全文获取类型
收费全文 | 743篇 |
免费 | 15篇 |
专业分类
化学 | 625篇 |
晶体学 | 4篇 |
力学 | 4篇 |
数学 | 36篇 |
物理学 | 89篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 13篇 |
2021年 | 25篇 |
2020年 | 19篇 |
2019年 | 27篇 |
2018年 | 36篇 |
2017年 | 28篇 |
2016年 | 20篇 |
2015年 | 19篇 |
2014年 | 23篇 |
2013年 | 60篇 |
2012年 | 23篇 |
2011年 | 46篇 |
2010年 | 39篇 |
2009年 | 32篇 |
2008年 | 40篇 |
2007年 | 54篇 |
2006年 | 40篇 |
2005年 | 37篇 |
2004年 | 31篇 |
2003年 | 21篇 |
2002年 | 26篇 |
2001年 | 15篇 |
2000年 | 7篇 |
1999年 | 10篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 10篇 |
1995年 | 6篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 4篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
排序方式: 共有758条查询结果,搜索用时 15 毫秒
101.
Irina V. Glinkina Vladimir A. Durov Galina A. Mel''nitchenko 《Journal of Molecular Liquids》2004,110(1-3):63-67
Modelling of the biologic solutions has a great importance for basic physicochemical backgrounds of the living processes, mechanism of the diseases and drugs action, etc. The modelling of the chemical equilibria in solution that served as a prototype of the blood plasma with application to calcification of the tissues is performed. The concentrations of molecular–ionic forms containing calcium and hydrogen cations and phosphate anions in the range of ionized-calcium and total phosphorus concentrations from 0.5 to 3.0 mM and at the solution pH of 7.1–7.8 were calculated. The activities of the ionized species were described in approach to Debye–Hückel's theory. The full set of the equilibria taking into consideration dissociation of the water, phosphoric acid, formation of both inert and ionic calcium phosphates was considered. The states of calcium hydrophosphate dihydrate CaHPO4·2H2O (CHPD), calcium phosphate Ca3(PO4)2 (CP), calcium hydrophosphate-phosphate dihydrate Ca4H(PO4)3·2H2O (CHPPD) and hydroxyapatite Ca3OH(PO4)3 (HA) with respect to the boundary of the region in which they crystallise were determined. A criterion has been introduced to characterize the degree of salt supersaturation with respect to crystallisation, which is based on the concentration distance between the states of a salt in solution and at the boundary of its crystallisation. This criterion is used to provide a quantitative characteristic of the supersaturation of the phosphates and their tendency to crystallise in blood's plasma. It was established that the most soluble of the phosphates, CaHPO4·2H2O, is undersaturated and the other phosphates are supersaturated with respect to crystallisation. Thus, this phosphate does not take part in the calcification, and this is the source for ionized calcium in a blood plasma from the soft tissues. The role of the other phosphates in calcification of the soft tissues is decreased in the series HA>CP>CHPPD. The dependencies of the supersaturation of the solution on the pH and on the concentrations of calcium and phosphorus in a mixture are discussed. 相似文献
102.
Mekki Terbeche Constantin Sacaliuc Galina Vornicescu 《Bulletin des Sciences Mathématiques》2002,126(5):379-387
A singular integral equation with a Holderian second member function on [a,b] is considered and solved for four different type of kernels in the class of functions that are unbounded at the end points of the interval. 相似文献
103.
Irina Odinets Tamás Kégl Oleg Artyushin Galina Molchanova Tatyana Mastryukova György Keglevich 《Journal of organometallic chemistry》2005,690(14):3456-3464
Asymmetrical cyclic phosphite and phosphinite ligands of a novel type bearing either trifluoromethyl or pentafluorophenyl group were synthesized using >PCl or >PN< species and racemic fluorinated alcohols. The P-ligands were converted to complexes of RhIII(L)(Cp∗)Cl2 type (where L = phosphite or phosphinite) and, in two instances, their stereostructures were evaluated by X-ray analysis. These complexes along with in situ systems, formed from Rh(CO)2(acac) precursor and the corresponding ligand, were tested in the hydroformylation of styrene. Both systems provided excellent hydroformylation activities at 100 °C. Using the RhI in situ systems, moderate and high regioselectivities towards the branched aldehyde (2-phenyl-propanal) were obtained at 100 and 40 °C, respectively. 相似文献
104.
