全文获取类型
收费全文 | 302077篇 |
免费 | 2822篇 |
国内免费 | 1105篇 |
专业分类
化学 | 142018篇 |
晶体学 | 4238篇 |
力学 | 16256篇 |
综合类 | 5篇 |
数学 | 56433篇 |
物理学 | 87054篇 |
出版年
2021年 | 1996篇 |
2020年 | 2253篇 |
2019年 | 2432篇 |
2018年 | 13063篇 |
2017年 | 12733篇 |
2016年 | 10321篇 |
2015年 | 3692篇 |
2014年 | 4574篇 |
2013年 | 10485篇 |
2012年 | 12269篇 |
2011年 | 20315篇 |
2010年 | 12358篇 |
2009年 | 12481篇 |
2008年 | 15546篇 |
2007年 | 17630篇 |
2006年 | 9172篇 |
2005年 | 9280篇 |
2004年 | 8891篇 |
2003年 | 8296篇 |
2002年 | 7261篇 |
2001年 | 7026篇 |
2000年 | 5536篇 |
1999年 | 4256篇 |
1998年 | 3546篇 |
1997年 | 3487篇 |
1996年 | 3303篇 |
1995年 | 2998篇 |
1994年 | 2834篇 |
1993年 | 2712篇 |
1992年 | 2983篇 |
1991年 | 2914篇 |
1990年 | 2843篇 |
1989年 | 2623篇 |
1988年 | 2678篇 |
1987年 | 2662篇 |
1986年 | 2483篇 |
1985年 | 3255篇 |
1984年 | 3481篇 |
1983年 | 2832篇 |
1982年 | 3020篇 |
1981年 | 2975篇 |
1980年 | 2845篇 |
1979年 | 2915篇 |
1978年 | 3021篇 |
1977年 | 2996篇 |
1976年 | 3016篇 |
1975年 | 2799篇 |
1974年 | 2788篇 |
1973年 | 2909篇 |
1972年 | 1855篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Binding energy spectra of the valence electrons of the open shell molecule NO have been obtained up to 55 eV at azimuthal angles of 0° and 7° using binary (e, 2e) spectroscopy at an impact energy of 1200 eV. The momentum distribution has been obtained for the least tightly bound (unpaired) electron, removal of which leads to formation of the X 1Σ+ ground state of NO+. Momentum distributions have also been measured at 21.0 and 40.5 eV. The measured momentum distributions are compared with several literature wavefunctions of varying complexity. They are found to be in excellent agreement with those calculated using the natural spin orbital wavefunctions of Kouba and Ohrn. 相似文献
112.
113.
本文讨论圆形区域内芽虫分布模型,特别研究了芽虫与天敌接触时产生与避免outbreak状态的可能性。 相似文献
114.
F. D. Saccone C. E. Rodrí guez Torres F. H. S nchez O. Gutfleisch 《Physica B: Condensed Matter》2002,320(1-4):312-315
In the present work, a quantitative analysis of the phase compositions by Mössbauer effect spectroscopy of solid and conventional hydrogen disproportionated Pr13.7Fe80.3B6.0 and Pr13.7Fe63.5Co16.7Zr0.1B6.0 alloys was carried out. Significant amounts of intermediate borides t-Fe3B and Pr(Fe, Co)12B6 were detected after solid hydrogen disproportionation treatment in Pr13.7Fe80.3B6.0 and Pr13.7Fe63.5Co16.7Zr0.1B6.0 alloys, respectively. After conventional hydrogenation–disproportionation–desorption–recombination treatment these phases were not detected and in no case residual Pr2Fe14B-phase was found. It was observed that the amount of intermediate borides after disproportionation can be correlated with the degree of texture after recombination at various temperatures. 相似文献
115.
116.
Thomas Andreae 《Journal of Graph Theory》2002,39(4):222-229
For a graph A and a positive integer n, let nA denote the union of n disjoint copies of A; similarly, the union of ?0 disjoint copies of A is referred to as ?0A. It is shown that there exist (connected) graphs A and G such that nA is a minor of G for all n??, but ?0A is not a minor of G. This supplements previous examples showing that analogous statements are true if, instead of minors, isomorphic embeddings or topological minors are considered. The construction of A and G is based on the fact that there exist (infinite) graphs G1, G2,… such that Gi is not a minor of Gj for all i ≠ j. In contrast to previous examples concerning isomorphic embeddings and topological minors, the graphs A and G presented here are not locally finite. The following conjecture is suggested: for each locally finite connected graph A and each graph G, if nA is a minor of G for all n ? ?, then ?0A is a minor of G, too. If true, this would be a far‐reaching generalization of a classical result of R. Halin on families of disjoint one‐way infinite paths in graphs. © 2002 Wiley Periodicals, Inc. J Graph Theory 39: 222–229, 2002; DOI 10.1002/jgt.10016 相似文献
117.
D. D. Bainov S. I. Kostadinov P. P. Zabreiko 《International Journal of Theoretical Physics》1992,31(8):1521-1526
Necessary and sufficient conditions for the existence of an exponential dichotomy of impulsive differential equations in a Hilbert space are found. 相似文献
118.
D. G. Sannikov 《Physics of the Solid State》1997,39(7):1139-1142
A theoretical temperature-electric field phase diagram is constructed for thiourea SC(ND2)2 using a phenomenological approach based on the representation of the thermodynamic potentials for all phases. The theoretical
diagram is compared with the experimental diagram.
Fiz. Tverd. Tela (St. Petersburg) 39, 1282–1286 (July 1997) 相似文献
119.
A. Jarid M. Aaid Y. Legoux J. Merini M. Loudet D. Gonbeau G. Pfister-Guillouzo 《Chemical physics》1991,150(3):353-360
The electronic and structural characteristics of CrF5, CrF4, RuF5 and RuF4 were studied. Ab initio (SCF-CI) calculations were performed with different structures and spin states for each complex. The favored conformation always corresponds to the highest multiplicity: doublet for CrF5 in D3h, triplet for CrF4 in Td, quadruplet for RuF5 in C4v and quintuplet for RuF4 in D4h symmetry. 相似文献
120.