全文获取类型
收费全文 | 47110篇 |
免费 | 2600篇 |
国内免费 | 3974篇 |
专业分类
化学 | 31065篇 |
晶体学 | 600篇 |
力学 | 621篇 |
综合类 | 716篇 |
数学 | 8887篇 |
物理学 | 11795篇 |
出版年
2023年 | 748篇 |
2022年 | 2020篇 |
2021年 | 1790篇 |
2020年 | 1064篇 |
2019年 | 1065篇 |
2018年 | 852篇 |
2017年 | 886篇 |
2016年 | 1061篇 |
2015年 | 1119篇 |
2014年 | 1448篇 |
2013年 | 2618篇 |
2012年 | 1929篇 |
2011年 | 2238篇 |
2010年 | 2092篇 |
2009年 | 2746篇 |
2008年 | 2831篇 |
2007年 | 2970篇 |
2006年 | 2295篇 |
2005年 | 1553篇 |
2004年 | 1415篇 |
2003年 | 1369篇 |
2002年 | 3845篇 |
2001年 | 1475篇 |
2000年 | 1042篇 |
1999年 | 844篇 |
1998年 | 814篇 |
1997年 | 598篇 |
1996年 | 691篇 |
1995年 | 586篇 |
1994年 | 567篇 |
1993年 | 571篇 |
1992年 | 555篇 |
1991年 | 380篇 |
1990年 | 324篇 |
1989年 | 277篇 |
1988年 | 298篇 |
1987年 | 207篇 |
1986年 | 219篇 |
1985年 | 369篇 |
1984年 | 258篇 |
1983年 | 173篇 |
1982年 | 315篇 |
1981年 | 509篇 |
1980年 | 460篇 |
1979年 | 487篇 |
1978年 | 407篇 |
1977年 | 311篇 |
1976年 | 260篇 |
1974年 | 130篇 |
1973年 | 208篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
291.
E. F. Kvashina 《Russian Chemical Bulletin》1994,43(12):2121-2121
The interaction of ditoluenetitanium with CO{in2} has been studied. Based on hydrolysis, thermolysis, and IR spectral data, the conclusion is drawn that a low-valent titanium oxalate is formed.This study was financially supported by the Russian Foundation for Basic Research (Project No. 93-03-5538).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2241–2242, December, 1994. 相似文献
292.
We consider the semilinear Cauchy problem for a class of pseudo-differential operators generating sub-Markovian semigroups.
Solutions of such problems with negative definite nonlinearity play an important role in constructing branching measure-valued
processes. We establish local existence and uniqueness of solutions in the context of the Dirichlet space associated to the
problem. Comparison and global properties of solutions are also studied.
Accepted 29 August 2001. Online publication 17 December 2001. 相似文献
293.
Bruno Zimmermann 《Monatshefte für Mathematik》2002,135(3):253-258
We give a list including all finite groups G which admit smooth orientation preserving actions on homology 3-spheres (arbitrary actions, i.e. possibly with fixed points;
if the action is free then the group G has periodic cohomology and the classification of such groups is well known). The main work in this direction is due to M.
Reni. In the present paper, we complete and extend his results for the case of nonsolvable groups G.
Received 19 March 2001; in revised form 15 September 2001 相似文献
294.
D.P. Woodruff 《Surface science》2002,500(1-3):147-171
The range of surface structural problems of interest in understanding the physics and chemistry of solid surfaces is reviewed with reference to the available methods and their strengths and limitations. Key challenges being addressed currently concern the achievable precision of measurements and their physical and chemical significance, and the complexity of the problems which may be solved. Past progress and future problems are illustrated with a series of examples ranging from the relaxation of simple clean metal surfaces through complex semiconductor reconstructions to large molecular adsorption and coadsorption systems and complex adsorbate-induced reconstructions. The strengths and limitations of scanning tunnelling microscopy as a complement to true quantitative structural methods are discussed, as is the role of chemical state specificity and elemental specificity in solving complex molecular adsorbate systems. 相似文献
295.
R_FN(O )R_F和R_FNO的F113溶液在室温下与一系列的对位取代苯甲醛反应,得到稳定的对位取代苯甲酰基全氟烷基氮氧自由基。由△a_N和△a_F~β的σ单参数相关以及△a_N与σ和σ 双参数相关表明:极性效应是影响氟烷基酰基氮氧自由基中氮原子自旋密度变化的主要因素,而自旋离域效应的影响是很小的。 相似文献
296.
Yuval Z. Flicker 《Mathematische Annalen》1993,297(1):199-219
297.
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
298.
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
299.
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
300.
In this paper,we research general Defective Cion Problem under the model S,i.e,the number d of Defective cions is not fixed. For d=O,1,or 2. we get some good results. 相似文献