全文获取类型
收费全文 | 74192篇 |
免费 | 8326篇 |
国内免费 | 4179篇 |
专业分类
电工技术 | 12019篇 |
技术理论 | 13篇 |
综合类 | 5201篇 |
化学工业 | 8666篇 |
金属工艺 | 2542篇 |
机械仪表 | 2959篇 |
建筑科学 | 9979篇 |
矿业工程 | 2025篇 |
能源动力 | 12662篇 |
轻工业 | 2089篇 |
水利工程 | 1391篇 |
石油天然气 | 2112篇 |
武器工业 | 605篇 |
无线电 | 5201篇 |
一般工业技术 | 7487篇 |
冶金工业 | 4820篇 |
原子能技术 | 1251篇 |
自动化技术 | 5675篇 |
出版年
2024年 | 498篇 |
2023年 | 1673篇 |
2022年 | 2684篇 |
2021年 | 2936篇 |
2020年 | 3125篇 |
2019年 | 2772篇 |
2018年 | 2333篇 |
2017年 | 2778篇 |
2016年 | 3128篇 |
2015年 | 3038篇 |
2014年 | 5093篇 |
2013年 | 4838篇 |
2012年 | 5317篇 |
2011年 | 5985篇 |
2010年 | 4622篇 |
2009年 | 4727篇 |
2008年 | 4267篇 |
2007年 | 4677篇 |
2006年 | 3725篇 |
2005年 | 2865篇 |
2004年 | 2392篇 |
2003年 | 2055篇 |
2002年 | 1804篇 |
2001年 | 1540篇 |
2000年 | 1318篇 |
1999年 | 1038篇 |
1998年 | 828篇 |
1997年 | 659篇 |
1996年 | 588篇 |
1995年 | 455篇 |
1994年 | 401篇 |
1993年 | 321篇 |
1992年 | 252篇 |
1991年 | 219篇 |
1990年 | 201篇 |
1989年 | 175篇 |
1988年 | 146篇 |
1987年 | 112篇 |
1986年 | 108篇 |
1985年 | 121篇 |
1984年 | 103篇 |
1983年 | 58篇 |
1982年 | 88篇 |
1981年 | 62篇 |
1980年 | 41篇 |
1979年 | 42篇 |
1977年 | 28篇 |
1968年 | 46篇 |
1965年 | 33篇 |
1964年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(2):1217-1228
In this article, pre-assembly hot-press pressure and thermal expansion effects in gas-diffusion layers (GDLs) are addressed to explore the practicalities of the constitutive model reported in the companion article. A facile technique is proposed to include deformation history dependent residual strain effects. The model is implemented in the numerical environment and compared with widely followed conventional models such as isotropic and orthotropic material models. With the normal and accelerated thermal expansion effects no significant variation in stresses or strains is reported with the compressible GDL model in contrast to the conventional incompressible form of the GDL model. The present work identifies the critical differences with advanced and extended variants of the model along with conventional GDL material models in terms of planar stress/strain distribution and the membrane response. Finally, the model is simulated for micro-cyclic stress loads of varying amplitudes that imitate the real working conditions of fuel cell. The inelastic energy dissipation in GDLs is predicted using the proposed model, which is utilized further to distinguish the safe (elastic) and unsafe (inelastic shakedown) operating limits. The inelastic collapse of GDLs is shown to be a active function of high amplitude micro-cyclic load with high initial clamping load. 相似文献
2.
《International Journal of Hydrogen Energy》2022,47(99):41783-41794
To satisfy arising energy needs and to handle the forthcoming worldwide climate transformation, the major research attention has been drawn to environmentally friendly, renewable and abundant energy resources. Hydrogen plays an ideal and significant role is such resources, due to its non-carbon based energy and production through clean energy. In this work, we have explored catalytic activity of a newly predicted haeckelite boron nitride quantum dot (haeck-BNQD), constructed from the infinite BN sheet, for its utilization in hydrogen production. Density functional theory calculations are employed to investigate geometry optimization, electronic and adsorption mechanism of haeck-BNQD using Gaussian16 package, employing the hybrid B3LYP and wB97XD functionals, along with 6–31G(d,p) basis set. A number of physical quantities such as HOMO/LUMO energies, density of states, hydrogen atom adsorption energies, Mulliken populations, Gibbs free energy, work functions, overpotentials, etc., have been computed and analysed in the context of the catalytic performance of haeck-BNQD for the hydrogen-evolution reaction (HER). Based on our calculations, we predict that the best catalytic performance will be obtained for H adsorption on top of the squares or the octagons of haeck-BNQD. We hope that our prediction of most active catalytic sites on haeck-BNQD for HER will be put to test in future experiments. 相似文献
3.
