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91.
《Journal of Process Control》2014,24(1):72-81
In this paper, a new model-order reduction (MOR) approach is presented for reducing large-scale differential-algebraic equation (DAE) systems with higher index. This approach is based upon the balanced truncation, single-point, and multi-point MOR methods. We decompose the DAE system into an ordinary differential equation (ODE) subsystem and a DAE subsystem. The DAE subsystem has the same index as the original DAE system. Then, the balanced truncation method is applied to the ODE subsystem. Both single-point and multi-point methods are used to reduce the DAE subsystem. In generally, the multi-point method can perform better than the single-point method across a wide-range of frequencies. Some numerical examples demonstrate the effectiveness of our approach. 相似文献
92.
《Ceramics International》2017,43(8):6502-6510
An one-pot method has been developed to synthesize a new type of composite material, which can be used as carbon source to produce electrode material for supercapacitors. Specifically, zeolitic imidazolate framework-67 (ZIF-67) crystal was synthesized firstly in 2-methylimidazol aqueous solution, then silica primary particles (from hydrolysis of tetraethylorthosilicate) and phenolic resin (from aggregation of resorcinol and formaldehyde) co-condensed on the surface of ZIF-67 crystal in the same system. The key to realize one-pot method is that 2-methylimidazol aqueous solution shows alkalescence, which can catalyze the hydrolysis of tetraethylorthosilicate and the aggregation of phenolic resin. After carbonization and remove of silica, the N-doped porous carbon (Carbon-ZSR) with high degree of graphitization, wide pore size distribution and maximum specific surface area was obtained. When it is used for supercapacitors as the electrode material, the Carbon-ZSR shows excellent electrochemical properties, large specific capacitance (305 Fg−1 at 1 Ag−1), high rate performance (229 Fg−1 keeps at 10 Ag−1) and excellent electrochemical stability (the specific capacitance maintains 98.4% after 5000 cycles at 10 Ag−1), which suggest that the ZIF-derived nitrogen-doped porous carbon is an outstanding electrode material for energy storage devices. 相似文献
93.
《Ceramics International》2017,43(16):13089-13093
A series of CaF2:xEu3+ (x = 0.01–0.05) phosphors were synthesized by coprecipitation and high temperature solid-state method. Three different F--Eu3+ charge transfer (CT) bands in CaF2:xEu3+ (x = 0.01–0.05) were detected through the PL spectra. Three local crystal environments (deformed Oh octahedron, C3V, C4V) were proposed in Eu3+ doped CaF2. The broad peak at 277 nm is F- → Eu3+ CT peak, in which Eu3+ ions located deformed Oh octahedron sites, the broad peak at 312 nm is due to Eu3+ ions situating at C4v sites, also, Eu3+ ions with C3v sites can make the F- → Eu3+ CT produce a 38-nm redshift to 315 nm. Density functional theory (DFT) was performed to calculate the energy band gap(Eg) according to the three models. The calculation results consist with the experiment. The excitation peaks can be tuned in the same host through changing the local structure of Eu3+. 相似文献
94.
95.
《Journal of the European Ceramic Society》2022,42(1):162-168
Excellent electrical properties and the improved long-term stability of ZnO varistor ceramics were simultaneously achieved by doping NiO. The microstructural features were investigated using X-ray diffractometer, scanning electron microscopy, and energy dispersive spectroscopy, while the intrinsic point defects were characterized using frequency domain dielectric spectroscopy and verified by photoluminescence and Raman spectra. The results indicated that in the ZnO varistor ceramics, a reverse manipulation of donor point defects, i.e., suppressing mobile zinc interstitial but increasing stable oxygen vacancy, was achieved. The long-term stability of NiO-doped ZnO ceramics was improved via a decrease in zinc interstitial density, with a degradation rate of 0.064 μA cm?2 h?0.5. Meanwhile, due to an increase in oxygen vacancy density, the excellent nonlinear current–voltage performance, i.e., a high nonlinear coefficient (72.9), low leakage current density (0.08 μA cm?2), and low grain resistivity (13.43 × 10?3 Ω m), was maintained. The findings of this study provide a possible method for developing high-performance ZnO varistor ceramics by manipulating point defects. 相似文献
96.
Reyila Abuduwayiti Feng-Yun Ma Xing Fan 《Frontiers of Chemical Science and Engineering》2022,16(10):1505
Four supported catalysts, nickel and ruthenium on a HZSM-5 support, were prepared by equal volume impregnation and in-situ decomposition of carbonyl nickel. The properties of catalysts were investigated by catalytic hydro-conversion of 2,2′-dinaphthyl ether as the model compound and extraction residue of Naomaohu lignite as the sample under an initial H2 pressure of 5 MPa and temperature at 150 °C. According to the catalytic hydro-conversion results of the model compound, Ni−Ru/HZSM-5 exhibited the best catalytic performance. It not only activated H2 into H···H, but also further heterolytically split H···H into immobile H‒ attached on the acidic centers of Ni−Ru/HZSM-5 and relatively mobile H+. Catalytic hydro-conversion of the extraction residue from Naomaohu lignite was further examined over the optimized catalyst, Ni−Ru/HZSM-5. Detailed molecular compositions of products from the extraction residue with and without hydrogenation were characterized by Fourier transform infrared spectroscopy and gas chromatography/mass spectrometry. The analytical results showed that the oxygen-containing functional groups in products of hydrogenated extraction residue were obviously reduced after the catalytic treatment. The relative content of oxygenates in the product with catalytic treatment was 18.57% lower than that in the product without catalytic treatment. 相似文献
97.
98.
99.
《International Communications in Heat and Mass Transfer》1988,15(5):615-626
The results of a numerical investigation of the natural convection process between isothermal vertically eccentric spheres with hotter inner core, are being presented. The Grashof and the Prandtl numbers have been kept constant at 4×104 and 10 respectively. Eccentricities varying from −0.75 to +0.75 have been studied. From the numerical solution, it is possible to explain the average results obtained previously for the regime where the steady crescent flow pattern exists. Negative eccentricities have been found to enhance convection while positive eccentricities have the reverse effect. Results also show that heat transfer actually increases slightly for very high positive eccentricities where conduction plays an important role. 相似文献
100.
以钾长石为原料,用液相合成法制备碳羟基磷灰石/钾长石吸附剂(CHAK)去除水中的重金属镍,用静态吸附实验考察了CHAK添加量、溶液初始pH、吸附时间、镍初始浓度等因素对镍去除效果的影响,并结合动力学及热力学拟合探究吸附机理。结果表明:随着CHAK量的增加,对Ni 2+的去除率增加,但吸附量会降低;溶液pH=6时吸附效果达到最佳;吸附时间为10 h时吸附达到平衡;Ni 2+溶液的初始质量浓度为50~4 000 mg/L时,CHAK对Ni 2+的吸附量呈先增长后平稳趋势,饱和吸附量与原材料相比增大7.1倍。动力学及热力学拟合结果显示:准二级模型更符合描述该吸附行为。ΔH>0,表明该吸附过程为吸热反应,升温有利于吸附。ΔG<0,表明该反应能自发进行。 相似文献