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711.
712.
Two efficient methods for the determination of 1,1-dichloro-1-fluoroethane (Freon F-141b) in formulated polyol and rigid polyurethane foam by dynamic-headspace-gas chromatography-ion trap-mass spectrometry were developed and validated. Rigid polyurethane foam was efficiently dissolved in dimethylformamide by heating at the temperature of 60 °C for 2 h.Validation was carried out in terms of limits of detection (LOD), limits of quantitation (LOQ), linearity, precision and recovery. LOD values of 4.00 g kg–1 for rigid polyurethane foam and 0.73 g kg–1 for formulated polyol were achieved, whereas linearity was statistically verified over one order of magnitude. Precision was evaluated testing two concentration levels. Good results were obtained both in terms of intra-day repeatability and between-day precision: RSD % lower than 4% (n = 6) at the concentration of 15 g kg–1 were calculated for intra-day repeatability. Extraction recoveries up to 92.6±1.6 % (n = 3) were also calculated by the addition of Freon F-141b to the samples analysed. Both the methods were applied for the analysis of a number of formulated polyol and rigid polyurethane foam samples. 相似文献
713.
A new flame retardant, i.e. expandable graphite (EG), has been used in polyisocyanurate-polyurethane (PIR-PUR) foams in order to improve fire behaviour of such foams. In order to obtain a completely halogen-free material, water-blown PIR-PUR foams have been prepared thus avoiding the use of hydrochlorofluorocarbons or hydrofluorocarbons. The influence of several EG amounts on physical-mechanical properties and fire performances of such foams has been analysed. The results obtained show that the use of EG affects significantly physical and mechanical properties, such as compression strength and thermal conductivity, particularly at very high EG content (25 wt.%), as it often happens in presence of fillers. The fire performances have been investigated by mean of cone calorimeter apparatus and oxygen index test; the results obtained show that the fire behaviour of PIR-PUR foams could be significantly improved by use of EG; in particular it has observed a dramatically decrease of rate of heat release even for relative low EG amount (15%). 相似文献
714.
开孔型聚合物微发泡材料制备技术 总被引:3,自引:0,他引:3
微发泡塑料是上世纪 80年代以后出现的一种新型材料 ,其特点是孔径小 (一般在 1 0 μm以下 ) ,分布均匀 ,泡孔密度非常高 (一般大于 1 0 9个 /cm3 )。目前微发泡塑料制备技术已经比较成熟 ,也得到了不同类型的商业化制品。聚合物微孔材料是一种功能性材料 ,相互连通的微观孔洞结构使其具有相当广泛的应用。本文介绍了目前几种微孔材料成型的主要方法 ,讨论了微发泡成型技术用于制备开孔型微发泡材料的必要性。对几种关于开孔型聚合物微发泡材料制备技术及研究方法进行了探讨 ,其分别是不相容聚合物共混、泡孔合并模型、熔融挤出发泡、开孔剂法和气体浓度阈 (值 )等方法。这些方法的微孔成型机理各不相同 ,所制备的材料微观结构也各有特点。文献分析表明微发泡方法用于开孔型微孔材料的制备是一种非常有前景的技术。 相似文献
715.
Spherical foam growth in Al alloy melt 总被引:6,自引:0,他引:6
The ultra light metal structure, realizing the light-ness and multifunction of structural material, has a bright future in high-tech and civil fields and is be-coming one of the hotspots in developed countries in 21 century[1―8]. Preparing Al foam by mel… 相似文献
716.
吐温—80固相化学发光测定痕量金的研究及其应用 总被引:6,自引:1,他引:6
研究了吐味-80与An(Ⅲ)的因相化学发光反应。比较了其在不同固相上的反应情况,用自制的固相化学发光仪,以巯基泡沫塑料(SPF)吸附溶液中Au(Ⅲ),采用圆表制片直接在SPF表面进行化学发光测定,建立了痕量金的固相化学发光分析法。方法的线性范围为0.01-10μgAu(Ⅲ),对1.0μg(Ⅲ)测定11次的相对标准偏差为4.2%,用于实际矿样痕量金的测定,结果满意。 相似文献
717.
