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81.
82.
Duncan A. J. Harding Eric G. Hope Gregory A. Solan John Fawcett 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(7):m321-m322
The reaction between carbonyl fluoride and [Ir(COD)(PPh3)2]BF4 (COD is cycloocta‐1,5‐diene) in dichloromethane solution affords the novel title iridium salt, [IrCl2(C18H15P)2(CO)2]BF4. The cation lies across a twofold rotation axis in the space group P21212 and its structure confirms the presence in a cis relationship of two metal‐bound chlorides, while the phosphine ligands occupy a trans pair of sites. The anion also lies across a twofold rotation axis, and the F atoms are disordered over two sets of sites. 相似文献
83.
I. Romanski I. Berkes D. E. Brown M. De Jesus R. Eder I. S. Grant E. Hagn P. Harding P. Herzog B. Hinfurtner B. Kastelein H. Postma J. Prinz P. Richards K. Schlösser N. J. Stone L. Vanneste E. Zech Nicole Isolde 《Hyperfine Interactions》1992,75(1-4):457-470
The methods of time-resolved and time-integral on-line nuclear orientation have been applied to study short lived nuclei with
the NICOLE facility (Nuclear Implantation into Cold On-Line Equipment) at ISOLDE-3 in CERN using beams of182–186Hg. The half-lives in these decay chains are of the order of seconds and therefore comparable to the spin-lattice relaxation
times of the nuclei in iron. As the relaxation rate depends strongly on the g-factor, g-factors of nuclei in the decay chains
can be deduced from the observation of the time evolution of γ-ray anisotropy. Using this technique the existence of an isomer
in184Au has been found and the g-factors of184Au,184mAu and182Au have been determined. Accurate half-lives have been extracted from the data.
Time-integral nuclear orientation has been observed for short lived as well as longer lived isotopes of the Hg decay chains.
From these measurements, after proper correction for incomplete relaxation, the magnetic moments of183mPt,183Ir and182Ir have been derived.
The applicability of the time-resolved nuclear orientation technique for nuclei far from stability and its possible limitations
is discussed. 相似文献
84.
85.
We show that the variety of ortholattices has the strong amalgamation property and that the variety of orthomodular lattices has the strong Boolean amalgamation property, i.e. that two orthomodular lattices can be strongly amalgamated over a common Boolean subalgebra. We give examples to show that the variety orthomodular lattices does not have the amalgamation property and that the variety of modular ortholattices does not even have the Boolean amalgamation property. We further show that no non-Boolean variety of orthomodular lattices which is generated by orthomodular lattices of bounded height can have the Boolean amalgamation property. 相似文献
86.
Ditopic symmetrical bis(pyridyl) ligands incorporating the chiral dibenzobicyclo[b,f][3.3.1]nona-5a,6a-diene-6,12-dione cleft have been synthesised and characterised by NMR spectroscopy, mass spectrometry and X-ray crystallography. The ligands, which incorporate pyridyl groups directly connected to the carbocyclic cleft core or via alkyne or phenyl linkers were accessed from palladium-catalysed coupling reactions of 2,8-dibromodibenzobicyclo[b,f][3.3.1]nona-5a,6a-diene-6,12-dione. X-ray crystal analyses show the interplanar angles between the two cleft aromatic rings in these molecules, which range from 97.80(3) to 109.80(4)°. 相似文献
87.
Lester MI Pond BV Marshall MD Anderson DT Harding LB Wagner AF 《Faraday discussions》2001,(118):373-85; discussion 419-31
A hydrogen-bonded complex composed of the OH and CO reactants has been identified along the OH + CO-->HOCO reaction pathway. IR action spectroscopy in the OH overtone region has been used to examine the vibrational modes of the linear OH-CO complex, including intermolecular bending modes that probe portions of the reaction path leading to HOCO. The spectroscopic measurements have accessed highly excited intermolecular levels, with energies up to 250 cm-1 above the zero-point level, which lie in close proximity to the transition state for reaction. The OH-CO binding energy, D0 < or = 430 cm-1, has also been established from the quantum state distribution of the OH fragments following vibrational predissociation of the OH-CO complex. Complementary electronic structure calculations have been performed to characterize the OH-CO and OH-OC complexes, the transition state for HOCO formation, and the direct reaction path that connects the experimentally observed OH-CO complex to the HOCO intermediate. 相似文献
88.
ÜMMÜHAN OCAK HALIT KANTEKIN YAŞAR GÖK H. BASIR ŞENTÜRK 《Journal of inclusion phenomena and macrocyclic chemistry》2006,55(1-2):87-91
The selective liquid–liquid extraction of various transition metal cations from the aqueous phase to the organic phase was carried out using a 14-membered N2O2S2-macrobicycle. Metal picrates such as Pb2+, Co2+, Zn2+, Ni2+,Cu2+ and Cd2+ were used in this extraction studies. It was found that the ligand showed moderate selectivity towards Pb2+ only among the other metals. The extraction constant (log K
ex) was determined to be 13.8 for Pb2+ complex. 相似文献
89.
Barry CS Bushby N Harding JR Hughes RA Parker GD Roe R Willis CL 《Chemical communications (Cambridge, England)》2005,(29):3727-3729
Trapping intermediates on the Prins cyclisation pathway with carbon-based nucleophiles has given further insight into factors affecting the acid-mediated reactions of homoallylic alcohols with aldehydes, enabling the design of efficient syntheses of 4-hydroxy-2,6-disubstituted tetrahydropyrans. 相似文献
90.
Tsang WY Ahmed N Hinchliffe PS Wood JM Harding LP Laws AP Page MI 《Journal of the American Chemical Society》2005,127(49):17556-17564
Beta-sultams are the sulfonyl analogues of beta-lactams, and N-acyl beta-sultams are novel inactivators of the class C beta-lactamase of Enterobacter cloacae P99. They sulfonylate the active site serine residue to form a sulfonate ester which subsequently undergoes C-O bond fission and formation of a dehydroalanine residue by elimination of the sulfonate anion as shown by electrospray ionization mass spectroscopy. The analogous N-acyl beta-lactams are substrates for beta-lactamase and undergo enzyme-catalyzed hydrolysis presumably by the normal acylation-deacylation process. The rates of acylation of the enzyme by the beta-lactams, measured by the second-order rate constant for hydrolysis, kcat/K(m), and those of sulfonylation by the beta-sultams, measured by the second-order rate constant for inactivation, k(i), both show a similar pH dependence to that exhibited by the beta-lactamase-catalyzed hydrolysis of beta-lactam antibiotics. Electron-withdrawing groups in the aryl residue of the leaving group of N-aroyl beta-lactams increase the rate of alkaline hydrolysis and give a Bronsted beta(lg) of -0.55, indicative of a late transition state for rate-limiting formation of the tetrahedral intermediate. Interestingly, the corresponding Bronsted beta(lg) for the beta-lactamase-catalyzed hydrolysis of the same substrates is -0.06, indicative of an earlier transition state for the enzyme-catalyzed reaction. By contrast, although the Bronsted beta(lg) for the alkaline hydrolysis of N-aroyl beta-sultams is -0.73, similar to that for the beta-lactams, that for the sulfonylation of beta-lactamase by these compounds is -1.46, compatible with significant amide anion expulsion/S-N fission in the transition state. In this case, the enzyme reaction displays a later transition state compared with hydroxide-ion-catalyzed hydrolysis of the beta-sultam. 相似文献