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91.
碳沉积法制富氮用炭分子筛的研究 总被引:1,自引:0,他引:1
本文提出的碳沉积法是用煤焦油馏分油的有机溶液浸渍煤炭化物,然后热解以进行“孔调变”。确定了最佳工艺条件,制得富氮性能良好的炭分子筛。并用D-A方程求取了各种样品的微孔结构参数。 相似文献
92.
Propylene epoxidation over Ti/MCM-41 catalysts prepared by chemical vapor deposition 总被引:3,自引:0,他引:3
Ti-containing mesoporous catalysts were prepared by chemical vapor deposition (CVD) of TiCl4 on silica MCM-41 in the 700–900 °C temperature range. These samples were characterized (with XRD, ICP, nitrogen adsorption, FT-IR, ESCA, and TEM) and evaluated for the epoxidation of propylene with two alkyl hydroperoxides. The increase of CVD temperature resulted in the decrease of titanium content, catalyst hydroxyl population, crystallinity, and surface area. Catalyst selectivity to the desired product – propylene oxide – was highly sensitive to the deposition temperature. The best Ti/MCM-41 catalyst was prepared at the temperature of 800 °C, which had the maximum propylene oxide yield of 94.3%. 相似文献
93.
Preparation of methanol oxidation electrocatalysts: ruthenium deposition on carbon-supported platinum nanoparticles 总被引:3,自引:0,他引:3
Methanol oxidation electrocatalysts were prepared from Ru electrochemical or spontaneous deposition on commercial-grade carbon-supported Pt nanoparticles (Pt-Vulcan XC72, E-TEK). The resulting Ru coverage was estimated by cyclic voltammetry in supporting electrolyte. The maximum electrocatalytic activity for methanol oxidation at room temperature was observed at lower Ru coverage for spontaneous deposition than for electrodeposition;
Ru 10% vs 20%, respectively. On the other hand, higher current densities for methanol oxidation were obtained in the case of electrodeposited Ru. These two results were related to the presence of non-reducible ruthenium oxides in the spontaneous deposit. The present work provides evidence that (i) efficient DMFC electrocatalysts can be achieved by Ru deposition on Pt nanoparticles, and (ii) formation of a PtRu alloy is not a required condition for effective methanol electrooxidation. 相似文献
94.
95.
Bo He Fei Li Hong Zhou Yongbing Dai Baode Sun 《Journal of Coatings Technology and Research》2007,4(3):335-340
Two kinds of thermal barrier coatings (TBCs), consisting of NiCoCrAlY bond coats (BCs) deposited by electron beam-physical
vapor deposition (EB-PVD) and high velocity oxy-fuel (HVOF) thermal spraying, respectively, and top 8 wt%Y2O3–ZrO2 (8YSZ) ceramic layers deposited by EB-PVD were prepared on near-α titanium alloys. The field emission scanning electronic
microscopy and microhardness indentation are used to study the microstructure and microhardness. Different failure features
including cracking patterns and the delamination degree of these two TBCs are discussed according to the thermal cycling tests
in the atmosphere. It is found that the morphology of the two BCs deposited by different methods (EB-PVD and HVOF) determines
the microstructure and microhardness of their corresponding top 8YSZ layers. The BC prepared by EB-PVD is dense and homogeneous,
which leads to a dense and hard 8YSZ with clustered slim columnar grains. The BC prepared by HVOF, however, is porous and
inhomogeneous in microstructure and, as a result, the top ceramic layer is loose with low microhardness and clustered coarse
columnar grains. 相似文献
96.
Robert J. Andrews 《Carbon》2006,44(2):341-347
Single walled nanotubes have been synthesized by chemical vapor deposition from camphor, camphor analogs (camphorquinone, norcamphor, norbornane, camphene, fenchone), and various other precursors (menthone, 2-decanone, benzene, methane). The high temperature conditions (865 °C) and Fe/Mo alumina catalyst used in the syntheses are archetypal conditions for the production of single walled carbon nanotubes. It has been shown that the mechanism of tube growth is unlikely to depend upon the production of reactive five- and six-member rings, as has been previously suggested. The results suggest that the presence of oxygen in the precursor does not significantly improve the quality of tubes by etching amorphous carbon: it is suggested that the control of the flux of the precursor to the catalyst is more important in the production of high quality tubes. There is, however, evidence for different distributions of tube diameter being produced from different precursors. 相似文献
97.
The influence of cobalt on the electrodeposition of zinc onto AISI 1018 steel was studied in weakly alkaline glycine solutions. Thermodynamic calculations were performed to construct predominance-zone diagrams to identify the stability of the zinc and cobalt glycine complexes, and experimental studies of electrochemical behavior and deposit properties were conducted. When zinc is present, cobalt deposition shifts to more negative potentials, producing ZnCo alloys. Two main reduction steps were observed for electrodeposition from the ZnCo bath: the first at low potentials was due to ZnCo electrodeposition. In the second, at more negative potentials, cobalt content in the deposit increased forming a range of intermediate phases, and the hydrogen-evolution reaction became significant. The presence of Co(II) in the bath modified the morphology of the deposits as well as reducing the faradaic metal-deposition efficiency. ZnCo-deposit morphology was modified by the applied current density as well as the metal composition of the coating. X-ray diffraction studies revealed that cobalt oxide or hydroxide is formed during ZnCo electrodeposition, indicating that an elevation of the interfacial pH plays a role in the alloy deposition process. 相似文献
98.
99.
100.
Ying Wang 《Electrochimica acta》2006,51(23):4865-4872
Thin films of orthorhombic V2O5 have been prepared by sol electrophoretic deposition (EPD) followed by post-treatment at 500 °C. Their electrochemical and optical performances have been investigated for possible applications in electrochemical/electrochromic devices. Li+-intercalation properties of the films have been explored in two voltage ranges: 0.4 to −1.1 V and 0.4 to −1.6 V versus Ag/Ag+, respectively. High capacities of over 300 mAh/g are acquired in the wider voltage range at a current density of 50 μA/cm2 and moderate capacities of 140 and 110 mAh/g are obtained in the narrower voltage range at a current density of 25 and 50 μA/cm2, respectively. Electrochemical measurements have shown that the films demonstrate good cyclability in both voltage ranges. X-ray diffraction, scanning electron microscopy and optical spectra have been used to examine the changes in crystallinity, microstructure, morphology and transmittance of the films during cycling. Films cycled to a deeper voltage of −1.6 V versus Ag/Ag+ deliver higher capacity with appreciable morphological change, while films cycled in the narrower voltage range show moderate capacity and maintain the morphology, optical responses and crystalline structure. Voltage range can be optimized in between to acquire both high capacity and stability in structure, electrochemical and optical properties. High Li+-intercalation capacity and good cyclic stability are attributed to the porous structure of V2O5 films prepared by EPD. 相似文献