全文获取类型
收费全文 | 262836篇 |
免费 | 20929篇 |
国内免费 | 10660篇 |
专业分类
电工技术 | 14551篇 |
技术理论 | 29篇 |
综合类 | 17419篇 |
化学工业 | 43288篇 |
金属工艺 | 14917篇 |
机械仪表 | 16764篇 |
建筑科学 | 20588篇 |
矿业工程 | 8305篇 |
能源动力 | 7399篇 |
轻工业 | 17584篇 |
水利工程 | 4380篇 |
石油天然气 | 18053篇 |
武器工业 | 2032篇 |
无线电 | 28898篇 |
一般工业技术 | 30676篇 |
冶金工业 | 13939篇 |
原子能技术 | 2722篇 |
自动化技术 | 32881篇 |
出版年
2024年 | 488篇 |
2023年 | 4074篇 |
2022年 | 6091篇 |
2021年 | 9832篇 |
2020年 | 7965篇 |
2019年 | 6672篇 |
2018年 | 7548篇 |
2017年 | 8482篇 |
2016年 | 7649篇 |
2015年 | 10288篇 |
2014年 | 13142篇 |
2013年 | 15532篇 |
2012年 | 16939篇 |
2011年 | 18431篇 |
2010年 | 16103篇 |
2009年 | 15289篇 |
2008年 | 15025篇 |
2007年 | 14293篇 |
2006年 | 14675篇 |
2005年 | 12720篇 |
2004年 | 8656篇 |
2003年 | 7283篇 |
2002年 | 6485篇 |
2001年 | 5701篇 |
2000年 | 6134篇 |
1999年 | 7133篇 |
1998年 | 6007篇 |
1997年 | 4899篇 |
1996年 | 4543篇 |
1995年 | 3901篇 |
1994年 | 3084篇 |
1993年 | 2162篇 |
1992年 | 1720篇 |
1991年 | 1354篇 |
1990年 | 1026篇 |
1989年 | 808篇 |
1988年 | 605篇 |
1987年 | 356篇 |
1986年 | 316篇 |
1985年 | 210篇 |
1984年 | 148篇 |
1983年 | 110篇 |
1982年 | 129篇 |
1981年 | 112篇 |
1980年 | 85篇 |
1979年 | 44篇 |
1978年 | 28篇 |
1977年 | 21篇 |
1976年 | 42篇 |
1973年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
991.
Fire Technology - A cross-region transfer learning method is proposed to identify community (e.g. car parks, public spaces and shopping centers) fire hazards based on text input provided by... 相似文献
992.
Zehu Xie Na Peng Tingting Liu Xing Cheng Wuquan Ye Runtian Zheng Jundong Zhang Haoxiang Yu Jie Shu 《Ceramics International》2019,45(9):11812-11818
Here, LiY(WO4)2 nanotubes are prepared via a feasible electrospinning technique. This new anode material shows excellent electrochemical properties. The capacity loss of LiY(WO4)2 nanotubes is as low as 6.9% after 156 cycles, while bulk LiY(WO4)2 presents the capacity loss higher than 55.0%. Even after 600 long-life cycles, the capacity loss of the nanotubes is only 9%. It can be seen that the hollow structure with a rough surface and a porous morphology contributes to the improvement of electrochemical performance. Furthermore, online X-ray diffraction (XRD) method is firstly applied to understand the lithium ions insertion/extraction mechanism of LiY(WO4)2 nanotubes. It can be concluded that it is an asymmetrical two-phase reaction. A phase transformation from LiY(WO4)2 to Li3Y(WO4)2 can be obviously seen from the in situ XRD during discharge process. While Li2Y(WO4)2 appears as an intermediate phase with a reverse charge reaction. In addition, in situ XRD also demonstrates that LiY(WO4)2 nanotubes have surprised electrochemical reversibility. All the above results indicate that LiY(WO4)2 nanotubes can be expected to be anode candidate for rechargeable lithium ion batteries (LIBs). 相似文献
993.
目前管道泄漏检测方法可有效检测突发泄漏,对于缓慢泄漏则存在检测灵敏度低、定位不准确等问题。基于此,提出了一种基于信号增强的缓慢泄漏检测方法。通过信号压缩(抽取及移位)克服缓慢泄漏压力信号下降平缓的缺点;根据声波信号具有波形尖锐突出、对突发泄漏敏感的优点,通过建立以压力为输入、虚拟声波为输出的声波信号变送器模型,将压力信号转换为声波信号,克服了泄漏压力信号容易被淹没在管道压力波动及背景噪声中的缺点,实现了缓慢泄漏信号的增强;利用临近插值方法重构虚拟声波信号,基于延时互相关分析实现了缓慢泄漏的准确定位。实验结果表明,该方法具有显著的信号增强效果和定位精度,实现了缓慢泄漏的准确检测。 相似文献
994.
