全文获取类型
收费全文 | 1240篇 |
免费 | 170篇 |
国内免费 | 174篇 |
专业分类
电工技术 | 13篇 |
综合类 | 44篇 |
化学工业 | 314篇 |
金属工艺 | 38篇 |
机械仪表 | 16篇 |
建筑科学 | 78篇 |
矿业工程 | 4篇 |
能源动力 | 66篇 |
轻工业 | 21篇 |
水利工程 | 14篇 |
石油天然气 | 73篇 |
武器工业 | 7篇 |
无线电 | 265篇 |
一般工业技术 | 210篇 |
冶金工业 | 21篇 |
原子能技术 | 6篇 |
自动化技术 | 394篇 |
出版年
2023年 | 40篇 |
2022年 | 20篇 |
2021年 | 40篇 |
2020年 | 63篇 |
2019年 | 25篇 |
2018年 | 22篇 |
2017年 | 41篇 |
2016年 | 34篇 |
2015年 | 46篇 |
2014年 | 70篇 |
2013年 | 101篇 |
2012年 | 127篇 |
2011年 | 146篇 |
2010年 | 113篇 |
2009年 | 143篇 |
2008年 | 88篇 |
2007年 | 150篇 |
2006年 | 127篇 |
2005年 | 62篇 |
2004年 | 50篇 |
2003年 | 14篇 |
2002年 | 26篇 |
2001年 | 17篇 |
2000年 | 8篇 |
1999年 | 8篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有1584条查询结果,搜索用时 15 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(80):34244-34256
A conducting and anticorrosive coating is crucial for the application of metal bipolar plates (BP) in proton exchange membrane fuel cell (PEMFC). In this work, a Ti3C2Tx (T)-carbon black (C)-acrylic epoxy (AE) coating is prepared on 304 stainless steel (SS) with enhanced corrosion resistance and conductivity. The corrosion resistance of the T-C-AE coating is investigated in a 0.5 M H2SO4 solution as compared to the AE, T, and T-AE coatings. The T-C-AE coated 304SS exhibits the strongest corrosion resistance with the most positive corrosion potential and the lowest corrosion current density of 0.00673 μA cm?2 in all the samples, while retaining intact and compact surface morphology with the lowest metal ion dissolution even after immersed for 720 h. The addition of Ti3C2Tx and carbon black into the AE matrix greatly decreases interfacial contact resistance (ICR), and the T-C-AE coating achieves a low ICR of 15.5 mΩ cm?2 under 140 N cm?2 compaction force. The excellent anticorrosion performance is mainly attributed to the physical barrier and the cathodic protection provided by the stacked Ti3C2Tx (MXene) nanosheets in the T-C-AE coating. This eco-friendly, conducting, and anticorrosive T-C-AE coating has a good application prospect on SS BP of PEMFC. 相似文献
2.
《Journal of the European Ceramic Society》2021,41(14):6983-6990
Ternary 0.552Pb(Ni1/3Nb2/3)O3-xPbZrO3-(0.448-x)PbTiO3 (PNN-PZ-PT) ceramics near the triple point compositions were fabricated by an improved two-step sintering method. The triple point composition 0.552PNN-0.135PZ-0.313PT ceramic has outstanding piezoelectric performance with piezoelectric coefficient d33 = 1200 pC/N. Its easy fabrication and low cost make this piezoelectric material an excellent candidate for high sensitivity sensors and ultrasonic transducers. The evolution of domain structures for ceramics with composition near the triple point provides deeper insight into the mechanism of ultrahigh piezoelectric properties of PNN-PZ-PT ceramics. 相似文献
3.
The development of traditional urbanisation has generated environmental problems, so the Chinese Government has proposed a new-type of urbanisation path with uniquely Chinese characteristics. How does this new-type of urbanisation affect CO2 emissions? Based on panel data from 29 provinces in China (2005 to 2016), we apply an exploratory spatial data analysis model, a spatial econometric model, and a threshold model to analyse the spatial autocorrelation of CO2 emissions, the direct and indirect effects of new-type urbanisation on CO2 emissions, and the threshold characteristics produced by technological progress, respectively. The key results are: (1) CO2 emissions show significant positive autocorrelation in China, and the spatial distribution of CO2 emissions is HH (High-High) or LL (Low-Low) clustered in most provinces; (2) new-type urbanisation has a paradoxical effect on CO2 emissions. Energy-saving technology has a rebound effect on CO2 emissions, but environmental technology inhibits CO2 emissions; (3) by eliminating the rebound effect of energy-saving technology on CO2 emissions and promoting environmental technology, new-type urbanisation indirectly inhibits CO2 emissions; (4) new-type urbanisation exhibits a threshold effect on CO2 emissions due to the different levels of energy-saving technology and environmental technology. Finally, policy recommendations for CO2 emissions reduction are proposed from the perspective of new-type urbanisation, energy-saving technology, and environmental technology. 相似文献
4.
《Ceramics International》2019,45(10):12994-13003
The temperature and dc bias stability of the dielectric constant and loss tangent of CaCu3Ti4O12 samples sintered under different oxygen atmospheres are discussed. The results suggest that the metal-oxygen vacancy related defects not only provide the charge carriers for the conduction (defect doping) but also contribute to the huge permittivity in the way of defect dipoles repositioning under charge carrier hopping. The charge localization in a specific copper-oxygen vacancy defect complex is the reason of the huge and stable permittivity and low dielectric loss in the middle temperature range, 90 K-200 K (20 Hz), while the implementation of the large barrier layer height needs a contribution by the titanium oxygen vacancy related trap charges in the grain boundaries, which also lead to a second permittivity stable range in a higher temperature range 200 K–300 K. 相似文献
5.
