全文获取类型
收费全文 | 32859篇 |
免费 | 4265篇 |
国内免费 | 2424篇 |
专业分类
化学 | 5611篇 |
晶体学 | 109篇 |
力学 | 5375篇 |
综合类 | 560篇 |
数学 | 14184篇 |
物理学 | 13709篇 |
出版年
2024年 | 68篇 |
2023年 | 336篇 |
2022年 | 876篇 |
2021年 | 892篇 |
2020年 | 1017篇 |
2019年 | 913篇 |
2018年 | 851篇 |
2017年 | 1157篇 |
2016年 | 1353篇 |
2015年 | 998篇 |
2014年 | 1700篇 |
2013年 | 2614篇 |
2012年 | 1778篇 |
2011年 | 2129篇 |
2010年 | 1854篇 |
2009年 | 2216篇 |
2008年 | 2073篇 |
2007年 | 2094篇 |
2006年 | 1742篇 |
2005年 | 1554篇 |
2004年 | 1397篇 |
2003年 | 1249篇 |
2002年 | 1175篇 |
2001年 | 928篇 |
2000年 | 881篇 |
1999年 | 769篇 |
1998年 | 722篇 |
1997年 | 551篇 |
1996年 | 450篇 |
1995年 | 422篇 |
1994年 | 368篇 |
1993年 | 319篇 |
1992年 | 286篇 |
1991年 | 215篇 |
1990年 | 186篇 |
1989年 | 149篇 |
1988年 | 151篇 |
1987年 | 157篇 |
1986年 | 130篇 |
1985年 | 156篇 |
1984年 | 149篇 |
1983年 | 82篇 |
1982年 | 113篇 |
1981年 | 70篇 |
1980年 | 36篇 |
1979年 | 44篇 |
1978年 | 36篇 |
1977年 | 33篇 |
1976年 | 24篇 |
1973年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
We consider a two-dimensional Coulomb gas of positive and negative pointlike unit charges interacting via a logarithmic potential. The density (rather than the charge) correlation functions are studied. In the bulk, the form-factor theory of an equivalent sine-Gordon model is used to determine the density correlation length. At the surface of a rectilinear plain wall, the universality of the asymptotic behavior of the density correlations is suggested. A scaling analysis implies a local form of the compressibility sum rule near a hard wall. A symmetry of the Coulomb system with respect to the Möbius conformal transformation, which induces a gravitational source acting on the particle density, is established. Among the consequences, a universal term of the finite-size expansion of the grand potential is derived exactly for a disk geometry of the confining domain. 相似文献
132.
金融时间序列分析与建模 总被引:1,自引:0,他引:1
胡锡健 《新疆大学学报(理工版)》2007,24(2):150-158
介绍了金融时间序列分析与建模的主要理论、方法,着重论述了近20多年发展起来的非平稳时间序列的建模方法及工具,指出进一步的研究方向.最后,对上证综合指数这一金融时间序列进行了实证分析. 相似文献
133.
Rostislav Vodák 《Mathematical Methods in the Applied Sciences》2007,30(1):43-75
We consider a sequence of curved rods which consist of isotropic material and which are clamped on the lower base or on both bases. We study the asymptotic behaviour of the stress tensor and displacement under the assumptions of linearized elasticity when the cross‐sectional diameter of the rods tends to zero and the body force is given in the particular form. The analysis covers the case of a non‐smooth limit line of centroids. We show how the body force and the choice of the approximating curved rods can affect the strong convergence and the limit form of the stress tensor for the curved rods clamped on both bases. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
134.
The fully frustrated planar rotator and fully frustrated XY models in two dimensions have two phase transitions: one of the Berezinskii–Kosterlitz–Thouless type and other in the Ising universality class. We use Monte Carlo simulation to study both models. We fix our attention in the Ising-like transition, which we show can be understood as a percolation transition. We obtain the critical temperature as well as the critical exponents of the mean cluster size, γ, and Fisher's exponent τ. The critical temperature agree very well with other calculations. We found that the critical exponents are smaller than in the pure two-dimensional percolation case. We interpret this as due to the long-range interaction between vortex and antivortex. 相似文献
135.
136.
We study the large-sample properties of a class of parametric mixture models with covariates for competing risks. The models allow general distributions for the survival times and incorporate the idea of long-term survivors. Asymptotic results are obtained under a commonly assumed independent censoring mechanism and some modest regularity conditions on the survival distributions. The existence, consistency, and asymptotic normality of maximum likelihood estimators for the parameters of the model are rigorously derived under general sufficient conditions. Specific conditions for particular models can be derived from the general conditions for ready check. In addition, a likelihood-ratio statistic is proposed to test various hypotheses of practical interest, and its asymptotic distribution is provided. 相似文献
137.
Shengqiang Liu Lansun ChenYoulin Jiang 《Journal of Mathematical Analysis and Applications》2002,271(1):124-138
In this paper, a two-species competitive model with stage structure is presented and studied. Results on the global extinction and permanence are given, which generalize the well-known three theorems for the two species competitive system and, moreover, they confirm the negative effect of stage structure on the permanence of populations as well as estimate the degree of such effect. Conclusions in this paper suggest that for a competitive community stage structure is also one of the important reasons that cause permanence and extinction. 相似文献
138.
Suppose there is a Poisson process of points X
i
on the line. Starting at time zero, a grain begins to grow from each point X
i
, growing at rate A
i
to the left and rate B
i
to the right, with the pairs (A
i
, B
i
) being i.i.d. A grain stops growing as soon as it touches another grain. When all growth stops, the line consists of covered intervals (made up of contiguous grains) separated by gaps. We show (i) a fraction 1/e of the line remains uncovered, (ii) the fraction of covered intervals which contain exactly k grains is (k–1)/k!, (iii) the length of a covered interval containing k grains has a gamma(k–1) distribution, (iv) the distribution of the grain sizes depends only on the distribution of the total growth rate A
i
+B
i
, and other results. Similar theorems are obtained for growth processes on a circle; in this case we need only assume the pairs (A
i
, B
i
) are exchangeable. These results extend those of Daley, et al. (2000) who studied the case where A
i
=B
i
=1. Simulation results are given to illustrate the various theorems. 相似文献
139.
140.
通过考虑同类核子相干对间的四极相互作用,在IBM2中对Ce偶-偶同位素^128Ce-^138Ce的低激发态能谱和E2跃迁几率及分支比进行了理论分析,计算结果有效地改善了IBM中这些核的γ带能谱的Staggering现象描述,与实验观察到的低激发态结果基本一致。 相似文献