全文获取类型
收费全文 | 96946篇 |
免费 | 11407篇 |
国内免费 | 7651篇 |
专业分类
化学 | 46933篇 |
晶体学 | 659篇 |
力学 | 4664篇 |
综合类 | 515篇 |
数学 | 8452篇 |
物理学 | 25621篇 |
综合类 | 29160篇 |
出版年
2024年 | 391篇 |
2023年 | 1723篇 |
2022年 | 2734篇 |
2021年 | 2964篇 |
2020年 | 2841篇 |
2019年 | 2566篇 |
2018年 | 2398篇 |
2017年 | 2213篇 |
2016年 | 3261篇 |
2015年 | 3596篇 |
2014年 | 4507篇 |
2013年 | 5631篇 |
2012年 | 6684篇 |
2011年 | 6797篇 |
2010年 | 4969篇 |
2009年 | 4912篇 |
2008年 | 5277篇 |
2007年 | 4864篇 |
2006年 | 4491篇 |
2005年 | 4088篇 |
2004年 | 3282篇 |
2003年 | 2572篇 |
2002年 | 2350篇 |
2001年 | 2238篇 |
2000年 | 2188篇 |
1999年 | 3075篇 |
1998年 | 2709篇 |
1997年 | 2606篇 |
1996年 | 2669篇 |
1995年 | 2228篇 |
1994年 | 2106篇 |
1993年 | 1823篇 |
1992年 | 1601篇 |
1991年 | 1418篇 |
1990年 | 1274篇 |
1989年 | 1128篇 |
1988年 | 889篇 |
1987年 | 712篇 |
1986年 | 511篇 |
1985年 | 393篇 |
1984年 | 217篇 |
1983年 | 189篇 |
1982年 | 157篇 |
1981年 | 114篇 |
1980年 | 84篇 |
1978年 | 59篇 |
1977年 | 53篇 |
1975年 | 57篇 |
1974年 | 52篇 |
1973年 | 59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.
提出建立在非对称度量空间之间的上收缩映射和下收缩映射的概念.考虑到非对称度量的不对称性,进一步定义了非对称度量空间到自身映射的左不动点和右不动点.最后,给出了非对称度量空间上的两个不动点定理. 相似文献
133.
某库岸滑坡稳定分析及治理措施研究 总被引:1,自引:0,他引:1
从地质条件出发,详细分析了滑坡的成因,以大型的岩土工程数值分析软件(ADINA)为研究手段,建立有限元计算模型,用强度折减的方法分析了滑坡体在初始工况、蓄水工况、暴雨工况、水位骤降工况和地震工况下的稳定情况,根据滑坡的失稳情况,在综合考虑的基础上,提出了削坡减载和地表排水相结合的治理措施,计算结果表明,治理措施是可行的,研究结果对设计和施工具有较大的参考价值. 相似文献
134.
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
135.
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
136.
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
137.
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
138.
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
139.
140.