全文获取类型
收费全文 | 87494篇 |
免费 | 6303篇 |
国内免费 | 2959篇 |
专业分类
电工技术 | 4420篇 |
技术理论 | 9篇 |
综合类 | 4713篇 |
化学工业 | 15727篇 |
金属工艺 | 4516篇 |
机械仪表 | 5274篇 |
建筑科学 | 7092篇 |
矿业工程 | 2008篇 |
能源动力 | 2508篇 |
轻工业 | 4986篇 |
水利工程 | 1482篇 |
石油天然气 | 4602篇 |
武器工业 | 506篇 |
无线电 | 10531篇 |
一般工业技术 | 11383篇 |
冶金工业 | 4718篇 |
原子能技术 | 841篇 |
自动化技术 | 11440篇 |
出版年
2024年 | 328篇 |
2023年 | 1337篇 |
2022年 | 2328篇 |
2021年 | 3165篇 |
2020年 | 2381篇 |
2019年 | 2056篇 |
2018年 | 2286篇 |
2017年 | 2545篇 |
2016年 | 2394篇 |
2015年 | 2987篇 |
2014年 | 4074篇 |
2013年 | 5117篇 |
2012年 | 5312篇 |
2011年 | 5582篇 |
2010年 | 4959篇 |
2009年 | 4776篇 |
2008年 | 4512篇 |
2007年 | 4457篇 |
2006年 | 4707篇 |
2005年 | 4170篇 |
2004年 | 2811篇 |
2003年 | 2513篇 |
2002年 | 2209篇 |
2001年 | 2030篇 |
2000年 | 2295篇 |
1999年 | 2576篇 |
1998年 | 2401篇 |
1997年 | 1899篇 |
1996年 | 1757篇 |
1995年 | 1449篇 |
1994年 | 1221篇 |
1993年 | 884篇 |
1992年 | 658篇 |
1991年 | 545篇 |
1990年 | 410篇 |
1989年 | 368篇 |
1988年 | 318篇 |
1987年 | 176篇 |
1986年 | 165篇 |
1985年 | 112篇 |
1984年 | 98篇 |
1983年 | 63篇 |
1982年 | 60篇 |
1981年 | 55篇 |
1980年 | 38篇 |
1979年 | 32篇 |
1978年 | 13篇 |
1977年 | 33篇 |
1976年 | 16篇 |
1975年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
891.
An organic‐solvent‐soluble disperse dye was introduced into an aqueous phase by a reaction with a self‐emulsified, aqueous‐based polyurethane (PU), and this resulted in the formation of a homogeneous, aqueous polymeric dye dispersion. This aqueous polymeric dye was stable in a water phase with excellent color extension upon application. It was formulated with a latent curing agent, polyaziridine (e.g., TMPTA‐AZ), as a single‐component, self‐curable, aqueous polymeric dye. The curing reaction took place between PU carboxylic acid and the latent curing agent upon drying. A self‐cured polymeric dye was obtained with excellent color extension and fastness and resistance to organic solvents and water after drying. This single‐component, self‐curable, aqueous‐based PU system containing a dye has potential for printing, writing, and dyeing applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 2006 © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3741–3747, 2006 相似文献
892.
物流服务作为对地区生产力提高和社会经济增长有重要意义的4个服务性行业之一,在全国范围内已经被广泛地得到认可。其快速的发展对景德镇陶瓷经济的增长有着同样重要的意义。通过分析物流业发展对景德镇陶瓷业发展的重要作用和景德镇物流业发展现状,结合实际提出了景德镇现代物流业发展的建议。 相似文献
893.
Polymer blends of poly(propylene) (PP) and polyacetal (polyoxymethylene, POM) with ethylene vinyl alcohol (EVOH) copolymers were investigated by differential scanning calorimetry (DSC), rheological, tensile, and impact measurements, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The PP–POM–EVOH blends were extruded with a co‐rotating twin‐screw extruder. The ethylene group in the EVOH is partially miscible with PP, whereas the hydroxyl group in the EVOH can form hydrogen bonding with POM. The EVOH tends to reside along the interface, acting as a surfactant to reduce the interfacial tension and to increase the interfacial adhesion between the blends. Results from SEM and mechanical tests indicate that a small quantity of the EVOH copolymer or a smaller vinyl alcohol content in the EVOH copolymer results in a better compatibilized blend in terms of finer phase domains and better mechanical properties. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1471–1477, 2003 相似文献
894.
895.
896.
The permeation and diffusion of helium, nitrogen, methane, ethane, and propane through γ-irradiated polyethylene films were investigated. These studies were carried out with two objectives in mind: (1) to determine the effect of crosslinking by γ irradiation on permeability and diffusivity using the gas molecules as molecular probes; and (2) to study the plasticizing effects of the low hydrocarbons on the polyethylene film. The γ-ray-induced crosslinking efficiency of polyethylene was investigated in the following irradiation atmospheres: vacuum, acetylene, and nitrogen–acetylene mixtures. Results showed that irradiation in acetylene decreased the crosslinking efficiency while an acetylene–nitrogen atmosphere increased the efficiency compared to irradiation in vacuum. Both the permeation constants and the diffusion coefficients were found to decrease with increasing irradiation dose while the activation energies increased. The permeation constants of the organic gases through polyethylene increased with molecular diameter while the diffusion coefficients decreased. This increase in permeability was attributed to an increase in the solubility due to solubilization of the membrane by the penetrant. For example, the molecular diameter of propane is 4.397 Å compared with 2.807 Å for methane; however, propane permeated the polyethylene film at a rate twice that of methane. Nitrogen and methane have approximately the same molecular diameters—2.7085 and 2.807 Å, respectively—but owing to the plasticizing effect of methane, it permeated the film at a rate three times greater than that of nitrogen. It is interesting to note that the stronger the plasticizing ability of the penetrant, the greater the effect of the irradiation dose. The permeability of propane decreased by 40.7%, while the permeability of helium decreased by 6.4% after an irradiation dose of 50 Mrad. 相似文献
897.
