全文获取类型
收费全文 | 324篇 |
免费 | 31篇 |
国内免费 | 1篇 |
专业分类
化学 | 284篇 |
晶体学 | 3篇 |
力学 | 3篇 |
数学 | 31篇 |
物理学 | 35篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 8篇 |
2020年 | 6篇 |
2019年 | 7篇 |
2018年 | 8篇 |
2017年 | 5篇 |
2016年 | 16篇 |
2015年 | 15篇 |
2014年 | 18篇 |
2013年 | 20篇 |
2012年 | 43篇 |
2011年 | 35篇 |
2010年 | 16篇 |
2009年 | 13篇 |
2008年 | 19篇 |
2007年 | 26篇 |
2006年 | 13篇 |
2005年 | 14篇 |
2004年 | 19篇 |
2003年 | 24篇 |
2002年 | 5篇 |
2001年 | 1篇 |
1999年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有356条查询结果,搜索用时 11 毫秒
351.
N-heterocyclic carbenes derived from triazolium salts are effective catalysts between 10 and 15 mol % for the hydroacylation of activated ketones. The reducing equivalent is generated via the interaction of a nucleophilic carbene species and an aromatic aldehyde. The subsequent alcohol product can undergo an acylation event with the resulting acyl heteroazolium intermediate formed in situ between the NHC and the aldehyde. This unprecedented multiple bond-forming reaction can accommodate aromatic aldehydes as the hydride source and various electron-deficient ketones. Preliminary mechanistic evidence indicates that the reduction and acylation steps are sequential operations. The intramolecular variant of this organocatalytic reaction affords benzofuranones in good yield. 相似文献
352.
We present the synthesis, properties, and biological applications of Leadfluor-1 (LF1), a new water-soluble, turn-on fluorescent sensor that is capable of selectively imaging Pb2+ in aqueous solution and in living cells. LF1 combines a fluorescein chromophore and a pseudocrown receptor to provide good selectivity for Pb2+ over a range of biologically and environmentally relevant metal ions in aqueous solution, with sensitivity to parts per billion EPA limits for allowable lead in drinking water. In addition to these attributes, imaging experiments further show that LF1 is the first small-molecule reagent that can be delivered into living cells and report changes in intracellular Pb2+ levels. 相似文献
353.
An analytical methodology for quality control analyses of IgG and their impurities is presented using a new UV‐LIF (266 nm) detector inside the cassette of a CE instrument and its performance was evaluated. The observed sensitivity was very close to that obtained by silver staining of slab gels (LOD of 25 ng/mL), while the sensitivity of the analysis is 80 times better than with CE/UV absorption (214 nm). Examples of the analysis of pharmaceutical and other commercial IgGs are provided and the kinetics of the reduction of IgG by β‐mercaptoethanol is reported, demonstrating the ease of performing the analysis. 相似文献
354.
Audrey Dupont Andréa Carneiro Linhares Christian Artigues Dominique Feillet Philippe Michelon Michel Vasquez 《European Journal of Operational Research》2009
In this paper, we consider a frequency assignment problem occurring in a military context. The main originality of the problem pertains to its dynamic dimension: new communications requiring frequency assignments need to be established throughout a battlefield deployment. The problem resolution framework decomposes into three phases: assignment of an initial kernel of communications, dynamic assignment of new communication links and a repair process when no assignment is possible. Different solution methods are proposed and extensive computational experiments are carried out on realistic instances. 相似文献
355.
Audrey Di Martino Jean Pierre Broyer Roger Spitz Günter Weickert Timothy F. McKenna 《Macromolecular rapid communications》2005,26(4):215-220
Summary: A quenched‐flow reactor is introduced as an effective means for the production of polyolefin particles with precisely controlled reaction times as low as 40 ms. The use of off‐line scanning electron microscopy and induced‐coupled plasma yields experimental data on the development of the kinetics and morphology of nascent structures during the polymerisation of ethylene on a heterogeneous TiCl4 MgCl2 Ziegler–Natta catalyst. Initial ex situ observations revealed the development of specific morphologies very early during the reaction (e.g., cracks in platelike surfaces, fines, extrudates, etc.) that can potentially lead to fines, and the kinetic analysis showed extremely high reaction rates at very short times.
356.
Julie Meimoun Yupin Phuphuak Remi Miyamachi Yong Miao Marc Bria Cyril Rousseau Guilherme Nogueira Andreia Valente Audrey Favrelle-Huret Philippe Zinck 《Molecules (Basel, Switzerland)》2022,27(3)
Cyclodextrins (CDs) are cyclic oligosaccharides used in many fields. Grafting polymers onto CDs enables new structures and applications to be obtained. Polylactide (PLA) is a biobased, biocompatible aliphatic polyester that can be grafted onto CDs by -OH-initiated ring-opening polymerization. Using 4-dimethylaminopyridine (DMAP) as an organocatalyst, a quantitative functionalization is reached on native α-, β-, γ- and 2,3-dimethyl- β-cyclodextrins. Narrow molecular weight distributions are obtained with the native CDs (dispersity < 1.1). The DMAP/β-CD combination is used as a case study, and the formation of an inclusion complex (1/1) is shown for the first time in the literature, which is fully characterized by NMR. The inclusion of DMAP into the cavity occurs via the secondary rim of the β-CD and the association constant (Ka) is estimated to be 88.2 M−1. Its use as an initiator for ring-opening polymerization leads to a partial functionalization efficiency, and thus a more hydrophilic β-CD-PLA conjugate than that obtained starting from native β-CD. Polymerization results including also the use of the adamantane/β-CD inclusion complex as an initiator suggest that inclusion of the DMAP catalyst into the CD may not occur during polymerization reactions. Rac-lactide does not form an inclusion complex with β-CD. 相似文献