全文获取类型
收费全文 | 248篇 |
免费 | 4篇 |
国内免费 | 1篇 |
专业分类
化学 | 90篇 |
晶体学 | 1篇 |
力学 | 1篇 |
数学 | 117篇 |
物理学 | 44篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 5篇 |
2015年 | 4篇 |
2014年 | 6篇 |
2013年 | 24篇 |
2012年 | 15篇 |
2011年 | 15篇 |
2010年 | 10篇 |
2009年 | 13篇 |
2008年 | 17篇 |
2007年 | 4篇 |
2006年 | 11篇 |
2005年 | 14篇 |
2004年 | 6篇 |
2003年 | 9篇 |
2002年 | 14篇 |
2001年 | 6篇 |
2000年 | 9篇 |
1998年 | 4篇 |
1997年 | 1篇 |
1996年 | 9篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 1篇 |
1989年 | 4篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1973年 | 2篇 |
1966年 | 1篇 |
1935年 | 2篇 |
排序方式: 共有253条查询结果,搜索用时 15 毫秒
71.
72.
Viorel Barbu Irena Lasiecka Mohammad A. Rammaha 《Transactions of the American Mathematical Society》2005,357(7):2571-2611
In this article we focus on the global well-posedness of the differential equation , where is a sub-differential of a continuous convex function . Under some conditions on and the parameters in the equations, we obtain several results on the existence of global solutions, uniqueness, nonexistence and propagation of regularity. Under nominal assumptions on the parameters we establish the existence of global generalized solutions. With further restrictions on the parameters we prove the existence and uniqueness of a global weak solution. In addition, we obtain a result on the nonexistence of global weak solutions to the equation whenever the exponent is greater than the critical value , and the initial energy is negative. We also address the issue of propagation of regularity. Specifically, under some restriction on the parameters, we prove that solutions that correspond to any regular initial data such that , are indeed strong solutions.
73.
Viorel?BadescuEmail author Peter T.?LandsbergEmail author 《Foundations of Physics Letters》2005,18(3):205-226
Ideal Bose and Fermi systems are studied on the basis of a canonical ensemble, subject to the condition that their temperature is less than a given temperature Tmax. A single new parameter (the tau-parameter, τ) is needed to keep account of the new constraint. The parameter τ is shown to be the exponential of a pseudo-chemical potential that is linearly dependent on temperature. The inclusion of the τ- parameter leads to generalizations of usual thermodynamic quantities (internal energy, heat capacity and entropy) and various particular cases are discussed. The heat capacity of a Bose system can exhibit a maximum at a temperature less than the maximum temperature Tmax. The number of micro-states in the canonical ensemble is found to increase with τ. The heat capacity cV of a Fermi system of non-interacting spins exhibits a Schottky anomaly. The peak depends on τ, and for some cases cV/k can significantly exceed unity. The influence of τ on the entropy of the Fermi system and on the number of micro-states in the canonical ensemble is significant but not spectacular. 相似文献
74.
Silvia ScĂrlĂtescu-Murea 《Rendiconti del Circolo Matematico di Palermo》2000,49(3):561-574
This paper is concerned with the connection between the structure space of a locally C*-algebra and the set of its continuous
topologically irreducible *-representations. Properties of primitive ideals in such algebras are further investigated, for
instance, closed ideals are expressed as intersections of primitive ideals, by using that the Jacobson radical reduces to
0. 相似文献
75.
Zeitschrift für Physik C Particles and Fields - We perform an analysis of predictions of the multi-Regge cluster model and compare them with available longitudinal and transverse data. We show... 相似文献
76.
77.
Gini G Craciun MV König C Benfenati E 《Journal of chemical information and computer sciences》2004,44(6):1897-1902
Most quantitative structure-activity relationship (QSAR) models are linear relationships and significant for only a limited domain of compounds. Here we propose a data-driven approach with a flexible combination of unsupervised and supervised neural networks able to predict the toxicity of a large set of different chemicals while still respecting the QSAR postulates. Since QSAR is applicable only to similar compounds, which have similar biological and physicochemical properties, large numbers of compounds are clustered before building local models, and local models are ensembled to obtain the final result. The approach has been used to develop models to predict the fish toxicity of Pimephales promelas and Tetrahymena pyriformis, a protozoan. 相似文献
78.
Florentina L. Chiriac Monica Ili Augustin Madalan Doina Manaila-Maximean Mihail Secu Viorel Cîrcu 《Molecules (Basel, Switzerland)》2021,26(7)
This work focuses on the investigation of the liquid crystalline behavior and luminescence properties of the lanthanide complexes of Eu(III), Sm(III) and Tb(III) with N-biphenyl-alkylated-4-pyridone ligands. The organic ligands having a biphenyl group attached via a long flexible spacer with either 9 or 10 carbon atoms were synthesized by the reaction between 4-hydroxypyridine and the corresponding bromide compounds. The chemical structures of the organic and lanthanide complexes were assigned based on elemental analysis, single-crystal X-ray diffraction, 1H, 13C NMR and IR spectroscopies, and thermogravimetric analysis (TGA). The X-ray diffraction analysis of a parent compound shows that the lanthanide ions are surrounded by three monodentate pyridone ligands and three bidentate nitrate ions, giving a 9-coordinate environment. The mesogenic behavior and the type of liquid crystalline phases exhibited by the new complexes were analyzed by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM), and powder X-ray diffraction (XRD) studies. Only the lanthanide complexes with longer spacer (10) display a monotropic SmA phase, typically on a short thermal range (less than 10 °C). The complexes with shorter flexible chains (9) show no liquid crystalline properties with melting temperatures lower than their analogs with longer spacers. The emission spectra recorded in solid state at room temperatures show typical emission bands for each lanthanide ion employed (Eu(III), Tb(III) and Sm(III)). 相似文献
79.
80.