全文获取类型
收费全文 | 44128篇 |
免费 | 3915篇 |
国内免费 | 2110篇 |
专业分类
电工技术 | 2405篇 |
技术理论 | 3篇 |
综合类 | 3081篇 |
化学工业 | 7436篇 |
金属工艺 | 2231篇 |
机械仪表 | 2845篇 |
建筑科学 | 3548篇 |
矿业工程 | 1195篇 |
能源动力 | 1401篇 |
轻工业 | 2478篇 |
水利工程 | 769篇 |
石油天然气 | 3052篇 |
武器工业 | 344篇 |
无线电 | 5157篇 |
一般工业技术 | 5459篇 |
冶金工业 | 1953篇 |
原子能技术 | 552篇 |
自动化技术 | 6244篇 |
出版年
2024年 | 138篇 |
2023年 | 644篇 |
2022年 | 1108篇 |
2021年 | 1638篇 |
2020年 | 1236篇 |
2019年 | 1105篇 |
2018年 | 1207篇 |
2017年 | 1382篇 |
2016年 | 1259篇 |
2015年 | 1564篇 |
2014年 | 2060篇 |
2013年 | 2464篇 |
2012年 | 2538篇 |
2011年 | 2831篇 |
2010年 | 2456篇 |
2009年 | 2342篇 |
2008年 | 2380篇 |
2007年 | 2254篇 |
2006年 | 2397篇 |
2005年 | 1996篇 |
2004年 | 1466篇 |
2003年 | 1662篇 |
2002年 | 1921篇 |
2001年 | 1673篇 |
2000年 | 1321篇 |
1999年 | 1395篇 |
1998年 | 1010篇 |
1997年 | 861篇 |
1996年 | 869篇 |
1995年 | 666篇 |
1994年 | 579篇 |
1993年 | 445篇 |
1992年 | 305篇 |
1991年 | 225篇 |
1990年 | 174篇 |
1989年 | 154篇 |
1988年 | 153篇 |
1987年 | 92篇 |
1986年 | 53篇 |
1985年 | 32篇 |
1984年 | 23篇 |
1983年 | 16篇 |
1982年 | 22篇 |
1981年 | 14篇 |
1980年 | 10篇 |
1979年 | 10篇 |
1976年 | 1篇 |
1971年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
951.
Zou Rui Huang Junjian Shi Junpeng Huang Lin Zhang Xuejie Wong Ka-Leung Zhang Hongwu Jin Dayong Wang Jing Su Qiang 《Nano Research》2017,10(6):2070-2082
Near-infrared (NIR) persistent-luminescence nanoparticles have emerged as a new class of background-free contrast agents that are promising for in vivo imaging.The next key roadblock is to establish a robust and controllable method for synthesizing monodisperse nanoparticles with high luminescence brightness and long persistent duration.Herein,we report a synthesis strategy involving the coating/etching of the SiO2 shell to obtain a new class of small NIR highly persistent luminescent ZnGa2O4∶Cr3+,Sn4+ (ZGOCS) nanoparticles.The optimized ZGOCS nanoparticles have an excellent size distribution of ~15 nm without any agglomeration and an NIR persistent luminescence that is enhanced by a factor of 13.5,owing to the key role of the SiO2 shell in preventing nanoparticle agglomeration after annealing.The ZGOCS nanoparticles have a signal-to-noise ratio ~3 times higher than that of previously reported ZnGa2O4∶Cr3+ (ZGC-1) nanoparticles as an NIR persistent-luminescence probe for in vivo bioimaging.Moreover,the persistent-luminescence signal from the ZGOCS nanoparticles can be repeatedly re-charged in situ with external excitation by a white lightemitting diode;thus,the nanoparticles are suitable for long-term in vivo imaging applications.Our study suggests an improved strategy for fabricating novel high-performance optical nanoparticles with good biocompatibility. 相似文献
952.
Wei Zheng Biao Xu Lin Zhou Yilong Zhou Haimei Zheng Chenghan Sun Enzheng Shi Tanner Dale Fink Yue Wu 《Nano Research》2017,10(5):1498-1509
Thermoelectric materials,which can convert waste heat into electricity,have received increasing research interest in recent years.This paper describes the recent progress in thermoelectric nanocomposites based on solution-synthesized nanoheterostructures.We start our discussion with the strategies of improving the power factor of a given material by using nanoheterostructures.Then we discuss the methods of decreasing thermal conductivity.Finally,we highlight a way of decoupling power factor and thermal conductivity,namely,incorporating phase-transition materials into a nanowire heterostructure.We have explored the lead telluride-copper telluride thermoelectric nanowire heterostructure in this work.Future possible ways to improve the figure of merit are discussed at the end of this paper. 相似文献
953.
Yueyue Wang Feifei Qin Junfeng Lu Jitao Li Zhu Zhu Qiuxiang Zhu Ye Zhu Zengliang Shi Chunxiang Xu 《Nano Research》2017,10(10):3447-3456
It is essential to develop a single mode operation and improve the performance of lasing in order to ensure practical applicability of microlasers and nanolasers.In this paper,two hexagonal microteeth with varied nanoscaled air-gaps of a ZnO microcomb are used to construct coupled whispering-gallery cavities.This is done to achieve a stable single mode lasing based on Vernier effect without requiring any complicated or sophisticated manipulation to achieve positioning with nanoscale precision.Optical gain and the corresponding ultraviolet lasing performance were improved greatly through coupling with localized surface plasmons of Pt nanoparticles.The ZnO/Pt hybrid microcavities achieved a seven-fold enhancement of intensity of single mode lasing with higher sidemode suppression ratio and lower threshold.The mechanism that led to this enhancement has been described in detail. 相似文献
954.
