全文获取类型
收费全文 | 233篇 |
免费 | 5篇 |
专业分类
化学 | 157篇 |
晶体学 | 7篇 |
力学 | 6篇 |
数学 | 17篇 |
物理学 | 51篇 |
出版年
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 9篇 |
2015年 | 2篇 |
2014年 | 5篇 |
2013年 | 10篇 |
2012年 | 11篇 |
2011年 | 8篇 |
2010年 | 8篇 |
2009年 | 4篇 |
2008年 | 9篇 |
2007年 | 17篇 |
2006年 | 4篇 |
2005年 | 18篇 |
2004年 | 11篇 |
2003年 | 12篇 |
2002年 | 11篇 |
2001年 | 5篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1968年 | 1篇 |
1961年 | 1篇 |
1959年 | 2篇 |
1957年 | 3篇 |
1941年 | 2篇 |
排序方式: 共有238条查询结果,搜索用时 31 毫秒
31.
Natarajan Raju Rama S. Ranganathan Mike F. Tweedle Rolf E. Swenson 《Tetrahedron letters》2005,46(9):1463-1465
Synthesis of a new scaffold derived from iminodipropionic acid for the preparation of peptide dimers and tetramers is described. 相似文献
32.
33.
34.
Adenine has been used as the template for the directed synthesis of 5-substituted imidazoles. A Novel intermediate involved in the cyclic operation has been characterised. 相似文献
35.
For the first time, group transfer polymerisation of methyl methacrylate (MMA) has been successfully carried out at ambient temperatures in an ionic liquid to produce living polymers of improved polydispersity. 相似文献
36.
It is shown that using the basis elements of the generalized Clifford algebra Cmn we can construct a group G?mn called the generalized Clifford group (G.C.G.) which is a generalization of the Dirac group of the 16 Dirac matrices and their negative counterparts. We have studied the irreducible representations of G.C.G. and we have found the connection with the group of linear transformations leaving invariant the expression for m>2. 相似文献
37.
The effect of trifluoroacetylation on the 13C chemical shifts of 2-acetamido-2-deoxyhexoses was examined. Studies of the 2-acetamido derivatives of glucose, galactose and mannose established that no regular trend in the 13C shifts occurred on trifluoroacetylation. This was in marked contrast to the results obtained for the 1H chemical shifts. 相似文献
38.
Isabella Karle Richard D. Gilardi Ch. Chandrashekhar Rao K.M. Muraleedharan Subramania Ranganathan 《Journal of chemical crystallography》2003,33(10):727-749
Benzenehexacarboxylic acid, mellitic acid (MA), has been used as a core motif to study possible radial self-assembly using complementary aromatic bases. By mixing water solutions of the components, crystals of the salts of MA with 4-aminopyridine (AP), 4-dimethylamino-pyridine (DM), 2,2-bipyridine (DP), o-phenanthroline (PL), and melamine (ML) have been obtained. The MA–n
ions have assembled in either extended sheets for MA–2 or extended ribbons for MA–4 by direct hydrogen bonding between MA and MA and additionally through mediation of hydrogen bonds to water molecules that distribute the negative charges throughout the MA sheet or ribbon. Most of the O atoms in carboxyl groups in the MA ions in the five complexes have been rotated significantly out of the plane of the central benzene ring. There are multiple base molecules, two or four, for each mellitic acid ion in the five complexes. Most of the NH+ moieties in all five bases make direct NH+ O–C hydrogen bonds with MA–n
. The planar base ions are generally arranged in stacks in which the components range from being parallel, with interplanar separations of 3.5 Å, to having a considerable tilt with respect to each other with nearest interplanar separation of atoms greater than 3.9 Å. These geometric characteristics are reflected in the color of the crystals. The three-dimensional networking makes some of the crystals very hard. Cell dimensions: 1, C32H30N8O12 2H2O, C2/c, a =13.764(2) Å, b =18.053(3) Å, c =14.876(4) Å, =105.99(2)° 2, C26H26N4O12 3H2O, P21/n, a =15.891(1) Å, b =10.444(1) Å, c =18.242(1) Å, =97.00(1); 3, C64H44N8O24
7H2O, P21/c, a =23.016(4) Å, b =15.241(2) Å, c =19.124(2) Å, =100.60(1)° 4, C36H22N4O12, P21/n, a =14.581(1) Å, b =10.472(1) Å, c =20.607(2) Å, =106.43(1); 5, C18H18N12O12 2H2O,
, a =8.257(2) Å, b =8.986(2) Å, c =9.383(1) Å, =98.60(1)°, =96.38(2)°, =117.07(1)°. 相似文献
39.
A diastereoselective palladium-catalyzed arylation of 4-substituted cyclohexyl esters has been developed. The reaction proceeds at room temperature in the presence of [(t-Bu3P)PdBr]2 providing products in up to 37:1 dr. 相似文献
40.