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891.
W. Xu K. Daub X. Zhang J.J. Noel D.W. Shoesmith J.C. Wren 《Electrochimica acta》2009,54(24):5727-5738
Surface oxide film growth and conversion processes on carbon steel were studied using a range of electrochemical techniques and ex situ surface analyses. The electrochemical study included (i) cyclic voltammetry as a function of various scan conditions and (ii) 7-day potentiostatic oxidation at a range of potentials while periodically performing Electrochemical Impedance Spectroscopy. Carbon steel surfaces at various stages of electrochemical oxidation were examined by SEM, Raman and X-ray photoelectron spectroscopy (XPS). These studies yield a consistent picture of film formation/conversion processes on carbon steel at pH 10.6, which is different to that reported for basic solutions (pH > 13). Oxide film formation/conversion mechanisms for three potential regions are proposed. In region I (≤−0.6 V vs SCE), the main oxide formed is Fe3O4 which grows via a solid-state process; in region II (−0.5 V ≤ E (vs SCE) ≤ −0.2 V), continuous growth of the Fe3O4 layer is accompanied by its anodic conversion to a more maghemite (γ-Fe2O3)-like phase near, or at, the oxide/solution interface by a similar solid-state mechanism to that described for region I; in region III (0.0 V < E (vs SCE) < 0.4 V), the anodic conversion of this Fe3O4/γ-Fe2O3 oxide to γ-FeOOH leads to a significant structural change, which can lead to film fracture and the introduction of enhanced transport pathways in the film. 相似文献
892.
Siddhartha Suveda Aarya Kapil Dev Mohd Shakir Bashir Ahmed M. A. Wahab 《应用聚合物科学杂志》2012,125(5):3575-3581
The structural, optical, and morphological properties of Co60 γ irradiation on poly(ethylene terephthalate) polymer samples were studied with X-ray diffraction (XRD), ultraviolet–visible spectroscopy, scanning electron microscopy (SEM), and Raman spectroscopy. The diffraction pattern of virgin sample showed that the polymer was semicrystalline in nature. However, because of irradiation, the crystallinity decreased up to a dose level of 110 kGy and increased up to 300 kGy. The crystallite size, strain, and dislocation were calculated from the XRD data, and the crystallite size decreased from 291.07 to 346.90 Å. The absorption edge shifted from 315 to 330 nm, and the band gap of the samples decreased from 3.79 to 3.66 eV. The SEM micrographs showed radial bulging along with inhomogeneous liner exfoliation, and also, a rocky shape pattern with different sizes was observed. A significant change was found in the Raman spectra of the γ-irradiated polymer at the highest dose. The results of the structural, optical, and morphological studies show recovery characteristics at the highest dose level of 300 kGy. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
893.
The preparation of graft copolymers of poly(methyl methacrylate) with some alkyl methacrylates were carried out via atom transfer radical polymerization method catalyzed by CuCl/2,2′-bipyridine and using a macroinitiator, poly[(methyl methacrylate)-co-(3,5-bis(chloroacetoxy)phenyl methacrylate)], including an amount of 1 mol % having α-halogeno carbonyl group in the side groups. Although the number-average molecular weights of a graft copolymer series of n-butyl methacrylate (n-ButMA) ended at different times increased from 55,700 to 99,500, the polydispersities decreased from 1.85 to 1.39 with time. The thermal degradation kinetics of macroinitiator and a two-armed graft copolymer of n-ButMA with this macroinitiator, PMMA-g-PnButMA: 4% (by mol), were carried out at different heating rates by thermogravimetric analysis and the results were compared. Using both the Flynn–Wall–Ozawa and Kissinger methods, the decomposition activation energies for macroinitiator were determined as 168 and 162 kJ/mol, respectively; they were also calculated as 233 and 239 kJ/mol for PMMA-g-PnButMA: 4%. The solid state thermodegradation mechanisms of both macroinitiator and PMMA-g-PnButMA: 4% are R1-type mechanism, a phase boundary-controlled reaction, and F1-type mechanism, a random nucleation with one nucleus on the individual particle, respectively. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
894.
