全文获取类型
收费全文 | 1417篇 |
免费 | 16篇 |
国内免费 | 89篇 |
专业分类
化学 | 1466篇 |
力学 | 6篇 |
综合类 | 7篇 |
数学 | 4篇 |
物理学 | 39篇 |
出版年
2024年 | 3篇 |
2023年 | 28篇 |
2022年 | 13篇 |
2021年 | 19篇 |
2020年 | 33篇 |
2019年 | 79篇 |
2018年 | 41篇 |
2017年 | 76篇 |
2016年 | 49篇 |
2015年 | 32篇 |
2014年 | 53篇 |
2013年 | 50篇 |
2012年 | 73篇 |
2011年 | 96篇 |
2010年 | 63篇 |
2009年 | 62篇 |
2008年 | 80篇 |
2007年 | 96篇 |
2006年 | 81篇 |
2005年 | 86篇 |
2004年 | 93篇 |
2003年 | 48篇 |
2002年 | 28篇 |
2001年 | 30篇 |
2000年 | 31篇 |
1999年 | 35篇 |
1998年 | 25篇 |
1997年 | 27篇 |
1996年 | 23篇 |
1995年 | 13篇 |
1994年 | 6篇 |
1993年 | 10篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1988年 | 1篇 |
1987年 | 7篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 4篇 |
排序方式: 共有1522条查询结果,搜索用时 15 毫秒
1.
Varsha J. Thombare Craig A. Hutton 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(15):5052-5056
Peptide macrocyclization is often a slow process, plagued by epimerization and cyclodimerization. Herein, we describe a new method for peptide macrocyclization employing the AgI‐promoted transformation of peptide thioamides. The AgI has a dual function: chemoselectively activating the thioamide and tethering the N‐terminal thioamide to the C‐terminal carboxylate. Extrusion of Ag2S generates an isoimide intermediate, which undergoes acyl transfer to generate the native cyclic peptide, resulting in a rapid, traceless macrocylization process. Cyclic peptides are furnished in high yields within 1 hour, free of epimerization and cyclodimerization. 相似文献
2.
Lígia M. Rodrigues 《Tetrahedron》2004,60(40):8929-8936
Tetrapeptides containing one of a set of four different α,α-dialkyl glycines at the C-terminus were synthesized by conventional methods in solution and their conformational behavior investigated by 1H NMR spectroscopy in connection with molecular mechanics calculations. The results were consistent with conformations stabilized by a γ-turn in the case of compounds with alkyl groups larger than methyl, while the corresponding Aib derivative did not exhibit intramolecular hydrogen bonding. 相似文献
3.
4.
S. Aravinda N. Shamala Rituparna S. Roy P Balaram 《Journal of Chemical Sciences》2003,115(5-6):373-400
An overview of the use of non-protein amino acids in the design of conformationally well-defined peptides, based on work from
the author’s laboratory, is discussed. The crystal structures of several designed oligopeptides illustrate the useα-aminoisobutyric acid (Aib) in the construction of helices, D-amino acids in the design of helix termination segments andDPro-Xxx segments for nucleating ofβ-hairpin structures.β- andγ-amino acid residues have been used to expand the range of designed polypeptide structures.
Dedicated to Professor C N R Rao on his 70th birthday 相似文献
5.
6.
7.
8.
9.
Xuyuan GuScott Cowell Jinfa YingXuejun Tang Victor J. Hruby 《Tetrahedron letters》2003,44(31):5863-5866
(2S,3S)- and (2R,3R)-2-amino-3-phenyl-5-hexenoic acids have been synthesized in large scale by using Ni(II)-complexes as a template. The amino acids were used in the synthesis of [4,3,0]-bicyclic β-turn mimetics by a convergent methodology. The unique advantage of this strategy is the convenience of introducing side chain groups with predetermined chiralities on both the five- and six-membered heterocyclic rings. 相似文献
10.