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971.
Amitava Bhattacharyya Swapan Kumar Bhattacharya 《Journal of solution chemistry》2013,42(11):2149-2167
Standard transfer Gibbs energies, $ \Updelta_{\text{tr}} G^{^\circ } $ , of a series of homologues α-amino acids have been evaluated by determining the solubility of glycine, alanine, amino butyric acid and norvaline gravimetrically at 298.15 K. Standard entropies of transfer, $ \Updelta_{\text{tr}} S^{^\circ } $ , of the amino acids have also been evaluated by extending the solubility measurement to five equidistant temperatures ranging from 288.15 to 308.15 K. The chemical contributions $ \Updelta_{\text{tr,ch}} G^{^\circ } (i) $ of α-amino acids, as obtained by subtracting theoretically computed contributions to $ \Updelta_{\text{tr}} G^{ \circ } $ due to cavity and dipole–dipole interaction effects from the corresponding experimental $ \Updelta_{\text{tr}} G^{ \circ } $ , are indicative of the superimposed effect of increased basicity and dispersion and decreased hydrophobic hydration (hbh) in DMF–water solvent mixtures as compared to those in water, while, in addition, $ T\Updelta_{\text{tr,ch}} S^{^\circ } (i) $ is guided by structural effects. The computed chemical transfer energies of the –CH2– group, $ \Updelta_{\text{tr,ch}} P^{^\circ } $ (–CH2–) [P = G or S] as obtained by subtracting the value of lower homologue from that of immediately higher homologue, are found to change with composition indicating involvement of several opposing factors in the calculation of the chemical interactions. The $ \Updelta_{\text{tr,ch}} G^{^\circ } $ (–CH2–) values are found to be guided by the decreased hydrophobic effect in DMF–water mixtures, and are indicative of the nature of the three dimensional structure of the aquo-organic solvent system around each solute. 相似文献
972.
Ghosh Tapas Bandyopadhyay Chandrakanta Bhattacharya Sharmila Mukherjee Gurunath 《Transition Metal Chemistry》2004,29(4):444-450
Mixed-ligand oxovanadium(IV) and oxovanadium(V) complexes with a tridentate dinegative ONO donor Schiff base ligand [viz., 4-(1-hydroxybenzylidenehydrazono)-2-penten-2-ol (H2L)] and bidentate NN [viz., 2,2-bipyridine (bipy) and 1,10-phenanthroline (phen): complexes (1) and (2), respectively] or OO–[viz., ethylene glycol (H2gol), salicylaldehyde (Hsal) and vanillin (Hvan): complexes (3)–(5), respectively] donor ligands have been prepared and characterized by elemental analyses and by i.r., e.p.r., n.m.r., and u.v.–vis. spectroscopies. The complexes with NN donor ligands are one electron paramagnetic, displaying axial e.p.r. spectra and exhibiting two ligand-field transitions in the visible region, whereas the complexes with OO– donor ligands are diamagnetic and display only LMCT bands. 1H n.m.r. spectral data indicate that the pentavalent complexes (4) and (5) exist in two isomeric forms [(4A), (4B) and (5A), (5B) in 1:1 and 4:1 ratios, respectively]. The vanadyl(IV) complexes display an irreversible oxidation peak near +0.67 V while among the vanadyl(V) complexes, (3), displays an irreversible reduction peak near –0.20 V and (4) and (5) display a quasi-reversible one electron reduction peak near +0.25 V versus s.c.e. The trend in redox potential values and the selective stabilization of VO2+ and VO3+ motifs have been explained on the basis of the basicity of the bidentate auxiliary ligands. 相似文献
973.