Zheng Peng Si‐Dong Li Mao‐Fang Huang Kui Xu Chen Wang Pu‐Wang Li Xiao‐Guang Chen 《应用聚合物科学杂志》2002,85(14):2952-2955
The thermal degradations of methyl methacrylate‐graft‐natural rubber (MG) at different heating rates (B) in nitrogen were studied by thermogravimetric analysis. The results indicate that the thermal degradation of MG in nitrogen is a one‐step reaction. The degradation temperatures increase along with the increment of heating rates. The temperature of initial degradation (T0) is 0.448B + 362.4°C, the temperature at maximum degradation rate, that is, the peak temperature on a differential thermogravimetric curve (Tp) is 0.545B + 380.7°C, and the temperature of final degradation (Tf) is 0.476B + 409.4°C. The degradation rate at Tp is not affected by B, and its average value is 48.9%; the degradation rate at Tf is not affected by B either, and its average value is 99.3%. The reaction order (n) is 2.1 and is not affected by B. The reaction activation energy (E) and the frequency factor (A) increase along with B, and the apparent reaction activation energy (E0) is 254.6 kJ/mol. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2952–2955, 2002 相似文献
898.
Huang Yung-Sheng Lin Xiaorong Redden Peter R. Horrobin David F. 《Journal of the American Oil Chemists' Society》1995,72(6):625-631
The present study compared thein vitro hydrolysis of two 18:3n-6-rich oils—evening primrose oil (EPO) and borage oil (BO)—and different synthetic 18:3n-6-containing
triacylglycerols (TG). Incubation of EPO and BO with pancreatic lipase lipolyzed 18:3n-6 from the TG species. The rate of
lipolysis of TG species containing two or three molecules of 18:3n-6, which comprised 36% of total 18:3n-6 in BO and only
7% in EPO, was significantly slower than those containing only one molecule of 18:3n-6. This was found especially in those
with two molecules of linoleic acid, which constituted 20% of total 18:3n-6 in BO, whereas over 80% were present in EPO. In
a separate study, various synthetic 18:3n-6-containing TG were also subjected toin vitro hydrolysis by pancreatic lipase. Results showed that release of 18:3n-6 from thesn-1/sn-3 positions was significantly slower when two other stereospecific positions in the same TG molecule were occupied by either
palmitic acid (16:0) or monounsaturated (18:1 and 20:1) fatty acids than when occupied by 18:2n-6. The rate of hydrolysis
ofsn-2-γ-linolenyl-sn-1(3)-diacylglycerol to formsn-2-mono-γ-linolenyl glycerol was also significantly slower when both thesn-1 andsn-3 positions in TG molecules were occupied by either saturated fatty acids (16:0 and 18:0) or long-chain monounsaturated fatty
acids than when occupied by 18:2n-6. These findings suggest that the stereospecific position of 18:3n-6 in TG molecules and
the constituent of its neighboring fatty acids modulated availability of 18:3n-6 from 18:3n-6-containing TG or 18:3n-6-rich
oils. 相似文献
899.
Uniform polystyrene (PSt) particles with the size of 1.9 μm were first prepared via dispersion polymerization, and then used as the seeds in a second‐stage dispersion copolymerization of styrene (St) and methacrylic acid (MAA) to produce carboxyl‐carrying microspheres. The PSt seed particles were swollen by monomer mixture of St and MAA, including an oil‐soluble initiator 2,2′‐azobisiso‐butyronitrile (AIBN), before polymerization. Finally, uniform PS/P(St/MAA) (polydispersity index, PDI = 1.02) microspheres with the size of 2.2 μm were obtained. The average particle size and size distribution of the final microspheres were investigated. MAA contents between 54 and 97 mg/g were detected from the PS/P(St/MAA) particles produced under different conditions. Dispersion medium has great influence on the kinetics of polymerization, due to its effect on the partitioning of monomers, solvents, and initiator in the particle phase, probably as well as on the conformation of the dispersion agent on the surface of the particles. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3586–3591, 2006 相似文献
900.
A novel polymerization procedure, the concentrated‐emulsion graft polymerization of styrene monomer with poly(butyl acrylate) seed, was proposed for the production of a self‐compatibility macromolecule alloy. The effects of the butyl acrylate content, sodium dodecyl sulfate concentration, and polymerization temperature on the graft ratio were investigated. Scanning electron microscopy, transmission electron microscopy, and impact strength were used to characterize the microstructure and mechanical performance of the self‐compatibility macromolecule alloy. The results showed that increasing the butyl acrylate content, reducing the sodium dodecyl sulfate concentration, and improving the polymerization temperature all favored an increased graft ratio, which resulted in increased impact strength of the self‐compatibility macromolecule alloy. Therefore, the concentrated‐emulsion polymerization method is particularly suitable for seed‐graft polymerization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2915–2920, 2002; DOI 10.1002/app.10288 相似文献