全文获取类型
收费全文 | 4230篇 |
免费 | 650篇 |
国内免费 | 229篇 |
专业分类
化学 | 160篇 |
晶体学 | 2篇 |
力学 | 275篇 |
综合类 | 35篇 |
数学 | 3285篇 |
物理学 | 1352篇 |
出版年
2024年 | 10篇 |
2023年 | 96篇 |
2022年 | 85篇 |
2021年 | 145篇 |
2020年 | 254篇 |
2019年 | 234篇 |
2018年 | 212篇 |
2017年 | 231篇 |
2016年 | 177篇 |
2015年 | 131篇 |
2014年 | 248篇 |
2013年 | 391篇 |
2012年 | 201篇 |
2011年 | 222篇 |
2010年 | 144篇 |
2009年 | 204篇 |
2008年 | 229篇 |
2007年 | 239篇 |
2006年 | 186篇 |
2005年 | 168篇 |
2004年 | 157篇 |
2003年 | 160篇 |
2002年 | 153篇 |
2001年 | 110篇 |
2000年 | 131篇 |
1999年 | 111篇 |
1998年 | 70篇 |
1997年 | 60篇 |
1996年 | 39篇 |
1995年 | 34篇 |
1994年 | 28篇 |
1993年 | 31篇 |
1992年 | 17篇 |
1991年 | 24篇 |
1990年 | 12篇 |
1989年 | 14篇 |
1988年 | 14篇 |
1987年 | 21篇 |
1986年 | 11篇 |
1985年 | 11篇 |
1984年 | 12篇 |
1983年 | 5篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1979年 | 10篇 |
1978年 | 4篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1973年 | 11篇 |
1936年 | 4篇 |
排序方式: 共有5109条查询结果,搜索用时 0 毫秒
81.
Sarika Goyal 《Mathematische Nachrichten》2019,292(10):2189-2202
In this article, we study the eigenvalues of p‐fractional Hardy operator where , , , and Ω is an unbounded domain in with Lipschitz boundary containing 0. The weight function V may change sign and may have singular points. We also show that the least positive eigenvalue is simple and it is uniquely associated to a nonnegative eigenfunction. Moreover, we proved that there exists a sequence of eigenvalues as . 相似文献
82.
Ciprian A. Tudor Nakahiro Yoshida 《Stochastic Processes and their Applications》2019,129(9):3499-3526
We develop the asymptotic expansion theory for vector-valued sequences of random variables in terms of the convergence of the Stein–Malliavin matrix associated with the sequence . Our approach combines the classical Fourier approach and the recent Stein–Malliavin theory. We find the second order term of the asymptotic expansion of the density of and we illustrate our results by several examples. 相似文献
83.
Under the assumption that μ is a non-doubling measure on Rdwhich only satisfies the polynomial growth condition,the authors obtain the boundedness of the multilinear fractional integrals on Morrey spaces,weak-Morrey spaces and Lipschitz spaces associated with μ,which,in the case when μ is the d-dimensional Lebesgue measure,also improve the known results. 相似文献
84.
In this letter we propose a class of linear fractional difference equations with discrete-time delay and impulse effects. The exact solutions are obtained by use of a discrete Mittag-Leffler function with delay and impulse. Besides, we provide comparison principle, stability results and numerical illustration. 相似文献
85.
Harshal P. Mungse Niharika Bhakuni Deependra Tripathi Om P. Sharma Bir Sain Om P. Khatri 《Journal of Physical Organic Chemistry》2014,27(12):944-951
Graphene oxide (GrO) prepared by the Hummers method was separated into three different fractions (GrO5000, GrO2000, and GrOres) on the basis of their dispersion stability in the water. Infrared, nuclear magnetic resonance, X‐ray photoelectron spectroscopy, and elemental analyses revealed that GrO5000 possesses a high degree of oxygen functionalities including phenolic, carboxylic, and ?OSO2H groups, compared with the other fractions. The GrO5000 was found to be a highly efficient and reusable solid catalyst for the esterification of various carboxylic acids with a variety of alcohols to furnish corresponding esters in high to excellent yields. The catalytic activity of the GrO5000 was attributed to the ability of highly polar GrO5000 scaffold to adsorb/attract reactants, where the acid functionalities of GrO5000 facilitated the esterification process efficiently. The chemical and structural features of GrO5000 were discussed to understand the improved catalytic activity compared with GrO2000 and conventional solid acid catalysts. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
86.
87.
David Richard Alexander 《European Journal of Operational Research》2012,219(1):114-122
We treat real option value when the underlying process is arithmetic Brownian motion (ABM). In contrast to the more common assumption of geometric Brownian motion (GBM) and multiplicative diffusion, with ABM the underlying project value is expressed as an additive process. Its variance remains constant over time rather than rising or falling along with the project’s value, even admitting the possibility of negative values. This is a more compelling paradigm for projects that are managed as a component of overall firm value. After outlining the case for ABM, we derive analytical formulas for European calls and puts on dividend-paying assets as well as a numerical algorithm for American-style and other more complex options based on ABM. We also provide examples of their use. 相似文献
88.
Ground state solution for differential equations with left and right fractional derivatives 下载免费PDF全文
César Torres 《Mathematical Methods in the Applied Sciences》2015,38(18):5063-5073
In this work, we study the existence of positive solutions for a class of fractional differential equation given by (1) where . Using the mountain pass theorem and comparison argument, we prove that (1) at least has one nontrivial solution. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
89.
Juan Enrique Martínez-Legaz 《Optimization》2015,64(1):87-96
This article surveys the main contributions of K.-H. Elster to the theory of generalized conjugate functions and its applications to duality in nonconvex optimization. 相似文献
90.
Switching adaptive controllers to control fractional‐order complex systems with unknown structure and input nonlinearities 下载免费PDF全文
This article investigates the chaos control problem for the fractional‐order chaotic systems containing unknown structure and input nonlinearities. Two types of nonlinearity in the control input are considered. In the first case, a general continuous nonlinearity input is supposed in the controller, and in the second case, the unknown dead‐zone input is included. In each case, a proper switching adaptive controller is introduced to stabilize the fractional‐order chaotic system in the presence of unknown parameters and uncertainties. The control methods are designed based on the boundedness property of the chaotic system's states, where, in the proposed methods the nonlinear/linear dynamic terms of the fractional‐order chaotic systems are assumed to be fully unknown. The analytical results of the mentioned techniques are proved by the stability analysis theorem of fractional‐order systems and the adaptive control method. In addition, as an application of the proposed methods, single input adaptive controllers are adopted for control of a class of three‐dimensional nonlinear fractional‐order chaotic systems. And finally, some numerical examples illustrate the correctness of the analytical results. © 2014 Wiley Periodicals, Inc. Complexity 21: 211–223, 2015 相似文献