《International Journal of Hydrogen Energy》2022,47(78):33282-33307
‘Renewable energy is an essential part of our strategy of decarbonization, decentralization, as well as digitalization of energy.’ – Isabelle Kocher.Current climate, health and economic condition of our globe demands the use of renewable energy and the development of novel materials for the efficient generation, storage and transportation of renewable energy. Hydrogen has been recognised as one of the most prominent carriers and green energy source with challenging storage, enabling decarbonization. Photocatalytic H2 (green hydrogen) production processes are targeting the intensification of separated solar energy harvesting, storage and electrolysis, conventionally yielding O2/H2. While catalysis is being investigated extensively, little is done on bridging the gap, related to reactor unit design, optimisation and scaling, be it that of material or of operation. Herein, metals, oxides, perovskites, nitrides, carbides, sulphides, phosphides, 2D structures and heterojunctions are compared in terms of parameters, allowing for efficiency, thermodynamics or kinetics structure–activity relationships, such as the solar-to-hydrogen (STH). Moreover, prominent pilot systems are presented summarily. 相似文献
4.
《International Journal of Hydrogen Energy》2022,47(5):2926-2935
Development of highly efficient and cheap electrocatalysts towards the hydrogen evolution reaction (HER) is of great importance for electrochemical water splitting. Herein, hybrid Cu/NiMo-P nanowires on the copper foam were successfully fabricated via a simple two-step method. The hierarchically structured Cu/NiMo-P exhibits large surface areas and rapid electron transfer ability, leading to enhanced catalytic activity. The as-prepared Cu/NiMo-P electrodes need overpotentials of 34 mV and 130 mV to obtain 10 mA cm?2 for HER in acidic and alkaline solutions, respectively. Density functional theory (DFT) calculations reveal that the Cu/NiMo-P hybrid has a more thermo-neutral hydrogen adsorption free energy and enhanced charge transfer ability as well. 相似文献
5.
《International Journal of Hydrogen Energy》2022,47(22):11472-11491
Eco-friendly quantum dots (QDs) can be termed green QDs which stand as an attractive choice to modify the properties of known semiconductors in the direction of getting efficient photoelectrodes for solar-induced photoelectrochemical (PEC) splitting of water, due to their peculiar properties. Thus, it is of high significance to analyze their merit/demerit as an effective scaffold in PEC cell. QDs are known for their excellent optical properties however, the coupling of green QDs with semiconductor is not only useful in improving absorption characteristics but also promotes charge transfer. This review has undertaken the critical analysis on the worldwide research going on the green QDs modified photoelectrode with respect to their optical, electrical & photoelectrochemical properties, role, usefulness, efficiency, and finally the success in PEC system for hydrogen production. Various methods on the facile synthesis & sensitization techniques of green QDs available in the literature have also been discussed. Further, recent advances on the development of green QDs based photo-electrode, along with major challenges of using green QDs in this field have also been presented. 相似文献
6.
