全文获取类型
收费全文 | 92362篇 |
免费 | 8072篇 |
国内免费 | 5934篇 |
专业分类
化学 | 27465篇 |
晶体学 | 535篇 |
力学 | 8145篇 |
综合类 | 1410篇 |
数学 | 46360篇 |
物理学 | 22453篇 |
出版年
2024年 | 134篇 |
2023年 | 763篇 |
2022年 | 1216篇 |
2021年 | 2240篇 |
2020年 | 2138篇 |
2019年 | 2294篇 |
2018年 | 1990篇 |
2017年 | 2108篇 |
2016年 | 2514篇 |
2015年 | 2231篇 |
2014年 | 3630篇 |
2013年 | 7007篇 |
2012年 | 3860篇 |
2011年 | 4694篇 |
2010年 | 4415篇 |
2009年 | 5402篇 |
2008年 | 5712篇 |
2007年 | 5844篇 |
2006年 | 4815篇 |
2005年 | 4100篇 |
2004年 | 3699篇 |
2003年 | 3557篇 |
2002年 | 5898篇 |
2001年 | 3089篇 |
2000年 | 2531篇 |
1999年 | 2240篇 |
1998年 | 2111篇 |
1997年 | 1759篇 |
1996年 | 1535篇 |
1995年 | 1255篇 |
1994年 | 1164篇 |
1993年 | 994篇 |
1992年 | 1006篇 |
1991年 | 747篇 |
1990年 | 649篇 |
1989年 | 506篇 |
1988年 | 497篇 |
1987年 | 395篇 |
1986年 | 408篇 |
1985年 | 533篇 |
1984年 | 467篇 |
1983年 | 271篇 |
1982年 | 486篇 |
1981年 | 637篇 |
1980年 | 558篇 |
1979年 | 602篇 |
1978年 | 462篇 |
1977年 | 356篇 |
1976年 | 311篇 |
1973年 | 186篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Willem Hundsdorfer. 《Mathematics of Computation》1998,67(221):183-190
In this note some stability results are derived for the Douglas splitting method. The relevance of the theoretical results is tested for an advection-reaction equation.
992.
We use boundary value methods to compute consistent initial values for fully implicit nonlinear differential-algebraic equations.
The obtained algorithm uses variable order formulae and a deferred correction technique to evaluate the error. A rigorous
theory is stated for nonlinear index 1, 2 and 3 DAEs of Hessenberg form. Numerical tests on classical index 1, 2 and 3 DAE
problems are reported.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
993.
Comparison of Two Reformulation-Linearization Technique Based Linear Programming Relaxations for Polynomial Programming Problems 总被引:3,自引:0,他引:3
In this paper, we compare two strategies for constructing linear programmingrelaxations for polynomial programming problems using aReformulation-Linearization Technique (RLT). RLT involves an automaticreformulation of the problem via the addition of certain nonlinear impliedconstraints that are generated by using the products of the simple boundingrestrictions (among other products), and a subsequent linearization based onvariable redefinitions. We prove that applying RLT directly to the originalpolynomial program produces a bound that dominates in the sense of being atleast as tight as the value obtained when RLT is applied to the jointcollection of all equivalent quadratic problems that could be constructed byrecursively defining additional variables as suggested by Shor. 相似文献
994.
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
995.
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
996.
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
997.
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
998.
吕海深 《Annals of Differential Equations》2004,20(2):133-139
Under suitable conditions on f(·,u), it is shown that the two-point boundaryvalue problem((u'))' + λq(t)f(u) = 0in (0, 1),u(0) = u(1) = 0,has two positive solution or at least one positive solution for λ in a compatibleinterval. 相似文献
999.
1000.