全文获取类型
收费全文 | 846篇 |
免费 | 15篇 |
国内免费 | 5篇 |
专业分类
化学 | 612篇 |
晶体学 | 9篇 |
力学 | 13篇 |
数学 | 38篇 |
物理学 | 194篇 |
出版年
2023年 | 5篇 |
2022年 | 5篇 |
2021年 | 6篇 |
2020年 | 7篇 |
2019年 | 10篇 |
2016年 | 5篇 |
2015年 | 9篇 |
2014年 | 10篇 |
2013年 | 28篇 |
2012年 | 17篇 |
2011年 | 36篇 |
2010年 | 11篇 |
2009年 | 14篇 |
2008年 | 37篇 |
2007年 | 20篇 |
2006年 | 32篇 |
2005年 | 46篇 |
2004年 | 23篇 |
2003年 | 25篇 |
2002年 | 34篇 |
2001年 | 25篇 |
2000年 | 24篇 |
1999年 | 24篇 |
1998年 | 16篇 |
1997年 | 25篇 |
1996年 | 43篇 |
1995年 | 15篇 |
1994年 | 27篇 |
1993年 | 17篇 |
1992年 | 23篇 |
1991年 | 14篇 |
1990年 | 26篇 |
1989年 | 20篇 |
1988年 | 11篇 |
1987年 | 14篇 |
1986年 | 17篇 |
1985年 | 16篇 |
1984年 | 12篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 11篇 |
1980年 | 5篇 |
1979年 | 8篇 |
1978年 | 12篇 |
1977年 | 8篇 |
1976年 | 9篇 |
1974年 | 7篇 |
1973年 | 5篇 |
1971年 | 4篇 |
1939年 | 5篇 |
排序方式: 共有866条查询结果,搜索用时 15 毫秒
81.
Luu T Medos BJ Graham ER Vallee DM McDonald R Ferguson MJ Tykwinski RR 《The Journal of organic chemistry》2010,75(24):8498-8507
Terminal di-, tri-, tetra-, and pentaynes substituted with a variety of functional groups react with benzyl azide in the presence of CuSO(4)·5H(2)O and ascorbic acid to give derivatives of 4-ethynyl-, 4-butadiynyl-, 4-hexatriynyl-, and 4-octatetraynyl-1,2,3-triazoles in moderate to good yields. These reactions appear to proceed regioselectively, and functionalization occurs exclusively at the terminal alkyne moiety. As well, no evidence of multiple azide additions to the polyyne framework is observed. X-ray crystallographic analysis of nine derivatives is used to document the regioselectivity of the reaction as well as outline structural characteristics of the 1,2,3-triazole products. 相似文献
82.
83.
84.
Reactivity Tuning of Metal-Free Artificial Photoenzymes through Binding Site Specific Bioconjugation
Thomas Kuckhoff Dr. Richard C. Brewster Dr. Calum T. J. Ferguson Dr. Amanda G. Jarvis 《European journal of organic chemistry》2023,26(13):e202201412
The design and development of artificial metal-free photoenzymes aims to combine the selectivity of enzymatic reactions with the benefits of modern synthetic photocatalysts. Removing the need for rare earth metals and allowing for milder reaction conditions, leading to a more sustainable catalytic system. Here, we present the design of a novel artificial photoenzyme by integrating an organophotocatalytic moiety based on a donor-acceptor design into a steroid carrier protein (SCP-2L). SCP-2L possesses a hydrophobic tunnel facilitating substrate binding in aqueous media. The photocatalyst was site-selectively bound to three SCP-2L variants, possessing a non-native cysteine residue strategically placed around the hydrophobic tunnel of the protein. The three modified photoenzymes were shown to be selective for the oxidation of organic sulfides giving up to 192 turnovers. 相似文献
85.
Hannah J. Dokken Brandon L. Frenette Dr. Michael J. Ferguson Prof. Dr. Eric Rivard 《欧洲无机化学杂志》2023,26(26):e202300202
We report the synthesis and reactivity of the geminal-linked fluorene-derived P/B frustrated Lewis pair (FLP) iPr2P(C13H8)BCy2 ( 1 ). Compound 1 displays anomalous behavior towards small molecules, acting as a “masked” FLP. This behavior stems from significant polarization of the B−C(fluorene) bond in 1 , as identified by density functional theory (DFT) computations. We exploit this B−C bond polarity through reactions with PhPCl2, H3N ⋅ BH3, and iPrNH2, demonstrating P−Cl and N−H bond activation, respectively. 相似文献
86.
The catalytic system composed of CuCl2 and 2,2′-biquinoline-4,4′-dicarboxylic acid dipotassium salt (BQC) was found to be highly efficient for the selective α-oxidation of internal alkynes to the corresponding α,β-acetylenic ketones, with aqueous tert-butyl hydroperoxide under mild conditions. For the first time, full conversions of alkynes were reached with excellent selectivities, and propargylic tert-butylperoxy ethers were observed and suggested as the reaction intermediates. In the case of terminal alkynes, the oxidations are sluggish and low yields ranging from 32% to 40% were obtained. 相似文献
87.
Volle CB Ferguson MA Aidala KE Spain EM Núñez ME 《Colloids and surfaces. B, Biointerfaces》2008,67(1):32-40
Bacterial biofilms were imaged by atomic force microscopy (AFM), and their elasticity and adhesion to the AFM tip were determined from a series of tip extension and retraction cycles. Though the five bacterial strains studied included both Gram-negative and -positive bacteria and both environmental and laboratory strains, all formed simple biofilms on glass surfaces. Cellular spring constants, determined from the extension portion of the force cycle, varied between 0.16+/-0.01 and 0.41+/-0.01 N/m, where larger spring constants were measured for Gram-positive cells than for Gram-negative cells. The nonlinear regime in the extension curve depended upon the biomolecules on the cell surface: the extension curves for the smooth Gram-negative bacterial strains with the longest lipopolysaccharides on their surface had a larger nonlinear region than the rough bacterial strain with shorter lipopolysaccharides on the surface. Adhesive forces between the retracting silicon nitride tip and the cells varied between cell types in terms of the force components, the distance components, and the number of adhesion events. The Gram-negative cells' adhesion to the tip showed the longest distance components, sometimes more than 1 microm, whereas the shortest distance adhesion events were measured between the two Gram-positive cell types and the tip. Fixation of free-swimming planktonic cells by NHS and EDC perturbed both the elasticity and the adhesive properties of the cells. Here we consider the biochemical meaning of the measured physical properties of simple biofilms and implications to the colonization of surfaces in the first stages of biofilm formation. 相似文献
88.
89.
Dr. Bozheng Sun Dr. Meagan S. Oakley Dr. Kota Yoshida Yanwen Yang Prof. Matteo Tommasini Dr. Chiara Zanchi Dr. Andrea Lucotti Dr. Michael J. Ferguson Dr. Frank Hampel Prof. Mariusz Klobukowski Prof. Rik R. Tykwinski 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(38):e202200616
Cyclic tetraaryl[5]cumulenes ( 1 a–f ) have been synthesized and studied as a function of increasing ring strain. The magnitude of ring strain is approximated by the extent of bending of the cumulenic core as assessed by a combination of X-ray crystallographic analysis and DFT calculations. Trends are observed in 13C NMR, UV-vis, and Raman spectra associated with ring strain, but the effects are small. In particular, the experimental HOMO-LUMO gap is not appreciably affected by bending of the [5]cumulene framework from ca. 174° (λmax=504 nm) in 1 a to ca. 178° (λmax=494 nm) in 1 f . 相似文献
90.