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131.
The [Fe(II)(Cys)(4)](2-) site of rubredoxin from Clostridium pasteurianum (Rd(red)) has been studied by M?ssbauer spectroscopy in both purified protein and whole cells of Escherichia coli overproducing it. Excellent fits were obtained to an S = 2 spin Hamiltonian for D = 5.7(3) cm(-1), E/D = 0.25(2), delta = 0.70(3) mm/s, DeltaE(Q) = -3.25(2) mm/s, eta = 0.75(5), A(x) = -20.1(7) MHz, A(y) = -11.3(2) MHz, and A(z) = -33.4(14) MHz. These parameters were analyzed with crystal-field theory for the (5)D manifold of iron(II), revealing a d(z(2)) orbital ground state that is admixed by approximately 0.21 d(x(2) - y(2)). The spin-Hamiltonian parameters are consistent within the (5)D theory, apart from the zero-field splitting parameter, D. This problem was solved by extending the crystal-field treatment with spin-orbit coupling to spin-triplet d-d excited states of the iron. Theoretical estimates are given for the spin-triplet (D(T)) and spin-quintet contributions (D(Q)) to D based on excitation energies derived from time-dependent density functional theory, TD-DFT. The computational results were interpreted in terms of crystal-field theory, yielding the Racah parameters B = 682 cm(-1) and C = 2583 cm(-1). The theoretical analysis gives the relative magnitudes D(Q):D(T):D(ss) = 51%: 42%:7% (D(ss) originates from spin-spin interaction). The DFT analysis corroborates the pivotal role of the torsion angles (omega(i)) of the C-S(i) bonds in shaping the electronic structure of the iron(II) site. Rd(red) in overexpressing whole cells accounts for 60% of the M?ssbauer absorption. The Rd(red) spectra from whole cells are virtually identical to those of the purified protein. By using the theoretical omega dependence of the spin Hamiltonian parameters, the torsions for Rd(red) in whole cells and purified protein samples are estimated to be the same within 2 degrees. These findings establish M?ssbauer spectroscopy as a structural tool for investigating iron sites in whole cells. 相似文献
132.
The formation of chlorinated phenols during the analysis of chromatographically pure polychloroalicyclic ketones by gas chromatography and gas chromatography-mass spectrometry was observed. Also in the mass spectra obtained by direct inlet, the presence of small amounts of chlorophenols was detected. The reasons of the formation of chlorophenols are discussed and qualitative and quantitative results obtained are interpreted. 相似文献
133.
Andrew G. Ogienko Elissa A. Ukraintseva Tatyana A. Chingina Vladislav Yu. Komarov Andrey Yu. Manakov 《Journal of inclusion phenomena and macrocyclic chemistry》2005,53(3-4):231-236
The phase diagram of the pyridine–iron(III) chloride system has been studied for the 223–423 K temperature and 0–56 mass-% concentration ranges using differential thermal analysis (DTA) and solubility techniques. A solid with the highest pyridine content formed in the system was found to be an already known clathrate compound, [FePy3Cl3]·Py. The clathrate melts incongruently at 346.9 ± 0.3 K with the destruction of the host complex: [FePy3Cl3]·Py(solid)=[FePy2Cl3](solid) + liquor. The thermal dissociation of the clathrate with the release of pyridine into the gaseous phase (TGA) occurs in a similar way: [FePy3Cl3]·Py(solid)=[FePy2Cl3](solid) + 2 Py(gas). Thermodynamic parameters of the clathrate dissociation have been determined from the dependence of the pyridine vapour pressure over the clathrate samples versus temperature (tensimetric method). The dependence experiences a change at 327 K indicating a polymorphous transformation occurring at this temperature. For the process ${1 \over 2}[\hbox{FePy}_{3}\hbox{Cl}_{3}]\cdot \hbox{Py}_{\rm (solid)} = {1 \over 2}[\hbox{FePy}_{2}\hbox{Cl}_{3}]_{\rm (solid)} + \hbox{Py}_{\rm (gas)}$ in the range 292–327 K, ΔH $^{0}_{298}$ =70.8 ± 0.8 kJ/mol, ΔS $^{0}_{298}$ =197 ± 3 J/(mol K), ΔG $^{0}_{298}$ =12.2 ± 0.1 kJ/mol; in the range 327–368 K, ΔH $^{0}_{298}$ =44.4 ± 1.3 kJ/mol, ΔS $^{0}_{298}$ =116 ± 4 J/(mol K), ΔG $^{0}_{298}$ =9.9 ± 0.3 kJ/mol. 相似文献
134.
