全文获取类型
收费全文 | 145篇 |
免费 | 9篇 |
国内免费 | 2篇 |
专业分类
化学 | 112篇 |
力学 | 2篇 |
数学 | 21篇 |
物理学 | 21篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 9篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 2篇 |
2016年 | 3篇 |
2015年 | 5篇 |
2014年 | 6篇 |
2013年 | 7篇 |
2012年 | 11篇 |
2011年 | 16篇 |
2010年 | 6篇 |
2009年 | 4篇 |
2008年 | 10篇 |
2007年 | 10篇 |
2006年 | 10篇 |
2005年 | 7篇 |
2004年 | 6篇 |
2003年 | 3篇 |
2002年 | 6篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有156条查询结果,搜索用时 62 毫秒
111.
Yael Dror Yachin Cohen Rachel Yerushalmi‐Rozen 《Journal of Polymer Science.Polymer Physics》2006,44(22):3265-3271
Gum arabic, a natural polysaccharide derived from exudates of Acacia senegal and Acacia seyal trees, is a commonly used food hydrocolloid. The complex chemical structure of the gum has been widely studied revealing a multifraction material consisting mainly of a highly branched polysaccharide and a protein–polysaccharide complex (GAGP) as a minor component. This work investigates its mesoscopic structure in aqueous solution by small‐angle X‐ray and neutron scattering combined with cryotransmission electrons microscopy. Scattering measurements reveal an intricate shape composed of many spheroidal aggregates assigned to the polysaccharide with a small amount of larger coils. A scattering peak is observed at moderate to high concentrations, the spacing of which exhibits a c?1/3 power law relation to polymer concentration (c). Upon addition of salt, this peak disappears, indicating its electrostatic nature. The large coils contribute a q?2 power law at the low scattering vector (q) range. However, at low concentration in which the interaggregate peak is not observed, a q?1 power law at the low q range indicates the possible existence of a fraction with a locally extended conformation. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3265–3271, 2006 相似文献
112.
Ariel Shemesh Tanya Blank Shai Meltzman Sara Stolyarova Rachel Edrei Elena Borzin Yael Nemirovsky Yoav Eichen 《Journal of polymer science. Part A, Polymer chemistry》2014,52(15):2124-2130
A new approach to the chemo‐mechanical detection of trace amounts of nitroaromatics, even in the presence of high concentrations of background materials, is presented. The detection scheme is based on the plasticization of an aminopropyl silane layer that is harnessed to a silicon beam following its reaction with nitroaromatic systems. The reaction‐induced plasticization attenuates the temperature induced bending of the polymer‐beam sandwich, offering a simple and very sensitive tool for the detection of nitroaromatic systems. Using this approach, it was possible to detect a sample of 100 pg TNT even in the presence of a ~109 fold excess of a background material such as acetonitrile. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2124–2130 相似文献
113.
Salman H Tal S Chuvilov Y Solovey O Abraham Y Kapon M Suwinska K Eichen Y 《Inorganic chemistry》2006,45(14):5315-5320
3-(3-Ethoxymethyl-1H-imidazol-2-yl)-3-(1-ethoxymethyl-1H-imidazol-2-yl)-3H-benzo[de]isochromen-1-one, 4, is a novel photoinduced electron transfer (PET) chemosensor that becomes fluorescent upon binding metal ions and shows a strong preference toward Zn(II) ions. The new bisimidazol PET sensor and its zinc complex were prepared and characterized in terms of their crystal structures, absorption and emission spectra, and orbital energy diagrams. Free 4 is a weakly luminescent species. On the basis of detailed DFT calculations, we suggest that the poor luminescence yield of free 4 originates from its orbital structure in which two pi-orbitals of the two imidazole rings, HOMO and HOMO-1, are situated between two pi-orbitals of the isochromene-one system, HOMO-2 and LUMO. The absorption and emission processes occur between the two pi-orbitals of the isochromene-one system, HOMO-2 and LUMO, and the two pi-imidazole orbitals serve as quenchers for the excited state of the molecule through nonradiative processes. Upon binding Zn(II) ions, 4 becomes a highly luminescent species having a luminescence maximum peaking at 375 nm (lambda(ex) = 329 nm). The significant 900-fold enhancement in luminescence upon binding of the Zn(II) ions is attributed to the stabilization of the pi-orbitals of the imidazole rings upon their engagement in new bonds with the zinc ion. The affinity of 4 to zinc ions in acetonitrile is found to be very high, Ka > 3 x 10(6) M(-1), while with other metals ions, the association constants are considerably weaker. 相似文献
114.
