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71.
Crystallization of a semi-crystalline polyolefin in the presence of low molecular weight modifiers was quantified by differential scanning calorimetry and optical microscopy. The polyolefin was a commercial grade of isotactic poly(1-butene) (iPB). Two modifiers were used: an oligomeric plasticizer, designated HOAO, which decreased the glass transition temperature (Tg) of the system, and an oligomeric tackifier, designated HOCP, which increased Tg. Binary iPB/modifier blends containing 10% or 20% by weight of HOAO or HOCP were examined to determine how their addition affects Tg, while ternary iPB/HOAO/HOCP blends containing 10% or 20% by weight of total modifier were examined to determine the effects of dilution by using a ratio of HOAO to HOCP that matched the Tg of iPB. The addition of modifier decreased the nucleation rate, spherulitic crystal growth rate, and final crystallinity of each blend. However, only the nucleation rate showed a dependence on the type of modifier, with nucleation retarded more by HOCP than by HOAO. A Hoffman-Weeks analysis of the melting point as a function of crystallization temperature confirmed that the driving force for nucleation was reduced, and that the effect was larger for HOCP. An Avrami analysis of the bulk crystallization kinetics was consistent with these observations, as the Avrami exponents were in the range of 3-4. 相似文献
72.
<正>The effect ofαphase nucleating agent(NA) 1,3:2,4-bis(3,4-dimethylbenzylidene) sorbitol(DMDBS) on crystallization and physical properties of polypropylene/calcium carbonate(PP/CaCO_3) composites has been comparatively investigated.Compared with binary PP/CaCO_3 composites,in which CaCO_3 exhibits weak heterogeneous nucleation, inconspicuous reinforcement and toughening effects for PP,the introduction of a few amounts of DMDBS induces a great increase of the degree of crystallinity.Largely improved tensile properties,fracture toughness at relatively higher temperature and heat deformation temperature(HDT) are observed for DMDBS nucleated PP/CaCO_3 composites. 相似文献
73.
Two series of tin containing molybdophosphate and tungstophosphate glasses and glass-ceramics were achieved by means of a domestic microwave oven under air. During melting, a redox reaction takes place between Sn2+ and Mo6+ generating the crystallization of a Na(SnIV,MoIV)(PO4)3 solid solution with a NZP (NaZr2P3O12) type structure. Such reactivity was not underlined in the case of the W-series. All the samples were characterized from a thermal and mechanical point of view as a function of the RO3 (R = Mo, W) for SnO substitution. Two types of behaviors were identified. For the Mo-series, all the characteristics, except density, present an extremum value for the chemical composition with a 1:1 SnO-MoO3 molar ratio. This is strongly correlated to the amount of NZP crystals present in the glass ceramic, the different behavior observed for the density being due to the low compactness of the NZP phase. For the W-series, all these different characteristics varies monotonously according to a progressive strengthening of the network by replacement of a low field strength ion (Sn2+) by a higher field strength ion (W6+). In addition, the solid state reactivity of a 1:1 SnO-RO3 mixture was examined confirming the absence of any redox process between SnO and WO3 during the glass synthesis. 相似文献
74.
E.E. Assem 《Physica B: Condensed Matter》2011,406(3):421-425
The effect of halide ions on density, electrical, magnetic and crystallization kinetics for (20X-50P2O5-30V2O5) mole% has been investigated, where X=CaO, CaF2, CaCl2 and CaBr2. Halide ions reduce the glass transition temperature, crystallization temperature and activation energy of crystallization. Density, electrical conductivity and magnetic susceptibility increase while molar volume, glass thermal stability and interatomic distance between transition metal ions decrease as the halide ions replace the oxygen ions in these glasses. 相似文献
75.
Mousa M.A. Imran 《Physica B: Condensed Matter》2011,406(22):4289-4295
Results of crystallization kinetics, viscosity, specific heat, thermal stability, and glass forming ability of Se85−xSb15Snx (x=10, 11, 12.5, and 13) chalcogenide glasses, using differential scanning calorimeter (DSC), under non-isothermal condition have been reported and discussed. The variation of the peak temperature of crystallization Tp with the heating rate β has been used to investigate the growth kinetics using Kissinger, Takhor, and Augis-Bennet models. The activation energy of crystallization Ec has been found to increase with Sn content and the crystal growth occurs in one dimension. The increasing trend of Ec is interpreted in terms of enhancement of the degree of cross-linking due to the formation of SnSe4/2 structural units of energies higher than that of Se-Se and Se-Sb bond energies. The viscosity η against 1/T curves has also been drawn and indicated that the atoms of ternary Se-Sb-Sn glasses required more energy, with the addition of Sn, to complete the transformation from amorphous to crystalline state. The demand for thermal stability has been ensured through the calculations of the enthalpy released ΔHc during the crystallization process and S-parameter, while the obtained values of the reduced glass transition temperature Trg and Hurby number HR have been used to estimate the glass forming ability (GFA). Results reveal that, both thermal stability and GFA enhanced with increasing Sn content and the studied samples were prepared from strong glass-forming liquids. The obtained values for the specific heat difference ΔCp, between the equilibrium liquid and the glass, have been found to decrease with increasing Sn content and are in support of the results of thermal stability and GFA. 相似文献
76.