Holba Vladislav Benko Ján Grančičová Ol'ga Vollárová Ol'ga 《Transition Metal Chemistry》1985,10(3):84-89
Summary The kinetics of oxidation of [Co(NH3)5(NCS)]2+ by peroxodisulphate and periodate were investigated at different ionic strengths, and at different temperatures and concentrations
of perchloric acid. Rate constants and activation parameters are also reported in mixed water-organic solvents. It was shown
that the acid-base equilibria involving S2O
8
−2
, and IO
4
−
ions are important in the reactions studied. Solvent effects on the oxidation are interpreted in terms of the solvation of
both the initial state and the activated complex. 相似文献
135.
Efremov D Kuznetsova T Doronin V Sadykov V 《The journal of physical chemistry. B》2005,109(15):7451-7459
The article discusses the properties of several model zirconium dioxide complexes (ZrO(2))(n)() intercalated into the interlayer space of montmorillonite clay. Grand canonical Monte Carlo simulation was used in a series of numerical experiments during analysis of the low-temperature nitrogen adsorption in the micropores thus generated. The goal of such experiments was to determine the geometrical parameters of introduced molecular complexes of different types inside micropores of various widths. The obtained information was used to characterize textural and structural properties of three pillared interlayer materials prepared by using pillaring species synthesized via aging of zirconyl chloride solutions containing as additives chlorides of Ca, Sr, or Ba. It was found that in the cases of Ba and Ca the interlayer micropores are filled with isolated tetramers (ZrO(2))(4). Meanwhile, the presence of Sr in the pillaring solution, most likely, favors the preservation of larger sheetlike complexes (ZrO(2))(8). 相似文献
136.
137.
Aliphatic isocyanides react with o-aminobenzophenones in dichloromethane under Lewis acid catalysis at ambient temperature to give, unexpectedly, 4-aryl-4-hydroxy-3,4-dihydroquinazolines in good to excellent yields. The outcome of the reaction is rationalized by a skeletal rearrangement of the initially formed ‘intramolecular Passerini’ reaction products, 2-amino-3-hydroxy-3-aryl-3H-indoles. 相似文献
138.
Vladislav Z. Parchinsky 《Tetrahedron letters》2006,47(38):6891-6894
The Groebke-type multi-component reaction (MCR) between 3-amino-1,2,4-triazole, aromatic aldehydes and isonitriles has been studied from the viewpoint of convenient generation of combinatorial arrays of imidazo[1,2-b][1,2,4]triazoles. However, it was established that the desired heterocyclic structures can be produced in moderate to good yields in an oxidized form, when benzylic isonitriles are used. Oxidation occurred at the benzylic position to produce N-alkylidene-4H-imidazo[1,2-b][1,2,4]triazol-6-amines that proved to be unusually stable towards acid hydrolysis and reduction. The presence of an easily oxidized benzylic position in the target structures is thought to be the prerequisite for successful Groebke-type MCR of 3-amino-1,2,4-triazole. 相似文献
139.
Andrey V. Blinov Shahida A. Siddiqui Andrey A. Nagdalian Anastasiya A. Blinova Alexey A. Gvozdenko Vladislav V. Raffa Natalya P. Oboturova Alexey B. Golik David G. Maglakelidze Salam A. Ibrahim 《Arabian Journal of Chemistry》2021,14(7):103229
To solve the problem of insufficient intake of essential macro - and micronutrients into the human body, particularly in the case of the essential trace element Zinc, the possibility of enriching a socially significant product (milk) with various forms of Zinc is considered. The influence of Zinc-containing compounds on the colloidal milk system's dispersed composition and stability, photon correlation spectroscopy methods, acoustic and electroacoustic spectroscopy was established in this research. It has been shown that Zinc lysinatoriboflavinate, is a colloidal and chelated organic form of the essential trace element Zinc, having the most negligible effects on the composition and stability of the dispersed phase particles. This increases the average hydrodynamic radius of the dispersed phase by 5% and the ζ-potential by 10%.A quantum-chemical simulation of the interaction of milk κ-casein sites with various forms of the essential trace element Zinc in the QChem program was performed using the IQmol molecular editor. The mechanism of action of various forms of Zinc on the components of the dispersed system of milk, in particular milk protein (casein), is suggested. 相似文献
140.
Efremova Irina E. Savelev Igor I. Baichurin Ruslan I. Gurzhiy Vladislav V. 《Chemistry of Heterocyclic Compounds》2022,58(8-9):449-453
Chemistry of Heterocyclic Compounds - A number of tetracyclic compounds with annulated nitrosulfolane and pyranochromenone rings were synthesized by reacting... 相似文献