全文获取类型
收费全文 | 27730篇 |
免费 | 3167篇 |
国内免费 | 1415篇 |
专业分类
化学 | 1828篇 |
晶体学 | 153篇 |
力学 | 4507篇 |
综合类 | 257篇 |
数学 | 18008篇 |
物理学 | 7559篇 |
出版年
2024年 | 58篇 |
2023年 | 281篇 |
2022年 | 321篇 |
2021年 | 422篇 |
2020年 | 737篇 |
2019年 | 726篇 |
2018年 | 687篇 |
2017年 | 778篇 |
2016年 | 803篇 |
2015年 | 674篇 |
2014年 | 1193篇 |
2013年 | 2587篇 |
2012年 | 1212篇 |
2011年 | 1538篇 |
2010年 | 1303篇 |
2009年 | 1679篇 |
2008年 | 1698篇 |
2007年 | 1696篇 |
2006年 | 1578篇 |
2005年 | 1359篇 |
2004年 | 1221篇 |
2003年 | 1215篇 |
2002年 | 1144篇 |
2001年 | 915篇 |
2000年 | 927篇 |
1999年 | 832篇 |
1998年 | 694篇 |
1997年 | 640篇 |
1996年 | 457篇 |
1995年 | 357篇 |
1994年 | 319篇 |
1993年 | 295篇 |
1992年 | 221篇 |
1991年 | 207篇 |
1990年 | 167篇 |
1989年 | 119篇 |
1988年 | 110篇 |
1987年 | 100篇 |
1986年 | 81篇 |
1985年 | 125篇 |
1984年 | 141篇 |
1983年 | 70篇 |
1982年 | 94篇 |
1981年 | 104篇 |
1980年 | 80篇 |
1979年 | 79篇 |
1978年 | 90篇 |
1977年 | 60篇 |
1976年 | 43篇 |
1974年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
对求解非线性方程方法的探索 总被引:2,自引:0,他引:2
BaiCL在2001年提出了双曲函数法,并把解设成具体的双曲函数,即sinhw和coshw的线性组合.本文把解设成是由2个函数f(ξ)和g(ξ)组成的线性组合,它们可以有多种取法,从而使方程更直接、更有效.借助数学软件Maple,用改进后的方法和吴文俊消元法,求解Bai C L文中的一个例子,获得了包含Bai文结果在内的更为丰富、精确的行波解. 相似文献
73.
François Nicoleau 《Journal of Differential Equations》2004,205(2):354-364
We study an inverse scattering problem for a pair of Hamiltonians (H,H0) on L2(Rn), where H0=-Δ and H=H0+V, V being a short- or long-range potential. By an elementary constructive method, we show that the scattering operator S, which is localized near a fixed energy λ>0, determines the asymptotics of the potential V at infinity, in dimension n?3. This is done by studying the action of the scattering operator on suitable wave packets. 相似文献
74.
We treat here of the question of absorbing boundary conditionsfor nonlinear diffusion equations. We use the conditions designedfor the linear equation, we prove them to be well posed forthe nonlinear problem, and through numerical experiments thatthey are well suited for reactiondiffusion equations. 相似文献
75.
V. I. Sakharov 《Fluid Dynamics》2007,42(6):1007-1016
The results of numerical simulation are presented for thermally and chemically nonequilibrium air plasma flows in a plasmatron discharge channel and underexpanded dissociated and partially ionized air jets flowing past a cylindrical model with a blunt leading edge and cooled copper surface under the experimental conditions realized in a VGU-4 100 kW induction plasmatron (Institute for Problems in Mechanics of the Russian Academy of Sciences) (see, for example, [1, 2]). The nonequilibrium excitation of the vibrational degrees of freedom of the molecules in the modal approximation and the difference between the electron and translational heavy-particle temperatures are taken into account in the calculations. The calculated data on the heat transfer and pressure at the stagnation point are compared with the results obtained within the framework of the thermally equilibrium model. Comparison with the experimental data obtained in the Institute for Problem in Mechanics of the Russian Academy of Sciences (Laboratory for interaction between plasma and radiation and materials) and kindly provided for comparison purposes gives satisfactory agreement. 相似文献
76.
The title compound (C2H7NO·C7H4N2O6) has been obtained by the reaction of etha- nolamine with 3,5-dinitrobenzoic acid in deionized water at room temperature. The crystal crystal- lizes in orthorhombic, space group P212121 with a = 6.048(2), b = 9.146(3), c = 21.955(7)(A), C9H11N3O7, Mr = 273.21, Z = 4, V = 1214.3(7)(A)3, Dc = 1.494 g/cm3, F(000) = 568, μ(MoKα) = 0.131 mm-1, R1 = 0.0338 and wR2 = 0.0497. The new organic adduct is composed of one ethanolamine and one 3,5-dinitrobenzoic acid, which are linked up by O-H…O and N-H…O types of hydrogen bonds to form a nine-membered ring and an eleven-membered ring, extending into a one-dimensional network structure. 相似文献
77.
78.
Lihong Wang 《Annals of the Institute of Statistical Mathematics》2004,56(2):251-264
The purpose of this paper is to investigate the asymptotic properties of the least squares estimates (L
2-estimates) and the least absolute deviation estimates (L
1-estimates) of the parameters of a nonlinear regression model subject to a set of equality and inequality restrictions, which
has a long-range dependent stationary process as its stochastic errors. Then we will compare the asymptotic relative efficiencies
of the above estimators. 相似文献
79.
Frank Jochmann 《Journal of Differential Equations》2004,203(2):232-254
In this paper, Maxwell's equations involving generally nonlinear polarization and field-dependent currents are studied. The main objective is the asymptotic behavior of the solution for t→∞ if no damping term occurs in the equation governing the polarization field. 相似文献
80.
提出了一种比较系统的求解非线性发展方程精确解的新方法, 即试探方程法. 以一个带5阶 导数项的非线性发展方程为例, 利用试探方程法化成初等积分形式,再利用三阶多项式的完 全判别系统求解,由此求得的精确解包括有理函数型解, 孤波解, 三角函数型周期解, 多项 式型Jacobi椭圆函数周期解和分式型Jacobi椭圆函数周期解
关键词:
试探方程法
非线性发展方程
孤波解
Jacobi椭圆函数
周期解 相似文献