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21.
Navneet Kaur Jasvinder Singh Gargi Dhaka Richa Rani Vijay Luxami 《Supramolecular chemistry》2013,25(7-8):453-459
2-Hydroxy-1-naphthaldehyde-based benzothiazole chemosensor (1) undergoes absorption and fluorescence changes with addition of CN? and Cu2+ ions. Addition of CN? ions results in the appearance of two new bands at 420 and 440 nm. However, Cu2+ addition causes decrease in absorption band at 370 nm up to 12 equiv., while addition of higher equiv. of Cu2+(~190 equiv.) results in the appearance of two new bands at 400 and 800 nm. Differential absorption changes observed with addition of Cu2+ and CN? ions results in the construction of ‘NOR’ and ‘INHIBIT’ logic gates at 370 and 440 nm, respectively. 相似文献
22.
Metal–Ligand Cooperation on a Diruthenium Platform: Selective Imine Formation through Acceptorless Dehydrogenative Coupling of Alcohols with Amines 下载免费PDF全文
Biswajit Saha S. M. Wahidur Rahaman Prosenjit Daw Gargi Sengupta Prof. Jitendra K. Bera 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(21):6542-6551
Metal?metal singly‐bonded diruthenium complexes, bridged by naphthyridine‐functionalized N‐heterocyclic carbene (NHC) ligands featuring a hydroxy appendage on the naphthyridine unit, are obtained in a single‐pot reaction of [Ru2(CH3COO)2(CO)4] with 1‐benzyl‐3‐(5,7‐dimethyl‐1,8‐naphthyrid‐2‐yl)imidazolium bromide (BIN ? HBr) or 1‐isopropyl‐3‐(5,7‐dimethyl‐1,8‐naphthyrid‐2‐yl)imidazolium bromide (PIN ? HBr), TlBF4, and substituted benzaldehyde containing an electron‐withdrawing group. The modified NHC‐naphthyridine‐hydroxy ligand spans the diruthenium unit in which the NHC carbon and hydroxy oxygen occupy the axial sites. All the synthesized compounds catalyze acceptorless dehydrogenation of alcohols to the corresponding aldehydes in the presence of a catalytic amount of weak base 1,4‐diazabicyclo[2.2.2]octane (DABCO). Further, acceptorless dehydrogenative coupling (ADHC) of the alcohol with amines affords the corresponding imine as the sole product. The substrate scope is examined with 1 (BIN, p‐nitrobenzaldehyde). A similar complex [Ru2(CO)4(CH3COO)(3‐PhBIN)][Br], that is devoid of a hydroxy arm, is significantly less effective for the same reaction. Neutral complex 1 a , obtained by deprotonation of the hydroxy arm in 1 , is found to be active for the ADHC of alcohols and amines under base‐free conditions. A combination of control experiments, deuterium labeling, kinetic Hammett studies, and DFT calculations support metal–hydroxyl/hydroxide and metal–metal cooperation for alcohol activation and dehydrogenation. The bridging acetate plays a crucial role in allowing β‐hydride elimination to occur. The ligand architecture on the diruthenium core causes rapid aldehyde extrusion from the metal coordination sphere, which is responsible for exclusive imine formation. 相似文献
23.
Chandra B. Bhargava Amarendra N. Vishnoi Umesh C. Srivastava 《Transition Metal Chemistry》1981,6(2):114-118
Summary X-ray (K-) absorption edge spectrometric (XAES) investigations of some copper(II) chelates involving amino acids and a carbonato complex have been carried out employing a curved crystal spectrograph. Experimental edgewidths have been used to bear on the number of nearest neighbours around the central metal atom in the complexes in the solid state. Comparisons in respect of the nature of the metal-ligand bond have been made between inferences drawn on the basis of XAES, i.r. and optical spectral data. Average radii of the coordination sphere in the amino acid chelates have been reported using extended fine structure energy separations (Levy's method). In the carbonato complex, the possibility of determining different metal-donor distances within the coordination sphere has been suggested for the first time. 相似文献
24.
