全文获取类型
收费全文 | 154篇 |
免费 | 16篇 |
专业分类
化学 | 154篇 |
力学 | 3篇 |
数学 | 4篇 |
物理学 | 9篇 |
出版年
2023年 | 4篇 |
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 5篇 |
2017年 | 2篇 |
2016年 | 3篇 |
2015年 | 7篇 |
2014年 | 8篇 |
2013年 | 11篇 |
2012年 | 11篇 |
2011年 | 13篇 |
2010年 | 5篇 |
2009年 | 5篇 |
2008年 | 10篇 |
2007年 | 16篇 |
2006年 | 9篇 |
2005年 | 16篇 |
2004年 | 7篇 |
2003年 | 8篇 |
2002年 | 1篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1994年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
排序方式: 共有170条查询结果,搜索用时 15 毫秒
131.
José Enrique Gómez Dr. Wusheng Guo Silvia Gaspa Prof. Dr. Arjan W. Kleij 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(47):15231-15234
The first general asymmetric synthesis of γ,γ‐disubstituted γ‐amino acids by copper‐catalyzed ring opening of nonstrained lactones with amines is reported. This approach features ample scope, operational simplicity, and wide functional‐group diversity. The catalytic process allows access to a series of highly functionalized enantioenriched γ‐amino acids featuring quaternary stereocenters with excellent enantiomeric ratios of up to 98:2 and excellent yields of up to 98 %. 相似文献
132.
Catherine M. Clavel Patrycja Nowak-Sliwinska Emilia P?unescu Arjan W. Griffioen Paul J. Dyson 《Chemical science》2015,6(5):2795-2801
Hyperthermia used as an adjuvant with chemotherapy is highly promising in the treatment of certain cancers. Currently, the small molecule drugs used in combination with hyperthermia were not designed for this application. Herein, we report the evaluation of a chlorambucil and a ruthenium compound modified with a long fluorous chain, which exhibit thermoresponsive activity in colorectal adenocarcinoma xenografts in athymic mice in combination with mild hyperthermia (42 °C). Intraperitoneal injection of the derivatives followed by local hyperthermia showed a synergistic tumor growth reduction by 79% and 90% for the chlorambucil and ruthenium-based derivatives, respectively, with the latter exhibiting a higher synergy in combination with hyperthermia compared to the monotherapies. Histological analysis shows that both derivatives in combination with hyperthermia significantly decrease the number of proliferating tumor cells. 相似文献
133.
Dr. Wusheng Guo Joan Gónzalez‐Fabra Dr. Nuno A. G. Bandeira Prof. Dr. Carles Bo Prof. Dr. Arjan W. Kleij 《Angewandte Chemie (International ed. in English)》2015,54(40):11686-11690
The first chemo‐ and site‐selective process for the formation of N‐aryl‐carbamates from cyclic organic carbonates and aromatic amines is reported. The reactions proceed smoothly under extremely mild reaction conditions using TBD (triazabicyclodecene) as an effective and cheap organocatalyst, thus providing a sustainable and new methodology for the formation of a wide variety of useful N‐aryl carbamate synthons in good to excellent yields. Computational investigations have been performed and show the underlying reason for the observed unique reactivity as related to an effective proton‐relay mechanism mediated by the bicyclic guanidine base. 相似文献
134.
135.
136.
Michael J. Doyle Arjan P. Kouwenhoven Cornelis A. Schaap Bart van Oort 《Journal of organometallic chemistry》1979,174(3):C55-C58
Solutions of dodecacarbonyl-triangulo-triruthenium [Ru3(CO)12] have been shown to be catalyst precursors for the Fischer-Tropsch reaction; the catalyst formed under the reaction conditions is heterogeneous; no indication of homogeneous activity was found. 相似文献
137.
A spectrophotometric investigation of the protonation of HVO(4)(2-) has been conducted at vanadium(V) concentrations low enough (5 x 10(-5) mol dm(-3)) to prevent the formation of polynuclear ions. Equilibrium constants as well as enthalpy and entropy changes for the formation of H(2)VO(4)(-) and VO(2)(+) have been determined in ionic medium: 1.0 mol dm(-3) NaCl and NaClO(4), respectively. The percentage concentration of the neutral species, H(3)VO(4), is so low (apparently <1%) that the protonation of H(2)VO(4)(-) to form VO(2)(+) occurs virtually in a single step. The disproportionately great stability of VO(2)(+) relative to H(3)VO(4) is explained in terms of an increase in the coordination number of vanadium when the cationic species is formed. This explanation is based on a comparison of the thermodynamic quantities of the vanadium(V) species with those of various other oxyacids reported in the literature. 相似文献
138.
Recent advances in microcontact printing 总被引:4,自引:0,他引:4
Microcontact printing is a remarkable surface patterning technique. Developed about 10 years ago, it has triggered enormous interest from the surface science community, as well as from engineers and biologists. The last five years have been rich in improvements to the microcontact printing process itself, as well as in new technical innovations, many designed to suit new applications. In this review, we describe the evolution of microcontact printing over the past five years. The review is categorized into three main sections: the improvements made to the technique, new variations, and new applications. 相似文献
139.
Kleij AW Kuil M Tooke DM Lutz M Spek AL Reek JN 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(16):4743-4750
Zn(II)-salphen complexes are readily accessible and interesting supramolecular building blocks with a large structural diversity. Higher-order supramolecular assemblies, such as molecular boxes based on a bis-Zn(II)-salphen building block and various ditopic bipyridine ligands, have been constructed by means of supramolecular, coordinative Zn(II)-N(pyr) interactions. The use of bipyridine ligands of differing sizes enables the construction of structures with predefined box diameters. The features of the 2:2 box assemblies were investigated in detail by (variable temperature) NMR spectroscopy, UV-visible spectroscopy, NMR titrations, and X-ray crystallographic studies. The spectroscopic studies reveal a high association constant for the Zn(II)-salphen-pyridyl motif, which lies in the range 10(5)-10(6) M(-1). The strong interaction between the Zn(II) center and pyridine donors was supported by PM3 calculations that showed a relatively high Lewis acid character of the metal center in the salphen complex. Titration curves monitored by UV-visible show a cooperative effect between the two bipyridine ligands upon complexation to the bis-Zn(II) template, suggesting the formation of 2:2 complexes. The crystal structures of two supramolecular boxes have been determined. In both examples such a 2:2 assembly is present in the solid state, and the box size is different because they consist of different building blocks. Interestingly, the box assemblies line up in the solid state to form porous channels that are potentially useful in a number of applications. 相似文献
140.
Termaten AT Schakel M Ehlers AW Lutz M Spek AL Lammertsma K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(15):3577-3582
The novel phosphinidene complex [Cp*(NHC)Ir=PMes*] (3; NHC=1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) was prepared in high yield from [Cp*(NHC)IrCl(2)] (2) and [LiPHMes*].3 THF. It represents the first example of an NHC ligated transition metal phosphinidene complex. The X-ray crystal structure for 3 is also reported. DFT calculations on the N-heterocyclic carbene containing parent complexes [Cp(NHC)Ir=E] (E=PH, NH, CH(2)) show that the NHC ligand acts as good sigma-donor/weak pi-acceptor ligand and forms strong Ir-C(NHC) single bonds. The Ir=E double bonds result from strong triplet-triplet interactions between [Cp(NHC)Ir] and E. 相似文献