全文获取类型
收费全文 | 1346篇 |
免费 | 83篇 |
国内免费 | 41篇 |
专业分类
电工技术 | 10篇 |
综合类 | 56篇 |
化学工业 | 194篇 |
金属工艺 | 336篇 |
机械仪表 | 51篇 |
建筑科学 | 2篇 |
矿业工程 | 5篇 |
能源动力 | 162篇 |
轻工业 | 6篇 |
石油天然气 | 2篇 |
武器工业 | 2篇 |
无线电 | 31篇 |
一般工业技术 | 335篇 |
冶金工业 | 244篇 |
原子能技术 | 9篇 |
自动化技术 | 25篇 |
出版年
2023年 | 39篇 |
2022年 | 55篇 |
2021年 | 62篇 |
2020年 | 98篇 |
2019年 | 85篇 |
2018年 | 55篇 |
2017年 | 67篇 |
2016年 | 53篇 |
2015年 | 92篇 |
2014年 | 90篇 |
2013年 | 101篇 |
2012年 | 104篇 |
2011年 | 118篇 |
2010年 | 63篇 |
2009年 | 75篇 |
2008年 | 39篇 |
2007年 | 37篇 |
2006年 | 31篇 |
2005年 | 16篇 |
2004年 | 17篇 |
2003年 | 14篇 |
2002年 | 20篇 |
2001年 | 23篇 |
2000年 | 20篇 |
1999年 | 12篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 8篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 17篇 |
1986年 | 17篇 |
1985年 | 4篇 |
排序方式: 共有1470条查询结果,搜索用时 210 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(100):41994-42000
Hydrogen technology is widely considered a novel clean energy source, and electrolysis is an effective method for hydrogen evolution. Therefore, efficient hydrogen evolution reaction (HER) catalysts are urgently needed to replace precious metal catalysts and meet ecological and environmental protection standards. Herein, Ni–Mn–P electrocatalysts are synthesized using facile electrodeposition technology. The influence of the Mn addition on the catalytic behavior is studied by the comprehensive analysis of catalytic performance and morphology of the catalysts. Among them, the Ni–Mn–P0.01 catalyst exhibits small coral-like structures, greatly improving the adsorption and desorption of hydrogen ions and reducing the overpotential hydrogen evolution. Consequently, overpotential at 10 mA cm?2 electric current density is 113 mV, and the value of the Tafel slope achieves 74 mV/dec. Furthermore, the Ni–Mn–P catalyst shows long-time (20 h) stability at current densities of 10 and 60 mA/cm2. The results confirm that the synergistic effect of Ni, Mn, and P accelerates the electrochemical reaction. Meanwhile, the addition of manganese element can change the micromorphology of the catalyst, thereby exposing more active sites to participate in the reaction, enhancing water ionization, improving the catalytic performance. This study opens a new way toward improving the activity of the catalyst by adjusting Mn concentration during the electrodeposition process. 相似文献
2.
Jinming Wang Meng Yang Guodong Zou Di Liu Qiuming Peng 《Advanced functional materials》2021,31(21):2101180
Lithium (Li) metal, as an appealing candidate for the next-generation of high-energy-density batteries, is plagued by its safety issue mainly caused by uncontrolled dendrite growth and infinite volume expansion. Developing new materials that can improve the performance of Li-metal anode is one of the urgent tasks. Herein, a new MXene derivative containing pure rutile TiO2 and N-doped carbon prepared by heat-treating MXene under a mixing gas, exhibiting high chemical activity in molten Li, is reported. The lithiation MXene derivative with a hybrid of LiTiO2-Li3N-C and Li offers outstanding electrochemical properties. The symmetrical cell assembling lithiation MXene derivative hybrid anode exhibits an ultra-long cycle lifespan of 2000 h with an overpotential of ≈30 mV at 1 mA cm−2, which overwhelms Li-based anodes reported so far. Additionally, long-term operations of 34, 350, and 500 h at 10 mA cm−2 can be achieved in symmetrical cells at temperatures of −10, 25, and 50 °C, respectively. Both experimental tests and density functional theory calculations confirm that the LiTiO2-Li3N-C skeleton serves as a promising host for Li infusion by alleviating volume variation. Simultaneously, the superlithiophilic interphase of Li3N guides Li deposition along the LiTiO2-Li3N-C skeleton to avoid dendrite growth. 相似文献
3.
《Intermetallics》2015
An equiatomic CoCrFeNiMn high-entropy alloy was synthesized by mechanical alloying (MA) and spark plasma sintering (SPS). During MA, a solid solution with refined microstructure of 10 nm which consists of a FCC phase and a BCC phase was formed. After SPS consolidation, only one FCC phase can be detected in the HEA bulks. The as-sintered bulks exhibit high compressive strength of 1987 MPa. An interesting magnetic transition associated with the structure coarsening and phase transformation was observed during SPS process. 相似文献
4.
