全文获取类型
收费全文 | 29422篇 |
免费 | 4487篇 |
国内免费 | 2552篇 |
专业分类
化学 | 3476篇 |
晶体学 | 76篇 |
力学 | 4236篇 |
综合类 | 621篇 |
数学 | 15783篇 |
物理学 | 12269篇 |
出版年
2024年 | 50篇 |
2023年 | 267篇 |
2022年 | 491篇 |
2021年 | 563篇 |
2020年 | 700篇 |
2019年 | 678篇 |
2018年 | 706篇 |
2017年 | 879篇 |
2016年 | 972篇 |
2015年 | 766篇 |
2014年 | 1553篇 |
2013年 | 1892篇 |
2012年 | 1619篇 |
2011年 | 1970篇 |
2010年 | 1691篇 |
2009年 | 1947篇 |
2008年 | 1988篇 |
2007年 | 2080篇 |
2006年 | 1887篇 |
2005年 | 1804篇 |
2004年 | 1535篇 |
2003年 | 1418篇 |
2002年 | 1160篇 |
2001年 | 1092篇 |
2000年 | 971篇 |
1999年 | 818篇 |
1998年 | 750篇 |
1997年 | 674篇 |
1996年 | 510篇 |
1995年 | 443篇 |
1994年 | 360篇 |
1993年 | 305篇 |
1992年 | 262篇 |
1991年 | 237篇 |
1990年 | 210篇 |
1989年 | 162篇 |
1988年 | 147篇 |
1987年 | 120篇 |
1986年 | 93篇 |
1985年 | 105篇 |
1984年 | 89篇 |
1983年 | 60篇 |
1982年 | 85篇 |
1981年 | 73篇 |
1980年 | 48篇 |
1979年 | 45篇 |
1978年 | 32篇 |
1977年 | 28篇 |
1976年 | 30篇 |
1973年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
991.
J. Morais M. A. Pérez‐de la Rosa 《Mathematical Methods in the Applied Sciences》2015,38(17):4365-4387
Over the past few years, considerable attention has been given to the role played by the Lamé's Wave Functions (LWFs) in various problems of mathematical physics and mechanics. The LWFs arise via the method of separation of variables for the wave equation in ellipsoidal coordinates. The present paper introduces the Lamé's Quaternionic Wave Functions (LQWFs), which extend the LWFs to a non‐commutative framework. We show that the theory of the LQWFs is determined by the Moisil‐Theodorescu type operator with quaternionic variable coefficients. As a result, we explain the connections between the solutions of the Lamé's wave equation, on one hand, and the quaternionic hyperholomorphic and anti‐hyperholomorphic functions on the other. We establish analogues of the basic integral formulas of complex analysis such as Borel‐Pompeiu's, Cauchy's, and so on, for this version of quaternionic function theory. We further obtain analogues of the boundary value properties of the LQWFs such as Sokhotski‐Plemelj formulae, the ‐hyperholomorphic extension of a given Hölder function and on the square of the singular integral operator. We address all the text mentioned earlier and explore some basic facts of the arising quaternionic function theory. We conclude the paper showing that the spherical, prolate, and oblate spheroidal quaternionic wave functions can be generated as particular cases of the LQWFs. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
992.
994.
Synchronization behavior of bursting neurons is investigated in a neuronal network ring impulsively coupled, in which each neuron exhibits chaotic bursting behavior. Based on the Lyapunov stability theory and impulsive control theory, sufficient conditions for synchronization of the multiple systems coupled with impulsive variables can be obtained. The neurons become synchronous via suitable impulsive strength and resetting period. Furthermore, the result is obtained that synchronization among neurons is weakened with the increasing of the reset period and the number of neurons. Finally, numerical simulations are provided to show the effectiveness of the theoretical results.© 2014 Wiley Periodicals, Inc. Complexity 21: 29–37, 2015 相似文献
995.
