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161.
Hitoshi Tanaka Morimasa Tanimoto Akira Matsuda Takeo Uno Masaaki Kurihara Shoji Shiga 《Journal of Electronic Materials》1999,28(11):1216-1223
Pb-free solderable surface finishing is essential to implement Pb-free solder assembly in order to meet with the growing demand
of environmental consciousness to eliminate Pb from electronic products. Two types of widely applicable Pb-free surface finishing
technologies are developed. One is the multilayer-system including Pd with Ni undercoat. Heat-resistance of Pd enables whole-surface-plating
on to leadframe before IC-assembling process. The other is the double-layer-system with low-melting-point-materials, for example,
thicker Sn underlayer and thinner Sn-Bi alloy overlayer, dilutes Sn-Bi alloy’s defects of harmful reactivity along with substrate
metal and mechanical brittleness with keeping its advantages of solder-wettability and no whisker. 相似文献
162.
Well-dispersed Palladium Nanoparticles Catalysts Prepared by Wood Nanomaterials for Suzuki Coupling Reaction
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Herein, well-dispersed Palladium (Pd) nanoparticles (NPs) with good catalytic activities were prepared using a wood nanomaterial (WNM) as a reductant and a supporting agent. Various factors that influenced the NP morphologies, including reaction time, temperature, and precursor concentration were studied. The as-prepared Pd NPs/WNM showed good catalytic performance for Suzuki coupling reactions. 相似文献
163.
Recent progress in the practical applications of heteropolyacid and perovskite catalysts: Catalytic technology for the sustainable society 总被引:1,自引:0,他引:1
Recent progresses in practical applications of (i) supported heteropolyacid and (ii) Pd/perovskite catalysts are described. (i) Two industrial catalytic processes, ethyl acetate and acetic acid syntheses both from ethylene, utilize silicotungstic acid, alone and together with Pd, respectively, carefully supported on silica, and exhibit high performance from green chemical and economical viewpoints. The layer structure of heteropolyacid on silica and physical properties of silica are among the key factors of the high performance. (ii) Pd/perovskite catalyst is applied for the treatment of automotive emission, where the catalyst life is very much elongated by embedding Pd into the perovskite lattice and hence resulted in much reduced usage of Pd. These are good examples of green catalytic technology that will contribute to the sustainable society. 相似文献
164.
M.C. Román-Martínez J.A. Díaz-Auñón P.C. L'Argentière C. Salinas-Martínez de Lecea 《Catalysis Letters》2001,77(1-3):41-46
The catalytic activity of [PdCl2(NH2(CH2)12CH3)2] (named [Pd(TDA)]) and [RhCl(NH2(CH2)12CH3)3] (named [Rh(TDA)]) complexes for the hydrogenation of cyclohexene has been analysed both in homogeneous phase and heterogenised on activated carbon. The [Rh(TDA)] complex has been found to be more active than the [Pd(TDA)], both homogeneous and heterogenised. Experimental and modelled results indicate that these complexes follow a similar reaction mechanism, but with different rates. A clear positive effect of the carbon support has been found in the case of the complex [Rh(TDA)], which has been related to the anchorage of the aliphatic chains of the amine ligands on the activated carbon pores. Experiments in consecutive catalytic runs show that the heterogenised complexes can be used several times giving an acceptable conversion level. 相似文献
165.
Theoretical studies of CO hydrogenation to methanol over Cu, Pd, and Pt metals have been carried out using a quasi‐relativistic
density‐functional method. The metal surface is simulated by a M10 cluster model. Reaction energies for the elementary steps involved are determined. The activation energies are estimated
by the analytic BOC‐MP formula. The results support that these metals are active in CO hydrogenation to methanol. The rate‐determining
steps are shown to be different for the metals. The highest activation energies of reaction on the metals fall in the order
Cu < Pd < Pt, which corresponds to the order of the catalytic activities of the metals in CO hydrogenation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
166.