Bitton R Ben-Yehuda M Davidovich M Balazs Y Potin P Delage L Colin C Bianco-Peled H 《Macromolecular bioscience》2006,6(9):737-746
Adhesive materials extracted from the brown alga Fucus serratus are composed of phenolic polymer, alginate, and CaCl2. The phenolic polymer undergoes an oxidation reaction in the presence of bromoperoxidase, KI, and H2O2. The nanostructure of the adhesive was investigated using small angle X-ray scattering, light scattering, and cryo- transmission electron microscopy experiments. These have shown that the phenolic polymer undergoes self-assembly and forms flexible chain-like objects. Oxidation or adding alginate does not alter this structure. However, once calcium ions are added, a rigid network is formed. Presumably, this network is responsible for the cohesive strength of the glue. 相似文献
115.
We consider symplectic manifolds with Hamiltonian torus actions which are ``almost but not quite completely integrable": the dimension of the torus is one less than half the dimension of the manifold. We provide a complete set of invariants for such spaces when they are ``centered" and the moment map is proper. In particular, this classifies the preimages under the moment map of all sufficiently small open sets, which is an important step towards global classification. As an application, we construct a full packing of each of the Grassmannians and by two equal symplectic balls.
116.
Moran Feller Eyal Ben-Ari Yael Diskin-Posner 《Journal of Coordination Chemistry》2018,71(11-13):1679-1689
AbstractHerein we report the reversible activation of CO2 by the dearomatized complex [(tBuPNP*)Ir(COE)] (1) and by the aromatized complex [(tBuPNP)Ir(C6H5)] (2) via metal-ligand cooperation (MLC) (tBuPN = 2,6-bis-(di-tert-butylphosphinomethyl)pyridine; tBuPNP* = deprotonated PNP; COE = cyclooctadiene). The [1,3]-addition of CO2 to 1 and 2 is reversible at ambient temperature. While the dearomatized complex 1 reacts readily at ambient temperature with CO2 in THF or benzene, complex 2 reacts with CO2 upon heating in benzene at 80 °C or at ambient temperature in THF. The novel aromatized complex [(tBuPNP)IrCl] (10) does not react with CO2. Based on the reactivity patterns of 1, 2, and 10 with CO2, we suggest that CO2 activation via MLC takes place only via the dearomatized species, and that in the case of 2 THF plays a role as a polar solvent in facilitating formation of the dearomatized hydrido phenyl complex intermediate (complex II). 相似文献
117.
You-Quan Zou Quan-Quan Zhou Yael Diskin-Posner Yehoshoa Ben-David David Milstein 《Chemical science》2020,11(27):7188
A sustainable, new synthesis of oxalamides, by acceptorless dehydrogenative coupling of ethylene glycol with amines, generating H2, homogeneously catalyzed by a ruthenium pincer complex, is presented. The reverse hydrogenation reaction is also accomplished using the same catalyst. A plausible reaction mechanism is proposed based on stoichiometric reactions, NMR studies, X-ray crystallography as well as observation of plausible intermediates.Ruthenium catalyzed acceptorless dehydrogenative coupling of ethylene glycol and amines to oxalamides is reported. The reverse hydrogenation reaction is also accomplished. 相似文献
118.
