全文获取类型
收费全文 | 3556篇 |
免费 | 289篇 |
国内免费 | 571篇 |
专业分类
电工技术 | 50篇 |
综合类 | 295篇 |
化学工业 | 717篇 |
金属工艺 | 199篇 |
机械仪表 | 62篇 |
建筑科学 | 35篇 |
矿业工程 | 11篇 |
能源动力 | 133篇 |
轻工业 | 102篇 |
水利工程 | 11篇 |
石油天然气 | 12篇 |
武器工业 | 26篇 |
无线电 | 770篇 |
一般工业技术 | 849篇 |
冶金工业 | 60篇 |
原子能技术 | 199篇 |
自动化技术 | 885篇 |
出版年
2024年 | 4篇 |
2023年 | 94篇 |
2022年 | 76篇 |
2021年 | 71篇 |
2020年 | 127篇 |
2019年 | 90篇 |
2018年 | 59篇 |
2017年 | 116篇 |
2016年 | 108篇 |
2015年 | 125篇 |
2014年 | 250篇 |
2013年 | 314篇 |
2012年 | 387篇 |
2011年 | 410篇 |
2010年 | 284篇 |
2009年 | 380篇 |
2008年 | 269篇 |
2007年 | 415篇 |
2006年 | 328篇 |
2005年 | 150篇 |
2004年 | 71篇 |
2003年 | 40篇 |
2002年 | 66篇 |
2001年 | 48篇 |
2000年 | 39篇 |
1999年 | 35篇 |
1998年 | 21篇 |
1997年 | 8篇 |
1996年 | 7篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有4416条查询结果,搜索用时 31 毫秒
21.
《Journal of the European Ceramic Society》2020,40(4):1620-1625
The high radiation resistance and long time stability of Gd2Zr2O7 ceramics make it a promising candidate for high level waste (HLW) immobilization materials. In this study, single phase nanocrystalline Gd2Zr2O7 was successfully synthesized and consolidated at temperatures around 1050 °C for only 1 min by flash sintering for the first time. The phase evolution and microstructural development during flash sintering were systematically studied and compared with the conventionally sintered samples. The flash sintered Gd2Zr2O7 exhibit defect fluorite structure, and a following heat treatment at 1400 °C could transform the Gd2Zr2O7 ceramics from defect fluorite phase into pyrochlore phase. The MCC-1 leaching test shows that the flash sintered Gd2Zr2O7 samples exhibit good aqueous durability. 相似文献
22.
《International Journal of Hydrogen Energy》2020,45(46):24626-24635
In this paper, a series of alkaline earth metals oxides doped Ni/La2O3–Al2O3 catalysts were synthesized by the coprecipitation method combined with two step impregnation methods. n-decane reforming was used to investigate these catalysts, in order to develop an excellent catalyst with better hydrogen selectivity, activity, stability, as well as lower carbon deposition. Deactivation by carbon deposition, the catalyst regenerability and stability tests were also used to weigh the selected catalyst. These catalysts are characterized by N2 adsorption-desorption, XRD, NH3-TPD, Raman, and TEM. The introduction of alkaline earth metals modifiers enhances the activity, stability and anti-coking ability, meanwhile the SrO modified Ni/La2O3–Al2O3 shows the best catalytic activity. Moreover, the hydrogen selectivity and conversion over regenerative Ni/La2O3–Al2O3/SrO catalysts were quite close to the results of fresh ones. The enhancements of M oxides doped catalysts (especially Sr) can be due to the improved textural properties, basicity, metal-support interaction and anti-coking ability. As a consequence, loading different metals in different ways helps to gradually improve the stability, activity and coking inhibition of catalysts is an effective approach to obtain a multi-function catalyst. 相似文献
23.
