全文获取类型
收费全文 | 381237篇 |
免费 | 31190篇 |
国内免费 | 16137篇 |
专业分类
电工技术 | 22564篇 |
技术理论 | 33篇 |
综合类 | 24614篇 |
化学工业 | 63296篇 |
金属工艺 | 21350篇 |
机械仪表 | 24451篇 |
建筑科学 | 29695篇 |
矿业工程 | 12145篇 |
能源动力 | 11017篇 |
轻工业 | 24188篇 |
水利工程 | 6599篇 |
石油天然气 | 25187篇 |
武器工业 | 2913篇 |
无线电 | 43283篇 |
一般工业技术 | 44494篇 |
冶金工业 | 20018篇 |
原子能技术 | 3929篇 |
自动化技术 | 48788篇 |
出版年
2024年 | 1390篇 |
2023年 | 6057篇 |
2022年 | 11371篇 |
2021年 | 15856篇 |
2020年 | 11952篇 |
2019年 | 9760篇 |
2018年 | 11118篇 |
2017年 | 12501篇 |
2016年 | 11270篇 |
2015年 | 15073篇 |
2014年 | 19183篇 |
2013年 | 22872篇 |
2012年 | 24785篇 |
2011年 | 26671篇 |
2010年 | 23127篇 |
2009年 | 21858篇 |
2008年 | 21150篇 |
2007年 | 20009篇 |
2006年 | 20659篇 |
2005年 | 17945篇 |
2004年 | 12067篇 |
2003年 | 10236篇 |
2002年 | 9108篇 |
2001年 | 8183篇 |
2000年 | 8600篇 |
1999年 | 10111篇 |
1998年 | 8546篇 |
1997年 | 7079篇 |
1996年 | 6636篇 |
1995年 | 5489篇 |
1994年 | 4421篇 |
1993年 | 3115篇 |
1992年 | 2484篇 |
1991年 | 1910篇 |
1990年 | 1437篇 |
1989年 | 1144篇 |
1988年 | 869篇 |
1987年 | 543篇 |
1986年 | 446篇 |
1985年 | 307篇 |
1984年 | 231篇 |
1983年 | 173篇 |
1982年 | 191篇 |
1981年 | 158篇 |
1980年 | 128篇 |
1979年 | 63篇 |
1978年 | 51篇 |
1977年 | 43篇 |
1976年 | 61篇 |
1975年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Jinshuang Wang Luyao Chen Mengdi Chen Yuyang Wu Yinghui Wang Yongsheng Yu Junbin Sun Bing Liu Qiangshan Jing 《Ceramics International》2021,47(16):22965-22975
In this study, the destabilization resistance of Sc2O3 and CeO2 co-stabilized ZrO2 (SCZ) ceramics was tested in Na2SO4 + V2O5 molten salts at 750°C–1100 °C. The phase structure and microstructure evolution of the samples during the hot corrosion testing were analyzed with X-ray diffraction (XRD), Raman spectra, scanning electron microscopy (SEM), energy dispersive X-ray spectrum (EDS), and X-ray photoelectron spectroscopy (XPS). Results showed that the destabilization of SCZ ceramics at 750 °C was the result of the chemical reaction with V2O5 to produce m-ZrO2 and CeVO4, and little ScVO4 was detected in the Sc2O3-rich SCZ ceramics. The primary corrosion products at 900 °C and 1100 °C were CeO2 and m-ZrO2 due to the mineralization effect. The Sc2O3-rich SCZ ceramics exhibited excellent degradation resistance and phase stability owing to the enhanced bond strength and the decreased size misfit between Zr4+ and Sc3+. The destabilization mechanism of SCZ ceramic under hot corrosion was also discussed. 相似文献
62.
Hongli Liu Peng Wang Bo Zhang Hongyan Li Jing Li Yajing Li Zhong Chen 《Ceramics International》2021,47(5):6487-6495
A novel carbon/m-HNTs composite aerogel was synthesized by introducing the modified halloysite nanotubes (m-HNTs) into phenolic (PR) aerogels through chemical grafting, followed with carbonization treatment. In order to explore the best proportion of HNTs to phenolic, the micromorphology of PR/m-HNTs were investigated by SEM before carbonization, confirming 10 wt% of m-HNTs is most beneficial to the porous network of aerogels. The interaction between PR and HNTs was studied by FTIR spectra, and microstructure evolution of the target product-carbon/m-HNTs composite aerogel were illustrated by SEM and TEM techniques. SEM patterns indicated that the carbon/m-HNTs aerogels maintain a stable porous structure at 1000 °C (carbonization temperature), while a ~20 nm carbon layer was formed around m-HNTs generating an integral unit through TEM analysis. Specific surface area and pore size distribution of composite aerogels were analyzed based on mercury intrusion porosimetry and N2 adsorption–desorption method, the obtained results stayed around 500 m2g?1 and 1.00 cm3g?1 (pore volume) without significant discrepancy, compared with pure aerogel, showing the uniformity of pore size. The weight loss rate (26.76%) decreased greatly compared with pure aerogel, at the same time, the best volumetric shrinkage rate was only 30.83%, contributed by the existence of HNTs supporting the neighbor structure to avoid over-shrinking. The highest compressive strength reached to 4.43 MPa, while the data of pure aerogel was only 1.52 MPa, demonstrating the excellent mechanical property of carbon/m-HNTs aerogels. 相似文献
63.