Reaction of 2-(arylazo)phenols with [Ir(PPh(3))(3)Cl] in refluxing ethanol in the presence of a base (NEt(3)) affords complexes of three different types, viz. [Ir(PPh(3))(2)(NO-R)(H)Cl] (R = OCH(3), CH(3), H, Cl and NO(2)), [Ir(PPh(3))(2)(NO-R)(H)(2)] and [Ir(PPh(3))(2)(CNO-R)(H)]. Structures of the [Ir(PPh(3))(2)(NO-Cl)(H)Cl], [Ir(PPh(3))(2)(NO-Cl)(H)(2)] and [Ir(PPh(3))(2)(CNO-Cl)(H)] complexes have been determined by X-ray crystallography. In the [Ir(PPh(3))(2)(NO-R)(H)Cl] and [Ir(PPh(3))(2)(NO-R)(H)(2)] complexes, the 2-(arylazo)phenolate ligands are coordinated to the metal center as monoanionic bidentate N,O-donors, whereas in the [Ir(PPh(3))(2)(CNO-R)(H)] complexes, they are coordinated to iridium as dianionic tridentate C,N,O-donors. In all three products formed in ethanol, the two PPh(3) ligands are trans. Reaction of 2-(arylazo)phenols with [Ir(PPh(3))(3)Cl] in refluxing toluene in the presence of NEt(3) affords complexes of two types, viz. [Ir(PPh(3))(2)(CNO-R)(H)] and [Ir(PPh(3))(2)(CNO-R)Cl]. Structure of the [Ir(PPh(3))(2)(CNO-Cl)Cl] complex has been determined by X-ray crystallography, and the 2-(arylazo)phenolate ligand is coordinated to the metal center as a dianionic tridentate C,N,O-donor and the two PPh(3) ligands are cis. All of the iridium(III) complexes show intense MLCT transitions in the visible region. Cyclic voltammetry shows an Ir(III)-Ir(IV) oxidation on the positive side of SCE and an Ir(III)-Ir(II) reduction on the negative side for all of the products. 相似文献
974.
Temperature-sensitive hybrid microgels with magnetic properties 总被引:4,自引:0,他引:4
Pich A Bhattacharya S Lu Y Boyko V Adler HJ 《Langmuir : the ACS journal of surfaces and colloids》2004,20(24):10706-10711
In the present paper, we report the preparation of hybrid temperature-sensitive microgels which include magnetite nanoparticles in their structure. Polymeric microgels have been prepared by surfactant-free emulsion copolymerization of acetoacetoxyethyl methacrylate (AAEM) and N-vinylcaprolactam (VCL) in water with a water-soluble azo-initiator. The obtained microgels possess a low critical solution temperature (LCST) in water solutions, with a rapid decrease of the particle size being observed at elevated temperatures. Magnetite was deposited directly into microgels, leading to the formation of composite particles which combine both temperature-sensitive and magnetic properties. The influence of magnetite load on microgel size, morphology, swelling-deswelling behavior, and stability is discussed. 相似文献
975.
This study investigates the effect of additives in the nonsolvent water in terms of cloud point during the phase inversion of Polysulfone (PS) in dimethyl formamide (DMF). The exponential pattern is observed with PS concentration (0.2 to 0.6% (w/w)). It needs a low amount of water to get the cloud point at low temperature. The cloud point varied with the nature of water matrix and depended on the amount of salt, as well as the PS amount. The presence of salts (sodium chloride and sodium sulfate) lowers the cloud point of the solution. The network distribution of the particles at the cloud point is disturbed in the presence of salt. The requirement is more for Sodium lauryl sulfate (SLS) added water to reach the cloud point in the low range of PS solution up to 0.3% PS (w/w). The morphological and distribution pattern of PS particles are very different compared to PS particles produced from pure water. XRD study of PS particles produced from the mixed water system reflects relatively more amorphous character with respect to PS particles from pure water. The presence of both surfactant and salts in water systems also influences the cloud point in synergistic manner. 相似文献
976.
Debojit Bhattacharya Suranjan Shil Anirban Misra D. J. Klein 《Theoretical chemistry accounts》2010,127(1-2):57-67
We predict the intramolecular exchange coupling constant (J) for 10 different oxo- and thioxo-verdazyl-based hi-spin ground-state diradicals with linear polyacene couplers of varying length using the broken symmetry approach in an unrestricted DFT framework. The magnetic characteristics of these systems are explained using the spin-density distribution, and an analysis is made by “magnetic” orbitals. The nuclear independent chemical shift (NICS) values have been calculated for the diradicals. The average NICS(1) (1 Å above the ring surface) value per benzenoid ring increases as the size of the coupler increases. So-called ΔNICS(1) values [the difference among average NICS(1) per benzenoid ring in the coupler and the NICS(1) of the linear polyacene molecule] are correlated with J values. Bond orders and hyperfine coupling constants have also been evaluated and analyzed for the diradicals. 相似文献
977.
