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991.
Yo Jin Kim 《Electrochimica acta》2004,49(19):3227-3234
Palladinized Nafion™ was prepared via ion-exchange and chemical reduction method. Palladium precursors and solvent systems determined the efficiency of the incorporation and distribution of nanoparticles. The tortuous thin Pd film was formed on the surface of membrane when Na+-Nafion™ and water were used. Pd nanoparticles enhanced the water uptake of Nafion™ and reduced its methanol uptake. And dispersed Pd nanoparticles in Nafion™ disturbed the proton conduction and methanol permeation simultaneously in Nafion™ cluster. In order to reduce methanol permeation of Nafion™ and keep its high conductivity, it was more efficient for Pd nanoparticles to distribute near the surface of membrane. Palladinized Nafion™ improved the performance of DMFC single cell operation by reducing the methanol permeation. 相似文献
992.
Synthesis of silver/polymer colloidal composites from surface-functional porous polymer microspheres
This study presents a different colloidal silver (Ag)/polymer system where Ag nanoparticles are deposited uniformly onto surface-functional porous poly(ethylene glycol dimethacrylate-co-acrylonitrile) (poly(EGDMA-co-AN)) microspheres. The formation and morphology of the composite microspheres were characterized from electron microscopy and X-ray diffraction analyses. The significance of the present report is that owing to the high affinity between Ag and nitrile group (CN) on the large surface of the microspheres, the Ag nanoparticles having a face-centered cubic phase were incorporated evenly into the deep pores of the microspheres with fine size and size distribution. In the preservation test, the Ag/poly(EGDMA-co-AN) composite microspheres obtained showed an excellent anti-bacterial performance, elucidating a high applicability for a new preservative. 相似文献
993.
In recent years, numerous analytical and experimental researches have been performed on the prediction of thermal stresses in mass concrete structures. However, due to the difficulty of the problem, limitations still exist for both analytical and experimental methods of measuring thermal stresses in mass concrete. In this research, a new experimental device measuring thermal stresses directly in a laboratory setting is developed. The equipment is located in a temperature chamber that follows the temperature history, which has been previously obtained from temperature distribution analyses. Thermal forces are measured continuously by two load cells in the device. The results show that the thermal stresses estimated by the newly developed device agree well with general stress variations in actual structures. 相似文献
994.
蛋白质在超滤过程中的膜污染和膜清洗 总被引:9,自引:0,他引:9
本文选用四种不同的膜清洗剂对牛血清蛋白溶液超滤后污染的三种超滤膜进行研究,结果表明:在蛋白质的等电点取得在不同PH值下蛋白质对膜污染的最佳清洗效果,清洗效率与蛋白质的所荷电荷有关。采用适宜的清洗过程将会延长膜使用寿命和增强超滤膜性能。 相似文献
995.
The curing behavior of an epoxy/clay nanocomposite system composed of a bifunctional epoxy resin with an aromatic amine curing agent and an organically modified clay was investigated. Differential scanning calorimetry (DSC) was used to investigate the curing behavior of the epoxy/clay nanocomposite system. The curing rate of the nanocomposite system increased with increasing clay content. A kinetic equation, considering an autocatalytic reaction mechanism, could describe fairly well the curing behavior of the epoxy/clay nanocomposite system. The reaction kinetic parameters of the kinetic equation were determined by fitting DSC conversion data to the kinetic equation, using a nonlinear numerical method. Dynamic mechanical analysis was used to investigate the thermomechanical properties of the epoxy/clay nanocomposite system. The glass transition temperature of the epoxy/clay nanocomposite system increased slightly with increasing clay content. The structure of the nanocomposite system was characterized by X‐ray diffraction analysis and transmission electron microscope imaging. The formation of intercalated structures was observed dominantly in the epoxy/clay nanocomposites, together with some exfoliated structures. POLYM. ENG. SCI., 46:1318–1325, 2006. © 2006 Society of Plastics Engineers 相似文献
996.