Si-based hydrolysis material system can be used in mobile/portable hydrogen source applications connected to fuel cells but is limited by alkaline solutions. In the present research, we reported an acid/alkaline free hydrolysis system combining silicon with NaBH4. Samples with different ratios between Si and NaBH4 are prepared via high energy ball milling and hydrolyzed in deionized water at different temperatures. Synergetic effect between silicon and NaBH4 was found in the hydrolysis process. 2Si-NaBH4 sample displays the best hydrolysis performances with the hydrogen yield of 1594 ml⋅g−1 in deionized water at 70 °C. Thereafter, AlCl3 is added into the 2Si-NaBH4 sample to further improve its comprehensive properties. The effect of AlCl3 content and promotion mechanism of the reaction are explored. 2Si-NaBH4–5 wt% AlCl3 sample shows a significant improvement with a high hydrogen yield of 1689 ml·g−1 in deionized water at 70 °C and a corresponding conversion rate of 95.8%, indicating that the Si-NaBH4-AlCl3 composite is promising to be a hydrogen source in applications of mobile/portable fuel-cell-powered facilities. 相似文献
24.
《中国有色金属学会会刊》2020,30(9):2459-2471
Taking a Ti−5Al−5Mo−5V−1Cr−1Fe alloy as exemplary case, the fatigue crack growth sensitivity and fracture features with various tailored α phase morphologies were thoroughly investigated using fatigue crack growth rate (FCGR) test, optical microscopy (OM) and scanning electron microscopy (SEM). The tailored microstructures by heat treatments include the fine and coarse secondary α phase, as well as the widmanstatten and basket weave features. The sample with coarse secondary α phase exhibits better comprehensive properties of good crack propagation resistance (with long Paris regime ranging from 15 to 60 MPa·m1/2), high yield strength (1113 MPa) and ultimate strength (1150 MPa), and good elongation (11.6%). The good crack propagation resistance can be attributed to crack deflection, long secondary crack, and tortuous crack path induced by coarse secondary α phase. 相似文献
25.
《Ceramics International》2020,46(3):3144-3165
The ceramic nanocomposites (CNCs) like zirconia toughened alumina (ZTA) ceramics are important futuristic materials for structural and functional applications in advanced strategic systems, structural components, biomedical prostheses and devices. In all structural materials including the ZTA CNCs, the very early stages of plastic deformation i.e., the incipient plasticity events (IPE) are most important to be understood so that the microstructure and mechanical properties can be tuned to suit a given end application. Here we report for the first time the mechanisms of IPE in the nanoindentation experiments conducted at 10–1000 mN loads in the 40 ZTA CNCs. Here 40 ZTA CNC stands for 40 vol% of 3 mol% Yttria partially stabilized zirconia toughened alumina (40ZTA) CNC. The role of load ranges in variations of the IPE related parameters in the 40 ZTA CNCs is also studied. Further, an attempt is made to assess how the amount of zirconia content in ZTA CNCs affects the variations of the IPE related parameters. Through the extensive usage of field emission scanning electron microscopy (FESEM) and theoretical estimations, efforts are also directed to check out the linkage, if any, between the localized shear deformation and/or microcracking with the IPE events that occur in the present CNCs. In addition, a new concept of damage resistance is introduced for the first time in the present work to explain the presence of a strong indentation size effect (ISE) in the 40 ZTA CNCs. Finally, an attempt is also directed to understand how the indentation load (P) controls the relative size of interaction zones of dislocation loops as well as the damage resistance and thereby, engineer the acuteness of the ISE in ZTA CNCs. The implication of these findings in futuristic design of especially the ZTA CNCs for various applications is also discussed. 相似文献
26.
《中国有色金属学会会刊》2020,30(8):2274-2282
The reduction kinetics of zinc calcine under a CO atmosphere was evaluated by isothermal reductive roasting in a temperature range of 600−800 °C. The extent of reaction of zinc calcine was measured using thermogravimetry (TG), and the decomposition mechanism of zinc ferrite in zinc calcine was analyzed based on variations in the soluble zinc and ferrous contents. The results indicate that the reaction was controlled by the nucleation of the products, with an apparent activation energy of 65.28 kJ/mol. The partial pressure of CO affected the reaction rate more strongly than the CO intensity (defined as PCO/(PCO+PCO2)). The generation rate of zinc oxide was higher than that of ferrous oxide; therefore, the nucleation of ferrous oxide is the rate-determining step of the reaction. 相似文献
27.
