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381.
A side chain liquid crystalline copolysiloxane, which would show electro-optic effects as known from low mass liquid crystal, was synthesized by hydrosilylation reaction, and the two homologous monomers with different length spacers containing Schiff's base mesogen with—NO_2 terminated group were grafted toa polysiloxane main chain. Residual monomer in crude product is effective in reinforcing the response to an electric field over that of pure polymeric liquid crystal. 相似文献
382.
The morphology of a special blend system composed of liquid crystalline aromatic random copolyester (LCP) and semiflexible polyester PET over the whole composition range has been studied by means of polarized microscope, density measurement, DSC, FTIR and SEM. Based on the microscopic observation, it is found that under suitable mechanical mixing condition, LCP may be rather homogeneously dispersed in the PET matrix, with the middle composition range of the contents of LCP at 30--70 wt % the anisotropic and isotropic phase segregation appears, while with LCP contents over 80 wt% the blends exhibit wholly anisotropie. The DSC thermographs of the melt-pressed and quenched films show single T_(?), T_(cc) and T_m. T_(?) increases with increasing content of LCP and ap, proaches to the T_(?) of pure LCP. The experimental results indicate that the two components of this blend system are miscible, there exist some specific interactions between them. 相似文献
383.
Osmotic coefficients have been determined for three isomeric methyl glycofuranosides, viz. methyl -D-lyxo-, -D-ribo-, and -D-ribofuranosides in aqueous solution by the isopiestic comparison method. The method was further applied to measure the osmotic coefficients for the ternary system consisting of calcium chloride, methyl glycofuranoside, and water. The results are analyzed in terms of an excess function from which the salting constants for the glycosides are derived. Relationships between the salting constants and the complexing of methyl glycofuranosides with calcium ion are discussed. 相似文献
384.
The novel odd-even polyamides 11,12 (P11, 12) and 11,10 (P11, 10) were synthesized via step-heating melting-polycondensation of 1,11-diaminoundecane with dodecanedioic acid and decanedioic acid, respectively. Their chemical structures were confirmed by various spectroscopic techniques (FTIR, Raman, NMR). The thermal properties of the polyamides under consideration were measured by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The crystalline transitions of the prepared polyamides were studied by wide angle X-ray diffraction (WAXD) and Fourier transform infrared spectroscopy (FTIR). The variable temperature WXRD results indicated that P11,10 undergoes the Brill transition during the heating process before melt while P11,12 does not. From the real time FTIR spectra of P11,10, it was found that the intensity of hydrogen bond becomes weak, and the twisting of the C-CO and C-N bonds becomes enhanced. The vibration of the methylene units strengthens and the trans-zigzag conformation decreases. The ordered stacking of the methylene segments becomes gradually disordered by insertion of the gauche conformation during the crystalline transition process. 相似文献
385.
Effect of crystalline structure on the hardness and interfacial adherence of flame sprayed poly(ether-ether-ketone) coatings 总被引:1,自引:0,他引:1
Flame sprayed PEEK (poly-ether-ether-ketone) coatings, with an amorphous structure, were subjected to isothermal treatments with annealing temperatures from 180 to 300 °C and holding times from 1 to 30 min. The coating structures were studied by means of differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analyses. All the annealed coatings exhibited semi-crystalline structures. Coexistence of thick and thin lamellae in the spherulites of annealed coatings can be deduced. The Knoop hardness and the interfacial adhesion of the coatings were examined. The annealed coatings exhibit higher hardness than the amorphous one. The formation of the thick lamellae is a determining factor for improving the coating hardness, which could restrict the motions and slippages of the polymer chains. However, the annealed coatings exhibit a weak adherence to the substrate. Some fissures or spherical porosities could be observed, in certain zones, on the coating/substrate interface. The formation of these fissures and porosities could be ascribed to the coating residual stress and the large volume contraction during the crystallization that occurred under the annealing conditions. 相似文献
386.
Synthesis, Crystal Structure, Vibrational Spectra, and Normal Coordinate Analysis of K2[OsCl5(CO)] · H2O The X-ray structure determination of K2[OsCl5(CO)] · H2O (monoclinic, space group P21/c a = 13.600(2), b = 7.122(1), c = 22.186(11) Å, β = 98.66(3)°, Z = 8) revealed two crystallographic independent bat very similar complex anions [OsCl5(CO)]2? with rough C4v point symmetry. Due to the stronger trans influence of the carbonyl group the bond lengths in the Cl? Os? CO axis Os? Cl = 2.449(2), 2.430(2) Å are langer as compared with the octahedron basis Os? Cl = 2.340-2.370 Å. The water of crystallization is coordinated to potassium (K? OH2 = 2.625-2.815 Å). Using the molecular parameters the IR and Raman spectra are assigned by normal coordinate analysis. The valence force constants are fd(CO) = 15.30, fd(OsC) = 3.88, fd(OsCl) = 1.81, fd(OsCl) = 1.36, fd(OH) = 7.65, 7.82, 7.79 mdyn/Å. The strengthening of the Os? C bond by stronger back donation of the OsIII(d5) complex in comparison with the isostructural OsIV (d4) compound is discussed. 相似文献
387.
