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71.
B. Abbaszadeh M. M. Sheikhi M. M. Fallah M. Eskandarzade 《Materialwissenschaft und Werkstofftechnik》2023,54(3):294-301
In the present study a new design of the equal channel angular pressing die and punch is introduced. The new design eliminates the deflection of the punch and at the same time lowers the frictional forces by reducing the contact area. In order to show the capability of the new design, the Al-7075 alloy samples were processed in two equal channel angular pressing dies. The measured data for the novel and conventional equal channel angular pressing processes were compared. The microstructure of the processed samples was examined with scanning electron microscopy and transmission electron microscopy. The results of the experimental study revealed that the novel die can fully eliminate the risk of the punch deflection and simultaneously reduce the maximum required pressing force by about 3.1 % to 9.8 % for 16 % to 40 % reduction in frictional contact surfaces. The analysis of experimental results showed that there is non-linear relation between the frictional contact area and the pressing load. In addition, it is shown that despites high contact pressures and high temperatures the use of graphite as a lubricant between sliding surfaces can considerably reduce the pressing load. 相似文献
72.
73.
Zahra Andaji‐Garmaroudi Mojtaba Abdi‐Jalebi Dengyang Guo Stuart Macpherson Aditya Sadhanala Elizabeth M. Tennyson Edoardo Ruggeri Miguel Anaya Krzysztof Galkowski Ravichandran Shivanna Kilian Lohmann Kyle Frohna Sebastian Mackowski Tom J. Savenije Richard H. Friend Samuel D. Stranks 《Advanced materials (Deerfield Beach, Fla.)》2019,31(42)
Mixed‐halide lead perovskites have attracted significant attention in the field of photovoltaics and other optoelectronic applications due to their promising bandgap tunability and device performance. Here, the changes in photoluminescence and photoconductance of solution‐processed triple‐cation mixed‐halide (Cs0.06MA0.15FA0.79)Pb(Br0.4I0.6)3 perovskite films (MA: methylammonium, FA: formamidinium) are studied under solar‐equivalent illumination. It is found that the illumination leads to localized surface sites of iodide‐rich perovskite intermixed with passivating PbI2 material. Time‐ and spectrally resolved photoluminescence measurements reveal that photoexcited charges efficiently transfer to the passivated iodide‐rich perovskite surface layer, leading to high local carrier densities on these sites. The carriers on this surface layer therefore recombine with a high radiative efficiency, with the photoluminescence quantum efficiency of the film under solar excitation densities increasing from 3% to over 45%. At higher excitation densities, nonradiative Auger recombination starts to dominate due to the extremely high concentration of charges on the surface layer. This work reveals new insight into phase segregation of mixed‐halide mixed‐cation perovskites, as well as routes to highly luminescent films by controlling charge density and transfer in novel device structures. 相似文献
74.
Ali Pourjavadi Mohammad Eskandari Seyed Hassan Hosseini Mojtaba Nazari 《国际聚合物材料杂志》2017,66(5):235-242
A noncovalent functionalization of the edges of reduced graphene oxide (RGO) with β-cyclodextrin-graft-hyperbranched polyglycerol (β-CD-g-HPG) was successfully performed via a host-guest interaction. The results showed that β-CD-g-HPG disperses the graphene sheets better than pure β-CD or HPG. The resulted supramolecular structure is stable in neutral water medium more than one week. However, in acidic medium the host-guest interaction is collapsed and graphene nanosheets precipitate. 相似文献
75.
Hossein Ali Rangkooy Mojtaba Nakhaei Pour Behzad Fouladi Dehaghi 《Korean Journal of Chemical Engineering》2017,34(12):3142-3149
Styrene monomer is a volatile organic compound that has many applications in plastics, rubber, and paint manufacturing industries. Exposure to styrene vapor has certain effects, including suppression of the central nervous system, loss of concentration, weakness and fatigue, and nausea and there is a possibility of carcinogenesis in long-term exposure. Therefore, it is necessary to control and eliminate this vapor. The aim of this study was to investigate the performance of zinc oxide nanoparticles on modified natural zeolites in removing styrene vapor from the air. Natural zeolites of clinoptilolite were modified using hydrochloric acid and diphenyldichlorosilane. Next, zinc oxide nanoparticles with different ratios of 3, 5, and 10 wt% were stabilized on the zeolites. To determine their characteristics, samples were used from BET, SEM and XRD analyses. The input styrene concentration and the ratio of nanoparticles stabilized on zeolites were studied as effective functional parameters on the removal process. The efficiency results of natural zeolites (Ze) and modified zeolites (Mze) in styrene adsorption from the air show that the styrene breakthrough in the bed of MZe compared to that of Ze increases approximately two times. Also, the results showed that the removal by the process of UV/MZe-ZnO 3%, UV/MZe-ZnO 5%, and UV/MZe-ZnO 10%, was 36.5%, 40%, and 26%, respectively. From the results it can be concluded that MZe can increase the efficiency of photocatalytic degradation. Clinoptilolites of Iran can be used as an adsorbent to remove polluted air in industries that have low concentrations and flow rates. 相似文献
76.