Statistical models based on canonical and grand canonical ensembles are extensively used to study intermediate energy heavy-ion collisions. The underlying physical assumption behind canonical and grand canonical models is fundamentally different, and in principle agree only in the thermodynamical limit when the number of particles become infinite. Nevertheless, we show that these models are equivalent in the sense that they predict similar results if certain conditions are met even for finite nuclei. In particular, the results converge when nuclear multifragmentation leads to the formation of predominantly nucleons and low mass clusters. The conditions under which the equivalence holds are amenable to present day experiments. 相似文献
25.
A new anisidine possessing benzothiaozle-based chemosensor (1) has been designed and synthesized. The chemosensor 1 was designed to provide hard base environment for ratiometric detection of comparatively less studied Al3+ ions. In CH3CN, the fluorescence spectra of chemosensor 1 red shifted from 368 to 430 nm with addition of Al3+ and Hg2+ ions; while Cu2+ ions caused quenching of emission intensity of 1. These differential changes observed with Al3+ and Cu2+ ions addition enabled chemosensor 1 to construct “NOR” and “TRANSFER” logic gates. 相似文献
26.
The stopped-flow measurements on the disappearance of alkaline osmium(VIII) at 402 nm indicated a first-order dependence each in [Os(VIII)] and [HCHO]. The pseudo first-order rate constant kobs ([HCHO] ? [Os(VIII)]) decreased with increasing [OH?]. The ionic strength, however, had no effect on kobs. The rapid scan spectra of the reaction mixture indicated the formation of an inert complex which absorbs at 319 nm. Therefore the rate determining step is considered to involve the bimolecular collision between OsO4(OH) and hydrated formaldehyde. The values of the rate limiting constant k and the equilibrium constant Kha for the formation of the alkoxide ion from the reaction of hydrated formaldehyde with OH? are evaluated. The equilibrium constant Kha, within the experimental limits, is independent of temperature. The pKa value, calculated from Kha, is 13.62 ± 0.05 which is in good agreement with the pKa value 13.27 for formaldehyde. The activation parameters, ΔH? = 40 ± 2 kJ mol?1 and ΔS? = ?51 ± 6 JK?1 mol?1, for the rate limiting constant k are determined. 相似文献
27.
The application of nanopipettes, developed first as a tool for electrochemistry and electrophysiology, as tools for mass spectrometry is considered. Recent examples of advances in electrospray ionization and sampling for mass spectrometry with nanopipettes is discussed. These examples show a scientific intersection that is ripe for further development. 相似文献
28.
29.
Asish R. Das Gargi Pal Pranabes Bhattacharyya Arnab K. Ghosh Debasri Mukherjee Debasish Bandyopadhyay 《Tetrahedron letters》2012,53(52):7060-7066
A series of novel coumarinyl 1,4-benzodioxanes were successfully synthesized from electronically diverse 2-[(o-iodophenoxy)methyl]oxiranes and different positional isomers of hydroxycoumarin via one-pot tandem nucleophilic displacement and copper-mediated intramolecular C–O coupling reaction using CuI and 1,10-phenanthroline as the efficient catalytic system. All the compounds were characterized by 1H, 13C NMR, IR, HRMS spectra and a selected set of newly synthesized compounds offered noticeable in vitro free hydroxyl radical scavenging activity in a systematic dose dependent manner which signifies their excellent biological potential. 相似文献
30.
The efficiency of bio-molecular motors stems from reversible interactions ∼ k
B
T; weak bonds stabilizing intermediate states (enabling direct conversion of chemical into mechanical energy). For their (unknown) origins, we suggest that a magnetically structured phase
(MSP) formed via accretion of superparamagnetic particles (S-PPs) during serpentinization (including magnetite formation) of igneous rocks
comprising the Hadean Ocean floor, had hosted motor-like diffusion of ligand-bound S-PPs through its ‘template’-layers. Ramifications
range from optical activity to quantum coherence. A gentle flux gradient offers both detailed-balance breaking non-equilibrium
and asymmetry to a magnetic dipole, undergoing infinitesimal spin-alignment changes. Periodic perturbation of this background
by local H-fields of templatepartners can lead to periodic high and low-template affinity states, due to the dipole’s magnetic
degree of freedom. An accompanying magnetocaloric effect allows interchange between system-entropy and bath temperature. We
speculate on a magnetic reproducer in a setting close to the submarine hydrothermal mound-scenario of Russell and coworkers
that could evolve bio-ratchets. 相似文献