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991.
Banerjee S Bhattacharya S Basu S 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(6):1039-1044
The extraction behaviour of Pr(III) from aqueous nitric acid medium employing benzoylacetone has been studied in presence of two crown ethers, viz., 15-crown-5 and benzo-15-crown-5 in chloroform medium using UV-vis absorption spectroscopy. The binary equilibrium constant (logk(ex)) for the complex [Pr(benzoylacetonate)(NO3(-))2(H(2)O)] in organic phase was found to be 1.170. The overall equilibrium constants (logK) for the ternary species [Pr(benzoylacetonate)(crown ether)(NO3(-))(2)] were estimated to be 4.01 and 4.41 for 15-crown-5 and benzo-15-crown-5, respectively. The trend in the equilibrium constant values were very much in accordance with the nature of substitution of the donor moiety. The extraction of Pr(III) by the benzoylacetone-crown ether combination was maximum at pH 3.0 and extraction decreases with increase in pH. It has been found that the extent of extraction of Pr(III) in organic phase as the binary as well as ternary complex [Pr(benzoylacetonate)(NO3(-))(2)(H(2)O)] and [Pr(benzoylacetonate)(crown ether)(NO3(-))(2)] increases with increase in concentration of the ligand. Similar trend is observed in the extraction by only donors. Enthalpies and entropies of formation for the ternary extraction process have been estimated. In addition, the effect of NaNO(3) as foreign salt was also studied and it was observed that with increase in ionic strength, percentage extraction increases. 相似文献
992.
Banerjee AL Swanson M Roy BC Jia X Haldar MK Mallik S Srivastava DK 《Journal of the American Chemical Society》2004,126(35):10875-10883
We elaborate on a novel strategy for enhancing the binding affinity of an active-site directed inhibitor by attaching a tether group, designed to interact with the surface-exposed histidine residue(s) of enzymes. In this approach, we have utilized the recombinant form of human carbonic anhydrase-II (hCA-II) as the enzyme source and benzenesulfonamide and its derivatives as inhibitors. The steady-state kinetic and the ligand binding data revealed that the attachment of iminodiacetate (IDA)-Cu(2+) to benzenesulfonamide (via a triethylene glycol spacer) enhanced its binding affinity for hCA-II by about 40-fold. No energetic contribution of either IDA or triethylene glycol spacer was found (at least in the ground state of the enzyme-inhibitor complex) when Cu(2+) was stripped off from the tether group-conjugated sulfonamide derivative. Arguments are presented that the overall strategy of enhancing the binding affinities of known inhibitors by attaching the IDA-Cu(2+) groups to interact with the surface-exposed histidine residues will find a general application in designing the isozyme-specific inhibitors as potential drugs. 相似文献
993.
Thorium and zirconium are determined in the presence of rare earths, alkaline earths and magnesium, when precipitated from weakly acid solution with 5:6-benzoquinaldinic acid. Thorium is completely precipitated at pH 3.0 as Th(C14H8O2N)4, but though zirconium is precipitated at the lower pH of 1.8, its composition is not stoichiometric and hence is ignited to the oxide before weighing. Co-precipitation of magnesium and alkaline earths is prevented by the addition of ammonium chloride. 相似文献
994.
[reaction: see text] A reagent combination of beta-SnO and catalytic [Rh(COD)Cl](2) in THF-H(2)O promotes the reaction of propargyl bromides and aldehydes and directs the regioselectivity toward the formation of either allenic alcohols or homopropargylic alcohols. This highly regioselective either/or transformation proceeds via a transmetalation from rhodium to tin, in which metallotropic rearrangement between a propargylmetal and allenylmetal is arrested. 相似文献
995.
Roy BC Banerjee AL Swanson M Jia XG Haldar MK Mallik S Srivastava DK 《Journal of the American Chemical Society》2004,126(41):13206-13207
The enzyme inhibitors are usually designed by taking into consideration the overall dimensions of the enzyme's active site pockets. This conventional approach often fails to produce desirable affinities of inhibitors for their cognate enzymes. To circumvent such constraints, we contemplated enhancing the binding affinities of inhibitors by attaching tether groups, which would interact with the surface exposed amino acid residues. This strategy has been tested for the inhibition of human carbonic anhydrase II. Benzenesulfonamide serves as a weak inhibitor for the enzyme, but when it is conjugated to iminodiacetate-Cu2+ (which interacts with the surface-exposed His residues) via a spacer group, its binding affinity is enhanced by about 2 orders of magnitude. This "two-prong" approach is expected to serve as a general strategy for converting weak inhibitors of enzymes into tight-binding inhibitors. 相似文献
996.
