全文获取类型
收费全文 | 108948篇 |
免费 | 11925篇 |
国内免费 | 8747篇 |
专业分类
化学 | 64377篇 |
晶体学 | 1105篇 |
力学 | 6720篇 |
综合类 | 672篇 |
数学 | 18513篇 |
物理学 | 38233篇 |
出版年
2024年 | 266篇 |
2023年 | 1587篇 |
2022年 | 2638篇 |
2021年 | 2847篇 |
2020年 | 3003篇 |
2019年 | 2900篇 |
2018年 | 3747篇 |
2017年 | 3732篇 |
2016年 | 4205篇 |
2015年 | 4151篇 |
2014年 | 4779篇 |
2013年 | 6312篇 |
2012年 | 10045篇 |
2011年 | 9337篇 |
2010年 | 6634篇 |
2009年 | 6316篇 |
2008年 | 5577篇 |
2007年 | 5084篇 |
2006年 | 4750篇 |
2005年 | 7930篇 |
2004年 | 6692篇 |
2003年 | 4439篇 |
2002年 | 2454篇 |
2001年 | 2072篇 |
2000年 | 1732篇 |
1999年 | 1916篇 |
1998年 | 1563篇 |
1997年 | 1343篇 |
1996年 | 1374篇 |
1995年 | 1189篇 |
1994年 | 1133篇 |
1993年 | 947篇 |
1992年 | 997篇 |
1991年 | 873篇 |
1990年 | 735篇 |
1989年 | 623篇 |
1988年 | 490篇 |
1987年 | 421篇 |
1986年 | 358篇 |
1985年 | 360篇 |
1984年 | 250篇 |
1983年 | 215篇 |
1982年 | 170篇 |
1981年 | 136篇 |
1980年 | 95篇 |
1978年 | 81篇 |
1976年 | 130篇 |
1975年 | 95篇 |
1974年 | 93篇 |
1973年 | 106篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
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
92.
We give counterexamples to the following conjecture of Auslander: given a finitely generated module M over an Artin algebra Λ, there exists a positive integer nM such that for all finitely generated Λ-modules N, if ExtΛi(M,N)=0 for all i?0, then ExtΛi(M,N)=0 for all i?nM. Some of our examples moreover yield homologically defined classes of commutative local rings strictly between the class of local complete intersections and the class of local Gorenstein rings. 相似文献
93.
It can be conjectured that the colored Jones function of a knot can be computed in terms of counting paths on the graph of
a planar projection of a knot. On the combinatorial level, the colored Jones function can be replaced by its weight system.
We give two curious formulas for the weight system of a colored Jones function: one in terms of the permanent of a matrix
associated to a chord diagram, and another in terms of counting paths of intersecting chords.
Electronic supplementary material to this article is available at and is accessible to authorized users.
* S. G. was partially supported by an NSF and by an Israel-US BSF grant.
† M. L. was partly supported by GAUK 158 grant and by the Project LN00A056 of the Czech Ministry of Education. 相似文献
94.
We study a class of shape optimization problems for semi-linear elliptic equations with Dirichlet boundary conditions in smooth
domains in ℝ2. A part of the boundary of the domain is variable as the graph of a smooth function. The problem is equivalently reformulated
on a fixed domain. Continuity of the solution to the state equation with respect to domain variations is shown. This is used
to obtain differentiability in the general case, and moreover a useful formula for the gradient of the cost functional in
the case where the principal part of the differential operator is the Laplacian.
Online publication 23 January 2004. 相似文献
95.
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
96.
97.
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
98.
Abnormalities in the cochlear function usually cause broadening of the auditory filters which reduces the speech intelligibility. An attempt to apply a spectral enhancement algorithm has been undertaken to improve the identification of Polish vowels by subjects with cochlear-based hearing-impairment. The identification scores of natural (unprocessed) vowels and spectrally enhanced (processed) vowels has been measured for hearing-impaired subjects. It has been found that spectral enhancement improves vowel scores by about 10% for those subjects, however, a wide variation in individual performance among subjects has been observed. The overall vowels identification scores obtained were 85% for natural vowels and 96% for spectrally enhanced vowels. 相似文献
99.
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
100.