全文获取类型
收费全文 | 2170篇 |
免费 | 59篇 |
国内免费 | 4篇 |
专业分类
化学 | 1662篇 |
晶体学 | 4篇 |
力学 | 18篇 |
数学 | 326篇 |
物理学 | 223篇 |
出版年
2023年 | 29篇 |
2022年 | 19篇 |
2021年 | 23篇 |
2020年 | 61篇 |
2019年 | 50篇 |
2018年 | 27篇 |
2017年 | 17篇 |
2016年 | 40篇 |
2015年 | 28篇 |
2014年 | 39篇 |
2013年 | 67篇 |
2012年 | 68篇 |
2011年 | 95篇 |
2010年 | 38篇 |
2009年 | 44篇 |
2008年 | 69篇 |
2007年 | 62篇 |
2006年 | 71篇 |
2005年 | 68篇 |
2004年 | 55篇 |
2003年 | 43篇 |
2002年 | 38篇 |
2001年 | 18篇 |
2000年 | 22篇 |
1999年 | 15篇 |
1998年 | 18篇 |
1996年 | 14篇 |
1995年 | 20篇 |
1994年 | 20篇 |
1991年 | 21篇 |
1990年 | 16篇 |
1987年 | 15篇 |
1986年 | 17篇 |
1985年 | 27篇 |
1984年 | 29篇 |
1983年 | 25篇 |
1982年 | 38篇 |
1981年 | 22篇 |
1980年 | 24篇 |
1979年 | 42篇 |
1978年 | 25篇 |
1977年 | 36篇 |
1976年 | 27篇 |
1975年 | 24篇 |
1974年 | 20篇 |
1973年 | 15篇 |
1967年 | 19篇 |
1959年 | 14篇 |
1956年 | 20篇 |
1934年 | 23篇 |
排序方式: 共有2233条查询结果,搜索用时 8 毫秒
1.
Vicenç Branchadell Roser Pleixats Claude Commandeur Max Malacria 《Journal of organometallic chemistry》2003,687(2):337-345
Regioselectivity of the Tsuji-Trost reaction on allyl acetates and carbonates substituted with silyl groups at the olefinic moiety has been analyzed. Silicon atom in the central carbon atom increases the stability of the intermediate π-allylpalladium cation with respect to the isomeric π-allylpalladium cation featuring the silicon in a terminal carbon atom. 相似文献
2.
3.
4.
5.
Enantioselective host-guest complexes between α-amino-alcohol salts and chiral tartrates can not be crystallised up to now. To study structural aspects of their enantioselectivity, crystal structures of the components were determined. Norephedrine was used as a reference guest α-amino-alcohol. (1R, 2S)-Norephedrine hydrochloride (monoclinic, space group P21 Z = 4, a = 8.455, b = 10.331, c = 12.570 Å, β = 107.45°) and (1R, 2R)-norpseudoephedrine hydrochloride (monoclinic, space group P21 Z = 2, a = 5.493, b = 8.052, c = 11.986 Å, β = 104.62°) both adopt M-synclinal conformations with respect to the ammonium and hydroxy groups. Rather short intramolecular N…?O distances indicate interaction between ammonium and hydroxy groups. 相似文献
6.
7.
8.
Erich Metzger Roland Aeschimann Martin Egli Gaby Suter Ren Dohner Daniel Ammann Max Dobler Wilhelm Simon 《Helvetica chimica acta》1986,69(8):1821-1828
Lipophilic neutral carriers were synthesized which show Li+/Na+ selectivities of up to ca. 80 in highly lipophilic liquid membranes. The sensor membranes exhibit improved response times and increased lifetimes as compared to systems described earlier. They allow reliable measurements of Li+ in blood serum within the clinical concentration range. A 1:1 Li+/ionophore complex of one representative (N,N,N′,N′-tetracyclohexyl-5,5-dimethyl-3,7-dioxaazelaamide) has been prepared, and its structure was elucidated by X-ray analysis. 相似文献
9.
Gerhard Laus Johannes Schütz Herwig Schottenberger Max Andre Klaus Wurst Mariana Spetea Karl‐Hans Ongania AdrianG. Müller Helmut Schmidhammer 《Helvetica chimica acta》2003,86(10):3274-3280
The two diastereoisomeric ferrocenyl‐substituted orvinols 2 and 3 were prepared. The modified alkaloids are still able to interact with opioid receptors (see Table). The ferrocene moiety allows highly selective and sensitive electrochemical detection. The X‐ray crystal structure of the major isomer 2 was determined. The combination of a metallocene and a morphinan alkaloid holds promise for useful antitumor activity. 相似文献
10.
Starting with 5-formyl-6,7-dimethyl-5,6,7,8-tetrahydropterine (II), a new synthesis of 5,6,7-trimethyl-5,6,7,8-tetrahydropterine (III) is described. Thereby the chemical behaviour of the 5-formyl group in II is investigated, in order to enable the unequivocal differentiation between formylation at position 5 and at position 10 in folic and tetrahydrofolic acid derivatives. 13C-NMR. spectra of II and III are discussed. 相似文献