全文获取类型
收费全文 | 10590篇 |
免费 | 507篇 |
国内免费 | 169篇 |
专业分类
电工技术 | 324篇 |
综合类 | 245篇 |
化学工业 | 2071篇 |
金属工艺 | 401篇 |
机械仪表 | 398篇 |
建筑科学 | 396篇 |
矿业工程 | 126篇 |
能源动力 | 357篇 |
轻工业 | 753篇 |
水利工程 | 133篇 |
石油天然气 | 193篇 |
武器工业 | 25篇 |
无线电 | 1227篇 |
一般工业技术 | 2312篇 |
冶金工业 | 1134篇 |
原子能技术 | 116篇 |
自动化技术 | 1055篇 |
出版年
2023年 | 134篇 |
2022年 | 261篇 |
2021年 | 377篇 |
2020年 | 273篇 |
2019年 | 200篇 |
2018年 | 322篇 |
2017年 | 286篇 |
2016年 | 276篇 |
2015年 | 282篇 |
2014年 | 333篇 |
2013年 | 671篇 |
2012年 | 450篇 |
2011年 | 517篇 |
2010年 | 428篇 |
2009年 | 402篇 |
2008年 | 396篇 |
2007年 | 346篇 |
2006年 | 319篇 |
2005年 | 265篇 |
2004年 | 239篇 |
2003年 | 216篇 |
2002年 | 201篇 |
2001年 | 172篇 |
2000年 | 219篇 |
1999年 | 227篇 |
1998年 | 301篇 |
1997年 | 262篇 |
1996年 | 233篇 |
1995年 | 195篇 |
1994年 | 181篇 |
1993年 | 170篇 |
1992年 | 148篇 |
1991年 | 150篇 |
1990年 | 101篇 |
1989年 | 107篇 |
1988年 | 113篇 |
1987年 | 109篇 |
1986年 | 90篇 |
1985年 | 128篇 |
1984年 | 121篇 |
1983年 | 134篇 |
1982年 | 96篇 |
1981年 | 96篇 |
1980年 | 85篇 |
1979年 | 89篇 |
1978年 | 75篇 |
1977年 | 66篇 |
1976年 | 72篇 |
1975年 | 57篇 |
1974年 | 54篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Mobile Networks and Applications - Inverse kinematics is an important basic theory in walking control of biped robot. This study focuses on the parameter setting using the improved algorithm in... 相似文献
2.
Jiajia Suo Bowen Yang Edoardo Mosconi Hyeon-Seo Choi YeonJu Kim Shaik M. Zakeeruddin Filippo De Angelis Michael Grätzel Hui-Seon Kim Anders Hagfeldt 《Advanced functional materials》2021,31(34):2102902
Surface passivation treatment is a widely used strategy to resolve trap-mediated nonradiative recombination toward high-efficiency metal-halide perovskite photovoltaics. However, a lack of passivation with mixture treatment has been investigated, as well as an in-depth understanding of its passivation mechanism. Here, a systematic study on a mixed-salt passivation strategy of formamidinium bromide (FABr) coupled with different F-substituted alkyl lengths of ammonium iodide is demonstrated. It is obtained better device performance with decreasing chain length of the F-substituted alkyl ammonium iodide in the presence of FABr. Moreover, they unraveled a synergistic passivation mechanism of the mixed-salt treatment through surface reconstruction engineering, where FABr dominates the reformation of the perovskite surface via reacting with the excess PbI2. Meanwhile, ammonium iodide passivates the perovskite grain boundaries both on the surface and top perovskite bulk through penetration. This synergistic passivation engineer results in a high-quality perovskite surface with fewer defects and suppressed ion migration, leading to a champion efficiency of 23.5% with mixed-salt treatment. In addition, the introduction of the moisture resisted F-substituted groups presents a more hydrophobic perovskite surface, thus enabling the decorated devices with excellent long-term stability under a high humid atmosphere as well as operational conditions. 相似文献
3.
4.
Silicon - This paper presents, analytical modeling of surface potential,threshold voltage and DIBL for a Dual-Metal Double-Gate Gate-All-Around (DM-DG-GAA) MOSFET considering the parabolic... 相似文献
5.
6.