Vuzman D Poverenov E Diskin-Posner Y Leitus G Shimon LJ Milstein D 《Dalton transactions (Cambridge, England : 2003)》2007,(48):5692-5700
The synthesis and characterization of several Pt(ii) complexes, including formyl complexes, based on the PCP-type pincer ligands C(6)H(4)[CH(2)P(iPr)(2)](2) ((iPr)PCP) and C(6)H(4)[CH(2)P(tBu)(2)](2) ((tBu)PCP) are described. The chloride complex ((iPr)PCP)PtCl (6) and the unsaturated cationic complexes [(PCP)Pt](+)X(-) (X = OTf(-), BF(4)(-)) (1, 7), based on both PCP ligands, were prepared and the latter reacted with carbon monoxide to give the corresponding cationic carbonyl complexes [(PCP)Pt(CO)](+)X(-) (X = OTf(-), BF(4)(-)) (2, 8a). Hydride nucleophilic attack on both carbonyl complexes resulted in rare neutral platinum formyl complexes ((iPr)PCP)Pt(CHO) (3) and ((tBu)PCP)Pt(CHO) (9). Complex 3 undergoes decarbonylation to the corresponding hydride complex within hours at room temperature, while the bulkier complex 9 is more stable and undergoes complete decarbonylation only after 3-4 d. This observation demonstrates the very significant steric effect of the ligand on stabilization of the corresponding formyl complexes. Reaction of complex 9 with triflic acid resulted in the carbonyl complex [((tBu)PCP)Pt(CO)](+) OTf(-) (8b) with liberation of H(2), an unusual transformation for a metal formyl. Reaction with methyl triflate resulted in the Fischer carbene-type complex, the methoxy-methylidene [((tBu)PCP)Pt(CHOCH(3))](+)OTf(-) (11). The X-ray structures of complexes 2, 6, 8a and 11 were determined. 相似文献
119.
Michal Segal-Rosenheimer Yael Dubowski 《Journal of photochemistry and photobiology. A, Chemistry》2008,200(2-3):262-269
Cypermethrin is a synthetic pyrethroid insecticide commonly used both indoors and outdoors. Following its application, cypermethrin residues are exposed to atmospheric oxidants, such as ozone and OH radicals, as well as to solar radiation. The current work focuses on the photochemical degradation of cypermethrin under 254 nm, 310 nm, and solar radiation; including kinetic analysis, quantum yields, and identification of volatile and non-volatile products. The investigation was done using a combined FTIR set-up for parallel analysis of condensed and gas phases. Complementary GC–MS analysis was conducted on the pesticide’s residues. Quantum yields of 0.41 and 0.25 were obtained under 254 and 310 nm, respectively. These values are in agreement with outdoor studies and are higher than the known yields for aqueous solution. The values obtained under all tested conditions suggest that photodegradation of adsorbed cypermethrin is a major outdoor degradation pathway. Oxygen presence was found to increase degradation rate and quantum yield.The identified photoproducts include 3-phenoxybenzaldehyde, 3-phenoxybenzoic acid, acetonitrile (m-phenoxyphenyl), and cypermethrin isomers on the surface and formic acid, CO2 and CO in the gas phase. The condensed phase products are more polar than the parent molecule, suggesting that they may be susceptible to a greater leaching rate in soils. 相似文献
120.
Yael Nissinkorn Naama Lahav‐Mankovski Dr. Aharon Rabinkov Dr. Shira Albeck Dr. Leila Motiei Dr. David Margulies 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(45):15981-15987
A methodology for creating fluorescent molecular sensors that respond to changes that occur on the surfaces of specific proteins is presented. This approach, which relies on binding cooperatively between a specific His‐tag binder and a nonspecific protein‐surface receptor, enabled the development of a sensor that can track changes on the surface of a His‐tag‐labeled calmodulin (His‐CaM) upon interacting with metal ions, small molecules, and protein binding partners. The way this approach was used to detect dephosphorylation of an unlabeled calmodulin‐dependent protein kinase II (CaMKII), and the binding of Bax BH3 to His‐tagged B‐cell lymphoma 2 (Bcl‐2) protein is also presented. 相似文献