poupot Dr. Jean‐Pierre Majoral Dr. 《Angewandte Chemie (International ed. in English)》2007,46(14):2334-2334
85.
A numerical model for the adsorption kinetics of proteins on the walls of a microchannel has been developed using the finite element method (FEM) to address the coupling with diffusion phenomena in the restricted microchannel volume. Time evolutions of the concentration of one species are given, both in solution and on the microchannel walls. The model illustrates the adsorption limitation sometimes observed when the microdimensions of these systems induce a global depletion of the bulk solution. A new non-dimensional parameter is introduced to predict the final value of the coverage of any microsystem under static adsorption. A working curve and a criteria (h/K[Gamma](max) > 10) are provided in order to choose, for given adsorption characteristics, the value of the volume-to-surface ratio (i.e. the channel height h) avoiding depletion effects on the coverage (relative coverage greater than 90% of the theoretical one). Simulations were compared with confocal microscopy measurements of IgG antibody adsorption on the walls of a PET microchannel. The fit of the model to the experimental data show that the adsorption is under apparent kinetic control. 相似文献
86.
Infrared and Raman spectra of gaseous cyclopropanecarboxylic acid (C3H5COOH and C3H5COOD) were measured from 250 to 4000 cm?1. The bands were assigned respectively to the monomer and to an associate. The depolarization ratio measurement, the vib—rot envelope study and the detailed analysis of the v(CO) and v(CH) regions enabled the symmetry and the conformation of the molecular entities in equilibrium to be determined. The monomer belongs to the Cs symmetry group and the conformation of its predominant fraction is trans/trans. The associate is a centrosymmetrical dimer (Ci symmetry) having (trans/cis)2 conformation. Some features of the geometry of the pseudocycle are discussed. 相似文献
87.
In this paper, the transport of Cu(II) in the presence of lipophilic Cu(II) organic complexes through permeation liquid membranes (PLMs) have been investigated. In natural waters, small organic compounds, which form liposoluble neutral complexes with Cu(II), are potentially toxic and bioavailable. Hence, to understand the role of liposoluble Cu(II) complexes in natural waters, four organic ligands: phthalic acid, bipyridyl, pyrocatechol and hydroxyquinoline, which form uncharged or lipophilic Cu(II) complexes, were tested. The results showed that the transport of lipophilic Cu(II) complexes through PLM depends on the lipophilicity of the complex. Applications of PLMs in natural waters are presented. 相似文献
88.
Jacques Darriet Marc Drillon Gérard Villeneuve Paul Hagenmuller 《Journal of solid state chemistry》1976,19(3):213-220
The cationic ordering in the oxides which crystallize with the 6H structure gives rise to Ru5+Ru5+ pairs in (Ru2O9) clusters. The magnetic properties have been analyzed on the basis of the Heisenberg-Dirac-Van Vleck model: The d electrons are localized on each Ru5+ ion and interact strongly through antiferromagnetic exchange. The susceptibility curves agree with the H.D.V.V. model. The values of the exchange integrals have been determined by fitting the experimental values. 相似文献
89.
Edgar Heilbronner Evi Honegger Jacques Lecoultre Cyril A. Grob Raymond Houriet Eric Rolli 《Helvetica chimica acta》1986,69(8):2114-2126
The n ionization energies I and the gas-phase basicities GB of CH3-, Cl-, or CN-substituted quinuclidines have been measured by PE and ICR spectroscopy. The dependence of the shifts ΔI and ΔGB (relative to the values of the parent molecule) allow conclusions about the charge dispersal accompanying the n ionization or the protonation of quinuclidine in the gas phase. The agreement with the results of a minimal basis set ab initio calculation is excellent. Comparison of the solution pKa values with either I or GB reveals that 2-substituted quinuclidines exhibit sizeable solvent-induced proximity effects, i.e. that the corresponding quinuclidinium ions are more acidic in solution than expected on the basis of the gas-phase basicities. This agrees with earlier results concerning 2-substituted pyridines. 相似文献
90.
Abohachem Laguecir Serge Ulrich Jérôme Labille Nicolas Fatin-Rouge Serge Stoll Jacques Buffle 《European Polymer Journal》2006,42(5):1135-1144
Monte Carlo simulations, experimental titrations and fluorescence correlation spectroscopy experiments were used to investigate the conformational and electrical properties of polyacrylic acids (PAA). On the one hand, titration curves were calculated to get an insight into the role of pH on the degree of ionization and conformation of PAA chains. On the other hand, experimental potentiometric titrations of PAA were also achieved for different PAA molecular weights and compared to the calculated titration curves obtained by Monte Carlo coarse grained simulations. It was found that for a large range at intermediate PAA ionizations, a good correlation is obtained between experimental and simulations data thanks to the prominence of electrostatic interactions in this domain. The effect of ionic concentration and PAA molecular weight on the titration curves was also investigated. In order to get a better understanding of PAA conformational behavior, we also investigated PAA diffusion properties in aqueous solutions as a function of pH and ionic strength by fluorescence correlation spectroscopy (FCS), thanks to its high sensitivity to measure diffusion coefficients of tracer solutes. Good qualitative agreements were observed between experimental diffusivities and polymer properties calculated from MC simulations. It was shown that the high molecular weight PAA chains display more significant changes in diffusivity in agreement with the ionization degrees and conformational changes observed in the simulations. 相似文献