《Ceramics International》2022,48(6):8325-8330
In this work, we propose a facile approach to fabricate Ti4+-doped Li3V2(PO4)3/C (abbreviated as C-LVTP) nanofibers using an electrospinning route followed by a high temperature treatment. In this designed nanocomposite, the ultrafine LVTP dots are homogeneously dispersed into one-dimensional carbon nanofibers and the Ti4+ doping does not destroy the crystal structure of monoclinic Li3V2(PO4)3. Compared to the undoped Li3V2(PO4)3/C (abbreviated as C-LVP), the as-fabricated C-LVTP fibers present higher reversible capacity, superior high-rate capability as well as better cyclic property. Especially, the C-LVT7%P cathode delivers not only high capacities of 187.2 and 160.3 mAh g?1 at 0.5 and 10 C respectively, but also stable cyclic property with the reversible capacity of 135.8 mAh g?1 at 20 C following 500-cycle spans. The good battery characteristics of C-LVT7%P can be mainly ascribed to Ti4+ doping, which can increase the electrical conductivity and Li+ diffusion coefficient. 相似文献
7.
Gabriela Pitolli Lyra Valdemir Santos Eliria Maria de Jesus Agnolon Pallone Ruth Herta Goldschmidt Aliaga Kiminami Bruno Carlos De Santis João Adriano Rossignolo 《International Journal of Applied Ceramic Technology》2021,18(3):705-715
This work aimed to examine the performance of the hybrid sintering of clay ceramic in a microwave furnace, compared to the sintering process in a conventional furnace. The raw materials were subjected to X-ray fluorescence, loss on ignition (LOI), X-ray diffraction, particle size distribution, real specific mass, and thermogravimetric analyses. The red clay ceramic mass was prepared, extruded, pre-sintered in a conventional furnace at 600°C/60 min, and sintered at temperatures between 700 °C and 1100 °C. The sintering conventional (resistive oven) was carried out for 60 min with a heating rate of 10°C/min. In the microwave furnace, the sintering times were 5, 10, and 15 min, with a heating rate of 50°C/min, with a sintering chamber coated with silicon carbide (susceptor). The sintered specimens were characterized according to linear shrinkage, water absorption, apparent porosity, apparent specific mass, X-ray diffraction, Raman spectroscopy analysis, spectroscopy analysis in the ultraviolet and visible regions, microhardness, and scanning electron microscopy. The results showed that microwave sintering promoted an increase in the microhardness and apparent specific mass, and reduction in water absorption and apparent porosity values, due to greater densification in the microstructure. The best results occurred for specimens sintered at 1100°C. 相似文献
8.
《Ceramics International》2021,47(23):33223-33231
The effects of pH of the reaction solution and the concentration of phosphoric acid on the crystal growth behavior of LaPO4 crystallites were investigated and the mechanical properties of rare-earth phosphates were compared. As a result, the concentration of phosphoric acid of 10% was beneficial to the crystal growth of LaPO4 nanocrystalline. When the pH value of the reaction solution was 2, the size of LaPO4 crystallites increased gradually with the increasing reaction temperature, and the smallest crystallite size of 43.27 nm was obtained after heat-treatment at 1000 °C. Simultaneously, the activation energy for crystal growth of LaPO4 nanocrystalline was relatively lower (26.82 kJ mol−1). With the decreasing radii of rare-earth ions, the hardness, Young's modulus and fracture toughness of the bulk rare-earth phosphates exhibited a reduced tendency, resulted from the increase of porosity under the same preparation process. 相似文献
9.
Chaozhong Sun Xiaoying Guo Rui Ji Changzheng Hu Laijun Liu Liang Fang Zhenxiang Cheng Nengneng Luo 《Ceramics International》2021,47(4):5038-5043
The triboelectric effect has recently demonstrated its great potential in environmental remediation and even new energy applications for triggering a number of catalytic reactions by utilizing trivial mechanical energy. In this study, Ba4Nd2Fe2Nb8O30 (BNFN) submicron powders were used to degrade organic dyes via the tribocatalytic effect. Under the frictional excitation of three PTFE stirring rods in a 5 mg/L RhB dye solution, BNFN demonstrates a high tribocatalytic degradation efficiency of 97% in 2 h. Hydroxyl radicals (?OH) and superoxide radicals (?O2-) were also detected during the catalysis process, which proves that triboelectric energy stimulates BNFN to generate electron-hole pairs. The tribocatalysis of tungsten bronze BNFN submicron powders provides a novel and efficient method for the degradation of wastewater dye by utilizing trivial mechanical energy. 相似文献