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991.
《Analytical letters》2012,45(9):1396-1410
This study establishes an analytical method for the determination of eighteen preservatives in water-based adhesives. The method was based on liquid–liquid extraction by methyl tertiary-butyl ether and subsequent determination by gas chromatography–mass spectrometry. Experimental conditions (instrumental parameters, extraction solvent, extraction mode, dispersant volume, and extraction time) were optimized and validated. When the method was applied to water-based adhesives, the limits of detection and recovery were 2.29–17.59 milligrams per kilogram and 85.7 ? 93.9 percent, respectively, and the repeatability was below 5 percent for all analytes. None of the analytes were found in five cigarette adhesives. 相似文献
992.
Electrohydrodynamics of spherical polyampholyte‐grafted nanoparticles: Multiscale simulations by coupling of molecular dynamics and lattice‐boltzmann method
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Qianqian Cao Lujuan Li Chuncheng Zuo 《Journal of Polymer Science.Polymer Physics》2017,55(19):1435-1448
We perform multiscale simulations based on the coupling of molecular dynamics and lattice‐Boltzmann (LB) method to study the electrohydrodynamics of a polyampholyte‐grafted spherical nanoparticle. The long‐range hydrodynamic interactions are modeled by coupling the movement of particles to a LB fluid. Our results indicate that the net‐neutral soft particle moves with a nonzero mobility under applied electric fields. We systematically explore the effects of different parameters, including the chain length, grafting density, electric field, and charge sequence, on the structures of the polymer layer and the electrophoretic mobility of the soft particle. It shows that the mobility of nanoparticles has remarkable dependence on these parameters. We find that the deformation of the polyampholyte chains and the ion distribution play dominant roles in modulating the electrokinetic behavior of the polyampholyte‐grafted particle. The enhancement or reduction in the accumulation of counterions around monomers can be attributed to the polymer layer structure and the conformational transition of the chains in the electric field. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1435–1447 相似文献
993.
An efficient protocol for the synthesis of biologically active benzoheterocyclic compounds such as benzothiazoles, benzimidazoles, benzospirothiazoles, and quinoxaline scaffolds have been accomplished via solid state melt reaction (SSMR) with excellent yields. The new protocol does not require any catalyst, solvent, and workup. Two anti-tumor agents have been prepared to demonstrate the application of this new method. 相似文献
994.
Lei Yan David A. Dillard Robert L. West Kenneth J. Rubis Glenn V. Gordon 《Journal of Polymer Science.Polymer Physics》2012,50(13):929-937
The mechanical properties in shear of unfilled and nanoparticle‐filled polydimethylsiloxane (PDMS) networks are reported. The effect of silicate‐based nanoparticles on the mechanical response was studied as functions of rate and temperature using the time–temperature superposition principle. An apparent yielding phenomenon was observed in the filled polymer in spite of the more typical elastomeric behavior exhibited by the pure PDMS network. The time–temperature superposition principle was applied to capture the shear strain rate (10?4–10?1 s?1) and temperature (?40 to 60°C) dependence of the stress response of the filled PDMS at different strains and at the yield point. A power‐law relationship was found to adequately describe the resulting master curves for yield stress in shear. Using a triangular shear displacement profile at 10?2 s?1, the effect of temperature (?20 to 80°C) on the recovery from a particularly pronounced Mullins effect was investigated as a function of rest time. Given adequate rest time (between 10 and 102 min), recovery was observed for the temperature range studied. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012 相似文献
995.
Based on scaling concepts a methodology of research of non-equilibrium polymer systems has been elaborated. Polymers with flexible chains (melt-crystallized linear high density polyethylene is chosen as an example) are solutions in melt as well as in solid state, the ends of a chain serving as a solvent for it. At critical polymerization degree all phases (melt, solid isotropic or oriented state) are identical. The square of the neck draw ratio is equal to the product of the square of the draw ratio at break and the chain ends collision probability. This probability in its turn is proportional to the average thickness of amorphous layers in the isotropic material. Depending on the type of polymer statistics (Gauss or Lévy–Khinchin) and the number of components of an ordering field for the second case, the melt viscosity and the self-diffusion coefficient vs. the molecular weight of linear flexible-chain polymer follow the power laws with the 3.50, 3.41 or 3.33 and −2.50, −2.05 or −1.65 exponents, respectively, within the reptation model near the critical point. Vibrational–rotational Brownian motions of chain ends about the polymer melt flow direction were taken into account to find better agreement with the experiment. The recent experimental results of dynamic mechanic and dielectric spectroscopy show the value 3.5 ± 0.1 for the viscosity exponent of long chains, while NMR data result in −2.3 ± 0.1 for the self-diffusion coefficient exponent of short chains. Possible reasons are discussed. 相似文献
996.
