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121.
Suparna Baksi Haregewine Tadesse Samaresh Bhattacharya 《Journal of organometallic chemistry》2010,695(8):1111-190
Reaction of 2-(2′,6′-diethylphenylazo)-4-methylphenol (L2) with [Ir(PPh3)3Cl] afforded two organoiridium complexes 3 and 4 via C-H bond activation of an ethyl group in the arylazo fragment of the L2 ligand. In both the complexes the azo ligand binds to iridium as a dianionic tridentate C,N,O-donor. Two triphenylphosphines and a hydride (in the case of complex 3) or chloride (in the case of complex 4) are also coordinated to the metal center. A similar reaction of [Ir(PPh3)3Cl] with 2-(2′,6′-diisopropylphenylazo)-4-methylphenol (L3) yielded another organoiridium complex 5, where migration of one iso-propyl group from its original location (say, the 2′ position) to the corresponding third position (say, the 4′ position) took place through C-C bond activation. In this complex the modified azo ligand binds to iridium as a dianionic tridentate C,N,O-donor. Two triphenylphosphines and a hydride are also coordinated to the metal center. The structures of complexes 3 and 4 have been optimized through DFT calculations. The structure of complex 5 has been determined by X-ray crystallography. All the complexes show characteristic 1H NMR signals and intense transitions in the visible region. Cyclic voltammetry on all the complexes shows an oxidation within 0.66-1.10 V vs SCE, followed by a second oxidation within 1.15-1.33 V vs SCE and a reduction within −0.96 to −1.07 V vs SCE. 相似文献
122.
Koplienko (Sib Math J 25(5): 735–743, 1984) gave a trace formula for perturbations of self-adjoint operators by operators of Hilbert–Schmidt class ${\mathcal{B}_2(\mathcal{H})}$ . Recently Gesztesy et?al. (Basics Z Mat Fiz Anal Geom 4(1):63–107, 2008) gave an alternative proof of the trace formula when the operators involved are bounded. In this article, we give a still another proof and extend the formula for unbounded case by reducing the problem to a finite dimensional one as in the proof of Krein trace formula by Voiculescu (On a Trace Formula of M. G. Krein. Operator Theory: Advances and Applications, vol. 24, pp. 329–332. Birkhauser, Basel, 1987), Sinha and Mohapatra (Proc Indian Acad Sci (Math Sci) 104(4):819–853, 1994). 相似文献
123.
A Mukherjee TK Sen PK Ghorai PP Samuel C Schulzke SK Mandal 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(34):10530-10545
Herein, we report the synthesis and characterization of two organozinc complexes that contain symmetrical phenalenyl (PLY)-based N,N-ligands. The reactions of phenalenyl-based ligands with ZnMe(2) led to the formation of organozinc complexes [N(Me),N(Me)-PLY]ZnMe (1) and [N(iPr),N(iPr)-PLY]ZnMe (2) under the evolution of methane. Both complexes (1 and 2) were characterized by NMR spectroscopy and elemental analysis. The solid-state structures of complexes 1 and 2 were determined by single-crystal X-ray crystallography. Complexes 1 and 2 were used as catalysts for the intramolecular hydroamination of unactivated primary and secondary aminoalkenes. A combined approach of NMR spectroscopy and DFT calculations was utilized to obtain better insight into the mechanistic features of the zinc-catalyzed hydroamination reactions. The progress of the catalysis for primary and secondary aminoalkene substrates with catalyst 2 was investigated by detailed kinetic studies, including kinetic isotope effect measurements. These results suggested pseudo-first-order kinetics for both primary and secondary aminoalkene activation processes. Eyring and Arrhenius analyses for the cyclization of a model secondary aminoalkene substrate afforded ΔH(≠) =11.3?kcal?mol(-1) , ΔS(≠) =-35.75?cal?K(-1) mol(-1) , and E(a) =11.68?kcal?mol(-1) . Complex 2 exhibited much-higher catalytic activity than complex 1 under identical reaction conditions. The in situ NMR experiments supported the formation of a catalytically active zinc cation and the DFT calculations showed that more active catalyst 2 generated a more stable cation. The stability of the catalytically active zinc cation was further supported by an in situ recycling procedure, thereby confirming the retention of catalytic activity of compound 2 for successive catalytic cycles. The DFT calculations showed that the preferred pathway for the zinc-catalyzed hydroamination reactions is alkene activation rather than the alternative amine-activation pathway. A detailed investigation with DFT methods emphasized that the remarkably higher catalytic efficiency of catalyst 2 originated from its superior stability and the facile formation of its cation compared to that derived from catalyst 1. 相似文献
124.
The layered vanadyl phosphate, VOPO(4)2H(2)O, is employed to prepare nanosized conducting polypyrrole by redox intercalation method. Transport and dielectric properties of various compositions have been investigated by impedance technique over a temperature range of 300-120 K. Grain boundary conductivity is larger than the bulk conductivity. The conductivity reveals a discontinuity at about 212-235 K. The conductivity is predominantly ionic at high temperature and electronic at low temperature. The dielectric spectra reveal a peak in the frequency range up to 2 MHz for higher concentration of intercalated polypyrrole. The activation energy of conductivity relaxation is different from that of total conductivity derived from the impedance plot. 相似文献
125.