A combined hot-injection and heat-up method was developed to synthesize monodisperse and uniform CoMn2O4 quantum dots (CMO QDs).CMO QDs with average size of 2.0,3.9,and 5.4 nm were selectively obtained at 80,90,and 105 ℃,respectively.The CMO QDs supported on carbon nanotubes (CNTs) were employed as catalysts for the oxygen reduction/evolution reaction (ORR/OER) in alkaline solution to investigate their size-performance relationship.The results revealed that the amount of surface-adsorbed oxygen and the band gap energy,which affect the charge transfer in the oxygen electrocatalysis processes,strongly depend on the size of the CMO QDs.The CMO-3.9/CNT hybrid,consisting of CNT-supported CMO QDs of 3.9 nm size,possesses a moderate amount of surfaceadsorbed oxygen,a lower band gap energy,and a larger charge carrier concentration,and exhibits the highest electrocatalytic activity among the hybrid materials investigated.Moreover,the CMO-3.9/CNT hybrid displays ORR and OER performances similar to those of the benchmark Pt/C and RuO2 catalysts,respectively,due to the strong carbon-oxide interactions and the high dispersion of CoMn2O4 QDs on the carbon substrate;this reveals the huge potential of the CMO-3.9/CNT hybrid as a bifunctional OER/ORR electrocatalyst.The present results highlight the importance of controlling the size of metal oxide nanodots in the design of active oxygen electrocatalysts based on spinel-type,nonprecious metal oxides. 相似文献
955.
Crystallographic analysis on small fatigue crack propagation behaviour of a nickel-based single crystal superalloy 下载免费PDF全文
W. Qiu X. Ma S. Rui H.-J. Shi 《Fatigue & Fracture of Engineering Materials & Structures》2017,40(1):3-11
In situ observations by scanning electron microscopy show that small fatigue cracks in a nickel-based single crystal superalloy are inclined to the loading direction and propagate in dominant crystallographic manners. In order to evaluate the driving forces for inclined crack propagation, three-dimensional anisotropic linear elastic finite-element analysis is conducted. The plastic zone size on the dominant slip plane has been calculated and proposed to correlate the fatigue crack growth. It is shown that this parameter takes into account both material anisotropy and octahedral fracture modes, and it can effectively characterize small crack propagation behaviour. 相似文献
956.
Ji-Lei Shi Dong-Dong Xiao Xu-Dong Zhang Ya-Xia Yin Yu-Guo Guo Lin Gu Li-Jun Wan 《Nano Research》2017,10(12):4201-4209
High-capacity Li-rich cathode materials can significantly improve the energy density of lithium-ion batteries, which is the key limitation to miniaturization of electronic devices and further improvement of electrical-vehicle mileage. However, severe voltage decay hinders the further commercialization of these materials. Insights into the relationship between the inherent structural stability and external appearance of the voltage decay in high-energy Li-rich cathode materials are critical to solve this problem. Here, we demonstrate that structural evolution can be significantly inhibited by the intentional introduction of certain adventive cations (such as Ni2+) or by premeditated reservation of some of the original Li+ ions in the Li slab in the delithiated state. The voltage decay of Li-rich cathode materials over 100 cycles decreased from 500 to 90 or 40 mV upon introducing Ni2+ or retaining some Li+ ions in the Li slab, respectively. The cations in the Li slab can serve as stabilizers to reduce the repulsion between the two neighboring oxygen layers, leading to improved thermodynamic stability. Meanwhile, the cations also suppress transition metal ion migration into the Li slab, thereby inhibiting structural evolution and mitigating voltage decay. These findings provide insights into the origin of voltage decay in Li-rich cathode materials and set new guidelines for designing these materials for high-energy-density Li-ion batteries. 相似文献
957.
Anatase TiO2 with a variant percentage of exposed (001) facets was prepared under hydrothermal processes by adjusting the volume of HF, and the photocatalytic mechanism was studied from atomic-molecular scale by HRTEM and Raman spectroscopy. It was revealed that: 1) From HRTEM observations, the surface of original TiO2 with exposed (001) facets was clean without impurity, and the crystal lattice was clear and completed; however, when mixed with methylene blue (MB) solution, there were many 1 nm molecular absorbed at the surface of TiO2; after the photocatalytic experiment, MB molecules disappeared and the TiO2 lattice image became fuzzy. 2) The broken path of the MB chemical bond was obtained by Raman spectroscopy, i.e., after the irradiation of the light, the vibrational mode of C-N-C disappeared due to the chemical bond breakage, and the groups containing C-N bond and carbon rings were gradually decomposed. Accordingly, we propose that the driving force for breaking the chemical bond and the disappearance of groups is from the surface lattice distortion of TiO2 during photocatalyzation. 相似文献
958.
H. Tatsuno W. B. Doriese D. A. Bennett C. Curceanu J. W. Fowler J. Gard F. P. Gustafsson T. Hashimoto R. S. Hayano J. P. Hays-Wehle G. C. Hilton M. Iliescu S. Ishimoto K. Itahashi M. Iwasaki K. Kuwabara Y. Ma J. Marton H. Noda G. C. O’Neil S. Okada H. Outa C. D. Reintsema M. Sato D. R. Schmidt H. Shi K. Suzuki T. Suzuki J. Uhlig J. N. Ullom E. Widmann S. Yamada J. Zmeskal D. S. Swetz 《Journal of Low Temperature Physics》2016,184(3-4):930-937
959.
Junwei?Xie Yurong?Shi Feng?ZhangEmail author Guoqiang?LiEmail author 《Journal of Materials Science》2016,51(16):7471-7479
960.