A series of uniaxial ratcheting experiments on anisotropic conductive adhesive film (ACF) were conducted under stress-control at elevated temperature using a DMA-Q800. The ratcheting behavior of ACF specimens with different hygrothermal aging times was investigated at room temperature and 120 °C. The effects of loading rate, mean stress and stress amplitude on the ratcheting behavior of unaged and aged specimens were compared. The results show that the ratcheting strains of aged specimens are smaller than those of unaged specimens under the same experimental conditions. The cycling stability of aged specimens is increased by hygrothermal aging. At room temperature, with the increase of aging time, the ratcheting strains of aged specimens increase with hygrothermal aging time when it is less than or equal to 96 h but, however, decrease when it exceeds 96 h. At 120 °C the ratcheting strains of ACF only decrease with the increase of hygrothermal aging time. Additionally, the effects of loading rate, mean stress and stress amplitude on the ratcheting behavior of unaged and aged ACF are different and their effects are weakened by hygrothermal aging. 相似文献
997.
《先进技术聚合物》2018,29(6):1804-1814
Urea formaldehyde microsphere (UFM) was prepared and used with organic montmorillonite (OMMT) to modify the flame retardant efficiency of ethylene vinyl acetate copolymer (EVA)/intumescent flame retardant (IFR) composites. The results show that single IFR may modify the flame retardancy of EVA, but its efficiency is not good enough. The EVA composite containing 21 wt% IFR is just classified the UL_94 V2 and has a limiting oxygen index (LOI) 24.7 vol%. Combining UFM with IFR does not improve the flame retardancy of EVA/IFR composites, and blending OMMT with IFR only improves its LOI. Adding 2 wt% UFM, 2 wt% OMMT, and 17 wt% IFR into EVA, it obtains the UL_94 V0 without melt dripping and a LOI 29.0 vol%. Also, the peak heat release rate and total heat release decrease a lot. Good synergistic effects among IFR, UFM, and OMMT improve the char residues and modify the char micromorphology of EVA composites, which provide better protect for the underlying resin. 相似文献
998.
The rapid quenching processes of Fe75Cu25 melt at different cooling rate are investigated by molecular dynamics simulation based on embedded atom method. Fe75Cu25 alloy ribbons are prepared by single roller rapid quenching. Liquid–liquid phase separation (LLPS) happens and the Cu-rich droplets embedded in the Fe-rich matrix can be observed both in simulation and experiments. Stronger interaction of homogeneous atom pairs than that of heterogeneous atom pairs leads to LLPS, controlled by nucleation growth mechanism in Fe75Cu25 melt, and quite different from that in Fe50Cu50 melt, which is controlled by spinodal decomposition mechanism. During the crystallisation process after LLPS, the new nuclei form only in Fe-rich regions; various multiply twinning boundaries are formed due to the minimisation of interfacial energy and only the homogeneous atomic stacking shows mirror symmetry along twinning boundary. The results provide atomic-scale understanding of phase separation mechanism and structure transition of Fe75Cu25 melt during rapid cooling processes. 相似文献
999.
Phase relations around langasite (LGS, La3Ga5SiO14) were studied on the basis of phase assemblage observed during calcination and crystallization process of samples of various compositions in the ternary system La2O3–Ga2O3–SiO2. A ternary compound of apatite structure, La14GaxSi9–xO39–x/2 was found for the first time. Crystallization of this compound was observed in the cooling process of molten samples of stoichiometric LGS as well as LGS single crystal, demonstrating that LGS is an incongruent-melting compound. A phase diagram was established primarily based on the crystallization sequence in the cooling process. 相似文献
1000.
Kazuo Nakajima Toshihiro Kusunoki Yukinaga Azuma Noritaka Usami Kozo Fujiwara Toru Ujihara Gen Sazaki Toetsu Shishido 《Journal of Crystal Growth》2002,240(3-4):373-381
The effect of the supply of depleted Si solute elements on the compositional variation in the Si-rich SiGe bulk crystals was studied using the method which was used to grow Ge-rich SiGe single crystals with a uniform composition. By selecting the proper pulling rate, we can obtain Si-rich Si1−xGex bulk crystals with uniform composition of x=0.1 without using the supply mechanism of depleted Si solute elements. When the supply mechanism of Si solute elements was used, the initial composition in Si-rich SiGe crystals can be much more easily determined by controlling the growth temperature than that in Ge-rich crystals because the Si seed crystal is not melted down. The supply of Si solute elements is very effective to change the compositional variation even for Si-rich SiGe crystals. 相似文献