895.
Thermally assisted alkali activation of silica-rich glass powder to produce sustainable binders is investigated. Glass powder activated using NaOH provides higher compressive strengths than NaOH activated fly ash binders at lower heat curing temperatures. Sodium silicate gel is the reaction product when glass powder alone is used as the source material, while a combination of sodium silicate and sodium aluminosilicate (N–A–S–H) gels form in activated glass powder–fly ash blends. The activated glass powder-containing binders are found to disintegrate and lose strength when exposed to moisture or an alkaline solution, with the pure glass powder binders suffering the highest strength loss. Structural changes to the reaction product on exposure to moisture are explained using microstructural and FTIR spectroscopic observations. Doping the systems with Al containing (metakaolin) and Ca containing (slag) source materials, while retaining glass powder as the major component (50% or more), result in the formation of moisture-stable reaction products thereby mitigating the strength loss to a large extent. 相似文献
896.
《Materials Research Bulletin》2013,48(11):4718-4722
A reliable and facile pathway is described here for preparing high-quality bismuth nanoparticles. Combined with hydrothermal method and confined growing effect of polymer, bismuth nanoparticles with uniform size and shape were obtained with remarkable productivity. The nanoparticles is proved to be pure Rhombohedral structure Bi crystals with R-3m space group and the diameter of the nanoparticles is about 80 nm with a quite narrow particle size distribution. Those bismuth nanoparticles were predicted to grow from a rolling process by sheet-like Bi nanocrystal intermediates. The obtained bismuth nanoparticles were used to prepare modified electrode for the detection of Cd2+ and Pb2+ in water solution by stripping analysis. Compared with naked glassy carbon electrodes, the modified electrode showed two obvious responses at −0.85 V and −0.62 V, corresponding to the reduction process of Pb2+ and Cd2+ and this well-resolved stripping response can be observed when the concentration is as low as 10 μg/L, indicating potential application in electroanalysis for environmental inspection. 相似文献
897.
就L-半胱氨酸盐酸电化学生产工艺的工业化进行了讨论,并分布了工业化实验一些研究成果。 相似文献
898.
A.A. Hambardzumyan S.L. Kharatyan H.L. Khachatryan J.A. Puszynski 《International Journal of Refractory Metals and Hard Materials》2010
Opportunities on combustion synthesizing the WSi2-SiC ceramic composites in a wide range of compositions under the thermal activated mode were studied. Tungsten, silicon powders and carbon black were used as initial reagents, and Magnesium–Teflon mixture was used as an activating additive. The stepwise character of the combustion process evolution, being characterized by low- and high-temperature regimes, was revealed. The end-products were subjected to SEM, XRD and DTA/TG analyses. 相似文献
899.
Natalya V. Likhanova Octavio Olivares-Xometl Noel Nava-Entzana Hector Dorantes 《Corrosion Science》2010,52(6):2088-2097
Ionic liquids with chemical formula 1,3-dioctadecylimidazolium bromide and N-Octadecylpyridinium bromide were synthesized by conventional and microwave-assisted reactions, respectively. Ionic liquids tested as corrosion inhibitors after polarization curves displayed corrosion protection efficiency within 82-88% at 100 ppm for mild steel in a 1 M aqueous solution of sulfuric acid. Standard free energy indicated that corrosion inhibition occurred by a chemical adsorption process. Surface analysis (SEM, EDX) completed by XRD and Mössbauer spectroscopy indicated the presence of carbon species pertaining to inhibitor and corrosion products, which was rationalized in an inhibition mechanism. 相似文献
900.
介绍了SDA5000数字电视分析仪和漳州广电双向网络的改造方案,并简单地阐述了双向放大器的概念。介绍了SDA5000数字电视分析仪3个接口的作用,结合实际案例说明怎样用SDA5000数字电视分析仪测试双向放大器的插入损耗。 相似文献