全文获取类型
收费全文 | 2346篇 |
免费 | 54篇 |
国内免费 | 8篇 |
专业分类
化学 | 1660篇 |
晶体学 | 26篇 |
力学 | 84篇 |
数学 | 188篇 |
物理学 | 450篇 |
出版年
2021年 | 14篇 |
2020年 | 26篇 |
2019年 | 20篇 |
2018年 | 20篇 |
2017年 | 23篇 |
2016年 | 19篇 |
2015年 | 28篇 |
2014年 | 47篇 |
2013年 | 105篇 |
2012年 | 84篇 |
2011年 | 111篇 |
2010年 | 58篇 |
2009年 | 49篇 |
2008年 | 118篇 |
2007年 | 124篇 |
2006年 | 119篇 |
2005年 | 121篇 |
2004年 | 113篇 |
2003年 | 93篇 |
2002年 | 84篇 |
2001年 | 69篇 |
2000年 | 59篇 |
1999年 | 45篇 |
1998年 | 31篇 |
1997年 | 25篇 |
1996年 | 39篇 |
1995年 | 22篇 |
1994年 | 25篇 |
1993年 | 37篇 |
1992年 | 41篇 |
1991年 | 32篇 |
1990年 | 21篇 |
1989年 | 19篇 |
1988年 | 17篇 |
1987年 | 19篇 |
1986年 | 20篇 |
1985年 | 48篇 |
1984年 | 27篇 |
1983年 | 32篇 |
1982年 | 36篇 |
1981年 | 31篇 |
1980年 | 37篇 |
1979年 | 29篇 |
1978年 | 29篇 |
1977年 | 28篇 |
1976年 | 16篇 |
1975年 | 26篇 |
1974年 | 26篇 |
1973年 | 20篇 |
1972年 | 14篇 |
排序方式: 共有2408条查询结果,搜索用时 15 毫秒
41.
An action spectrum for UV photocarcinogenesis 总被引:5,自引:0,他引:5
42.
Davies IW Marcoux JF Wu J Palucki M Corley EG Robbins MA Tsou N Ball RG Dormer P Larsen RD Reider PJ 《The Journal of organic chemistry》2000,65(15):4571-4574
Substituted acetic acids or acetyl chlorides react with phosphorus oxychloride in DMF to yield the vinamidinium salts 3a-j in moderate to excellent recrystallized yields (28-90%). The cations are conveniently isolated as their hexafluorophosphate salts, which are easily handled nonhygroscopic solids. The nitro compound 3l is prepared in 91% yield by nitration of the parent vinamidinium 3k. The X-ray crystal structure is reported for the 2-phenyl isomer 3e and displays minimal overlap of the two pi-systems. 相似文献
43.
Bailey S Davies SG Smith AD Withey JM 《Chemical communications (Cambridge, England)》2002,(23):2910-2911
The asymmetric synthesis of (1R,2S,3R)-3-methyl-2-amino-cyclopentane carboxylic acid has been achieved via kinetic resolution of racemic tert-butyl 3-methyl-cyclopentene-1-carboxylate with homochiral lithium (S)-N-benzyl-N-alpha-methylbenzylamide. 相似文献
44.
Williams DH Davies NL Koivisto JJ 《Journal of the American Chemical Society》2004,126(43):14267-14272
Two models (A and B) have been proposed to account for decreased downfield chemical shifts of a proton bound by noncovalent interactions at a ligand/antibiotic interface as the number of ligand/antibiotic interactions is decreased. In model A, the proton involved in the noncovalent bond suffers a smaller downfield shift because the bond is, with a relatively large probability, broken, and not because it is longer. In model B, the proton involved in the noncovalent bond suffers a smaller downfield shift because the bond is longer, and not because it is, with a relatively large probability, broken. We show that model A cannot account for the chemical shift changes. Model B accounts for the process of positively cooperative binding, in which noncovalent bonds are reduced in length and thereby increase the stability of the organized state. 相似文献
45.
Abernethy Colin D. Baker Robert J. Cole Marcus L. Davies Aaron J. Jones Cameron 《Transition Metal Chemistry》2003,28(3):296-299
The reactivity of the carbene stabilised indium trihydride complex, [InH3(IMes)] IMes = 1,3-dimesitylimidazol-2-ylidene, toward a variety of transition metal complexes has been investigated. The study has shown that the InH3 complex can act as a carbene and/or hydride transfer reagent to transition metal centres but does not yield heterobimetallic materials. Two new complexes, [Cp2Ti(-Cl)2Zn(IMes)Cl] and [CpNi(H)(IMes)], have resulted from this work, both of which have been spectroscopically and structurally characterised. 相似文献
46.
47.
48.
49.
50.
John S. Davies Mark C. Eaton M. Nazar Ibrahim 《Journal of heterocyclic chemistry》1980,17(8):1813-1814
Dedicated to Professor John C. Sheehan on the occasion of his sixty-fifth birthday Nmr and glc analysis of diastereoisomeric mixtures of dipeptides has been used to study the asymmetric hydrogenation of model benzoyldidehydro- and trifluoroacetyldidehydro-dipeptide methyl esters. Chiral enhancement of one isomeric form appears to be independent of the N-terminal acyl group, but is significantly influenced by the choice of amino-acid in the C-terminal position. C-Terminal aromatic amino-acids and their derivatives give the best chiral enhancement during hydrogenation of a neighbouring dehydroamino-acid residue. 相似文献