全文获取类型
收费全文 | 1506篇 |
免费 | 50篇 |
国内免费 | 26篇 |
专业分类
化学 | 849篇 |
晶体学 | 21篇 |
力学 | 28篇 |
数学 | 377篇 |
物理学 | 307篇 |
出版年
2023年 | 7篇 |
2022年 | 23篇 |
2021年 | 22篇 |
2020年 | 26篇 |
2019年 | 28篇 |
2018年 | 12篇 |
2017年 | 22篇 |
2016年 | 36篇 |
2015年 | 35篇 |
2014年 | 32篇 |
2013年 | 82篇 |
2012年 | 89篇 |
2011年 | 82篇 |
2010年 | 55篇 |
2009年 | 49篇 |
2008年 | 80篇 |
2007年 | 86篇 |
2006年 | 100篇 |
2005年 | 90篇 |
2004年 | 78篇 |
2003年 | 54篇 |
2002年 | 72篇 |
2001年 | 18篇 |
2000年 | 33篇 |
1999年 | 22篇 |
1998年 | 27篇 |
1997年 | 16篇 |
1996年 | 23篇 |
1995年 | 16篇 |
1994年 | 29篇 |
1993年 | 23篇 |
1992年 | 24篇 |
1991年 | 16篇 |
1990年 | 17篇 |
1989年 | 13篇 |
1988年 | 8篇 |
1986年 | 9篇 |
1985年 | 6篇 |
1984年 | 9篇 |
1983年 | 9篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1978年 | 13篇 |
1977年 | 8篇 |
1976年 | 7篇 |
1975年 | 12篇 |
1973年 | 7篇 |
1972年 | 7篇 |
1971年 | 4篇 |
排序方式: 共有1582条查询结果,搜索用时 15 毫秒
1.
Pál Sohár Gábor Bernáth Géza Stájer Angela E. Szabo 《Magnetic resonance in chemistry : MRC》1989,27(9):872-876
Pentacyclic isoxazolines were obtained by the cycloaddition of benzonitrile oxide to norbornene-azetidinone-fused 3,1-oxazines. The constitutions of two of the isomers obtained, and the configurations and conformations of all products, were determined by means of 1H and 13C NMR spectroscopy and DNOE experiments. 相似文献
2.
This report focuses on a theoretical study of the cobalt-cabon bond activation mechanism in Vitamin B12, its co enzyme complexes, and model compounds such as cobalamins (Cbl), cobaloximes and cobalt porphyrins. In particular, emphasis is placed on the nucleotide loop and its role in the base on and base off mechanism. 相似文献
3.
The regression problem in learning theory is investigated with least square Tikhonov regularization schemes in reproducing
kernel Hilbert spaces (RKHS). We follow our previous work and apply the sampling operator to the error analysis in both the
RKHS norm and the L2 norm. The tool for estimating the sample error is a Bennet inequality for random variables with values in Hilbert spaces.
By taking the Hilbert space to be the one consisting of Hilbert-Schmidt operators in the RKHS, we improve the error bounds
in the L2 metric, motivated by an idea of Caponnetto and de Vito. The error bounds we derive in the RKHS norm, together with a Tsybakov
function we discuss here, yield interesting applications to the error analysis of the (binary) classification problem, since
the RKHS metric controls the one for the uniform convergence. 相似文献
4.
5.
H. M. Phillips D. L. Callahan R. Sauerbrey G. Szabo Z. Bor 《Applied Physics A: Materials Science & Processing》1992,54(2):158-165
Periodic line structures with a period of 167 nm and linewidths varying from 30 to 100 nm have been produced in polyimide by direct ablation with a KrF laser using an interferometric technique. The characteristics of this interferometer as it applies to the ablation of these line structures, including linewidth and alignment sensitivity, are analyzed. The ability to control the linewidth by varying the average incident fluence is described theoretically and demonstrated experimentally. This externally generated period of 167 nm also prevents the spontaneous growth of laser induced periodic surface structures (LIPSS). 相似文献
6.
7.
8.
9.
Felipe Cucker Steve Smale Ding-Xuan Zhou 《Foundations of Computational Mathematics》2004,4(3):315-343
We describe a model for the evolution of the languages used by the agents of a
society. Our main result proves convergence of these languages to a common
one under certain conditions. A few special cases are elaborated in more
depth. 相似文献
10.
We give asymptotic formulas for the multiplicities of weights and irreducible summands in high-tensor powers Vλ⊗N of an irreducible representation Vλ of a compact connected Lie group G. The weights are allowed to depend on N, and we obtain several regimes of pointwise asymptotics, ranging from a central limit region to a large deviations region. We use a complex steepest descent method that applies to general asymptotic counting problems for lattice paths with steps in a convex polytope. 相似文献