In 1991,Hornik proved that the collection of single hidden layer feedforward neural networks(SLFNs)with continuous,bounded,and non-constant activation functionσis dense in C(K)where K is a compact set in R~s(see Neural Networks,4(2),251-257(1991)).Meanwhile,he pointed out"Whether or not the continuity assumption can entirely be dropped is still an open quite challenging problem".This paper replies in the affirmative to the problem and proves that for bounded and continuous almost everywhere(a.e.)activation functionσon R,the collection of SLFNs is dense in C(K)if and only ifσis un-constant a.e.. 相似文献
996.
997.
In this paper we try to solve a paradox related to the results of Theocharis (1960). When the number of competitors increases the Cournot–Nash equilibrium loses stability. We relax the assumption about homogeneity in the decision mechanism and show that if we admit heterogeneity than by increasing the number of competitors the stability region on the parameters’ space may enlarge instead of shrinking. 相似文献
998.
Global stability of humoral immunity virus dynamics models with nonlinear infection rate and removal
In this paper, we investigate the dynamical behavior of two nonlinear models for viral infection with humoral immune response. The first model contains four compartments; uninfected target cells, actively infected cells, free virus particles and B cells. The intrinsic growth rate of uninfected cells, incidence rate of infection, removal rate of infected cells, production rate of viruses, neutralization rate of viruses, activation rate of B cells and removal rate of B cells are given by more general nonlinear functions. The second model is a modification of the first one by including an eclipse stage of infected cells. We assume that the latent-to-active conversion rate is also given by a more general nonlinear function. For each model we derive two threshold parameters and establish a set of conditions on the general functions which are sufficient to determine the global dynamics of the models. By using suitable Lyapunov functions and LaSalle’s invariance principle, we prove the global asymptotic stability of the all equilibria of the models. We perform some numerical simulations for the models with specific forms of the general functions and show that the numerical results are consistent with the theoretical results. 相似文献
999.
Martin Schmid Hans‐Peter Steinrück J. Michael Gottfried 《Surface and interface analysis : SIA》2014,46(8):505-511
Asymmetric peak profiles for the application in spectroscopy can be obtained in a simple way by substituting the usually constant full width at half maximum parameter in Pseudo‐Voigt functions with an energy‐dependent expression, for instance of sigmoidal shape. While this approach has been successfully applied to vibrational spectra, we find that the resulting curves are less suitable for least‐squares fits of X‐ray photoelectron spectroscopy (XPS) data. However, if one additionally allows a variable displacement of the sigmoidal step relative to the peak, excellent fitting results can be obtained. We demonstrate the applicability of our extended approach on several inherently asymmetric XPS lines, i.e. the C 1s signal of graphite and C2H2/Pd(100), the 3d5/2–3d3/2 doublet of palladium, and the 4f7/2–4f5/2 doublet of platinum. Comparison of the corresponding fit results with the results obtained by the application of more elaborate, theory‐based line profiles (Doniach‐?unji? and Mahan functions) shows that the modified Pseudo‐Voigt function gives practically identical results in terms of peak shape and area, while requiring much less computational effort since no convolution procedures are required for its calculation. Thus, this function is most suitable for application in one of the following situations: (i) the peak shape of a given signal is known but cannot be calculated with ease, and (ii) the theoretical peak shape is not (yet) known, however, one wants to perform a first quantitative screening of the data at issue. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
1000.
Acceleration of self‐consistent field convergence in ab initio molecular dynamics simulation with multiconfigurational wave function
下载免费PDF全文
![点击此处可从《Journal of computational chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The Lagrange interpolation of molecular orbital (LIMO) method, which reduces the number of self‐consistent field iterations in ab initio molecular dynamics simulations with the Hartree–Fock method and the Kohn–Sham density functional theories, is extended to the theory of multiconfigurational wave functions. We examine two types of treatments for the active orbitals that are partially occupied. The first treatment, as denoted by LIMO(C), is a simple application of the conventional LIMO method to the union of the inactive core and the active orbitals. The second, as denoted by LIMO(S), separately treats the inactive core and the active orbitals. Numerical tests to compare the two treatments clarify that LIMO(S) is superior to LIMO(C). Further applications of LIMO(S) to various systems demonstrate its effectiveness and robustness. © 2014 Wiley Periodicals, Inc. 相似文献