全文获取类型
收费全文 | 2321篇 |
免费 | 81篇 |
国内免费 | 7篇 |
专业分类
化学 | 1658篇 |
晶体学 | 25篇 |
力学 | 56篇 |
数学 | 319篇 |
物理学 | 351篇 |
出版年
2022年 | 18篇 |
2021年 | 25篇 |
2020年 | 22篇 |
2019年 | 28篇 |
2018年 | 21篇 |
2017年 | 10篇 |
2016年 | 53篇 |
2015年 | 51篇 |
2014年 | 63篇 |
2013年 | 146篇 |
2012年 | 120篇 |
2011年 | 147篇 |
2010年 | 91篇 |
2009年 | 68篇 |
2008年 | 128篇 |
2007年 | 125篇 |
2006年 | 139篇 |
2005年 | 123篇 |
2004年 | 127篇 |
2003年 | 97篇 |
2002年 | 90篇 |
2001年 | 21篇 |
2000年 | 29篇 |
1999年 | 22篇 |
1998年 | 26篇 |
1997年 | 29篇 |
1996年 | 35篇 |
1995年 | 25篇 |
1994年 | 27篇 |
1993年 | 25篇 |
1992年 | 17篇 |
1991年 | 23篇 |
1990年 | 18篇 |
1989年 | 26篇 |
1988年 | 21篇 |
1987年 | 13篇 |
1986年 | 20篇 |
1985年 | 34篇 |
1984年 | 33篇 |
1983年 | 23篇 |
1982年 | 22篇 |
1981年 | 28篇 |
1980年 | 30篇 |
1979年 | 20篇 |
1978年 | 17篇 |
1977年 | 23篇 |
1976年 | 15篇 |
1975年 | 22篇 |
1974年 | 12篇 |
1973年 | 20篇 |
排序方式: 共有2409条查询结果,搜索用时 0 毫秒
61.
62.
63.
64.
65.
In 1977 the celebrated theorem of B. Dahlberg established that the harmonic measure is absolutely continuous with respect to the Hausdorff measure on a Lipschitz graph of dimension in , and later this result has been extended to more general non-tangentially accessible domains and beyond.In the present paper we prove the first analogue of Dahlberg's theorem in higher co-dimension, on a Lipschitz graph Γ of dimension d in , , with a small Lipschitz constant. We construct a linear degenerate elliptic operator L such that the corresponding harmonic measure is absolutely continuous with respect to the Hausdorff measure on Γ. More generally, we provide sufficient conditions on the matrix of coefficients of L which guarantee the mutual absolute continuity of and the Hausdorff measure. 相似文献
66.
67.
AbstractThe reactions of methyl radicals with MII-(ntp)(H2O)2 complexes were studied. The formation of an unstable intermediate (ntp)(H2O)MIII-CH3 is observed. This reaction is an equilibrium process, i.e. the MIII-C bond decomposes via homolysis. The (ntp)(H2O)MIII-CH3 complexes isomerize to a more stable form. The results compared to those obtained in analogous reactions of the MII-(nta)(H2O)2 complexes were shown to be similar with one exception – for the nta complexes no isomerization process is observed. 相似文献
68.
69.
70.
Richard Bonnett Robert G. Guy David Lanigan 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-3):95-103
Abstract Thiocyanogen reacts slowly with alkenes, in the presence of a radical inhibitor in benzene or acetic acid in the dark at 25°, to yield α,β-dithiocyanates, α-isothiocyanates-β-thiocyanates and, in acetic acid, α-acetoxy-β-thiocyanates in varying proportions. The additions to alkyl alkenes are trans-stereospecific, and, in the case of the α-isothiocyanato-β-thiocyanates, non-regiospecific. The additions to aryl alkenes are trans-stereoselective and regiospecific, yielding the Markownikov-orientated α-isothiocyanato-β-thiocyanates. A heterolytic mechanism involving a two-step, kinetically controlled addition, with the formation of a cyano-sulfonium ion intermediate, e.g., 35, in the case of alkyl alkenes and an open carbonium ion, e.g., 36, in the case of aryl alkenes, is suggested. The diothiocyanate: isothiocyanato-thiocyanate ratios are discussed in terms of kinetic and steric control of reaction. 相似文献