388.
The melt-direct intercalation method was employed to prepare polypropylene (PP)/maleic anhydride grafted polypropylene (PP-g-MAH)/organic-montmorillonite (Org-MMT), X-ray diffractometer was used to investigate the intercalation effect and crystallite size in composites and TEM micrograph to observe the dispersion of Org-MMT interlayers in polypropylene. The results showed that by introducing maleated polypropylene in PP/Org-MMT composite, macromolecule segments had intercalated into interlayer space of Org-MMT. As a result, Org-MMT interlayers were dispersed evenly in polypropylene and PP/PP-g-MAH/Org-MMT nanocomposite was synthesized. The crystallite size of nanocomposite perpendicular to the crystalline plane such as (0 4 0), (1 3 0), (1 1 1), (0 4 1) is smaller than that of pristine PP, which indicated that the crystallite size of PP in nanocomposite can be diminished by adding PP-g-MAH and Org-MMT in PP. Moreover, the nonisothermal crystallization kinetics of PP and PP/PP-g-MAH/Org-MMT nanocomposite was investigated by differential scanning calorimetry (DSC) with various cooling rates. The Avrami analysis modified by Jeziorny, Ozawa method and a method developed by Liu were employed to describe the nonisothermal crystallization process of these samples. The difference in the exponent n between PP and nanocomposite, indicated that nonisothermal kinetic crystallization corresponded to tridimensional growth with heterogeneous nucleation. The values of half-time, Zc, F(T) and K(T) showed that the crystallization rate of composites was faster than that of PP at a given cooling rate. 相似文献
389.
C. M. B. M. Barbosa E. Falabella M. J. Mendes N. M. Lima C. A. M. Abreu 《Reaction Kinetics and Catalysis Letters》1999,68(2):291-298
Hydrogenation of sucrose over Ru/NaY, Ru/USY and Ru/CaY catalysts was carried out in a slurry reactor at 135°C and 12 atm.
The catalysts were prepared by ion exchange followed by calcination and reduction. These were characterised as AA, TPR, DTA/TGA,
H2/Chemisorption, CO-FTIR, XRD and t-plot. To describe kinetic product distribution, the 4th order Runge-Kutta method was used for determining the kinetic parameters. 相似文献
390.
Savita Kumari Aswini K. Mishra Dipak K. Chattopadhyay K. V. S. N. Raju 《Journal of polymer science. Part A, Polymer chemistry》2007,45(13):2673-2688
Polyurethane (PU) coatings are widely used for variety of high‐performance applications in today's coating technology. The emerging hyperbranched polymers having three‐dimensional morphology have opened a new avenue to tailor the architecture of PU coatings. The methodology followed here is based on preparation of PU coatings from hyperbranched polyester. Initially, different hyperbranched polyester polyols (HPs) were synthesized by varying the hydroxyl‐terminated precursors that is, pentaerythritol, trimethylol propane or glycerol and keeping the diacid that is, adipic acid quantity constant at various mole ratios of 1:0.6, 1:0.8, 1:0.9, and 1:1, respectively. The obtained HPs were characterized by nuclear magnetic resonance (NMR) spectroscopy, matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF)‐mass spectrometry, and Fourier transform‐infrared (FTIR) spectroscopy. The degree of branching and the quantity of different structural units present in the various HPs were calculated by integrating the quaternary carbon and carbonyl zone in 13C NMR spectroscopy. The extent of condensation in different HPs was also calculated from 1H NMR spectra. Later on, NCO‐terminated PU prepolymers (NCO‐PU) were synthesized by reacting HPs with isophorone diisocyanate (IPDI) at NCO/OH ratio of 1.6:1. In the third step, the excess NCO content in the NCO‐capped PU prepolymers were reacted with atmospheric moisture and hyperbranched polyurethane (HPU) coatings were formed. The coating films were analyzed by FTIR and dynamic mechanical thermal analysis instruments. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2673–2688, 2007 相似文献