全文获取类型
收费全文 | 5344篇 |
免费 | 575篇 |
国内免费 | 247篇 |
专业分类
化学 | 334篇 |
晶体学 | 2篇 |
力学 | 471篇 |
综合类 | 92篇 |
数学 | 4146篇 |
物理学 | 1121篇 |
出版年
2024年 | 7篇 |
2023年 | 65篇 |
2022年 | 91篇 |
2021年 | 103篇 |
2020年 | 142篇 |
2019年 | 147篇 |
2018年 | 146篇 |
2017年 | 198篇 |
2016年 | 207篇 |
2015年 | 129篇 |
2014年 | 213篇 |
2013年 | 386篇 |
2012年 | 262篇 |
2011年 | 232篇 |
2010年 | 206篇 |
2009年 | 267篇 |
2008年 | 319篇 |
2007年 | 265篇 |
2006年 | 310篇 |
2005年 | 269篇 |
2004年 | 206篇 |
2003年 | 220篇 |
2002年 | 209篇 |
2001年 | 180篇 |
2000年 | 181篇 |
1999年 | 149篇 |
1998年 | 108篇 |
1997年 | 113篇 |
1996年 | 80篇 |
1995年 | 99篇 |
1994年 | 53篇 |
1993年 | 45篇 |
1992年 | 54篇 |
1991年 | 53篇 |
1990年 | 41篇 |
1989年 | 40篇 |
1988年 | 43篇 |
1987年 | 34篇 |
1986年 | 36篇 |
1985年 | 36篇 |
1984年 | 32篇 |
1983年 | 16篇 |
1982年 | 37篇 |
1981年 | 13篇 |
1980年 | 33篇 |
1979年 | 20篇 |
1978年 | 10篇 |
1977年 | 23篇 |
1976年 | 20篇 |
1975年 | 6篇 |
排序方式: 共有6166条查询结果,搜索用时 15 毫秒
1.
《Discrete Mathematics》2020,343(2):111679
A path in an edge-colored graph is called monochromatic if any two edges on the path have the same color. For , an edge-colored graph is said to be monochromatic -edge-connected if every two distinct vertices of are connected by at least edge-disjoint monochromatic paths, and is said to be uniformly monochromatic -edge-connected if every two distinct vertices are connected by at least edge-disjoint monochromatic paths such that all edges of these paths are colored with a same color. We use and to denote the maximum number of colors that ensures to be monochromatic -edge-connected and, respectively, to be uniformly monochromatic -edge-connected. In this paper, we first conjecture that for any -edge-connected graph , , where is a minimum -edge-connected spanning subgraph of . We verify the conjecture for . We also prove the conjecture for and with . When is a minimal -edge-connected graph, we give an upper bound of , i.e., . For the uniformly monochromatic -edge-connectivity, we prove that for all , , where is a minimum -edge-connected spanning subgraph of . 相似文献
2.
Paul S. Wesson 《General Relativity and Gravitation》2003,35(1):111-119
Results from 5D induced-matter and membrane theory with null paths are extended to show that a particle obeys the 4D Klein-Gordon equation but with a variable mass. The Dirac equation also follows, but raises concerns about 4D quantization in the two natural 5D gauges, and reopens the question of a Regge-like trajectory for the spin angular momenta and squared masses of gravitationally-dominated systems. 相似文献
3.
双掺(Tm3+,Tb3+)LiYF4激光器1.5 μm波长激光阈值分析 总被引:1,自引:0,他引:1
由速率方程推出了双掺(Tm^3 ,Tb^3 )离子准四能级系统的激光阈值解析式,讨论了Tm^3 和Tb^3 离子之间的相互作用。分析了1.5μm波长附近的激光阈值和Tm^3 、Tb^3 离子的掺杂原子数分数及晶体长度的关系。结果表明,对于对应Tm^3 离子^3H4→^3F4跃迁的约1.5μm波长的激光,激活离子Tm^3 的掺杂原子数分数过大时,交叉弛豫作用将使系统阈值迅速增加。Tb^3 离子的加入,一方面能抽空激光下能级,起到降低阈值的作用;另一方面亦减少了激光上能级的寿命,使阈值升高。故Tb^3 离子有最佳掺杂原子数分数。对于Tm原子数分数为y=0.01的Tm:LiYF4晶体,Tb^3 离子的最佳掺杂原子数分数为0.002左右,同时表明,激光阈值与晶体长度有关。最佳晶体长度与Tm^3 、Tb^3 离子的掺杂原子数分数以及晶体的衍射损耗和吸收损耗有关。 相似文献
4.
5.
Regis Guyonnet 《Journal of statistical physics》1991,65(1-2):269-289
The NMR properties of nuclei linked to long linear polymer molecules are sensitive to the influence of hard walls. In this context, the residual energy of tensorial spin-spin interactions is calculated using a path integral approach. Several thermodynamic quantities of the polymer system (free energy, equation of state,...) are also expressed, taking chain stiffness effects and the presence of two repulsive walls into consideration. 相似文献
6.
一类机器人系统的最优控制 总被引:1,自引:1,他引:0
王辉 《数学的实践与认识》2002,32(3):455-459
本文通过把结构阻尼系数当作控制变量来讨论一类弹性机器人系统的最优控制问题 ,并利用Banach空间几何性质证明了最优控制元的存在唯一性 相似文献
7.
Boban Marinković 《Mathematical Methods of Operations Research》2006,63(3):513-524
We present local sensitivity analysis for discrete optimal control problems with varying endpoints in the case when the customary regularity of boundary conditions can be violated. We study the behavior of the optimal solutions subject to parametric perturbations of the problem. 相似文献
8.
9.
Let G=(V(G),E(G)) be a graph. A (n,G, λ)‐GD is a partition of the edges of λKn into subgraphs (G‐blocks), each of which is isomorphic to G. The (n,G,λ)‐GD is named as graph design for G or G‐decomposition. The large set of (n,G,λ)‐GD is denoted by (n,G,λ)‐LGD. In this work, we obtain the existence spectrum of (n,P3,λ)‐LGD. © 2002 Wiley Periodicals, Inc. J Combin Designs 10: 151–159, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jcd.10008 相似文献
10.
Lance Nielsen 《Acta Appl Math》2002,74(3):265-292
Stability properties of Feynman's operational calculus are addressed in the setting of exponential functions of noncommuting operators. Applications of some of the stability results are presented. In particular, the time-dependent perturbation theory of nonrelativistic quantum mechanics is presented in the setting of the operational calculus and application of the stability results of this paper to the perturbation theory are discussed. 相似文献