全文获取类型
收费全文 | 791篇 |
免费 | 36篇 |
国内免费 | 9篇 |
专业分类
化学 | 587篇 |
晶体学 | 5篇 |
力学 | 10篇 |
数学 | 37篇 |
物理学 | 197篇 |
出版年
2021年 | 12篇 |
2020年 | 8篇 |
2019年 | 12篇 |
2018年 | 8篇 |
2017年 | 9篇 |
2016年 | 11篇 |
2015年 | 19篇 |
2014年 | 16篇 |
2013年 | 38篇 |
2012年 | 29篇 |
2011年 | 41篇 |
2010年 | 31篇 |
2009年 | 29篇 |
2008年 | 37篇 |
2007年 | 36篇 |
2006年 | 35篇 |
2005年 | 43篇 |
2004年 | 23篇 |
2003年 | 22篇 |
2002年 | 20篇 |
2001年 | 17篇 |
2000年 | 20篇 |
1999年 | 14篇 |
1998年 | 12篇 |
1997年 | 15篇 |
1996年 | 14篇 |
1995年 | 12篇 |
1993年 | 23篇 |
1992年 | 7篇 |
1991年 | 16篇 |
1990年 | 11篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 12篇 |
1983年 | 6篇 |
1982年 | 10篇 |
1981年 | 11篇 |
1980年 | 5篇 |
1978年 | 9篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 8篇 |
1939年 | 5篇 |
1936年 | 5篇 |
1935年 | 5篇 |
1933年 | 4篇 |
1909年 | 5篇 |
排序方式: 共有836条查询结果,搜索用时 281 毫秒
61.
62.
63.
Al-Anber M Vatsadze S Holze R Lang H Thiel WR 《Dalton transactions (Cambridge, England : 2003)》2005,(22):3632-3637
Electrochemical reduction potentials of a broad selection of nitrogen-containing molecules suitable as bridging (dipodal and tripodal) ligands in coordination and organometallic chemistry are reported and compared with results of semiempirical calculations. Trends of electrode potentials observed experimentally agree with respective calculated data, deviations can be explained by invoking peculiarities of the involved molecular orbitals and ligand-electrode surface interactions. 相似文献
64.
We consider the effect of distributed delays in predator-prey models and ecological food webs. Whereas the occurrence of delays in population dynamics is usually regarded a destabilizing factor leading to the extinction of species, we here demonstrate complementarily that delay distributions yield larger stability regimes than single delays. Food webs with distributed delays closely resemble nondelayed systems in terms of ecological stability measures. Thus, we state that dependence of dynamics on multiple instances in the past is an important, but so far underestimated, factor for stability in dynamical systems. 相似文献
65.
In this paper we show that two dynamical invariants, the second order Renyi entropy and the correlation dimension, can be estimated from recurrence plots (RPs) with arbitrary embedding dimension and delay. This fact is interesting as these quantities are even invariant if no embedding is used. This is an important advantage of RPs compared to other techniques of nonlinear data analysis. These estimates for the correlation dimension and entropy are robust and, moreover, can be obtained at a low numerical cost. We exemplify our results for the Rossler system, the funnel attractor and the Mackey-Glass system. In the last part of the paper we estimate dynamical invariants for data from some fluid dynamical experiments and confirm previous evidence for low dimensional chaos in this experimental system. 相似文献
66.
Local environments of Si suboxides at the interface between a thermally grown SiO2 film and Si(111) were studied by angle-scanned photoelectron diffraction. Si 2p core-level spectra containing chemically shifted components were recorded. The components were deconvoluted by least squares fitting and assigned to different Si oxidation states. The obtained diffraction patterns of the various suboxides exhibit different features. Comparison of these patterns with multiple scattering calculations including a multipole R-factor analysis shows that a simple chemical abrupt interface model describes well the environment of the suboxides and indicates ordered SiO2 close to the interface. 相似文献
67.
Stoldt CR Caspersen KJ Bartelt MC Jenks CJ Evans JW Thiel PA 《Physical review letters》2000,85(4):800-803
Ag(100) homoepitaxy constitutes one of the simplest systems in which to study thin-film growth. Yet we find that the roughness variation with temperature is extraordinarily complex. Specifically, as the deposition temperature is reduced from 300 to 50 K, the roughness of 25 monolayer films first increases, then decreases, then increases again. A transition from mound formation to self-affine (semifractal) growth occurs at approximately 135 K. The underlying mechanisms are postulated. An atomistic model incorporating these mechanisms reproduces the experimental data quantitatively. 相似文献
68.
We present a new computational method with associated computer program TROVE (Theoretical ROVibrational Energies) to perform variational calculations of rovibrational energies for general polyatomic molecules of arbitrary structure in isolated electronic states. The (approximate) nuclear kinetic energy operator is represented as an expansion in terms of internal coordinates. The main feature of the computational scheme is a numerical construction of the kinetic energy operator, which is an integral part of the computation process. Thus the scheme is self-contained, i.e., it requires no analytical pre-derivation of the kinetic energy operator. It is also general, since it can be used in connection with any internal coordinates. The method represents an extension of our model for pyramidal XY3 molecules reported previously [S.N. Yurchenko, M. Carvajal, P. Jensen, H. Lin, J.J. Zheng, W. Thiel, Mol. Phys. 103 (2005) 359]. Non-rigid molecules are treated in the Hougen-Bunker-Johns approach [J.T. Hougen, P.R. Bunker, J.W.C. Johns, J. Mol. Spectrosc. 34 (1970) 136]. In this case, the variational calculations employ a numerical finite basis representation for the large-amplitude motion using basis functions that are generated by Numerov-Cooley integration of the appropriate one-dimensional Schrödinger equation. 相似文献
69.
70.
This paper proposes bootstrap tests for the presence of unit roots in a seasonal autoregressive model. The asymptotic validity of the proposed bootstrap scheme is established, and Monte Carlo experiments are used to investigate the small-sample performance of the tests. 相似文献