Nur Lina Rashidah Mohd Rashid Abdullah Abdul Samat Abdul Azim Jais Mahendra Rao Somalu Andanastuti Muchtar Nurul Akidah Baharuddin Wan Nor Roslam Wan Isahak 《Ceramics International》2019,45(6):6605-6615
The performance of low-to-intermediate temperature (400–800?°C) solid oxide fuel cells (SOFCs) depends on the properties of electrolyte used. SOFC performance can be enhanced by replacing electrolyte materials from conventional oxide ion (O2-) conductors with proton (H+) conductors because H+ conductors have higher ionic conductivity and theoretical electrical efficiency than O2- conductors within the target temperature range. Electrolytes based on cerate and/or zirconate have been proposed as potential H+ conductors. Cerate-based electrolytes have the highest H+ conductivity, but they are chemically and thermally unstable during redox cycles, whereas zirconate-based electrolytes exhibit the opposite properties. Thus, tailoring the properties of cerate and/or zirconate electrolytes by doping with rare-earth metals has become a main concern for many researchers to further improve the ionic conductivity and stability of electrolytes. This article provides an overview on the properties of four types of cerate and/or zirconate electrolytes including cerate-based, zirconate-based, single-doped cerate–zirconate and hybrid-doped cerate–zirconate. The properties of the proton electrolytes such as ionic conductivity, chemical stability and sinterability are also systematically discussed. This review further provides a summary of the performance of SOFCs operated with cerate and/or zirconate proton conductors and the actual potential of these materials as alternative electrolytes for proton-conducting SOFC application. 相似文献
7.
Jiajia Ye Xuting Li Guang Xia Guanghao Gong Zhiqiang Zheng Chuanzhong Chen Cheng Hu 《材料科学技术学报》2021,77(18):100-107
We report for the first time a Na-ion battery anode material composed of P-doped CoSe2 nanoparticles(P-CoSe2)with the size of 5-20 nm that are uniformly embed in a 3D porous honeycomb-like carbon network.High rate capability and cycling stability are achieved simultaneously.The honeycomb-like carbon network is rationally designed to support high electrical conductivity,rapid Na-ion diffusion as well as the accommodation of the volume expansion from the active P-CoSe2 nanoparticles.In particular,heteroatom P-doping within CoSe2 introduces stronger P-Co bonds and additional P-Se bonds that signif-icantly improve the structure stability of P-CoSe2 for highly stable sodiation/desodiation over long-term cycling.P-doping also improves the electrical conductivity of the CoSe2 nanoparticles,leading to highly elevated electrochemical kinetics to deliver high specific capacities at high current densities.Benefiting from the unique nanostructure and atomic-level P-doping,the P-CoSe2(2∶1)/C anode delivers an excel-lent cycle stability with a specific capacity of 206.9 mA h g-1 achieved at 2000 mA g-1 after 1000 cycles.In addition,this material can be synthesized using a facile pyrolysis and selenization/phosphorization approach.This study provides new opportunities of heteroatom doping as an effective method to improve the cycling stability of Na-ion anode materials. 相似文献
8.
9.
10.
Mohan B. Ponnuchamy G. Mohan Muralikrishna Venkateswara Rao Mannava G. Srinivas Reddy 《Ceramics International》2018,44(13):15019-15023
Nanocrystalline nickel oxide (NiO) was prepared from nickel hydroxide by Spark plasma sintering (SPS) and the mechanisms involved in the densification of NiO were studied. Reverse precipitated nickel hydroxide powders were SPS processed at 400, 600 and 700?°C with 70?MPa pressure. Pure NiO with 12?nm crystallite size formed after 400?°C sintering process. However NiO grains had grown to 18 and 38?nm after 600 and 700?°C sintering respectively. NiO pellets prepared using 600 and 700?°C SPS sintering schedules had relative densities of 83% and 94% respectively. Two displacement rate regimes were observed during densification of NiO in both 600 and 700?°C sintering processes. Decomposition of nickel hydroxide and particle sliding of NiO led to first displacement rate maximum while inverse Hall-Petch based plastic deformation facilitated densification during the constant second displacement rate regime. No densification occurred during sintering holding times indicating the limited role that diffusion played during densification. 相似文献