全文获取类型
收费全文 | 95508篇 |
免费 | 9622篇 |
国内免费 | 8339篇 |
专业分类
化学 | 35328篇 |
晶体学 | 1126篇 |
力学 | 11911篇 |
综合类 | 1750篇 |
数学 | 36564篇 |
物理学 | 26790篇 |
出版年
2024年 | 132篇 |
2023年 | 828篇 |
2022年 | 1299篇 |
2021年 | 2732篇 |
2020年 | 2351篇 |
2019年 | 2255篇 |
2018年 | 2040篇 |
2017年 | 2648篇 |
2016年 | 3163篇 |
2015年 | 2680篇 |
2014年 | 4253篇 |
2013年 | 6280篇 |
2012年 | 4881篇 |
2011年 | 5609篇 |
2010年 | 4924篇 |
2009年 | 5890篇 |
2008年 | 5904篇 |
2007年 | 6137篇 |
2006年 | 5261篇 |
2005年 | 4507篇 |
2004年 | 3826篇 |
2003年 | 3657篇 |
2002年 | 5874篇 |
2001年 | 3212篇 |
2000年 | 2648篇 |
1999年 | 2307篇 |
1998年 | 2169篇 |
1997年 | 1815篇 |
1996年 | 1607篇 |
1995年 | 1316篇 |
1994年 | 1230篇 |
1993年 | 1069篇 |
1992年 | 1033篇 |
1991年 | 749篇 |
1990年 | 665篇 |
1989年 | 504篇 |
1988年 | 511篇 |
1987年 | 398篇 |
1986年 | 358篇 |
1985年 | 525篇 |
1984年 | 411篇 |
1983年 | 240篇 |
1982年 | 422篇 |
1981年 | 574篇 |
1980年 | 485篇 |
1979年 | 538篇 |
1978年 | 429篇 |
1977年 | 335篇 |
1976年 | 279篇 |
1973年 | 173篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
951.
Backlund transformation and variable separation solutions for the generalized Nozhnik—Novikov—Veselov equation 下载免费PDF全文
Using the extended homogeneous balance method, the B?cklund transformation for a (2+1)-dimensional integrable model, the generalized Nizhnik-Novikov-Veselov (GNNV) equation, is first obtained. Also, making use of the B?cklund transformation, the GNNV equation is changed into three equations: linear, bilinear and trilinear form equations. Starting from these three equations, a rather general variable separation solution of the model is constructed. The abundant localized coherent structures of the model can be induced by the entrance of two variable-separated arbitrary functions. 相似文献
952.
s个几乎相等的素数的k次方和(Ⅰ) 总被引:1,自引:0,他引:1
孟宪萌 《纯粹数学与应用数学》2002,18(1):5-12
假定pθ‖k,当p=2,2|k时,γ=θ 2;其它情况时,γ=θ 1。而R=П(p-1)|kp^γ。本文在GRH(广义Riemann假设下),证明了当s=2^k 1,1≤k≤11时,任何足够大的整N≡s(modR)都可以表示为s个几乎相等的素数的k次方程。 相似文献
953.
Liqun Qi 《Operations Research Letters》1997,20(5):223-228
We show that strong differentiability at solutions is not necessary for superlinear convergence of quasi-Newton methods for solving nonsmooth equations. We improve the superlinear convergence result of Ip and Kyparisis for general quasi-Newton methods as well as the Broyden method. For a special example, the Newton method is divergent but the Broyden method is superlinearly convergent. 相似文献
954.
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
955.
Experiments employing photoreflectance spectroscopy have uncovered band bending due to electrically active defects at the Si(1 1 1)–SiO2 interface after sub-keV Ar+ ion bombardment. The band bending of about 0.5 eV resembles that for Si(1 0 0)–SiO2, and both interfaces exhibit two kinetic regimes for the evolution of band bending upon annealing due to defects healing. The healing takes place about an order of magnitude more quickly at the (1 1 1) interface, however, probably because of less fully saturated bonding and higher compressive stress. 相似文献
956.
Koichi Itoh Takeji Takui 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2004,80(2):29
This review paper deals with an overview of molecule-based magnetism as a rapidly developing interdisciplinary field, topological symmetry rule as the first principle of spin alignment in organic open-shell systems in the ground state, the proposal of organic through-bond 1D and 2D ferro- and superparamagnets and the detection of the first organic high-spin molecule, m-phenylenebis(phenylmethylene) in the quintet ground state (S = 2), followed by extended organic high-spin systems with π-conjugation such as aromatic hydrocarbons having S = 3, 4, 5. The paper also describes a theoretical approach to the understanding of electronic spin structures of organic high-spin molecules by invoking both Heisenberg and Hubbard model Hamiltonians, weakly interacting intramolecular high-spin systems from both experimental and theoretical sides, the spin density distribution of the first organic high-spin molecule in terms of electron- nuclear multiple resonance spectroscopy and the detection and characterization of ionic high-spin hydrocarbons, emphasizing the establishment of high spin chemistry underlying organic molecular magnetism. 相似文献
957.
H. Kuramochi J. Okabayashi F. Takano M. Mizuguchi T. Manago H. Akinaga 《Surface science》2004,550(1-3):192-198
Strong magnetic poles at characteristic rectangular defects have been observed using a magnetic force microscope on a MnAs(
1 0 0) thin film with the thickness of 30 nm. The MnAs thin film was epitaxially grown on a GaAs(0 0 1) substrate. The magnetic poles were in one-arranging direction, being independent of the magnetization direction of the film. The poles were pinned at the edges of the rectangular defects until just below the Curie temperature, and formed a stable magnetic-field loop on the MnAs surface. The stability of the magnetic pole pinning shows the distinctive feature of the magnetic domain structure on the surface with a strong anisotropy, which was built in the heterostructure of MnAs and GaAs. 相似文献
958.
The problem of computing light scattering by cylindrical fibers with high aspect ratio in the framework of the Null‐Field method with discrete sources is treated. Numerical experiments for investigating the scattering properties of two fiber geometries are performed using distributed spherical vector wave functions as discrete sources. 相似文献
959.
960.
信息化对区域经济影响的数理分析 总被引:7,自引:0,他引:7
本文以信息化与经济指标资料为基础,运用加权回归、因子分析和聚类分析等方法,讨论了全国31个省(市、区)信息化水平及其与经济发展关系,给出地区综合发展水平的排行榜。并提出若干促进信息化建设的建议。 相似文献