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91.
ZHOU Hui DU Shao-Wu 《结构化学》2007,26(6):711-716
The self-assembly reactions of MIICl2 (M = Ni, Co) with the flexible bix ligand [bix = 1,4-bis(imidazole-1-ylmethyl)benzene] yielded a 2D network [NiII(bix)2Cl2]n 1 and a 1D chain [CoII(bix)Cl2]n 2. Their crystal structures have been determined by X-ray single-crystal diffraction analysis. Complex 1 characters a two-dimensional grid-type structure and crystallizes in monoclinic, space group P21/c with a = 7.7231(7), b = 12.7787(9), c = 13.9374(13) , β = 105.419(4)o, C28H28Cl2N8Ni, Mr = 606.19, Ζ = 2, V = 1326.0(2) 3, Dc = 1.518 g/cm3, μ = 0.969 mm-1, F(000) = 628, R = 0.0429 and wR = 0.0783 for 2503 observed reflections (I > 2σ(I)). Compound 2 is a one-dimensional chain and crystallizes in orthorhombic, space group Pbca with a = 11.3696(6), b = 10.2128(6), c = 14.4943(9) , C14H14Cl2CoN4, Mr = 368.12, Z = 4, V = 1683.01(17) 3, Dc = 1.453 g/cm3, μ = 1.334 mm-1, F(000) = 748, R = 0.0317 and wR = 0.0800 for 1778 observed reflections (I > 2σ(I)). Magnetic properties of the title complexes were also investigated. 相似文献
92.
The effects of electron beam irradiation doses on the poly-tetra-fluoroethylene (PTFE) have been studied. Several techniques, such as X-ray diffraction (XRD), differential scanning calorimetry (DSC), mechanical properties and Fourier transform infrared spectroscopy (FTIR) were applied to characterize the PTFE samples and to study the radiation effects on the crystal structure of the polymer.The irradiation dose up to 150 kGy showed an increase in the crystallinity degree of PTFE, which has been observed and confirmed during the DSC and XRD measurements. The increase in crystallinity was attributed to the scissions of the chain in the amorphous region. Moreover, the number-average molecular weights were estimated from the heat of crystallization measured by DSC technique. The results indicated that the molecular weights were decreased by increasing the heat of crystallization due to irradiation with doses up to 150 kGy. Radiation resistance of the irradiated and non-irradiated PTFE was investigated during its mechanical properties at room temperature. The dose at half value of the elongation at break is about 3.10 kGy while the dose at half value of the tensile strength is about 1.70 kGy. 相似文献
93.
Flame retardance and thermal stability of carbon nanotube epoxy composite prepared from sol-gel method 总被引:1,自引:0,他引:1
Chen-Feng Kuan Yi-Luen Li Hsu-Chiang Kuan 《Journal of Physics and Chemistry of Solids》2010,71(4):539-13298
Carbon nanotubes (CNTs) are functionalized by vinyltriethoxysilane (VTES) to incorporate the -O-C2H5 functional group and become VTES—CNT. The VTES—CNTs are added to the modified DGEBA epoxy resin that contains silicon to induce the sol-gel reaction. The final products are organic/inorganic nanocomposites. Thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC) are used to study the thermal property of nanocomposites. The Tg was increased from 118 to 160 °C and char yield of composites that contained 9 wt% CNT at 750 °C was increased by 46.94%. The integral procedural decomposition temperature (IPDT) was increased from 890 to 1571 °C. The limiting oxygen index (LOI) and UL-94 tests were classified as the flame retardance. The LOI of composites was increased from 22 to 27 and the UL-94 changed from V-1 to V-0 when the contents were increased to 9 wt%. The nanocomposites had a higher char yield and were highly flame retardant. The products can meet to the requirements of halogen-free and phosphorus-free ecological flame retardant. 相似文献
94.
Walter Klöpffer 《光谱学快报》2013,46(11):863-876
Energy transfer by excitons is now well established in films and solutions of aromatic polymers. Excitons in disordered systems can be considered as electronically excited states, which are transferred between the light absorbing groups in a random hopping process (the same is true in molecular crystals if, because of thermal vibrations, the coherence length of the exciton waves approaches the lattice constant and consequently the band model of the excitons breaks down). 相似文献
95.
Atactic polystyrene, both side group and main chain deuterated, was investigated by inelastic neutron scattering in a wide temperature range around the glass transition from 2 to 450 K. In the glass the Boson peak position is only very weakly influenced by the deuteration of the phenyl group. In the neighborhood of the glass transition temperatureT
g we find a fast relaxation process similar to other glasses. The onset of the fast relaxation in polystyrene, however, is observed already at temperaturesT
g — 200 K. Results from partially deuterated polystyrene suggest a change of the phenyl ring dynamics already far belowT
g. 相似文献
96.
