全文获取类型
收费全文 | 173236篇 |
免费 | 2011篇 |
国内免费 | 469篇 |
专业分类
化学 | 93586篇 |
晶体学 | 2148篇 |
力学 | 7297篇 |
综合类 | 16篇 |
数学 | 18493篇 |
物理学 | 54176篇 |
出版年
2021年 | 1325篇 |
2020年 | 1430篇 |
2019年 | 1453篇 |
2018年 | 1821篇 |
2017年 | 1769篇 |
2016年 | 2994篇 |
2015年 | 1991篇 |
2014年 | 2923篇 |
2013年 | 7134篇 |
2012年 | 5990篇 |
2011年 | 7427篇 |
2010年 | 4943篇 |
2009年 | 4925篇 |
2008年 | 6680篇 |
2007年 | 6732篇 |
2006年 | 6282篇 |
2005年 | 6279篇 |
2004年 | 5719篇 |
2003年 | 4755篇 |
2002年 | 4470篇 |
2001年 | 4785篇 |
2000年 | 3752篇 |
1999年 | 2844篇 |
1998年 | 2481篇 |
1997年 | 2410篇 |
1996年 | 2299篇 |
1995年 | 2178篇 |
1994年 | 2140篇 |
1993年 | 2009篇 |
1992年 | 2275篇 |
1991年 | 2334篇 |
1990年 | 2098篇 |
1989年 | 2084篇 |
1988年 | 2005篇 |
1987年 | 1901篇 |
1986年 | 1840篇 |
1985年 | 2388篇 |
1984年 | 2485篇 |
1983年 | 2046篇 |
1982年 | 2233篇 |
1981年 | 2105篇 |
1980年 | 2036篇 |
1979年 | 2145篇 |
1978年 | 2329篇 |
1977年 | 2177篇 |
1976年 | 2216篇 |
1975年 | 2115篇 |
1974年 | 2184篇 |
1973年 | 2162篇 |
1972年 | 1399篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
E. E. Roper W. P. White H. P. Brown O. A. Sliskonskaja F. Lieneweg I. Schrodt M. Benedict und P. Neubert 《Fresenius' Journal of Analytical Chemistry》1940,120(1-2):17-18
Ohne Zusammenfassung 相似文献
992.
L. Erlandsen G. Schenck H. Graf R. Wasicky G. Stern M. Zimet W. Schreber W. Hoffmann F. Schoofs V. F. Stewart H. J. Wollner J. R. Matchett und H. Quéré 《Fresenius' Journal of Analytical Chemistry》1940,120(3-4):147-151
Ohne Zusammenfassung 相似文献
993.
F. Despa R. S. Berry 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):37-40
Interpretive theoretical tools prove valuable in guiding
the analysis of experiments in the realm of atomic clusters.
Here, we review basic elements of an analytic approach that
makes it possible to find and visualize the effective
electrostatic potential and Coulomb correlations in multicenter
problems. To illustrate the utility of these concepts we apply
them to exploring molecular-doped metallic clusters. This study
is aiming at a systematic, visual assessment of changes induced
in screening, Coulomb correlation and effective potential by
varying the charge of the electronegative impurity and its
position in the cluster cage. 相似文献
994.
995.
996.
S. N. Dorogovtsev A. V. Goltsev J. F. F. Mendes 《The European Physical Journal B - Condensed Matter and Complex Systems》2004,38(2):177-182
We consider the general p-state Potts model on random networks with a given degree distribution (random Bethe lattices). We find the effect of the suppression of a first order phase transition in this model when the degree distribution of the network is fat-tailed, that is, in more precise terms, when the second moment of the distribution diverges. In this situation the transition is continuous and of infinite order, and size effect is anomalously strong. In particular, in the case of p = 1, we arrive at the exact solution, which coincides with the known solution of the percolation problem on these networks.Received: 3 December 2003, Published online: 17 February 2004PACS:
05.10.-a Computational methods in statistical physics and nonlinear dynamics - 05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion - 05.50. + q Lattice theory and statistics (Ising, Potts, etc.) - 87.18.Sn Neural networks 相似文献
997.
P. Budrugeac J. M. Criado F. J. Gotor J. Malek L. A. Prez‐Maqueda E. Segal 《国际化学动力学杂志》2004,36(6):309-315
The isoconversional method suggested by Friedman and the invariant kinetic parameters method (IKP) were used in order to examine the kinetics of the nonisothermal crystallization of (GeS2)0.3(Sb2S3)0.7. The objective of the paper is to show the usefulness of the IKP method both for determining the activation parameters as well as the model of the investigated process. It was shown that the kinetic triplet [(E, A, f(α), where E is the activation energy, A is the preexponential factor, and f(α) is the differential function of conversion], which results through the application of the IKP method, depends on the set of kinetic models considered. For different sets of kinetic models, proportional values of f(α) are obtained. A criterion for the selection of this set, the use of which lead to the true kinetic triplet corresponding to the analyzed process (E = 163.2 kJ mol?1; A = 2.47 × 1012 min?1 and the Avrami‐Erofeev model, Am, for m = 2.5–2.6 was suggested. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 309–315, 2004 相似文献
998.
The sorption, diffusion, and pervaporation (PV) properties of benzene/cyclohexane (Bz/Cx) mixtures on cation-exchange membranes containing copper ions (Cu(II)) were investigated. The equilibrium sorption isotherms of pure vapors in the membranes and the partial solubility of binary solutions in the membranes were described using the UNIQUAC model. The τiM and τMi values were 0.978 and 0.591 for Bz, and 0.922 and 0.475 for Cx. The transient regimes of vapor sorption were employed to calculate the concentration-dependent diffusion coefficients. Long’s model sufficiently explained the diffusivity of Bz and Cx in the membranes. The pre-exponential factors were 3×10−13 m2/s and the plasticization factors were 3.0 and 3.6 for Bz and Cx, respectively. Excellent agreement was found with the experimental results applying the solubility and diffusivity data to simulate the pervaporation performance (flux and selectivity) using the modified Maxwell–Stefan equation. The membrane containing Cu(II) demonstrates better facilitating capability for Bz transport than that with Na(I), mainly due to its preferential sorption property toward Bz. Replacing Na(I) with Cu(II) into a Neosepta membrane resulted in better separation efficiency and higher Bz flux throughout the entire Bz concentration range. 相似文献
999.
In this paper, we present a new algorithm to estimate a regression function in a fixed design regression model, by piecewise
(standard and trigonometric) polynomials computed with an automatic choice of the knots of the subdivision and of the degrees
of the polynomials on each sub-interval. First we give the theoretical background underlying the method: the theoretical performances
of our penalized least-squares estimator are based on non-asymptotic evaluations of a mean-square type risk. Then we explain
how the algorithm is built and possibly accelerated (to face the case when the number of observations is great), how the penalty
term is chosen and why it contains some constants requiring an empirical calibration. Lastly, a comparison with some well-known
or recent wavelet methods is made: this brings out that our algorithm behaves in a very competitive way in term of denoising
and of compression. 相似文献
1000.