全文获取类型
收费全文 | 42004篇 |
免费 | 1176篇 |
国内免费 | 167篇 |
专业分类
化学 | 27766篇 |
晶体学 | 243篇 |
力学 | 1027篇 |
综合类 | 9篇 |
数学 | 5592篇 |
物理学 | 8710篇 |
出版年
2023年 | 263篇 |
2022年 | 883篇 |
2021年 | 1067篇 |
2020年 | 737篇 |
2019年 | 715篇 |
2018年 | 705篇 |
2017年 | 650篇 |
2016年 | 1186篇 |
2015年 | 1101篇 |
2014年 | 1150篇 |
2013年 | 2039篇 |
2012年 | 2421篇 |
2011年 | 2699篇 |
2010年 | 1597篇 |
2009年 | 1513篇 |
2008年 | 2285篇 |
2007年 | 2262篇 |
2006年 | 1984篇 |
2005年 | 2360篇 |
2004年 | 2199篇 |
2003年 | 1658篇 |
2002年 | 1283篇 |
2001年 | 789篇 |
2000年 | 708篇 |
1999年 | 479篇 |
1998年 | 424篇 |
1997年 | 408篇 |
1996年 | 505篇 |
1995年 | 418篇 |
1994年 | 392篇 |
1993年 | 414篇 |
1992年 | 389篇 |
1991年 | 350篇 |
1990年 | 276篇 |
1989年 | 280篇 |
1988年 | 243篇 |
1987年 | 232篇 |
1986年 | 229篇 |
1985年 | 292篇 |
1984年 | 305篇 |
1983年 | 234篇 |
1982年 | 261篇 |
1981年 | 242篇 |
1980年 | 225篇 |
1979年 | 198篇 |
1978年 | 236篇 |
1977年 | 178篇 |
1976年 | 167篇 |
1974年 | 147篇 |
1973年 | 138篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
We investigate analytical properties of a measure geometric Laplacian which is given as the second derivative w.r.t. two atomless finite Borel measures μ and ν with compact supports supp μ ? supp ν on the real line. This class of operators includes a generalization of the well‐known Sturm‐Liouville operator as well as of the measure geometric Laplacian given by . We obtain for this differential operator under both Dirichlet and Neumann boundary conditions similar properties as known in the classical Lebesgue case for the euclidean Laplacian like Gauß‐Green‐formula, inversion formula, compactness of the resolvent and its kernel representation w.r.t. the corresponding Green function. Finally we prove nuclearity of the resolvent and give two representations of its trace. 相似文献
92.
Isothermal vapor-liquid equilibrium (VLE) data, at 25° C were determined by a saturation method for each of the six methanol or methyl acetate binary systems with dichloromethane, chloroform, and 1,2-trans-dichloroethylene. The experimental data satisfy the Redlich-Kister consistency test, and were correlated with five Gibbs free energy models. All the binary mixtures of methanol with the chlorinated compounds exhibit strong positive deviations from ideality while the mixtures of methyl acetate with the chlorinated compounds present negative deviations from ideal behavior.Communicated at the Festsymposium celebrating Dr. Henry V. Kehiaian's 60th birthday, Clermont-Ferrand, France, 17–18 May 1990. 相似文献
93.
D. Kast A. Jungclaus K.P. Lieb M. Górska G. de Angelis P.G. Bizzeti A. Dewald C. Fahlander H. Grawe R. Peusquens M. De Poli H. Tiesler 《The European Physical Journal A - Hadrons and Nuclei》1998,3(2):115-128
In the neutron deficient isotopes 104,105In lifetimes of high spin states in the range from 0.5 ps to 600 ps have been measured in a coincidence recoil distance Doppler
shift (RDDS) experiment. By combining the Doppler shift attenuation (DSA) and RDDS methods at few μm flight distances, the
problem of delayed feeding has been avoided and very short lifetimes in the range 0.5–0.8 ps have been determined. Shell model
calculations with strong restrictions for the neutron orbitals reveal good agreement with experimental level energies and
still fair agreement for most measured B(M1) and B(E2) values.
Received: 30 June 1998 相似文献
94.
95.
This contribution discusses the phenomena of retrograde condensation of one or two liquids. It w1 be shown that both phenomena can be well understood. Also the relation of retrograde condensation of one liquid phase with the condensation behavior of natural gas will be discussed. Similarly that of two liquid phases with multiple phase behavior occurring in low temperature reservoir fluids will be pointed out. 相似文献
96.
P. A. J. van den Bogert R. de Borst 《Archive of Applied Mechanics (Ingenieur Archiv)》1994,64(2):136-146
Summary The mechanical behaviour of rubberlike materials is modelled in a phenomenological approach using a strain-energy formulation. Nonhomogeneous shear experiments on solid rubber specimens have been carried out as well as simple elongation tests on the same rubber compound. The elongation tests have been used to determine the model constants. By a comparison between experiment and numerical simulation of the nonhomogeneous shear test the predictive capabilities of the Mooney-Rivlin, the Ogden and the Besseling model have been assessed for compression-shear deformation paths. An analytical study explains the numerically observed behaviour.
Über das Verhalten von Gummimaterialien unter Druck und Schubverformungen
Übersicht Das mechanische Verhalten von Gummimaterialien wird phänomenologisch modelliert unter Anwendung einer Formänderungsenergiefunktion. Es sind nicht-homogene Schubversuche auf dreidimensionale Versuchsproben aus Gummi so wie auch einfache Verlängerungsversuche auf Gummiproben der gleichen Zusammenstellung durchgeführt worden. Die Verlängerungsversuche sind durchgeführt worden um die Stoffkennwerte feststellen zu können. In einer Vergleichung zwischen dem Experiment und der numerischen Simulation von nicht-homogenen Schubversuchen ist die Genauigkeit des Mooney-Rivlinschen Modells, des Ogdenschen Modells und des Besselingschen Modells für kombinierte Druck-Schubverformungen festgestellt worden. In einem analytischen Studium wird das numerisch betrachtete Verhalten auseinandergesetzt.相似文献
97.
The equilibrium statistical volume distribution in foams, which has been previously demonstrated to be the so-called log-normal, is accounted on probability grounds by a scaling law on the bubble's volume time-evolution. This law states that the conditional probability for a given bubble to have the volume v(t + Δt), he assumption that it was v(t), to depend solely on the relationship v(t + Δt)/v(t), and in particular, to be independent of the time t. The theoretical results, however, allow to go further. Indeed, since the time dependece of its parameters (expectation and variance) are given functions of time, only two parameters are necessary to describe completely the foam. 相似文献
98.
Ilda Abe Rafael E. de Ges Jos L. Fabris Hypolito J. Kalinowski Mrcia Müller Meire C. Fugihara Rosane Falate Barbara W. Diesel Ricardo C. Kamikawachi Carmen L. Barbosa 《Optics and Lasers in Engineering》2003,39(5-6):537-548
In this work, we report production and modelling of both Bragg gratings and rocking filters in high birefringence fibre optics. Bragg gratings are produced by UV (257.0 nm) external interferometric exposition of a frequency-doubled Ar+ ion laser, whereas for rocking filters formation the visible Ar+ ion laser lines in 488.0 and 514.5 nm are used in an internal method. The spectral characteristics due to the birefringence properties are studied through numerical methods and experimental techniques. The spectral responsivity of the structures under temperature changes and stress application is presented. 相似文献
99.
100.