Microstructural and chemical changes in a NiO-YSZ electrocatalytic electrode were studied. The microstructural changes in the NiO-YSZ electrocatalytic electrode after the cell operation was compared with the electrode quenched under the applied voltage to suppress the oxidation process. The reversible reduction of NiO into Ni and the formation of intergranular Ni layers at the NiO/YSZ interface were investigated. It was shown that in a compositional range of the NiO-YSZ electrodes from 1/3 to 2/3 the value of the ambipolar conductivity increased with increasing voltage applied to the electrochemical cell. The observed reversible increase in the value of ambipolar conductivity of the electrocatalytic electrode is described in frames of the model of reversible reduction of NiO into Ni under the conditions of cell operation. 相似文献
105.
106.
Bruce J. West Ary L. Goldberger Galina Rovner Valmik Bhargava 《Physica D: Nonlinear Phenomena》1985,17(2):198-206
Under physiologic conditions, the AV junction is traditionally regarded as a passive conduit for the conduction of impulses from the atria to the ventricles. An alternative view, namely that subsidiary pacemakers play an active role in normal electrophysiologic dynamics during sinus rhythm, has been suggested based on nonlinear models of cardiac oscillators. A central problem has been the development of a simple but explicit mathematical model for coupled nonlinear oscillators relevant both to stable and perturbed cardiac dynamics. We use equations describing an analog electrical circuit with an external d.c. voltage source (V0) and two nonlinear oscillators with intrinsic frequencies in the ratio of 3:2, comparable to the SA node and AV junction rates. The oscillators are coupled by means of a resistor. 1:1 (SA:AV) phase-locking of the oscillators occurs over a critical range of V0. Externally driving the SA oscillator at increasing rates results in 3:2 AV Wenckebach periodicity and a 2:1 AV block. These findings appear with no assumptions about conduction time or refractoriness. This dynamical model is consistent with the new interpretation that normal sinus rhythm may represent 1:1 coupling of two or more active nonlinear oscillators and also accounts for the appearance of an AV block with critical changes in a single parameter such as the pacing rate. 相似文献
107.
Ivan Khyzhniy Elena Savchenko Sergey Uyutnov Galina Gumenchuk Alexey Ponomaryov Vladimir Bondybey 《Radiation measurements》2010,45(3-6):353-355
Solid nitrogen was investigated by activation spectroscopy methods – thermally stimulated luminescence and thermally stimulated exoelectron emission (TSL and TSEE) in combination with luminescence analysis. TSEE from solid nitrogen pre-irradiated by an electron beam was measured and investigated for the first time. A set of peaks both in TSL and TSEE were observed. It was found that one of the peaks in the TSEE curve is caused by release of electrons in the course of the α-β phase transition of solid nitrogen. The corresponding activation energy was estimated. 相似文献
108.
Pavel A. Zagrebin Galina A. Tsirlina Renat R. Nazmutdinov Oleg A. Petrii Michael Probst 《Journal of Solid State Electrochemistry》2006,10(3):157-167
The advantages of corrected Marcus plots as compared to the more traditional corrected Tafel plots are discussed and illustrated
by the treatment of experimental data. The procedures are proposed to avoid the uncertainties of EDL correction and to estimate
the reliable values of transmission coefficient and total reorganization energy. Special emphasis is placed on the diagnostics
of activationless reactions in frames of the same method.
Dedicated to Professor M.A. Vorotyntsev on the occasion of his 60th birhtday.
相似文献
Galina A. TsirlinaEmail: |
109.
110.
Irina I. Koptyug Anna A. Lysova Galina A. Kovalenko Larisa V. Perminova Igor V. Koptyug 《Applied magnetic resonance》2010,37(1-4):483-495
Heterogeneously catalyzed enzymatic glucose isomerization was considered as a model process to extend the application of nuclear magnetic resonance (NMR) and magnetic resonance imaging techniques to the studies of biocatalytic processes and heterogeneous biocatalysts. It has been demonstrated that the T 2 times of glucose are different for its aqueous solution in the pores of an unmodified porous support and in a heterogeneous biocatalyst, comprising bacterial cells immobilized on the same support. This observation has been used to map the spatial distribution of the active component within a packed bed of biocatalyst in a model reactor. 13C NMR spectroscopy was applied to follow the progress of glucose isomerization catalyzed by the heterogeneous biocatalyst in a batch reactor. The utilization of proton spin decoupling and nuclear Overhauser effect was shown to be necessary to obtain high signal-to-noise ratio in the natural abundance 13C NMR spectra of a glucose–fructose syrup present in the packed bed of biocatalyst. The spectra thus obtained were suitable for the quantification of the glucose-to-fructose ratio achieved in the biocatalytic reaction. 相似文献