Physical and Morphological Properties of Combined Treated Wood Polymer Composites by Maleic Anhydride and Methyl Methacrylate 总被引:1,自引:0,他引:1
Wood polymer composites were prepared by consecutive impregnation with maleic anhydride (MAN) and methyl methacrylate (MMA). Samples impregnated with MAN alone, were heated at 120°C and 150°C for 4 and 8 h. Based on the Fourier transform infrared (FT-IR) analysis and soaking-drying test results, treatment with MAN at 150°C for 4 h resulted in formation of stable crosslinks. In the second stage, MMA was used for in situ polymerization within MAN-treated wood. Field emission scanning electron microscopy observation and FT-IR analysis indicated that MMA copolymerized with MAN, and the resultant polymer filled up the lumen and is also grafted on to the cell wall. Improvement of water repellency and dimensional stability were observed in the treated samples, particularly in combined treated samples. The MAN/MMA treatment improved interaction between polymer and wood. 相似文献
77.
Mojtaba Abbasian Mousa Pakzad Kobra Nazari 《Polymer-Plastics Technology and Engineering》2017,56(8):857-865
A bionanocomposite of grafted cellulose and organo-modified clay was synthesized through solution intercalation method. For this purpose, chloromethylstyrene was grafted onto cellulose using acryloylchloride and the subsequent free radical polymerization. The synthesized cellulose-graft-polychloromethylstyrene was used as an atom transfer radical polymerization macroinitiator of acrylonitrile in the presence of CuCl/2,2′-bipyridine catalyst system, to prepare the cellulose-graft-polychloromethylstyrene-graft-polyacrylonitrile terpolymer. For preparing the modified clay, Na-montmorillonite was mixed with hexadecyl trimethyl ammonium chloride salt. Finally, cellulose-graft-polychloromethylstyrene-graft-polyacrylonitrile/organoclay bionanocomposite was prepared in CCl4 by solution intercalation method. 相似文献
78.
Reza Ramezanian Sahar Fallah Sanami Mohsen Shafiei Nikabadi 《The International Journal of Advanced Manufacturing Technology》2017,88(9-12):2389-2403
The aim of this paper is to study a simultaneous lot-sizing and scheduling in multi-product, multi-period flexible flow shop environments. A new mixed integer programming (MIP) model is proposed to formulate the problem. The objective function includes the total cost of production, inventory, and external supply. In this study, in case of not meeting the demand of customers, this demand should be met by foreign suppliers in higher price. Due to the high computational complexity of the studied problem, a rolling horizon heuristic (RHH) and particle swarm optimization algorithm (PSO) are implemented to solve the problem. These algorithms find a feasible and near-optimal from production planning and scheduling. Additionally, Taguchi method is conducted to calibrate the parameters of the PSO algorithm and select the optimal levels of the influential factors. The computational results show that the algorithms are capable of achieving results with good quality in a reasonable time and PSO has better objective values in comparison with RHH. Also, the real case study for tile industry with real features is applied. Sensitivity analysis is used to evaluate the performance of the model. 相似文献
79.
Water resources allocation problems are mainly categorized in two classes of simulation and optimization. In most cases, optimization problems due to the number of variables, constraints and nonlinear feasible search space are known as a challenging subject in the literature. In this research, by coupling particle swarm optimization (PSO) algorithm and a network flow programming (NFP) based river basin simulation model, a PSO-NFP hybrid structure is constructed for optimum water allocation planning. In the PSO-NFP model, the NFP core roles as the fast inner simulation engine for finding optimum values for a large number of water discharges in the network links (rivers and canals) and nodes (reservoirs and demands) while the heuristic PSO algorithm forms the outer optimization cover to search for the optimum values of reservoirs capacities and their storage priorities. In order to assess the performance of the PSO-NFP model, three hypothetical test problems are defined, and their equivalent nonlinear mathematical programs are developed in LINGO and the results are compared. Finally, the PSO-NFP model is applied in solving a real river basin water allocation problem. Results indicate that the applied method of coupling PSO and NFP has an efficient ability for handling river basin-scale water resources optimization problems. 相似文献
80.
The characterization of sinusoidal signals with time varying amplitude and phase is useful and applicable for many
fields. Therefore several algorithms have been suggested to estimate main aspects of these signals. Within no
standard approach to test the properties of these algorithms, it seems to be helpful to discuss a large class of
algorithms according to their properties. In this paper, six methods of estimating dynamic phasor have been reviewed
and discussed which three of them are based on least square and others are based on Kalman filter. Taylor expansion
is used as a first step and continued with least square or Kalman filter in accordance with the proposal observer of
each method. The theoretical processes of these methods are briefly clarified. The characterizations have been made
by some tests in time and frequency domains. The tests include amplitude step, phase step, frequency step,
frequency response, total vector error, transient monitor, noise, sample number, computation time, harmonic and DC
offset which build a framework to compare the different methods. 相似文献