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991.
992.
An ampholytic N-carboxyethyl chitosan (CEC), with various isoelectric points (IPs), was synthesized by grafting acrylic acid on chitosan utilizing Michael's reaction. Compared to native chitosan, CEC has enhanced water solubility and dramatically accelerated enzymatic degradation; the rate of degradation is proportional to the degree of substitution (DS). The results from turbidimetric titration and fluorescence studies revealed that CEC formed complexes with either hyaluronic acid (HA) or bovine serum albumin (BSA) within a certain pH range. The HA/CEC/BSA ternary complexes could be prepared by colloid titration with quantitative yield and BSA entrapment. The rate of BSA release from the complexes was affected by pH, ionic strength, DS of CEC, and the molecular weight (MW) of HA. The endurance of BSA release from the complexes could be extended up to 20 d by formulating them with high-MW HA and CEC with low DS.BSA release profiles from HA/CEC-2/BSA complexes. 相似文献
993.
Derek G. Leaist 《Journal of solution chemistry》1988,17(4):359-369
Diaphragm cells have been used to measure ternary diffusion coefficients for I2+NaI and I2+KI in aqueous solution at 25°C. Although most of the iodine molecules are bound to iodide ions and are transported as the triiodide species [I2(aq)+I–(aq)=I
3
–
(aq)], diffusion of the iodide salts produces relatively small countercurrent coupled flows of the iodine component. The ternary diffusivity of the iodine component in the solutions is 10 to 20% larger than the diffusivity of the triiodide species. This behavior can be understood by considering electrostatic coupling of the ionic flows. The diffusion equations for I2+NaI and I2+KI components are reformulated in terns of NaI3+NaI and KI3+KI mixed electrolyte components. 相似文献
994.
New Germanides with an Ordered Variant of the Ce3Pt4Ge6 Type of Structure – The Compounds Ln3Pt4Ge6 (Ln: Pr–Dy) Six new germanides Ln3Pt4Ge6 with Ln = Pr–Dy were synthesized by heating mixtures of the elements at 900 °C, annealing the inhomogeneous powders at 1050‐1100 °C for six days and then cooling down from 700 °C in the course of two months. The crystal structures of Pr3Pt4Ge6 (a = 26.131(5), b = 4.399(1), c = 8.820(2) Å), Sm3Pt4Ge6 (a = 25.974(3), b = 4.356(1), c = 8.748(1) Å), and Dy3Pt4Ge6 (a = 26.079(5), b = 4.311(1), c = 8.729(2) Å) were determined by single crystal X‐ray methods. The compounds are isotypic (Pnma, Z = 4) and crystallize with an ordered variant of the Ce3Pt4Ge6 type of structure (Cmcm, Z = 2) consisting of CaBe2Ge2‐ and YIrGe2‐analogous units. The platinum atoms are located in distorted square pyramids of germanium atoms and build up with them a three‐dimensional network. The coordination polyhedra of the platinum and germanium atoms around the rare‐earth metal atoms are pentagonal and hexagonal prisms. These are completed by some additional atoms resulting in coordination numbers of 14 and 15 respectively. The other germanides were investigated by powder methods resulting in the following lattice constants: a = 26.067(6), b = 4.388(1), c = 8.800(2) Å for Ln = Nd; a = 25.955(7), b = 4.337(1), c = 8.728(2) Å for Ln = Gd; a = 25.944(5), b = 4.322(1), c = 8.698(2) Å for Ln = Tb. The atomic arrangement of Ln3Pt4Ge6 is compared with the well‐known monoclinic structure of Y3Pt4Ge6. 相似文献
995.
Jacques E. Desnoyers Gérald Perron Lévon Avédikian Jean-Pierre Morel 《Journal of solution chemistry》1976,5(9):631-644
The enthalpies of solution of urea (U) in water (W)-tert-butanol (TBA) mixtures and of TBA in W-U mixtures, the enthalpies of dilution of TBA in W, and the enthalpies of mixing of U and TBA aqueous solutions were measured with a solution calorimeter and a flow microcalorimeter. Enthalpies of transfer of U and TBA to the mixed solvents were derived. Also, pair and triplet interaction parameters between the various solutes were derived from the mixing and dilution experiments. The enthalpic pair parameter hU-TBA is positive, suggesting that the main contribution to this parameter is the decrease in hydrophobic hydration of TBA in the presence of U. 相似文献
996.
IntroductionZincisanessentialtraceelementtothelife .Manydiseasesarousedfromadeficiencyofzincelementhavere ceivedconsiderableattention .L α Aminoacidsarebasicunitsofproteins .L α Trytophanisoneoftheeightspeciesofaminoacidsindispensableforlife ,whichhastobeab sorbedfromfoodbecauseitcannotbesynthesizedinthehumanbody .InviewofthecomplexesofL α trytophanandessentialelementsasaddictiveswidelyusedinsuchfieldsasfoodstuff,medicineandcosmetic ,1 3theyhaveabroadenprospectforapplications .Briefly ,ab… 相似文献
997.
998.
O.V. Shcheritsa O.S. Mazhorova I.A. Denisov Yu.P. Popov A.V. Elyutin 《Journal of Crystal Growth》2006,290(2):350-356
The paper deals with computer simulation for growth and dissolution of ternary CdHgTe compounds in liquid-phase epitaxy (LPE) systems. The mathematical model accounts for the matter transport in both solid and liquid phases and the equilibrium phase diagram. The study displays the effect of solid-state diffusion on compositional grading at the substrate-layer boundary, on the formation of concentration distribution in both phases and on interface motion. The simulation has been done for isothermal conditions. 相似文献
999.
Mehtap Emirdag George L. Schimek Joseph W. Kolis 《Journal of chemical crystallography》1998,28(9):705-711
Syntheses of the title compounds were achieved from supercritical amines. The single crystal X-ray characterization of both MAgSe4 (M=Rb, Cs) members indicates that they are isostructural. The structure is built from five membered AgSe4 rings that are stitched together through tetrahedrally coordinated Ag(I) ions to form one dimensional chains running parallel to the a-axis. These chains are separated from each other by the alkali metal cations. Crystal data: orthorhombic, P212121, Z = 4. RbAgSe4: a = 5.809(2), b = 8.927(3), c = 13.435(4) Å, U = 698.2(4) Å3, and D
c = 4.851 g/cm3. CsAgSe4: a = 5.855(2), b = 9.090(3), c = 13.885(4) Å, U = 739.0(4) Å3, and D
c = 5.003 g/cm3. The anionic chain found in the title compounds has been observed previously, and comparisons among these phases show that the silver ion coordination in the chain varies as a function of cation size. Both the title compounds are valence precise and optical diffuse reflectance studies show that they are semiconductors with moderately large band gaps. 相似文献
1000.
The method of different orbitals for different spins is considered in the new context of ultrasmall, low-dimensional semiconductor structures. We solved the self-consistent wave equations for two interacting electrons in a quantum wire with a cross bar section. Such a quantum structure is of basic interest because one finds bound states in a potential that is classically open. The self-consistent solutions show that two electrons do not occupy one and the same bound state because orbital splitting is induced by Coulomb interactions. The state of one of the electrons becomes more squeezed while the other one appears delocalized because of screening effects from the first electron. Comparison is made with the Hylleraas' model for the orbital splitting in the helium atom. The effect of orbital splitting on electric transport is discussed briefly. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 667–673, 1997 相似文献