全文获取类型
收费全文 | 3894篇 |
免费 | 87篇 |
国内免费 | 34篇 |
专业分类
化学 | 2545篇 |
晶体学 | 40篇 |
力学 | 138篇 |
数学 | 598篇 |
物理学 | 694篇 |
出版年
2022年 | 30篇 |
2021年 | 36篇 |
2020年 | 39篇 |
2019年 | 30篇 |
2018年 | 27篇 |
2017年 | 26篇 |
2016年 | 75篇 |
2015年 | 68篇 |
2014年 | 63篇 |
2013年 | 170篇 |
2012年 | 180篇 |
2011年 | 239篇 |
2010年 | 134篇 |
2009年 | 105篇 |
2008年 | 191篇 |
2007年 | 206篇 |
2006年 | 174篇 |
2005年 | 179篇 |
2004年 | 161篇 |
2003年 | 134篇 |
2002年 | 146篇 |
2001年 | 94篇 |
2000年 | 77篇 |
1999年 | 68篇 |
1998年 | 40篇 |
1997年 | 35篇 |
1996年 | 66篇 |
1995年 | 45篇 |
1994年 | 46篇 |
1993年 | 57篇 |
1992年 | 40篇 |
1991年 | 54篇 |
1990年 | 54篇 |
1989年 | 56篇 |
1988年 | 40篇 |
1987年 | 35篇 |
1986年 | 40篇 |
1985年 | 52篇 |
1984年 | 64篇 |
1983年 | 46篇 |
1982年 | 57篇 |
1981年 | 51篇 |
1980年 | 47篇 |
1979年 | 35篇 |
1978年 | 31篇 |
1977年 | 33篇 |
1976年 | 38篇 |
1975年 | 45篇 |
1974年 | 25篇 |
1973年 | 33篇 |
排序方式: 共有4015条查询结果,搜索用时 15 毫秒
81.
82.
83.
Given an expansive action α of ?2 by automorphisms of a compact connected metrizable abelian groupX, we show how the entropy of the action may be decomposed into local contributions, 1 $$h(\alpha ) = \sum\limits_{p \leqslant \infty } {h_p^{(a,b)} } (\alpha )$$ in which the summandh p (a,b) (α) represents thep-adic entropy due to arithmetic or geometric hyperbolicity in the direction (a, b). We recognize thep-adic contribution as an integral over thep-adic unit circle, in analogy with the global counterpart. As (a, b) changes, the decomposition (1) changes only when the line through (a, b) passes through one of a finite collection of critical directions, which are explicitly identified. 相似文献
84.
Cellular algebras 总被引:4,自引:0,他引:4
85.
86.
P. Strasser K. Ishida S. Sakamoto M. Iwasaki E. Torikai K. Nagamine G. M. Marshall 《Hyperfine Interactions》1993,82(1-4):543-549
Slow – production via dd-CF using a two-layer arrangement is investigated. To determine its feasibility, experimental measurements are now in progress using the muonic X-ray detection method. The following experimental steps are being considered: (1) measurement of the number of – stopped inside a solid H2/D2 layer by detecting p K X-rays, (2) hot d emission detection by placing a secondary target at a distance of 10–30 mm from the layer and by detecting specific delayed X-rays, (3) measurement of the disappearance of d emission as the added D2 layer is increased, (4) dd-CF measurement by detecting fusion protons, and (5) slow – emission detection. Results of the initial test experiment are presented. 相似文献
87.
88.
Nimitsiriwat N Marshall EL Gibson VC Elsegood MR Dale SH 《Journal of the American Chemical Society》2004,126(42):13598-13599
In an unprecedented transformation, amide ligands are found to attack the imine carbon centers of tridentate Schiff base ligands attached to tin. The process is reversible, and the resultant (masked) amide species can be exploited as latent single-site initiators for the controlled polymerization of rac-lactide. 相似文献
89.
The thermally stable, terminal phosphinidene complexes [CpM(CO)2(eta1-PNiPr2)]AlCl4(Cp= Cp, Cp*; M = Fe) and [Cp*M(CO)3(eta1-PNiPr2)]AlCl4 (M = Cr, Mo, W) react with Ph2C=N=N to form terminal P-coordinated eta1-phosphaazine and eta3-diazaphosphaallene ligands, respectively, whereas [CpFe(CO)2(eta1-PNiPr2)]AlCl4 reacts with Me3SiCHN2 affording a terminal phosphorus bound eta1-phosphaalkene complex. 相似文献
90.
Graham R. Underwood Brajeswar Paul M. Alice Becker 《Journal of heterocyclic chemistry》1976,13(6):1229-1232
Pyridoxol, protected by acetylation of the hydroxyl groups, has been converted to its N-oxide which upon reaction with perfluoroacetie anhydride yields a 2-nor-2-hydroxymethylpyridoxol derivative as an intermediate. This compound undergoes acyl migration from the 3-position. Protection of the pyridoxol hydroxyls by benzylalion followed by the same treatment yields the unrearranged α2-hydroxy derivative. This compound has been converted to a series of α2-substituted pyridoxols (X = -Cl, -Br, -OCOCH3, -OCH3, -OC2H5). 相似文献