Chen YF Banerjee IA Yu L Djalali R Matsui H 《Langmuir : the ACS journal of surfaces and colloids》2004,20(20):8409-8413
Ferrocene nanotubes were fabricated by binding carboxylic acid-derivatized ferrocenes onto template peptide nanotubes via hydrogen bonding. When these ferrocene-functionalized nanotubes were incubated with beta-cyclodextrin (beta-CD) self-assembled monolayers (SAMs) coated on patterned Au substrates in solution, the ferrocene nanotubes recognized and attached onto the beta-CD SAMs via host-guest molecular recognition. The ferrocene nanotubes were also observed to recognize the certain cavity size of CD. The attachment/detachment of nanotubes on the beta-CD SAMs was controlled electrochemically by tuning the redox states of ferrocene nanotubes. This electric field-responsive building block may be applied to build nanometer-sized switching components in electronics and sensors. 相似文献
997.
A thermal investigation of M(N2H5)2(SO4)2, where M = Mn(II) or Co(II), has been carried out. On heating, the complexes become MSO4 via an intermediate compound, M(N2H4)0·5(HSO4)(SO4)0·5. The intermediate compound has been isolated and characterised by elemental analyses, IR spectra, diffuse reflectance spectra, magnetic and conductance data. The intermediate compound seems to possess pseudo-tetrahedral coordination where one SO4 group is tetradentate and bonded with four different metal ions which are surrounded by HSO4 groups and hydrazines bridging two metal ions. The X-ray powder diffraction pattern of the intermediate derived from the cobalt(II) complex has been obtained and the d-values are reported. Activation energies (E*) and enthalpy changes (ΔH) for each decomposition step have also been calculated. The probable mechanisms of decompositions are discussed. 相似文献
998.
A. Banerjee S. B. Duttachoudhury Abhik Kumar Sanyal 《General Relativity and Gravitation》1986,18(5):461-477
A spatially homogeneous and locally rotationally symmetric Bianchi type-II cosmological model under the influence of both shear and bulk viscosity has been studied. Exact solutions are obtained with a barotropic equation of state (p=) and considering the linear relationships between, 2, and 2, which represent the fluid density, the expansion, and the shear scalars, respectively. Special cases with vanishing bulk viscosity coefficients and with the perfect fluid in the absence of viscosity have also been studied. The formal appearance of the solutions is the same for both the viscous as well as the perfect fluids. The difference is only in choosing a constant parameter which appears in the solutions. In the cases of either a fluid with bulk viscosity alone or a perfect fluid, the barotropic equation of state is no longer an additional assumption to be imposed; rather it follows directly from the field equations. 相似文献
999.
The Gibbs free energy of formation of CaRh2O4(s) has been determined using two techniques viz., quadrupole mass spectrometer coupled to a Knudsen cell and solid-state cell incorporating CaF2(s) as the solid electrolyte. In the former method, equilibrium O2(g) pressures were measured over the phase field Rh(s)+Rh2O3(s), in the temperature range 793.7-909.1 K and over the three phase mixture CaRh2O4(s)+Rh(s)+CaO(s) was measured from 862.1 to 1022.7 K.The Gibbs free energy of formation of Rh2O3(s) from elements in their standard state can be given by
1000.
Anuradha Dhur Sarmistha Das R. N. Banerjee D. Banerjea 《Transition Metal Chemistry》1982,7(2):125-127
Summary The kinetics of dissociation of glycinepentaamminecobalt(III) and tetraaquomonoacetylacetonatochrormium(III) ions in moderately strong perchloric acid media have been investigated spectrophotometrically. From the dependence of the rate on various acidity functions and the observed isokinetic and free energy relationships, both the complexes appear to react by an associative process involving interaction of the conjugate acid form of the substrate complex and H3O+. 相似文献