In this work thermal
transitions and thermal stability of polyurethane intermediates and polyurethanes
were investigated. The intermediates were obtained by glycolysis of waste
polyurethane (PUR) in the reaction with hexamethylene glycol (HDO). The excess
of HDO was not separated from the product after the glycolysis process was
finished. The effects of different mass ratio of HDO to PUR foam on selected
physicochemical properties (hydroxyl number, Brookfield viscosity and density)
were also determined.
The polyurethanes were synthesized from
the obtained intermediates by the prepolymer method using diisocyanate (MDI)
and glycolysis product of molecular mass in range 700/1000 g mol–1.
Hexamethylene glycol, 1,4-butanediol and ethylene glycol were used as chain
extender agents. Influence of NCO groups concentration in prepolymer on glass
transition temperature (T
g)
and storage and loss modulus (E’, E’’) of polyurethanes were investigated
by the DMTA method. Thermal decomposition of obtained glycolysates and polyurethanes
was followed by thermogravimetry coupled with Fourier transform infrared spectroscopy.
Main products of thermal decomposition were identified. 相似文献
718.
The two steps thermal decomposition of titanium hydride and two steps foaming of Al alloy 总被引:2,自引:0,他引:2
SHANG Jintang & HE Deping South-east University Nanjing ChinaReceived April 《中国科学B辑(英文版)》2005,48(6):523-529
1 Introduction Al alloy foam with closed pores prepared by melt foaming, realizing the lightness, high specific strength and multifunction of structure material, is becoming one of the hotspots[1―11]. In order to meet the demand of high-tech, preparing s… 相似文献
719.
A system for molybdenum separation and enrichment aiming its determination in water and biological samples by graphite furnace atomic absorption spectrometry (GFAAS) is proposed. The procedure is based on the sorption of the molybdenum (VI) thiocyanate complex onto a mini-column packed with polyurethane foam (PUF). The elution is accomplished by a 3.0 mol l−1 nitric acid solution. Flow variables were optimized and an enrichment factor of 10 as well as a limit of detection (LOD) (3 s) of 0.08 μg l−1 in the sample solution were achieved. The coefficient of variation showed values of 3 and 2% for molybdenum solutions of 2.0 and 10.0 μg l−1, respectively. The accuracy of the method was confirmed by the good concordance between found and certified values in the analysis of certified reference materials (CRMs) (CASS-3 Nearshore Seawater, NIST 1547 Peach Leaves, NIST 1515 Apple Leaves and NIST 1572 Citrus Leaves). The procedure was also applied for the molybdenum determination in mineral waters as well as in produced water samples. The results obtained for the mineral water samples compared well with those obtained by ICP-MS. Concerning the produced water samples, in spite of their large salinity, recoveries of 90 to 120% at the 1 μg l−1 were observed. 相似文献
720.
Cardoso E. C. L. Lugo A. B. Andrade E. Silva L. G. 《Radiation Physics and Chemistry》1998,52(1-6):197-200
Polyethylene foams, produced by radio-induced crosslinking, show a smooth and homogeneous surface, when compared to chemical crosslinking method using peroxide as crosslinking agent. This process fosters excellent adhesive and printability properties. Besides that, closed cells, intrinsic to theses foams, imparts opitmum mechanical, shocks and insulation resistance, indicating these foams to some markets segments as: automotive and transport; buoyancy, flotation and marine: building and insulation: packaging: domestic sports and leisure goods. We were in search of an ideal foam, by adding 5 to 15% of blowing agent in LDPE. A series of preliminary trials defined 203° C as the right blowing agent decomposition temperature. At a 22.7 kGy/dose ratio, the lowest dose for providing an efficient foam was 30 kGy, for a formulation comprising 10% of azodicarbonamide in LDPE, within a 10 minutes foaming time. 相似文献