全文获取类型
收费全文 | 98238篇 |
免费 | 2218篇 |
国内免费 | 992篇 |
专业分类
电工技术 | 1610篇 |
技术理论 | 2篇 |
综合类 | 3135篇 |
化学工业 | 13961篇 |
金属工艺 | 5685篇 |
机械仪表 | 3957篇 |
建筑科学 | 3272篇 |
矿业工程 | 1073篇 |
能源动力 | 1528篇 |
轻工业 | 4426篇 |
水利工程 | 1502篇 |
石油天然气 | 1523篇 |
武器工业 | 102篇 |
无线电 | 10852篇 |
一般工业技术 | 18053篇 |
冶金工业 | 3446篇 |
原子能技术 | 400篇 |
自动化技术 | 26921篇 |
出版年
2024年 | 78篇 |
2023年 | 298篇 |
2022年 | 472篇 |
2021年 | 650篇 |
2020年 | 520篇 |
2019年 | 448篇 |
2018年 | 14864篇 |
2017年 | 13822篇 |
2016年 | 10344篇 |
2015年 | 1188篇 |
2014年 | 983篇 |
2013年 | 1001篇 |
2012年 | 4044篇 |
2011年 | 10352篇 |
2010年 | 9115篇 |
2009年 | 6358篇 |
2008年 | 7605篇 |
2007年 | 8491篇 |
2006年 | 881篇 |
2005年 | 1842篇 |
2004年 | 1635篇 |
2003年 | 1598篇 |
2002年 | 955篇 |
2001年 | 453篇 |
2000年 | 512篇 |
1999年 | 452篇 |
1998年 | 342篇 |
1997年 | 303篇 |
1996年 | 282篇 |
1995年 | 220篇 |
1994年 | 182篇 |
1993年 | 127篇 |
1992年 | 114篇 |
1991年 | 87篇 |
1990年 | 62篇 |
1989年 | 45篇 |
1988年 | 37篇 |
1987年 | 25篇 |
1968年 | 43篇 |
1967年 | 33篇 |
1966年 | 42篇 |
1965年 | 44篇 |
1963年 | 28篇 |
1960年 | 30篇 |
1959年 | 35篇 |
1958年 | 37篇 |
1957年 | 36篇 |
1956年 | 34篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Lili Hou Axel Olesund Shameel Thurakkal Xiaoyan Zhang Bo Albinsson 《Advanced functional materials》2021,31(47):2106198
Developing high-performance visible-to-UV photon upconversion systems based on triplet–triplet annihilation photon upconversion (TTA-UC) is highly desired, as it provides a potential approach for UV light-induced photosynthesis and photocatalysis. However, the quantum yield and spectral range of visible-to-UV TTA-UC based on nanocrystals (NCs) are still far from satisfactory. Here, three different sized CdS NCs are systematically investigated with triplet energy transfer to four mediators and four annihilators, thus substantially expanding the available materials for visible-to-UV TTA-UC. By improving the quality of CdS NCs, introducing the mediator via a direct mixing fashion, and matching the energy levels, a high TTA-UC quantum yield of 10.4% (out of a 50% maximum) is achieved in one case, which represents a record performance in TTA-UC based on NCs without doping. In another case, TTA-UC photons approaching 4 eV are observed, which is on par with the highest energies observed in optimized organic systems. Importantly, the in-depth investigation reveals that the direct mixing approach to introduce the mediator is a key factor that leads to close to unity efficiencies of triplet energy transfer, which ultimately governs the performance of NC-based TTA-UC systems. These findings provide guidelines for the design of high-performance TTA-UC systems toward solar energy harvesting. 相似文献
2.
Kedong Xia Shuoshuo Yu Yunling Li Huijuan Han Lingyao Duan Zhenyu Hou Xiao Liu 《Journal of the European Ceramic Society》2021,41(4):2375-2385
In this study, C/SiOC and C/SiO2 composites were prepared by using carbonaceous microspheres with different surface functional groups. Carbonaceous microspheres based on hydrothermal reaction of glucose contains hydroxyl group, while the surface carboxyl group increases after NaOH etching. The hydroxyl group increases the oxygen-enriched structural units of SiOC ceramics, and the C spheres are closely enwrapped in SiOC matrix after pyrolysis at 900 °C. However, the interfacial reaction of surface carboxyl with Si–OH results in the formation of cristobalite SiO2, and C spheres are not only encased inside the SiOC matrix, but also dispersed outside of SiOC ceramics. After removal of C via calcination at 500 °C for 5 h, C/SiOC and C/SiO2 composites are transformed into amorphous SiO2 and cristobalite SiO2, respectively. The thermogravimetric analysis indicates the oxidation resistance of SiOC is superior to that of C and SiO2. 相似文献
3.
