全文获取类型
收费全文 | 83813篇 |
免费 | 12319篇 |
国内免费 | 8151篇 |
专业分类
化学 | 56944篇 |
晶体学 | 825篇 |
力学 | 5423篇 |
综合类 | 583篇 |
数学 | 9906篇 |
物理学 | 30602篇 |
出版年
2024年 | 274篇 |
2023年 | 1649篇 |
2022年 | 2750篇 |
2021年 | 2865篇 |
2020年 | 3060篇 |
2019年 | 2965篇 |
2018年 | 2677篇 |
2017年 | 2371篇 |
2016年 | 3605篇 |
2015年 | 3732篇 |
2014年 | 4481篇 |
2013年 | 5892篇 |
2012年 | 7094篇 |
2011年 | 7273篇 |
2010年 | 5023篇 |
2009年 | 4820篇 |
2008年 | 5135篇 |
2007年 | 4626篇 |
2006年 | 4308篇 |
2005年 | 3725篇 |
2004年 | 2963篇 |
2003年 | 2314篇 |
2002年 | 2077篇 |
2001年 | 1795篇 |
2000年 | 1701篇 |
1999年 | 1795篇 |
1998年 | 1539篇 |
1997年 | 1349篇 |
1996年 | 1395篇 |
1995年 | 1204篇 |
1994年 | 1180篇 |
1993年 | 982篇 |
1992年 | 886篇 |
1991年 | 750篇 |
1990年 | 637篇 |
1989年 | 562篇 |
1988年 | 406篇 |
1987年 | 379篇 |
1986年 | 326篇 |
1985年 | 329篇 |
1984年 | 222篇 |
1983年 | 185篇 |
1982年 | 159篇 |
1981年 | 119篇 |
1980年 | 95篇 |
1978年 | 60篇 |
1976年 | 60篇 |
1975年 | 64篇 |
1974年 | 57篇 |
1973年 | 64篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
131.
We discuss the matrix model in a class of 11D time dependent supersymmetric backgrounds as obtained in [B. Chen, Phys. Lett. B 632 (2006) 393, hep-th/0508191]. We construct the matrix model action through the matrix regularization of the membrane action in the background. We show that the action is exact to all orders of fermionic coordinates. Furthermore we discuss the fuzzy sphere solutions in this background. 相似文献
132.
Cao H. P. Chen G. Grechkoseeva M. A. Mazurov V. D. Shi W. J. Vasil'ev A. V. 《Siberian Mathematical Journal》2004,45(6):1031-1035
The spectrum of a finite group is the set of its element orders. A finite group G is said to be recognizable by spectrum, if every finite group with the same spectrum as G is isomorphic to G. The purpose of the paper is to prove that for every natural m the finite simple Chevalley group F
4(2
m
) is recognizable by spectrum. 相似文献
133.
In this paper, an interior point cutting plane method (IPCPM)is applied to solve optimal power flow (OPF) problems. Comparedwith the simplex cutting plane method (SCPM), the IPCPM is simpler,and efficient because of its polynomial-time characteristic.Issues in implementing IPCPM for OPF problems are addressed,including (1) how to generate cutting planes without using thesimplex tableau, (2) how to identify the basis variables inIPCPM, and (3) how to generate mixed integer cutting planes.The calculation speed of the proposed algorithm is further enhancedby utilizing the sparsity features of the OPF formulation. Numericalsimulations on IEEE 14-300-bus test systems have shown thatthe proposed method is effective. 相似文献
134.
S.H Chen 《Journal of luminescence》2004,109(2):93-102
The ZnS:Cu,Al,Au (P22G) phosphor powder was bombarded by an electron beam in an O2 ambient, Ar ambient and other mixture of gases. These gases consisted of mixtures of O2 and COx, and O2, COx and Ar gas. Auger electron spectroscopy (AES) was used to monitor changes in the surface composition of the P22G phosphor during electron bombardment. When the P22G phosphor powder was exposed to the electron beam in a water-rich O2 ambient, a chemically limited ZnO layer was formed on the surface. The electron beam degradation of the P22G phosphor powder was also performed in a dry O2 ambient and a layer of ZnSO4 was formed on the surface. The ZnSO4 formation decayed exponentially with time and it is postulated that this was due to the diffusion of the charge reactants through the ZnSO4 film to the reaction interfaces. The P22G phosphor exposed to the electron beam in an Ar ambient and to the other gas mixtures degraded at a lower rate than in the case of the O2 ambient. This suggests that Ar and COx may suppress the degradation of the P22G phosphor powder. 相似文献
135.
Molecular dynamics simulation of thermodynamic properties of NaCl at high pressures and temperatures 总被引:1,自引:0,他引:1
Qifeng Chen Lingcang Cai Dongquan Chen 《Journal of Physics and Chemistry of Solids》2004,65(6):1077-1081
The expansivity, constant-pressure heat capacity, and isothermal bulk modulus of sodium chloride (NaCl) have been obtained by using molecular dynamics method. The calculated thermodynamic parameters are found to be in agreement with the available experimental data. At an extended temperature and pressure ranges, these parameters have also been predicted. The thermodynamic properties of NaCl are summarized in the pressure 0-500 kbar ranges and the temperature up to 1000 K. 相似文献
136.
A New Cohomology Theory of Orbifold 总被引:7,自引:0,他引:7
Based on the orbifold string theory model in physics, we construct a new cohomology ring for any almost complex orbifold. The key theorem is the associativity of this new ring. Some examples are computed.Both authors partially supported by the National Science Foundation 相似文献
137.
This paper uses the method of linear approximation for impulsive systems and gets a theorem which guarantees a fishery modei to be asymptotically stable at its equilibrium point and gives the ecological explanation. 相似文献
138.
139.
140.