全文获取类型
收费全文 | 10241篇 |
免费 | 353篇 |
国内免费 | 556篇 |
专业分类
化学 | 1855篇 |
晶体学 | 57篇 |
力学 | 843篇 |
综合类 | 15篇 |
数学 | 5619篇 |
物理学 | 2761篇 |
出版年
2024年 | 11篇 |
2023年 | 97篇 |
2022年 | 107篇 |
2021年 | 110篇 |
2020年 | 160篇 |
2019年 | 164篇 |
2018年 | 176篇 |
2017年 | 198篇 |
2016年 | 223篇 |
2015年 | 239篇 |
2014年 | 502篇 |
2013年 | 891篇 |
2012年 | 532篇 |
2011年 | 733篇 |
2010年 | 595篇 |
2009年 | 724篇 |
2008年 | 734篇 |
2007年 | 742篇 |
2006年 | 508篇 |
2005年 | 386篇 |
2004年 | 354篇 |
2003年 | 333篇 |
2002年 | 270篇 |
2001年 | 226篇 |
2000年 | 242篇 |
1999年 | 227篇 |
1998年 | 197篇 |
1997年 | 228篇 |
1996年 | 151篇 |
1995年 | 158篇 |
1994年 | 139篇 |
1993年 | 93篇 |
1992年 | 81篇 |
1991年 | 54篇 |
1990年 | 54篇 |
1989年 | 35篇 |
1988年 | 23篇 |
1987年 | 38篇 |
1986年 | 37篇 |
1985年 | 46篇 |
1984年 | 47篇 |
1983年 | 34篇 |
1982年 | 39篇 |
1981年 | 34篇 |
1980年 | 42篇 |
1979年 | 48篇 |
1978年 | 28篇 |
1977年 | 28篇 |
1976年 | 14篇 |
1974年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
Jaume GINE 《数学学报(英文版)》2006,22(6):1613-1620
The centers of the polynomial differential systems with homogeneous polynomials have been studied for the degrees s = 2, 3, 4, 5. for s = 2, 3, and partially classified for s = 4, 5. In this paper we recall and we give new centers for s = 6, 7 a linear center perturbed by They are completely classified these results for s = 2, 3, 4, 5, 相似文献
102.
提出一种关于求解常微线性系统的离散波形松驰方法的新的加速收敛技巧。通过对系统矩阵A的分裂,该技巧使迭代矩阵((zI M)^-1N)具有理想的较小谱半径。在LU分解的基础上给出了一个迭代算法以及用该法与Gauss-Seidel方不垢敛速进行比较的数值例子。 相似文献
103.
Th. Friedrich I. Kath A. Moroianu U. Semmelmann 《Journal of Geometry and Physics》1997,23(3-4):259-286
A nearly parallel G2-structure on a seven-dimensional Riemannian manifold is equivalent to a spin structure with a Killing spinor. We prove general results about the automorphism group of such structures and we construct new examples. We classify all nearly parallel G2-manifolds with large symmetry group and in particular all homogeneous nearly parallel G2-structures. 相似文献
104.
An approximate method is developed to solve the full nonlinear equations governing two-dimensional irrotational flow in a free waterfall, falling under the influence of gravity, at high Froude number based on conditions far upstream. Schwarz—Christoffel transformation is used to map the region, in the complex potential-plane, onto the upper half-plane. The Hilbert transformation as well as the perturbation technique, for large Froude number, are used as a basis for the approximate solution of the problem. A complete solution, up to second-order approximation, for the downstream free-surfaces profiles, for different Froude number, is discussed and illustrated. The obtained approximate solutions are compared with those of other authors. Favourable agreement with other results suggests that this method is effective in dealing with flow problems strongly influenced by gravity and high Froude number. The results obtained by this method are sufficiently accurate for practical purposes. 相似文献
105.
The asymptotic null distribution of the likelihood ratio test for two cases of ordered hypotheses in a particular genetic model is considered. A simple iterative process is proposed in order to get the restricted estimates. It is shown that both tests have asymptotically a chi-bar squared distribution and the same size. A simulation study is also conducted in order to compare the usual unrestricted test with the corresponding one of ordered hypotheses. Finally, the results are extended to some special cases. 相似文献
106.
A mean-field model of nonlinearly coupled oscillators with randomly distributed frequencies and subject to independent external white noises is analyzed in the thermodynamic limit. When the frequency distribution isbimodal, new results include subcritical spontaneous stationary synchronization of the oscillators, supercritical time-periodic synchronization, bistability, and hysteretic phenomena. Bifurcating synchronized states are asymptotically constructed near bifurcation values of the coupling strength, and theirnonlinear stability properties ascertained. 相似文献
107.
We investigate the propeties of differential algebras generated by an operator d satisfying the property dN = 0 instead of d2 = 0 as in the usual case. Several examples of realizations of such differential algebras are given, either in the context of ZN-graded N × N matrix algebras, or as a generalized differential calculus on manifolds. 相似文献
108.
大型稀疏无约束最优化问题的行列修正算法 总被引:3,自引:0,他引:3
本文提出了一类适用于大型稀疏最优化问题的简单易行的行列修正算法,获得了新算法的局部超一性收敛性,大量的数值试验表明这是一个较为理想的修正算不。新算法同样可以用来求解大型对称性非线性方程组。 相似文献
109.
Alain Lascoux 《Bulletin des Sciences Mathématiques》2006,130(4):354-359
Eliminating the arbitrary coefficients in the equation of a generic plane curve of order n by computing sufficiently many derivatives, one obtains a differential equation. This is a projective invariant. The first one, corresponding to conics, has been obtained by Monge. Sylvester, Halphen, Cartan used invariants of higher order. The expression of these invariants is rather complicated, but becomes much simpler when interpreted in terms of symmetric functions. 相似文献
110.
TANGWEIJUN 《高校应用数学学报(英文版)》1997,12(4):427-440
In this paper, a new method of boundary reduction is proposed, which reduces thesteady-state heat transfer equation with radiation. Moreover, a boundary element method is pre-sented for its solution and the error estimates of the numerical approximations are given. 相似文献