《Ceramics International》2020,46(6):7774-7782
In order to inhibit the metal catalytic coking and improve oxidation resistance of single TiN coating, the TiN/Al2O3 double layer coatings were designed as a chemically inert coating for methylcyclohexane supercritical pyrolysis. Internal TiN coatings were prepared by atmospheric pressure chemical vapor deposition using TiCl4–H2–N2 system. The external Al2O3 coatings with different thicknesses were prepared on the TiN surface by polymer-assisted deposition, and the coating with the most suitable thickness was further annealed at different temperatures of 600, 700, 800 and 900 °C. The morphology, elemental and phase composition of TiN/Al2O3 coatings were characterized by SEM, EDX and XRD respectively. The chemical state information of the coating elements was based on Ti 2p, Al 2p core level X-ray photoelectron spectroscopy (XPS) spectra. The results indicated that the external Al2O3 coating will partially peel off at 900 °C annealing temperature. The thermogravimetric analysis results indicated that all TiN/Al2O3 coatings show better oxidation resistance than single-layer TiN coating. The anti-coking test with methylcyclohexane supercritical pyrolysis showed that the TiN/Al2O3 coatings can effectively cover the metal catalytic sites and eliminate metal catalytic coking. However, the acid sites of external Al2O3 coating slightly promoted coking, so the anti-coking ratios of TiN/Al2O3 coatings were smaller than that of TiN. Thus, the addition of external Al2O3 coating can greatly improve the oxidation resistance of TiN coatings with little loss of coking resistance. 相似文献
28.
《International Journal of Hydrogen Energy》2019,44(18):9210-9219
This paper presents an efficient framework for converting renewable energy to gas and reducing Carbon dioxide (CO2) footprint at the same time. The problem is presented in two levels. The first level is a minimization programming that minimizes operational cost and CO2 of generators. The CO2 is forwarded to the second level. In the second level, Carbon Capture and Storage (CCS) is designed to capture CO2. The CO2 is combined with Hydrogen and makes Methane (CH4). The required Hydrogen is obtained from water electrolyzer that is supplied by the solar system. The capacity and size of water electrolyzer, solar system, and CCS is designed by the planning in the second level while this programming maximizes profit from selling Methane. As a result, the first level presents minimization programming (i.e., minimizing cost and CO2) and the second level presents maximization programming (i.e., maximizing profit). The programming is developed taking into account solar uncertainty. The stochastic programming is implemented to cope with uncertainties. The problem is formulated as binary mixed integer linear programming and solved by GAMS software. The proposed power to gas (P2G) procedure efficiently designs proper solar system and deals with intermittency of solar energy, reduces CO2 footprint, maximizes profit, and minimizes operational cost of generators at the same time. 相似文献
29.
Yichao Gong Zhong Chen Mao Yang Hailiang Wang Chen Dang Wanxia Huang Tiecheng Lu 《Ceramics International》2018,44(14):16209-16213
Li4SiO4 has been widely studied as attractive tritium breeding materials due to its innate merits. Considering the potential advantages of nanostructure in tritium breeding materials, a distinctive process was developed to obtain nanostructured Li4SiO4 pebbles. In brief, ultrafine precursor powders were synthesized by solvothermal method without using surfactants, and then indirect wet method was adopted to generate the green spheres with homogeneous microstructure. After that, the suitable sintering conditions were defined by studying the effects of sintering parameters on the grain size evolution, and nanostructured Ti-doped Li4SiO4 pebbles were first obtained by two-step sintering method. This study will be expected to provide references for fabricating other Li-based tritium breeding materials. 相似文献
30.
Telecommunication Systems - Confidentiality and integrity are fundamental requirements when transmitting and storing data. In order to guarantee the confidentiality and integrity of speech signal,... 相似文献