We report, using first principles density functional calculations, the relative stabilities, structural and electronic properties of various conformers of hydrogenated BN sheet (BHNH). The already known chair and boat BHNH conformers are structurally similar to those of graphane. We propose a third BHNH conformer called ‘stirrup’ which turns out to be the most stable one, as also verified by frequency analysis. In this conformer, the B–H and N–H bonds of a hexagon alternate in 3‐up and 3‐down fashion on either side of the sheet. We also explore that any other alternative hydrogenation of the BN sheet disrupts its periodic puckered geometry and turns out to be energetically less stable. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
978.
Bhattacharya S Banerjee S Nayak SK Chattopadhyay S Mukherjee AK 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(5):1099-1104
Molecular complex formation between [60]- and [70]fullerenes with a series of phosphine oxides, namely, tri-n-octyl phosphine oxide, triphenyl phosphine oxide and tri-n-butyl phosphine oxide has been studied in CCl4 medium by NMR spectrometric method. Both [60]- and [70]fullerenes have been shown to form 1:1 adducts with the above series of phosphine oxides. Formation constants (K) for all the complexes have been determined from the systematic variation of NMR chemical shifts of specific protons of the donors in presence of [60]- and [70]fullerenes. Trends in the values of K suggest that [70]fullerene binds stronger with the phosphine oxides relative to [60]fullerene. 相似文献
979.
Kazi Sabnam Banu Tanmay Chattopadhyay Arpita Banerjee Santanu Bhattacharya Ennio Zangrando Debasis Das 《Journal of molecular catalysis. A, Chemical》2009,310(1-2):34-41
Five dinuclear copper(II) complexes, [Cu2L1(N3)2·2H2O] (1), [Cu2L2(N3)2·2H2O] (2), [Cu2L3(N3)2·2H2O] (3), [Cu2L4(N3)2·2H2O] (4) and [Cu2L5(N3)2·2H2O] (5) of Robson type macrocyclic Schiff-base ligands derived from [2 + 2] condensation of 4-methyl-2,6-diformylphenol with 1,3-diaminopropane (H2L1), 1,2-diaminoethane (H2L2), 1,2-diaminopropane (H2L3), 1,2-diamino-2-methylpropane (H2L4) and 1,2-diaminocyclohexane (H2L5), respectively have been synthesized and characterized. Catecholase activity of those complexes using 3,5-di-tert-butylcatechol as substrate has been investigated in two solvents, methanol and acetonitrile. The role of the solvent and of the steric properties of the macrocyclic ligand of these complexes on their catecholase activity has been examined thoroughly. Acetonitrile is observed to be a better solvent than methanol as far as their catalytic activity is concerned. However, methanol reveals to be a better choice to identify the enzyme–substrate adduct. The investigation also prompted that chelate ring size does affect on the catalytic efficiency: 6-membered ring (as in H2L1) exhibits better activity than its 5-membered counterpart (as in H2L2). The activity of the 5-membered counter parts also depend upon the steric factor. Moreover, the catalytic activity of the complexes is enhanced to a significant extent by increasing the bulkiness of the substituents on the backbone of macrocyclic H2L2 ligands. 相似文献
980.
Diptendu Das V. A. Juvekar S. B. Roy R. Bhattacharya 《Journal of Radioanalytical and Nuclear Chemistry》2014,300(1):333-343
Equilibrium and kinetics of co-extraction of hexavalent uranium and mineral acids from aqueous solutions into a hydrocarbon phase (paraffin) using tri n-butyl phosphate (TBP), tri-n-octyl phosphine oxide (TOPO) and tri-n-octyl amine (TOA) has been studied. Relative rates of extraction of uranium(VI) and mineral acid by different complexing ligands were measured simultaneously using bulk-liquid membrane system. Acid extraction by complexing ligands was found to be significant. Wherever there was a possibility of the formation of the third phase, isodecanol was used as an organic phase modifier. Study revealed that isodecanol promotes acid extraction and substantially reduces distribution coefficient of U(VI) into the hydrocarbon phase. The rate of acid extraction by different ligand was in the order of TOPO > TOA > TBP–isodecanol > TBP, whereas the rate of extraction of uranium(VI) was in the order TOPO > TOA > TBP > TBP–isodecanol. A kinetic model was developed to predict concentration of acid and U(VI) in the feed, organic and the strip phase during extraction. The mass transfer coefficients for acid and metal were determined by fitting the model to the observed concentration–time data. 相似文献