Methanol decomposition to synthesis gas over supported Pd catalysts prepared from synthetic anionic clays 总被引:2,自引:0,他引:2
Ryuji Shiozaki Takashi Hayakawa Yan-yong Liu Tomoko Ishii Mikio Kumagai Satoshi Hamakawa Kunio Suzuki Tatehiko Itoh Tetsuya Shishido Katsuomi Takehira 《Catalysis Letters》1999,58(2-3):131-140
Supported Pd or Rh catalysts were prepared by the solid-phase crystallization method starting from hydrotalcite anionic clay
minerals based on [Mg6Al2(OH)16CO
2
2−
]·4H2O as the precursors. The precursors were prepared by a coprecipitation method from the raw materials containing Pd2+ and various trivalent metal ions which can replace each site of Mg2+ and Al3+ in the hydrotalcite. Rh3+ was also used for preparing the catalyst as comparison. The precursors were then thermally decomposed and reduced to form
supported Pd or Rh catalysts and used for the methanol decomposition to synthesis gas. Among the precursors tested, use of
Mg–Cr hydrotalcite containing Pd2+ resulted in the formation of efficient Pd supported catalysts for the production of synthesis gas by selective decomposition
of methanol at low temperature. Although Pd2+ cannot well replace the Mg2+ site in the hydrotalcite, the Pd supported catalyst (Pd/Mg–Cr) prepared by the solid-phase crystallization method formed
highly dispersed Pd metal particles and showed much higher activity than that prepared by the conventional impregnation method.
When the precursor was prepared under mild conditions, more fine particles of Pd metal were formed over the catalyst, resulting
in high activity. It is likely that the high activity may be due to the highly dispersed and stable Pd metal particles assisted
by the role of Cr as the co-catalyst.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
167.
Molecular dynamics simulations have been performed to investigate the thermal expansivity of MgO at high temperature using the very similar Lewis-Catlow and Stoneham-Sangster shell model potentials. In order to take account of non-central forces in crystals, the breathing shell model is also introduced in simulation. The volume thermal-expansion coefficient αP of MgO dependence of the temperature T at 0 and 135 GPa have been obtained and compared with the available experimental and theoretical results. Compared with shell model potentials, the molecular dynamics results obtained using breathing shell model potentials are more compressible. At an extended pressure and temperature ranges, αP has also been predicted. 相似文献
168.
以Pd/C为催化剂直接催化氢化2-氨基-4,6-二羟基-5-亚硝基嘧啶削备2,5-二氨基-4,6-羟基嘧啶,采用正交设计方法考察了碱的浓度、溶剂、催化剂用量、温度、反应时间等对反应的影响,收率在86%以上。 相似文献
169.
170.
Nichola J. Coulston Richard P.K. Wells Peter B. Wells Graham J. Hutchings 《Catalysis Today》2006,114(4):353-356
The enantioselective hydrogenation of N-acetyl dehydrophenylalanine methyl ester (NADPME) to N-acetyl phenylalanine methyl ester is investigated using cinchonine-modified Pd/TiO2 catalysts. The catalysts were prepared using deposition–reduction and wet impregnation methods and were evaluated for reaction using methanol as solvent with various cinchonine/NADPME molar ratios. Enantioselectivity was sensitive to this ratio and comparison with Pd/γ-Al2O3 showed that the Pd/TiO2 gave marginally higher enantioselectivity when tested under comparable conditions. The effect of Pd loading and dispersion was investigated and the maximum enantiomeric excess observed was dependent on the dispersion; the role of the Pd particle size is discussed in the context of cinchonine adsorption. The reactions were carried out in solvents (methanol and dimethyl formamide) and mixed solvents (methanol–water and dimethyl formamide–water); the enantiomeric excess was significantly enhanced using dimethyl formamide. The addition of water does not have a significant effect for the Pd/TiO2 catalysts. In this paper we report the highest enantiomeric excess for the hydrogenation of a prochiral ester using an immobilised catalyst. 相似文献