S. N. Rudnev O. B. Salamatina V. V. Voenniy E. F. Oleynik 《Colloid and polymer science》1991,269(5):460-468
Measurements of the plastic deformation kinetics for several glassy (PS, PC, PI-polyimide, PET, epoxy-amine network), semi crystalline polymers (PBT, PET) and blends (ABS, PC:ABS, PC: PBT) were performed for the unidirectional compression loading conditions by using constant temperature deformation calorimetry. The experiments have permitted us to follow the changes of the mechanical work (A), the heat of deformation (Q) and differences between these quantities, i.e., internal energy (U) stored in samples during their loading and unloading. Experiments have shown that the large portion (45–85%) of the mechanical work of deformation (A) is converted to heat (Q). The rest ofA is converted to internal energy (U) stored in deformed samples. U is quite high as compared with metals [1,2]. After complete unloading of plastically deformed samples, i.e., samples carrying irreversible atT
def
plastic deformation (
irr
), some amount (U) of stored energy disappeared. The amount of (U and (U) are different for different polymers. All data are analyzed in the framework of the model proposed in [3,4]. The experiments support the deformation model where the plasticity of glassy polymers is the process of nucleation and development of so-called PDs-plastic local shear defects of nonconformational and nondilatational nature.Dedicated to Prof. Dr. W. Pechhold on the occasion of his 60th birthday 相似文献
97.
Two coordination polymers, namely, two-dimensional complex 1 {[Cu(μ- L)1.5(ClO4)2(H2O)].(H2O)0.5}n (L = pyrazine-1,4-dioxide) and one-dimensional complex 2 [Co(μ-L)Br2(H2O)2]n, have been synthesized with pyrazine-1,4-dioxide as bridging ligands, and their crystal structures were determined by X-ray crystallography. Crystal data for complex 1: monoclinic system, space group C2/c, with a = 23.310(3), b = 12.2338(17), c = 10.6075(15) , β = 110.487(2)°, V = 2833.6(7) 3, Z = 8, C6H9Cl2CuN3O12.5, Mr = 457.60, Dc = 2.145 g/cm3, F(000) = 1832 and μ = 1.998 mm-1; and those for 2: monoclinic system, space group C2/c, with a = 11.012(3), b = 7.483(2), c = 11.451(3) , β = 101.654(4)°, V = 924.2(4) 3, Z = 4, C4H8Br2CoN2O4, Mr = 366.87, Dc = 2.637 g/cm3, F(000) = 700 and μ = 10.487 mm-1. 1 shows a two-dimensional sheet structure on the ac plane through the coordination of μ-L bridging ligands with Cu(II) ions, while 2 displays a zigzag one-dimensional chain along the c axis via the coordination of μ-L bridging ligand with Co(II) ions. Hydrogen bonds in 1 and 2 make the sheets (or chains) connect each other to form a three-dimensional structure. 相似文献
98.
Polar groups in the skeletons of conjugated microporous polymers (CMPs) play an important role in determining their porosity and gas sorption performance. Understanding the effect of the polar group on the properties of CMPs is essential for further advances in this field. To address this fundamental issue, we used benzene, the simplest aromatic system, as a monomer for the construction of two novel CMPs with multi-carboxylic acid groups in their skeletons (CMP-COOH@1 and CMP-COOH@2). We then explored the profound effect the amount of free carboxylic acid in each polymer had on their porosity, isosteric heat, gas adsorption, and gas selectivity. CMP-COOH@1 and CMP-COOH@2 showed Brunauer-Emmett-Teller (BET) surface areas of 835 and 765 m2·g-1, respectively, displaying high potential for carbon dioxide storage applications. CMP-COOH@1 and CMP-COOH@2 exhibited CO2 capture capabilities of 2.17 and 2.63 mmol·g-1 (at 273 K and 1.05 × 105 Pa), respectively, which were higher than those of their counterpart polymers, CMP-1 and CMP-2, which showed CO2 capture capabilities of 1.66 and 2.28 mmol·g-1, respectively. Our results revealed that increasing the number of carboxylic acid groups in polymers could improve their adsorption capacity and selectivity. 相似文献
99.
Paul M. Hergenrother 《Angewandte Chemie (International ed. in English)》1990,29(11):1262-1268
Research on high-temperature organic polymers was initiated in the late 1950s primarily to meet the needs of the aerospace and electronics industry. Since then, many different heat-resistant polymer systems have been reported, of which several are now commercially available. These polymers are used in many diverse applications such as circuitry in microelectronic components, coatings on cookware, binders in brake systems, sealants for fuel tanks in high-speed aircraft, gears in copying machines, structural components in high-speed aircraft, and space vehicles, films and wire coatings for electrical insulation. Worldwide use for high-temperature polymers in 1988 was estimated at 90 million kilograms with a value of $ 2.3 billion. This market is expected to double by the end of this decade. The major polymer classes discussed in the present paper are polyimides and poly(aryl ethers). 相似文献
100.
We report on the realization and characterization of electro-responsive and pressure sensitive polydimethylsiloxane (PDMS) conductive photonic structures combined with the reconfigurable properties of short pitch cholesteric liquid crystals (aligned in Grandjean configuration). By combining ion-implantation process and surface chemistry functionalization, we have overcome the insulating properties of PDMS and induced long range organization of cholesteric liquid crystals, thus controlling both diffraction and selective Bragg reflection of light by means of external perturbations (electric field, pressure). We have characterized our devices in terms of morphological, optical and electro-optical properties. 相似文献