At present, the development and implementation of digital transformation are the keys to promoting high-quality industry development. The new digital fabrication method of robotic 3D printing is a research area being studied by many to tackle the issue of the declining productivity of traditional construction methods. Although many studies have been done, most of the current 3D printing projects are facing limitations in terms of scale. In order to bridge the gap, this article proposed a mass customization 3D printing framework system for large-scale projects. This article discusses how mass customization is made possible through the joint operation of the FUROBOT software and 3D printing hardware. By taking the east gate of Nanjing Happy Valley Plaza as a case study, the article demonstrates and studies the feasibility of the large-scale mass customization 3D printing framework system. 相似文献
64.
Water Resources Management - Urban river not only has the important function in urban hydrological environment, but also is an area for entertainment. Water quality assessment is the core technique... 相似文献
65.
66.
67.
Wenlong Song Shoujun Wang Yang Lu Xuan Zhang Zixiang Xia Kai Sun Guangming Xin 《Ceramics International》2021,47(9):12631-12640
To enhance the tribological performance of Si3N4/TiC ceramics, MoS2/PTFE composite coatings were deposited on the ceramic substrate through spraying method. The micrographs and basic properties of the MoS2/PTFE coated samples were investigated. Dry sliding friction experiments against WC/Co ball were performed with the coated ceramics and traditional ones. These results showed that the composite coatings could significantly reduce the friction coefficient of ceramics, and protect the substrate from adhesion wear. The primary tribological mechanisms of the coated ceramics were abrasive wear, coating spalling and delamination, and the tribological property was transited from slight wear to serious wear with the increase of load because of the lower surface hardness and shear strength. The possible mechanisms for the effects of MoS2/PTFE composite coatings on the friction performance of ceramics were discussed. 相似文献
68.
针对某金矿,在回收金银的基础上,对金银浮选尾矿进行云母和长石浮选,以及提纯石英试验,最终获得SiO2品位99.91%的石英产品。提纯石英产品与比利时矽比科矿业有限公司石英产品进行对比试验,通过化学成分、粒度组成、熔制、粘度和热膨胀系数测试对比试验,得出金矿提纯石英达到甚至超过矽比科进口石英产品的各项技术指标。 相似文献
69.
70.
Liangtao Yang Liang-Yin Kuo Juan Miguel López del Amo Prasant Kumar Nayak Katherine A. Mazzio Sebastian Maletti Daria Mikhailova Lars Giebeler Payam Kaghazchi Teófilo Rojo Philipp Adelhelm 《Advanced functional materials》2021,31(38):2102939
A known strategy for improving the properties of layered oxide electrodes in sodium-ion batteries is the partial substitution of transition metals by Li. Herein, the role of Li as a defect and its impact on sodium storage in P2-Na0.67Mn0.6Ni0.2Li0.2O2 is discussed. In tandem with electrochemical studies, the electronic and atomic structure are studied using solid-state NMR, operando XRD, and density functional theory (DFT). For the as-synthesized material, Li is located in comparable amounts within the sodium and the transition metal oxide (TMO) layers. Desodiation leads to a redistribution of Li ions within the crystal lattice. During charging, Li ions from the Na layer first migrate to the TMO layer before reversing their course at low Na contents. There is little change in the lattice parameters during charging/discharging, indicating stabilization of the P2 structure. This leads to a solid-solution type storage mechanism (sloping voltage profile) and hence excellent cycle life with a capacity of 110 mAh g-1 after 100 cycles. In contrast, the Li-free compositions Na0.67Mn0.6Ni0.4O2 and Na0.67Mn0.8Ni0.2O2 show phase transitions and a stair-case voltage profile. The capacity is found to originate from mainly Ni3+/Ni4+ and O2-/O2-δ redox processes by DFT, although a small contribution from Mn4+/Mn5+ to the capacity cannot be excluded. 相似文献