全文获取类型
收费全文 | 5054篇 |
免费 | 485篇 |
国内免费 | 349篇 |
专业分类
化学 | 379篇 |
晶体学 | 20篇 |
力学 | 805篇 |
综合类 | 70篇 |
数学 | 2970篇 |
物理学 | 1644篇 |
出版年
2024年 | 17篇 |
2023年 | 49篇 |
2022年 | 77篇 |
2021年 | 108篇 |
2020年 | 129篇 |
2019年 | 125篇 |
2018年 | 148篇 |
2017年 | 123篇 |
2016年 | 148篇 |
2015年 | 127篇 |
2014年 | 241篇 |
2013年 | 353篇 |
2012年 | 202篇 |
2011年 | 266篇 |
2010年 | 252篇 |
2009年 | 286篇 |
2008年 | 292篇 |
2007年 | 285篇 |
2006年 | 296篇 |
2005年 | 252篇 |
2004年 | 197篇 |
2003年 | 238篇 |
2002年 | 202篇 |
2001年 | 150篇 |
2000年 | 150篇 |
1999年 | 148篇 |
1998年 | 108篇 |
1997年 | 125篇 |
1996年 | 81篇 |
1995年 | 81篇 |
1994年 | 68篇 |
1993年 | 67篇 |
1992年 | 67篇 |
1991年 | 68篇 |
1990年 | 47篇 |
1989年 | 31篇 |
1988年 | 27篇 |
1987年 | 28篇 |
1986年 | 21篇 |
1985年 | 30篇 |
1984年 | 29篇 |
1983年 | 11篇 |
1982年 | 26篇 |
1981年 | 16篇 |
1980年 | 22篇 |
1979年 | 19篇 |
1978年 | 10篇 |
1977年 | 11篇 |
1976年 | 13篇 |
1974年 | 7篇 |
排序方式: 共有5888条查询结果,搜索用时 31 毫秒
151.
152.
Raquel M. López José M. Vega-Guzmán 《Journal of Difference Equations and Applications》2013,19(4):543-554
We consider a six-parameter family of the square integrable wave functions for the simple harmonic oscillator, which cannot be obtained by the standard separation of variables. They are given by the action of the corresponding maximal kinematical invariance group on the standard solutions. In addition, the phase space oscillations of the electron position and linear momentum probability distributions are computer animated and some possible applications are briefly discussed. A visualization of the Heisenberg uncertainty principle is presented. 相似文献
153.
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
154.
A novel approach of calculating an insurance premium based on g-integrals and interval-valued integrals is introduced. The characterization theorem for the g-integral-based premium principle is proven, and the relations with some well-known premium principles are discussed. The main properties of the interval-valued premium principle based on the g-integral are presented and some illustrative examples are given. 相似文献
155.
利用“每课一题”这个教学环节从已有知识中提取基本原理,并应用于新知识的学习;提取学生的问题编制习题,让学生暴露产生问题的根源并从根本上解决。探讨了每课一题的必要性及其基本类型。 相似文献
156.
157.
Célestin Wafo Soh Fazal M. Mahomed 《Mathematical Methods in the Applied Sciences》2016,39(14):4139-4157
We review the theory of hypercomplex numbers and hypercomplex analysis with the ultimate goal of applying them to issues related to the integration of systems of ordinary differential equations (ODEs). We introduce the notion of hypercomplexification, which allows the lifting of some results known for scalar ODEs to systems of ODEs. In particular, we provide another approach to the construction of superposition laws for some Riccati‐type systems, we obtain invariants of Abel‐type systems, we derive integrable Ermakov systems through hypercomplexification, we address the problem of linearization by hypercomplexification, and we provide a solution to the inverse problem of the calculus of variations for some systems of ODEs. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
158.
A finite volume scheme preserving extremum principle for convection–diffusion equations on polygonal meshes 下载免费PDF全文
We propose a nonlinear finite volume scheme for convection–diffusion equation on polygonal meshes and prove that the discrete solution of the scheme satisfies the discrete extremum principle. The approximation of diffusive flux is based on an adaptive approach of choosing stencil in the construction of discrete normal flux, and the approximation of convection flux is based on the second‐order upwind method with proper slope limiter. Our scheme is locally conservative and has only cell‐centered unknowns. Numerical results show that our scheme can preserve discrete extremum principle and has almost second‐order accuracy. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
159.
Antonio M. Scarfone Hiroki Suyari Tatsuaki Wada 《Central European Journal of Physics》2009,7(3):414-420
We reformulate the Gauss’ law of error in presence of correlations which are taken into account by means of a deformed product
arising in the framework of the Sharma-Taneja-Mittal measure. Having reviewed the main proprieties of the generalized product
and its related algebra, we derive, according to the Maximum Likelihood Principle, a family of error distributions with an
asymptotic power-law behavior.
相似文献
160.
In this paper, we present a method for constructing multivariate tight framelet packets associated with an arbitrary dilation matrix using unitary extension principles.We also prove how to construct various tight frames for L2(Rd) by replac-ing some mother framelets. 相似文献