A new heterogeneous system for catalytic trimethylsilylcyanation of benzaldehyde has been developed by immobilizing Ti(IV) salen onto ordered mesoporous silica (MCM-41). The immobilization was performed according to different methods: (i) direct condensation of silanol on the silica surface with Ti(IV) salen and (ii) multigrafting of salicylaldehyde derivatives and diaminocyclohexane using 3-mercaptopropyl-functionalized MCM-41 as a starting material. The heterogenized salen catalysts showed a high enantioselectivity for the addition of trimethylsilyl cyanide to benzaldehyde. 相似文献
997.
Keizo Uematsu Jin-Young Kim Masayori Miyashita Nozomu Uchida Katsuichi Saito 《Journal of the American Ceramic Society》1990,73(8):2555-2557
The internal structure of spray-dried alumina granules was characterized by optical microscopy by immersing them in a liquid having a refractive index close to that of alumina. This method provides a unique technique for the detailed analysis of the internal structure of spray-dried granules. 相似文献
998.
Kentaro Terashima Suguru Tamura Sea-Hoon Kim Toshinobu Yoko 《Journal of the American Ceramic Society》1997,80(11):2903-2909
The third–order nonlinear optical susceptibility, χ(3) , of lanthanide (lanthanum, praseodymium, neodymium, and samarium) borate glasses has been measured by the third harmonic generation method. The structure of the present glass system has been studied by infrared and Raman spectroscopic methods. The network structures of the present Ln2 O3 –B2 O3 glasses have been confirmed to be basically similar to each other. Praseodymium, neodymium, and samarium borate glasses exhibit χ(3) values that are larger than lanthanum borate glasses, because of the optical resonance effect, in accordance with the f – f transition. Especially, the χ(3) value for 30Pr2 O3 ·70B2 O3 glass is 1.8 × 10−12 esu, which is a factor of ∼60 larger than that of SiO2 glass. This striking enhancement of χ(3) is mainly attributed to the large transition moment to the first excitation state. 相似文献
999.
High‐density polyethylene (HDPE) beads were successfully surface‐crosslinked in a modified plasma reactor. The modified plasma reactor treats large amounts of beads, which are uniformly surface‐crosslinked. In this study, effects of the gas pressure, radio‐frequency (RF) power, and the treatment time on the degree of surface crosslinking were systematically investigated. Degree of surface crosslinking was measured by solvent extraction method (boiling xylene method, BXM). The gel content of plasma‐treated HDPE increases from 0.0 to 1.05% within 10 min at 100 mTorr, 200 W. FTIR and DSC analyses show that the crosslinked layer after plasma treatment is limited only at HDPE surface without changing the bulk thermal property of HDPE. Through the analysis of FTIR, it was confirmed that main peaks corresponding to CH2 bands were decreased and two peaks corresponding to CF2 and CF3 were observed after plasma surface modification. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2921–2929, 2002; DOI 10.1002/app.10295 相似文献
1000.
Yeong-Chul Kim 《Korean Journal of Chemical Engineering》1996,13(3):282-287
The effects of motility and aggregation on the diffusion coefficient for bacteria were studied in an aqueous system. The effects
of cell concentrations, capillary tube sizes, and dilution rates on the diffusion coefficient were examined. In general, motile
cells can diffuse about 1000 times faster than non-motile cells.Pseudomonas aeruginosa, a motile cell, andKlebsiella pneumoniae, a non-motile cell, were used for this research. Diffusion coefficients were measured by the capillary tube assay developed
by Adler [1969]. From this procedure the diffusion coefficient ofPseudomonas aeruginosa was 2.1×10−5 (standard deviation: 1.0× 10−5) cm2/s and that ofKlebsiella pneumoniae was 0.9×10−5 (standard deviation : 0.5 × 10−5) cm2/s. The diffusion coefficient ofPseudomonas aeruginosa was about 2.3 times higher than that ofKlebsiella pneumoniae. The Stokes-Einstein equation could not be used for estimating the diffusion coefficients forKlebsiella pneumoniae andPseudomonas aeruginosa. The experimental value for the diffusion coefficient ofKlebsiella pneumoniae was about 2000 times higher than that (4.5×10−9 cm2/s) obtained from the Stokes-Einstein equation. This discrepancy was due to the aggregation ofKlebsiella pneumoniae. 相似文献