全文获取类型
收费全文 | 29741篇 |
免费 | 2286篇 |
国内免费 | 2773篇 |
专业分类
化学 | 3816篇 |
晶体学 | 230篇 |
力学 | 2165篇 |
综合类 | 309篇 |
数学 | 12192篇 |
物理学 | 2734篇 |
综合类 | 13354篇 |
出版年
2024年 | 62篇 |
2023年 | 216篇 |
2022年 | 281篇 |
2021年 | 425篇 |
2020年 | 574篇 |
2019年 | 564篇 |
2018年 | 534篇 |
2017年 | 688篇 |
2016年 | 740篇 |
2015年 | 654篇 |
2014年 | 1181篇 |
2013年 | 1663篇 |
2012年 | 1599篇 |
2011年 | 1776篇 |
2010年 | 1591篇 |
2009年 | 1784篇 |
2008年 | 1834篇 |
2007年 | 2178篇 |
2006年 | 1911篇 |
2005年 | 1698篇 |
2004年 | 1510篇 |
2003年 | 1524篇 |
2002年 | 1299篇 |
2001年 | 1087篇 |
2000年 | 964篇 |
1999年 | 899篇 |
1998年 | 760篇 |
1997年 | 720篇 |
1996年 | 588篇 |
1995年 | 555篇 |
1994年 | 493篇 |
1993年 | 359篇 |
1992年 | 358篇 |
1991年 | 316篇 |
1990年 | 282篇 |
1989年 | 231篇 |
1988年 | 210篇 |
1987年 | 147篇 |
1986年 | 94篇 |
1985年 | 85篇 |
1984年 | 64篇 |
1983年 | 27篇 |
1982年 | 64篇 |
1981年 | 51篇 |
1980年 | 46篇 |
1979年 | 34篇 |
1978年 | 19篇 |
1977年 | 16篇 |
1976年 | 12篇 |
1972年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
991.
992.
We describe the indecomposable involutive non-degenerate set-theoretic solutions of the Yang–Baxter equation as dynamical extensions of non-degenerate left cycle sets. Moreover we characterize the indecomposable dynamical extensions and we produce several examples. As an application we construct a family of finite indecomposable solutions whose structure groups have not the unique product property. 相似文献
993.
Awatif Alqahtani Mohamed Jleli Bessem Samet 《Mathematical Methods in the Applied Sciences》2019,42(3):861-870
In this paper, some nonlocal in time differential inequalities of Sobolev type are considered. Using the nonlinear capacity method, sufficient conditions for the nonexistence of nontrivial global classical solutions are provided. 相似文献
994.
Stevo Stevi Bratislav Iri
anin Witold Kosmala Zdenk marda 《Mathematical Methods in the Applied Sciences》2019,42(5):1687-1701
Some formulas for well‐defined solutions to four very special cases of a nonlinear fifth‐order difference equation have been presented recently in this journal, where some of them were proved by the method of induction, some are only quoted, and no any theory behind the formulas was given. Here, we show in an elegant constructive way how the general solution to the difference equation can be obtained, from which the special cases very easily follow, which is also demonstrated here. We also give some comments on the local stability results on the special cases of the nonlinear fifth‐order difference equation previously publish in this journal. 相似文献
995.
Claudianor O. Alves Daniel C. de Morais Filho Giovany M. Figueiredo 《Mathematical Methods in the Applied Sciences》2019,42(14):4862-4875
In this work, we prove the existence of positive solution for the following class of problems where λ>0 and is a potential satisfying some conditions. Using the variational method developed by Szulkin for functionals, which are the sum of a C1 functional with a convex lower semicontinuous functional, we prove that for each large enough λ>0, there exists a positive solution for the problem, and that, as λ→+∞, such solutions converge to a positive solution of the limit problem defined on the domain Ω=int(V?1({0})). 相似文献
996.
The aim of this paper is to complement existing oscillation results for third-order neutral delay differential equations by establishing sufficient conditions for nonexistence of so-called Kneser solutions. Combining newly obtained results with existing ones, we attain oscillation of all solutions of the studied equations. 相似文献
997.
ABSTRACTA striking feature of lyotropic chromonic liquid crystals confined in cylinder model exhibit double-twist director configurations. Evidence suggests that saddle-splay deformation is among the most important factors for the distortions of director. Previous researches limit the director to distort at a fixed plane (r-? plane) by using specific boundary conditions such as degenerate planar anchoring condition. In this work, we consider lyotropic chromonic liquid crystals confined between two coaxial cylinders with free-surface boundary conditions and Rapini-Papoular-type anchoring conditions. By using finite-difference iterative method to solve the numerical solution of Euler equation, we find that saddle-splay deformation leads to double-twist director configurations under free-surface boundary conditions, which consist of the result under degenerate planar anchoring conditions. Furthermore, at Rapini-Papoular-type anchoring conditions, saddle-splay deformation has a great influence on the director in the radial direction (r direction) and the director distorts in three-dimensional space. Remarkably, our method provides a more accurate theory basis for the measured values of saddle-splay elastic constant K24。 相似文献
998.
999.
《Mendeleev Communications》2022,32(6):742-744
A solution of a histone-like protein from Spiroplasma melliferum (HUSpm) was examined by small-angle X-ray scattering (SAXS). The experimental SAXS curve was compared with those calculated for the HUSpm structures from the PDB databank obtained by both X-ray diffraction analysis and nuclear magnetic resonance spectroscopy. The model of the HUSpm structure in solution, which best agrees with the experimental SAXS data, has a shorter distance between the centers of mass of the HUSpm monomers compared to the crystal structure, indicating that the HUSpm monomers can be located closer to each other in solution than in the crystalline state. 相似文献
1000.
许卫明 《长春工程学院学报(自然科学版)》2016,17(2)
针对传统解算器未能实现 GPU 上运行网格自适应加密过程,造成 GPU 与 CPU 之间繁琐的数据交换的问题,本文发展优化了一种 GPU 加速的基于非结构自适应加密网格的解算器 VA2DG。利用加密网格表的方式实现网格自适应加密过程在 GPU 上高速运行,并通过原子操作并行生成网格加密表,对废弃的网格及时回收,节约存储空间,加快运行速度。 相似文献