Rolling contact fatigue in bearing steels is manifested by dark-etching regions, which are attributed to deformation induced tempering. In order to quantitatively explain this phenomenon, a model is suggested for martensite tempering assisted by dislocation glide during rolling contact fatigue. In the model, dislocations transport carbon from the matrix to carbide particles, provided that the carbon is located at a certain distance range from the dislocation contributing to the tempering process. By calculating the amount of carbon in the matrix, the kinetics of carbide thickening and hardness reduction are computed. It is found that the dark-etching region kinetics can be controlled by both bearing operation conditions (temperature and deformation rate) and microstructure (type, size, and volume fraction of carbides). The model is validated against tested bearings, and its limitations are discussed. 相似文献
5.
《材料与设计》2015
To improve visible-light-driven photocatalytic activity of TiO2, the octahedral Bi2Ti2O7 nanoparticles have been successfully supported on TiO2 nanotubes (Bi2Ti2O7/TiO2) for the first time by a simple hydrothermal method. The structure and electro-optical property of the Bi2Ti2O7/TiO2 were characterized in detail. The obtained Bi2Ti2O7/TiO2 exhibited a markedly enhanced photocatalytic activity and good stability for degradation of organic pollutants under visible light. The study presents a new way to synthesize Bi2Ti2O7/TiO2 using TiO2 nanotubes as both supporter and reactant. 相似文献
6.
《International Journal of Hydrogen Energy》2021,46(66):33186-33196
Additive doping is one of the effective methods to overcome the shortcomings of MgH2 on the aspect of relatively high operating temperatures and slow desorption kinetics. In this paper, hollow g-C3N4 (TCN) tubes with a diameter of 2 μm are synthesized through the hydrothermal and high-temperature pyrolysis methods, and then nickel is chemically reduced onto TCN to form Ni/TCN composite at 278 K. Ni/TCN is then introduced into the MgH2/Mg system by means of hydriding combustion and ball milling. The MgH2–Ni/TCN composite starts to release hydrogen at 535 K, which is 116 K lower than the as-milled MgH2 (651 K). The MgH2–Ni/TCN composite absorbs 5.24 wt% H2 within 3500 s at 423 K, and takes up 3.56 wt% H2 within 3500 s, even at a temperature as low as 373 K. The apparent activation energy (Ea) of the MgH2 decreases from 161.1 to 82.6 kJ/mol by the addition of Ni/TCN. Moreover, the MgH2–Ni/TCN sample shows excellent cycle stability, with a dehydrogenation capacity retention rate of 98.0% after 10 cycles. The carbon material enhances sorption kinetics by dispersing and stabilizating MgH2. Otherwise, the phase transformation between Mg2NiH4 and Mg2NiH0.3 accelerates the re/dehydrogenation reaction of the composite. 相似文献
7.
《材料与设计》2015
In the present paper, the distributed dislocation technique is applied for the analysis of anisotropic materials weakened by cracks. Eringen's theory of nonlocal elasticity of Helmholtz type is employed. The non-singular screw dislocation within anisotropic elasticity is distributed to model cracks of mode III. The corresponding dislocation density functions are evaluated using the proper crack-face boundary conditions. The nonlocal stress field within a plane weakened by cracks is determined. The crack opening displacement is also discussed within the framework of nonlocal elasticity. The stress singularity of the classical linear elasticity is removed by the introduction of the nonlocal theory of elasticity. The general anisotropic case and the special case of orthotropic material are studied. The effect of material orthotropy is presented for a crack which is not necessarily aligned with the principal orthotropy direction. 相似文献
8.
《Diamond and Related Materials》2007,16(3):526-530
Vickers hardness of the cubic BC2N has been investigated using the microscopic hardness model, in which the parameters have been obtained using first principles calculations. Ionicities of the chemical bonds in the cubic BC2N depend on their surrounding chemical environments, which are included in the hardness calculations of the cubic BC2N using the population ionicity scale. For the four selected configurations of the cubic BC2N, the theoretical Vickers hardness has been found to lie between 70 and 72 GPa, consistent with the experimental value of 76 GPa. According to our calculations, it should be the cubic BC2N that ranks second among the superhard materials instead of the cubic BN. 相似文献
9.
《钢铁研究学报(英文版)》2006
Previous studies showed that the temperature coefficient of obviously decreases with increasing the content of heavy rare earth element in SmCo magnet. But the investigation on the hydrogen incorporation in SmCo magnet is limited. In this paper, we would like to report the effect of heavy rare earth dopant on hydrogen incorporation in SmCo 2:17 type magnet. The relationship between temperature and pressure in hydrogenatied magnet is studied using XRD, DTA, and magnetic measurement. Based on the experimental results, the initial hydrogenation temperature decreases with increasing the content of heavy rare earth, however, the initial saturation pressure enhances. During the hydrogenation, the temperature region shrinks with increasing heavy rare earth doping. 相似文献
10.
《Composites Part A》2007,38(11):2283-2293
The study of the variation of the curvature of non-symmetric composite laminates with temperature provides a measure of the magnitude of the thermal stresses and the mechanical behavior of the material with temperature. In the present work, an experimental method based on the pioneer use of a digital camera and image processing method is proposed to perform such measurements. Taking advantage of the method and by comparing experimental and CLT, extended-CLT and FEM simulation results, an evaluation of the residual stresses is described and an approach providing more precise determination of the residual thermal stresses in non-symmetric laminates is proposed. 相似文献