Yuelong Ma Le Zhang Tianyuan Zhou Bingheng Sun Chen Hou Shunshun Yang Jin Huang Rui Wang Farida A. Selim Zhongying Wang Ming Li Hao Chen Yun Wang 《Journal of the European Ceramic Society》2021,41(4):2834-2846
Ce:Y3Al5O12 transparent ceramics (TCs) with appropriate emission light proportion and high thermal stability are significant to construct white light emitting diode devices with excellent chromaticity parameters. In this work, strategies of controlling crystal-field splitting around Ce3+ ion and doping orange-red emitting ion, were adopted to fabricate Ce:(Y,Tb)3(Al,Mn)5O12 TCs via vacuum sintering technique. Notably, 85.4 % of the room-temperature luminescence intensity of the TC was retained at 150 °C, and the color rendering index was as high as 79.8. Furthermore, a 12 nm red shift and a 16.2 % increase of full width at half maximum were achieved owing to the synergistic effects of Tb3+ and Mn2+ ions. By combining TCs with a 460 nm blue chip, a warm white light with a low correlated color temperature of 4155 K was acquired. Meanwhile, the action mechanism of Tb3+ ion and the energy transfer between Ce3+ and Mn2+ ions were verified in prepared TCs. 相似文献
4.
Salim Hengky K. Padfield Rory Lee Chew Tin Syayuti Khadijah Papargyropoulou Effie Tham Mun Hou 《Clean Technologies and Environmental Policy》2018,20(3):529-538
Clean Technologies and Environmental Policy - Food production and consumption is one of the major causes of global environmental degradation. One way to address environmental impacts in the food... 相似文献
5.
Yan Jing Zhu Rongying Wu Fan Zhao Ziyin Ye Huan Hou Mengying Liu Yong Yin Lichen 《Nano Research》2020,13(10):2706-2715
Nano Research - Insufficient intratumoral penetration greatly hurdles the anticancer performance of nanomedicine. To realize highly efficient tumor penetration in a precisely and spatiotemporally... 相似文献
6.
Scientometrics - In traditional research, the application of quantitative measurement on the value and influence of uncited papers is not feasible owing to the lack of data. The rapid advancement... 相似文献
7.
8.
Replacement of precious single metal catalysts with cost-effective, highly-dispersed composite catalysts for catalytic hydrothermal conversion of residue holds tremendous promise for the residue upgrading technologies. Organic metals were added to the feed as the oil-soluble precursors, and transformed into the catalytic active phases in this work. Physical properties and structures of the composite catalysts had been investigated by X-ray fluorescence spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscope and transmission electron microscopy. The composite catalysts were found to be highly efficient in the catalytic hydrothermal conversion of both model compound and residue. Increased metal dispersion and synergistic effects of two metals played indispensable roles in such catalytic system. Results showed that under the test conditions in the article, the catalyst had the best catalytic performance when the mass ratio of molybdenum to iron was 1.5. 相似文献
9.
Mobile software applications have to cope with a particular environment that involves small size, limited resources, high autonomy requirements, competitive business models and many other challenges. To provide development guidelines that respond to these needs, several practices have been introduced; however, it is not clear how these guidelines may contribute to solve the issues present in the mobile domain. Furthermore, the rapid evolution of the mobile ecosystem challenges many of the premises upon which the proposed practices were designed. In this paper, we present a survey of the literature on software assurance practices for mobile applications, with the objective of describing them and assessing their contribution and success. We identified, organized and reviewed a body of research that spans in three levels: software development processes, software product assurance practices, and software implementation practices. By carrying out this literature survey, we reviewed the different approaches that researchers on Software Engineering have provided to address the needs that raise in the mobile software development arena. Moreover, we review the evolution of these practices, identifying how the constant changes and modernization of the mobile execution environment has impacted the methods proposed in the literature. Finally, we introduced discussion on the application of these practices in a real productive setting, opening an area for further research that may determine if practitioners have followed the proposed assurance paradigms. 相似文献
10.
This paper presents an integrated passive damping approach in hybrid metal-CFRP parts for structural applications. In this concept a viscoelastic material is embedded in the joint zone of the hybrid component. To examine the connection strength single-lap-joint specimens were produced and tested and the influence of the used material combinations, different surface structures, and different process parameters i.e. the moment of cross-linking were evaluated. Afterwards, the metal-CFRP hybrids were tested in quasi-static tests to assess their connection strength and failure behaviour. Dynamic cyclic tensile tests with step-wise increased loading conditions were performed to determine the specimens damping behaviour and to estimate their fatigue performance. Finally, these results are compared to a state of the art metal-CFRP hybrid with rivets connecting both materials. 相似文献