Liqian Wu Dongdong Shi Shiming Yan Wen Qiao Wei Zhong Youwei Du 《International Journal of Hydrogen Energy》2021,46(2):2086-2094
The exploration of efficient, low-cost and earth-abundant oxygen-evolution reaction (OER) electrocatalysts and the understanding of the intrinsic mechanism are important to advance the clean energy conversion technique based on electrochemical water oxidation. In this work, Fe-doping Co3N catalysts were successfully synthesized by a simple nitridation reaction of the Co3-xFexO4 precursor. This material exhibited a low overpotential of 294 mV at a current density of 10 mA cm?2, and a small Tafel slope of 49 mV dec?1 in 1 M KOH solution, superior to the performance of Co3N and IrO2. As revealed by the spectroscopic and electrochemical analyses, the enhanced OER performance mainly originates from the electronic modulation induced by the incorporation of Fe into Co3N, benefitting the formation of CoOOH as active surface species and thus facilitating the OER process. These findings also demonstrate the introduction of heterogeneous element is a simple and effective strategy to regulate the OER property of the cobalt nitrides (Co3N) catalysts. 相似文献
6.
7.
Zhengming Zhang Jun Li Weiping Zhou Chunbin Yang Qingqi Cao Dunhui Wang Youwei Du 《Ceramics International》2018,44(4):3760-3764
Studies on spintronics have provided solid evidence that the grain boundaries (GBs) in polycrystalline manganite can produce a strong extrinsic magnetoresistance (MR). This type of MR, called Low-field MR (LFMR), is larger than the intrinsic MR and can be triggered over a wide range of temperature. However, the existence of more GBs would bring about the weakening of magnetism and decrease the magnitude of MR simultaneously. Here we show that during annealing the application of electric-current to a representative ferromagnetic manganite perovskite, polycrystalline La2/3Sr1/3MnO3 (LSMO), can produce more GBs and improve low-field magnetization, which leads to enhanced MR effect and field-response sensitivity as compared to the traditional-annealed sample. By using static micromagnetic models combined with the theories of spin-polarized intergrain tunneling and charge carrier hopping across domain wall, the observed enhancement of magnetoresistive response in current-annealed LSMO can be well explained. 相似文献
8.
《International Journal of Hydrogen Energy》2020,45(1):565-573
Bimetallic phosphides have been widely investigated as electrocatalysts for oxygen evolution reaction (OER) due to their efficient activity and environmental friendliness. While the reasonable design and controllable synthesis of bimetallic phosphide with typical nanostructure is still a great challenge. Hence, we put forward a novel and straightforward way for constructing FeP nanoparticles coated Ni2P ultrathin nanotube arrays on the surface of Ni foil (FeP@Ni2P/NF), which is synthesized through two steps of electrodeposition and subsequent in-situ phosphorization process. The obtained FeP@Ni2P/NF shows excellent electrochemical activity for OER, and it only needs potential of 1.52 V vs. RHE to reach the current density of 50 mA cm−2 in an alkaline media. The excellent electrocatalytic activity of FeP@Ni2P/NF mainly benefits from: (i) the synergistic effect between FeP and Ni2P promoting electron transfer; (ii) the formation of the unique 3D ultrathin nanotube arrays increasing the quantity of active sites and avoiding the agglomeration of catalysts during testing. In addition, the influence of reaction condition on the electrochemical activity for OER has also been investigated through altering the phosphorization temperature of precursor. 相似文献
9.
《International Journal of Hydrogen Energy》2020,45(19):11089-11096
Palladium (Pd) nanoparticles (NPs) prepared by gas phase cluster deposition demonstrated excellent electrocatalytic activity. Herein, a series of Pd NPs modified freestanding electrodes with a super clean surface and easy repeating process for methanol oxidation reaction is reported. Pd NPs with different coverage were deposited on Ni foams and three-dimensional graphene-Ni foams, respectively. Owning to the special three-dimensional structure of Ni foam, the Pd NPs-Ni foam composite exhibited remarkable activity and unusually long-term stability for methanol electro-oxidation. The introduced three-dimensional graphene prepared by conventional chemical vapour deposition improved the electrocatalytic performance. The results can be attributed to the Pd NPs with high electrochemical activity and unique properties for three-dimensional supports. 相似文献
10.
《Ceramics International》2020,46(7):8766-8773
Multiwalled carbon nanotubes-graphene oxide nanoribbons (MWCNTs-GONRs) exhibit high specific surface area and good electroconductivity because of their unique three-dimensional cross-linking structure with the properties of both CNTs and GONRs. In this study, a hydrothermal method was employed to anchor MWCNTs–GONRs onto a Ni foam (NF) to obtain a precursor substrate. Subsequently, Co3O4 arrays were grown on the NF substrate to synthesize a MWCNTs–GONR/Co3O4 electrode. The electrode showed a capacitance of 846.2 F g−1 at 1 A g−1 and a capacitance retention of 90.1% after 3000 cycles. Furthermore, MWCNTs–GONRs/Co3O4 and active carbon (AC) were used as the positive and negative electrodes, respectively, to assemble a supercapacitor, which delivered a maximum energy density of 38.23 W h kg−1 and a high power density of 6.80 kW kg−1. In addition, the specific capacitance of the device reached a maximum of 91.5% after 9000 cycles. Thus, the MWCNTs–GONRs/Co3O4 electrode showed huge potential for supercapacitor applications. 相似文献