126.
Abstract The halogen-free Brønsted acidic ionic liquid methylimidazolium hydrogen sulfate ([Hmim]+ HSO4 ?) acts as a very efficient catalyst for the one-pot, two-component Baeyer condensation of a variety of aromatic aldehydes with dimethyl or diethyl aniline at room temperature. This “green” reagent behaves as both catalyst and solvent; that is, it exhibits “dual-reagent catalysis.” The room-temperature acidic ionic liquid could be recycled several times with almost no loss in the yield of the reaction. This is the first report of the Baeyer synthesis with a halogen-free ionic liquid. 相似文献
127.
Resonance Raman spectroscopic study for radial vibrational modes in ultra‐thin walled TiO2 nanotubes
Rajini P. Antony Arup Dasgupta Sudipta Mahana D. Topwal Tom Mathews Sandip Dhara 《Journal of Raman spectroscopy : JRS》2015,46(2):231-235
The study reports the observation of radial vibrational modes in ultra‐thin walled anatase TiO2 nanotube powders grown by rapid breakdown anodization technique using resonant Raman spectroscopic study. The as‐grown tubes in the anatase phase are around 2–5 nm in wall thickness, 15–18 nm in diameter and few microns in length. The Eg(ν1,ν5,ν6) phonon modes with molecular vibrations in the radial direction are predominant in the resonance Raman spectroscopy using 325 nm He–Cd excitation. Multi‐phonons including overtones and combinational modes of Eg(ν1,ν5,ν6) are abundantly observed. Fröhlich interaction owing to electron–phonon coupling in the resonance Raman spectroscopy of ultra‐thin wall nanotubes is responsible for the observation of radial vibrational modes. Finite size with large surface energy in these nanotubes energetically favor only one mode, B1g(ν4) with unidirectional molecular vibrations in the parallel configuration out of the three Raman modes with molecular vibration normal to the radial modes. Enhanced specific heat with increasing temperatures in these nanotubes as compared to that reported for nanoparticles of similar diameter may possibly be related to the presence of the prominent radial mode along with other energetic phonon mode. The findings elucidate the understanding of total energy landscape for TiO2 nanotubes. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
128.
Sulfated Galactans of Champia indica and Champia parvula (Rhodymeniales,Rhodophyta) of Indian Waters
Sanjay Kumar Devaki Nandan Ramavatar Meena Kamalesh Prasad Arup K. Siddhanta 《Journal of carbohydrate chemistry》2013,32(1):47-60
Sulfated galactans of the red seaweed species Champia indica and Champia parvula of Indian waters were extracted and purified by ion exchange chromatography. These were characterized by infrared and 13C NMR spectroscopy as well as by GC-MS analysis of alditol acetate derivatives produced by reductive hydrolysis/acetylation of sulfated and desulfated and their methylated samples. The sulfated galactans of these Champia species contained alternating β-(1→3)-linked galactopyranosyl units with sulfation at the 2-position and α-(1→4)-linked galactopyranosyl units having sulfation at both the 2- and 3-positions. Other minor substitutions included 6-O-methyl ether of the β-(1→3)-linked galactose residues only in Champia parvula. 相似文献
129.
Arup Gayen Tinku Baidya G. S. Ramesh R. Srihari M. S. Hegde 《Journal of Chemical Sciences》2006,118(1):47-55
A completely automated temperature-programmed reaction (TPR) system for carrying out gas-solid catalytic reactions under atmospheric
flow conditions is fabricated to study CO and hydrocarbon oxidation, and NO reduction. The system consists of an all-stainless
steel UHV system, quadrupole mass spectrometer SX200 (VG Scientific), a tubular furnace and micro-reactor, a temperature controller,
a versatile gas handling system, and a data acquisition and analysis system. The performance of the system has been tested
under standard experimental conditions for CO oxidation over well-characterized Ce1−−x−y
Ptx(La/Y)yO2-δ catalysts. Testing of 3-way catalysis with CO, NO and C2H2 to convert to CO2, N2 and H2O is done with this catalyst which shows complete removal of pollutants below 325°C. Fixed oxide-ion defects in Pt substituted
Ce1−y
(La/Y)
y
O2−y/2 show higher catalytic activity than Pt ion-substituted CeO2.
Dedicated to Prof J Gopalakrishnan on his 62nd birthday. 相似文献
130.
Arnold and Villaseñor (1999) raised several questions for upper records, including characterizing all limit distributions of normalized partial sums of upper records. We provide some answers in the case when the distribution from which the samples are drawn is bounded above. When the distribution is not bounded above, we give sufficient conditions on the distribution for the properly normalized partial sums to converge to a standard normal distribution. We show that our conditions are general enough so that the examples provided by Arnold and Villaseñor (1999) are covered by our results. 相似文献