全文获取类型
收费全文 | 1353篇 |
免费 | 11篇 |
国内免费 | 78篇 |
专业分类
化学 | 1402篇 |
力学 | 3篇 |
数学 | 1篇 |
物理学 | 36篇 |
出版年
2024年 | 3篇 |
2023年 | 29篇 |
2022年 | 11篇 |
2021年 | 16篇 |
2020年 | 34篇 |
2019年 | 74篇 |
2018年 | 39篇 |
2017年 | 71篇 |
2016年 | 47篇 |
2015年 | 29篇 |
2014年 | 47篇 |
2013年 | 43篇 |
2012年 | 67篇 |
2011年 | 98篇 |
2010年 | 62篇 |
2009年 | 59篇 |
2008年 | 80篇 |
2007年 | 91篇 |
2006年 | 80篇 |
2005年 | 80篇 |
2004年 | 88篇 |
2003年 | 43篇 |
2002年 | 24篇 |
2001年 | 27篇 |
2000年 | 28篇 |
1999年 | 31篇 |
1998年 | 23篇 |
1997年 | 25篇 |
1996年 | 23篇 |
1995年 | 15篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 4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1442条查询结果,搜索用时 0 毫秒
1.
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
2.
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
3.
4.
The study of possible chiral recognition of a series of peptide models (For-Gly-NH2, For-Ala-NH2 and four of their fluoro substituted derivatives) has been carried out by means of DFT calculations. Homo (L,L) and heterochiral (L,D) dimers formed by hydrogen bond (HB) complexation have been considered. Initially, the conformational preferences of the monomers have been calculated and used to generate all the possible homo and heterochiral dimers. The energetic results show that in most cases, the β monomers are the most stable while in the dimers, the γ–γ complexes show the strongest interaction energies. In three of the four chiral cases studied, a heterochiral dimer is the most stable one. In addition, the electron density and nuclear shielding of the complexes have been studied. 相似文献
5.
6.
7.
8.
对健康指甲和灰指甲的红外光谱特征吸收峰进行了指认,并对其相应官能团的吸收峰进行了对比分析.结果表明,灰指甲增厚、变脆的原因系α-角蛋白螺旋结构遭到破坏,肽链伸展并发生断裂,形成了不同化学环境的氨基酸,同时蛋白质分子的有序排列也发生了改变. 相似文献
9.
Affinity Chromatography of Insulin with a Heptapeptide Ligand Selected from Phage Display Library 总被引:1,自引:0,他引:1
A heptapeptide phage display library was screened with insulin to find its ligands for affinity chromatography. The peptide was synthesized and coupled to EAH Sepharose 4B (5.4 mol mL–1 bed). Then, insulin chromatography was carried out with mobile phases of different pH values and by the addition of urea and ethylene glycol. It was found that electrostatic interactions were predominant for the affinity binding, and hydrogen bonding might also contribute somewhat to the affinity. Finally, frontal analysis was performed and the dynamic binding capacity of the affinity column for insulin at 50% breakthrough was estimated at 60.6 mg mL–1 bed, which was about two times higher than the theoretical binding capacity of the monomeric insulin. The result suggests that insulin was bound in dimer state in a stoichiometric relationship with the coupled peptide, indicating the high binding efficiency of the peptide ligand for insulin. 相似文献
10.
Gary H. Van Domeselaar Glen S. Kwon Lena C. Andrew David S. Wishart 《Colloids and surfaces. B, Biointerfaces》2003,30(4):323-334
This work describes a simple, versatile solid-phase peptide-synthesis (SPPS) method for preparing micelle-forming poly(ethylene oxide)-block-peptide block copolymers for drug delivery. To demonstrate its utility, this SPPS method was used to construct two series of micelle-forming block copolymers (one of constant core-composition and variable length; the other of constant core length and variable composition). The block copolymers were then used to study in detail the effect of size and composition on micellization. The various block copolymers were prepared by a combination of SPPS for the peptide block, followed by solution–phase conjugation of the peptide block with a proprionic acid derivative of poly(ethylene oxide) (PEO) to form the PEO-b-peptide block copolymer. The composition of each block component was characterized by mass spectrometry (MALDI and ES-MS). Block copolymer compositions were characterized by 1H NMR. All the block copolymers were found to form micelles as judged by transmission electron microscopy (TEM) and light scattering analysis. To demonstrate their potential as drug delivery systems, micelles prepared from one member of the PEO-b-peptide block copolymer series were physically loaded with the anticancer drug doxorubicin (DOX). Micelle static and dynamic stability were found to correlate strongly with micelle core length. In contrast, these same micellization properties appear to be a complex function of core composition, and no clear trends could be identified from among the set of compositionally varying, fixed length block copolymer micelles. We conclude that SPPS can be used to construct biocompatible block copolymers with well-defined core lengths and compositions, which in turn can be used to study and to tailor the behavior of block copolymer micelles. 相似文献