Ting Liu Huimin Zhang Panfei Ma Aimin Chang Hui Jiang 《Journal of the American Ceramic Society》2019,102(8):4393-4398
Core–shell structures have been proposed to improve the electrical properties of negative-temperature coefficient (NTC) thermistor ceramics. In this work, Al2O3-modified Co1.5Mn1.2Ni0.3O4 NTC thermistor ceramics with adjustable electrical properties were prepared through citrate-chelation followed by conventional sintering. Co1.5Mn1.2Ni0.3O4 powder was coated with a thin Al2O3 shell layer to form a core–shell structure. Resistivity (ρ) increased rapidly with increasing thickness of the Al2O3 layer, and the thermal constant (B) varied moderately between 3706 and 3846 K. In particular, Co1.5Mn1.2Ni0.3O4@Al2O3 ceramic with 0.08 wt% Al2O3 showed the increase of ρ double, and the change in its B was less than 140 K. The Co1.5Mn1.2Ni0.3O4@Al2O3 NTC ceramics showed high stability, and their grain size was relatively uniform due to the protection offered by the shell. The aging coefficient of the ceramic was less than 0.2% after aging for 500 hours at 125°C. Taken together, the results indicate that as-prepared Co1.5Mn1.2Ni0.3O4@Al2O3 NTC ceramics with a core–shell structure may be promising candidates for application as wide-temperature NTC thermistor ceramics. 相似文献
995.
Aiqing Chen Li Tang Yan‐Jun Liu Ying Gao 《International Journal of Adaptive Control and Signal Processing》2019,33(9):1344-1358
This paper is concerned with adaptive tracking control for switched uncertain nonlinear systems, which contain the time‐varying output constraint (TVOC) and input asymmetric saturation characteristic. In response to the unknown functions, the fuzzy logic systems are adopted. The controller is constructed by the backstepping technique. Based on the Tangent Barrier Lyapunov Function (BLF‐Tan), an adaptive switched control scheme is designed. It is demonstrated that all signals in the resulted system are semiglobally uniformly ultimately bounded with TVOC under arbitrary switchings. Furthermore, the effectiveness of presented control method is validated via the simulation example. 相似文献
996.
The support flux was first investigated as a separate influencing factor for its effect on performances of ceramic filtration membranes. Three pre-membranes were prepared by tape-casting and then transfer-coated to supports to form dual-layer ceramic membranes after sintering. Experiments demonstrated that membrane layers with almost the same properties were obtained despite the huge difference in support flux. When the support flux increases from 3.120 to 97.53 m3m?2h?1, the flux of these three membrane series have increased by 75%, 186% and 228%, respectively. Experimental rules can provide structural design and evaluation from the perspective of permeability. The limit membrane flux of a certain system was derived according to the resistance distribution law of internal membrane structure and the Darcy's theorem. On this basis, a method for designing support flux was proposed. Furthermore, we present a criterion to quickly and easily evaluate the match between the support and the top layer, which is the ratio of membrane resistance to total resistance. Finally, the filtration resistance of penetration caused by suction of membrane particles into the support was measured for the first time, taking the advantage of the transfer-coating method that inherently free of penetration. Our works are expected to deepen the understanding of the ceramic membrane structure and provided guidance for its rational design and optimization. 相似文献
997.
Boya Qiu Senqing Fan Yu Chen Jiaojiao Chen Yilin Wang Yinan Wang Jingyun Liu Zeyi Xiao 《American Institute of Chemical Engineers》2021,67(8):e17272
A micromembrane adsorber with deep-permeation nanostructure (DPNS) has been successfully fabricated by flowing synthesis. The nanoparticles are in-situ assembled in membrane pores and immobilized in each membrane pore along the direction of membrane thickness. The nanoparticles with a lower size and thinner size distribution can be achieved owing to the confined space effect of the membrane pores. As a concept-of-proof, the nano ZIF-8 and ZIF-67 are fabricated in porous membrane pores for methyl orange (MO) and rhodamine B (RhB) adsorption. The adsorption rate is increased significantly owing to the enhanced contact and mass transfer in the confined space. The adsorption capacity for the RhB is also increased, since the size of the nanoparticles assembled in membrane pores is smaller with more active sites exposed. This micromembrane adsorber with DPNS has good reusability and can provide a promising prospect for industrial application. 相似文献
998.
Yongling An Yuan Tian Kai Zhang Yongpeng Liu Chengkai Liu Shenglin Xiong Jinkui Feng Yitai Qian 《Advanced functional materials》2021,31(26):2101886
Anode-free zinc batteries (AFZBs) are proposed as promising energy storage systems due to their high energy density, inherent safety, low cost, and simplified fabrication process. However, rapid capacity fading caused by the side reactions between the in situ formed zinc metal anode and electrolyte hinders their practical applications. To address these issues, aqueous AFZBs enabled by electrolyte engineering to form a stable interphase are designed. By introducing a multifunctional zinc fluoride (ZnF2) additive into the electrolyte, a stable F-rich interfacial layer is formed. This interfacial layer can not only regulate the growth orientation of zinc crystals, but also serve as an inert protection layer against side reactions such as H2 generation. Based on these synergy effects, zinc deposition/dissolution with high reversibility (Coulombic efficiency > 99.87%) and stable cycling performance up to 600 h of are achieved in the electrolyte optimized by ZnF2. With this electrolyte, the cycling life of AFZBs is significantly improved. The work may initiate the research of AFZBs and be useful for the design of high energy, high safety, and low-cost power sources. 相似文献
999.
Xiaolong Cai Chenglin Du Zixuan Sun Ran Ye Haijun Liu Yu Zhang Xiangyang Duan Hai Lu 《半导体学报》2021,42(5):37-48
Gallium nitride (GaN)-based high-electron mobility transistors (HEMTs) are widely used in high power and high frequency application fields,due to the outstanding physical and chemical properties of the GaN material.However,GaN HEMTs suffer from degradations and even failures during practical applications,making physical analyses of post-failure devices extremely significant for reliability improvements and further device optimizations.In this paper,common physical characterization techniques for post failure analyses are introduced,several failure mechanisms and corresponding failure phenomena are reviewed and summarized,and finally device optimization methods are discussed. 相似文献
1000.