Xianke GuGuojian Wang 《Applied Surface Science》2011,257(6):1952-1959
The scanning force microscope (SFM) was used to investigate morphology of poly(ethylene oxide) (PEO) and poly(acrylic acid) (PAA) blend. The effect of solvent and dewetting in surface structure of PEO film was reported. The results manifested that the crystallization of PEO could be suppressed completely in ultrathin region via using chloroform as a solvent, and the branched-like crystallization was recovered after dewetting. Also, the effect of thickness, the ratio of PEO/PAA and dewetting in surface morphology of PEO-PAA blend films were investigated. These results showed that the crystallization was highly dependent on the ratio of PEO/PAA and the thickness of blend film. Furthermore, we assembled the PEO/PAA layer-by-layer film by spin-casting method for the first time, which exhibited highly efficiency. As a complementary tool, we also used lateral force microscopy (LFM) to explore surface information of these films. The result was indicative of interfacial constraints in ultrathin region, and also was supported by the results showing the spin-casting PEO/PAA blends rather than heterogeneous mixture. 相似文献
77.
Crystal structure and magnetic properties of SmCo-based films deposited on hot Si (1 0 0) substrates
SmCo-based films were deposited on Si (1 0 0) substrates by the rf magnetron sputtering process. The growth conditions are improved for the films deposited on hot Si substrates without the annealing process. The dependence of crystal structure and intrinsic coercivity on substrate temperature is chiefly investigated. It is suggested that TbCu7 type structural films can be obtained with enhanced in-plane magnetic properties with proper substrate temperature. 相似文献
78.
The crystallization behavior and thermal stability of amorphous phases of Al65Cu20Ti15 alloy obtained by mechanical alloying were investigated by using in-situ X-ray diffraction and differential scanning calorimetry (DSC) under non isothermal and isothermal conditions. The result of a Kissinger analysis shows that the activation energy for crystallization is 1131 kJ/mol. The higher stability against crystallization of Al65Cu20Ti15 amorphous alloy is attributed to the stronger interaction of atoms in the Al-Cu-Ti system and formed of complicated compound like Al5CuTi2 and Al4Cu9 as primary phases. The isothermal crystallization was modeled by using the Johnson-Mehl-Avrami (JMA) equation. The Avarami exponents suggest that the isothermal crystallization is governed by a three-dimensional diffusion-controlled growth. 相似文献
79.
This study focuses on ultrasound-assisted anti-solvent crystallization of lactose, expanding on previous studies and presenting, for the first time, the results of large scale implementation of sonocrystallization for lactose. The results further clarify the interplay between solution chemistry – namely the role of β-lactose – and crystallization, representing a step forward in the fine tuning of lactose properties for pharmaceutical manufacturing applications. Batches manufactured at laboratory and pilot scales were extensively characterised, including an approach for the quantification of β-lactose in α-lactose based on powder X-ray diffraction (PXRD), which is described here. 相似文献
80.
Different inorganic salts, including NaSCN, NaCl, MgCl2 and Na2SO4, were added into the aqueous solution containing poly(ε-caprolactone)-b-poly(ethylene oxide)(PCL-b-PEO) semicrystalline micelles. The effects of inorganic salt on the micellar size and morphology were investigated with TEM and DLS. It is found that addition of NaSCN leads to increase of the micellar size, but the micelles remain to be spherical. By contrast, the other three inorganic salts can induce sphere-to-cylinder or sphere-to-lamella transformations of the PCL-b-PEO semicrystalline micelles. The alteration rate of the micellar size with the time after addition of the inorganic salts decreases in the following order: Na2SO4 NaCl ≈ MgCl2 NaSCN. These results were interpreted in terms of the "salting-out" ability of the cations and anions. The anions SO42- and Cl- have a stronger "salting-out" ability, driving the morphological transformations of the micelles and leading to a rapid change in micellar size. By contrast, SCN- has a weaker salting-out" ability. The cations Na+ and Mg2+ may associate with the PEO blocks, leading to a "salting-out" effect as well. However, the "salting-out" ability of cations is weaker than that of SO42- and Cl- anions, and the "salting-out" abilities of Na+ and Mg2+ are similar. 相似文献