全文获取类型
收费全文 | 288522篇 |
免费 | 22449篇 |
国内免费 | 11093篇 |
专业分类
电工技术 | 15373篇 |
技术理论 | 31篇 |
综合类 | 17434篇 |
化学工业 | 50188篇 |
金属工艺 | 16894篇 |
机械仪表 | 18428篇 |
建筑科学 | 22879篇 |
矿业工程 | 9525篇 |
能源动力 | 7954篇 |
轻工业 | 16662篇 |
水利工程 | 4779篇 |
石油天然气 | 20256篇 |
武器工业 | 2234篇 |
无线电 | 31462篇 |
一般工业技术 | 34397篇 |
冶金工业 | 15275篇 |
原子能技术 | 2859篇 |
自动化技术 | 35434篇 |
出版年
2024年 | 1216篇 |
2023年 | 4675篇 |
2022年 | 7916篇 |
2021年 | 11402篇 |
2020年 | 8525篇 |
2019年 | 7266篇 |
2018年 | 8166篇 |
2017年 | 9217篇 |
2016年 | 8024篇 |
2015年 | 11167篇 |
2014年 | 13769篇 |
2013年 | 16446篇 |
2012年 | 17755篇 |
2011年 | 19401篇 |
2010年 | 16752篇 |
2009年 | 15911篇 |
2008年 | 15444篇 |
2007年 | 15089篇 |
2006年 | 15975篇 |
2005年 | 14148篇 |
2004年 | 9049篇 |
2003年 | 7909篇 |
2002年 | 7310篇 |
2001年 | 6486篇 |
2000年 | 7102篇 |
1999年 | 8507篇 |
1998年 | 6848篇 |
1997年 | 5823篇 |
1996年 | 5453篇 |
1995年 | 4507篇 |
1994年 | 3760篇 |
1993年 | 2635篇 |
1992年 | 2137篇 |
1991年 | 1606篇 |
1990年 | 1177篇 |
1989年 | 936篇 |
1988年 | 759篇 |
1987年 | 524篇 |
1986年 | 389篇 |
1985年 | 266篇 |
1984年 | 183篇 |
1983年 | 120篇 |
1982年 | 130篇 |
1981年 | 86篇 |
1980年 | 70篇 |
1979年 | 24篇 |
1978年 | 2篇 |
1965年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
Chuntao Lan Haiyang Zou Longfei Wang Meng Zhang Shuang Pan Ying Ma Yiping Qiu Zhong Lin Wang Zhiqun Lin 《Advanced materials (Deerfield Beach, Fla.)》2020,32(47):2005481
Despite recent rapid advances in metal halide perovskites for use in optoelectronics, the fundamental understanding of the electrical-poling-induced ion migration, accounting for many unusual attributes and thus performance in perovskite-based devices, remain comparatively elusive. Herein, the electrical-poling-promoted polarization potential is reported for rendering hybrid organic–inorganic perovskite photodetectors with high photocurrent and fast response time, displaying a tenfold enhancement in the photocurrent and a twofold decrease in the response time after an external electric field poling. First, a robust meniscus-assisted solution-printing strategy is employed to facilitate the oriented perovskite crystals over a large area. Subsequently, the electrical poling invokes the ion migration within perovskite crystals, thus inducing a polarization potential, as substantiated by the surface potential change assessed by Kelvin probe force microscopy. Such electrical-poling-induced polarization potential is responsible for the markedly enhanced photocurrent and largely shortened response time. This work presents new insights into the electrical-poling-triggered ion migration and, in turn, polarization potential as well as into the implication of the latter for optoelectronic devices with greater performance. As such, the utilization of ion-migration-produced polarization potential may represent an important endeavor toward a wide range of high-performance perovskite-based photodetectors, solar cells, transistors, scintillators, etc. 相似文献
82.
83.
84.
85.
86.
Xiaoyan Qiu Yongqiang Zhang Haitao Wu Rui Yang Jun Yang Rongjuan Liu Yong Liu Zhiping Zhou Tongfan Hao Yijing Nie 《Polymer International》2019,68(2):218-224
The crystallization of capped ultrathin polymer films is closely dependent on film thickness and interfacial interaction. Using dynamic Monte Carlo simulations, the crystallization behaviors of polymer films confined between two substrates were investigated. The crystallization rate of confined polymers is reduced with high interfacial interactions. Above a critical strength of interfacial interaction, polymer crystallization in the thin film is inhibited within the simulation time scales. An increase in film thickness leads to a rise in critical interfacial interaction. In thicker films, the chains have more space to change conformation to form crystal stems. In addition, there are fewer absorbed segments in confined chains for the thicker films, and thus the chains have stronger ability to adjust their conformation. Therefore an increase in film thickness can cause a reduction in the entropic barrier required for the formation of crystals and thus an increase in the critical interfacial interaction. © 2018 Society of Chemical Industry 相似文献
87.
Chenxu Liu Shuguang Zhang Ruonan Ji Peng Wang Jin Zhang Yu Tian Yonggang Meng Yedong He 《Ceramics International》2019,45(4):4747-4755
Semiconductor particles doped Al2O3 coatings were prepared by cathode plasma electrolytic deposition in Al(NO3)3 electrolyte dispersed with SiC micro- and nano-particles (average particle sizes of 0.5–1.7?µm and 40?nm respectively). The effects of the concentrations and particle sizes of the SiC on the microstructures and tribological performances of the composite coatings were studied. In comparison with the case of dispersing with SiC microparticles, the dispersion of SiC nanoparticles in the coatings was more uniform. When the concentration of SiC nanoparticles was 5?g/L, the surface roughness of the composite coating was reduced by 63%, compared with that of the unmodified coating. Friction results demonstrated that the addition of 5?g/L SiC nanoparticles reduced the friction coefficient from 0.60 to 0.38 and decreased the wear volume under dry friction. The current density and bath voltage were measured to analyze the effects of SiC particles on the deposition process. The results showed that the SiC particles could alter the electrical behavior of the coatings during the deposition process, weaken the bombardment of the plasma, and improve the structures of the coatings. 相似文献
88.
Lu Zhang Junjie Shang Tim Pelton Leslee Francis Pelton 《Journal of Computer Assisted Learning》2020,36(4):540-548
With the advent of mobile technologies, well-designed fraction apps can be used to help children gain fraction knowledge, a challenging topic for both teachers and students. The present pilot study adopted a quasi-experimental design to investigate whether children can learn fraction concepts equally well if half of the lesson time (20 min) is replaced with game-based learning. Keeping the total lesson time (40 min) identical, the control group (N = 33) received traditional instruction, and the experimental group (N = 32) was presented with a blended learning approach spending half of the class time (20 min) playing tablet-based fraction games, where each of the learners had their own tablet. The results suggested that in the posttest, the experimental group achieved similar learning gains to the control group and appear to have achieved better performance in the transfer test than the control group. This paper also discusses the efficiency of game-based learning, the mechanism of how fraction games might enhance learning, and the potential of integrating game-based learning in educational settings. 相似文献
89.
针对传统低压回路电阻测试仪只能在被测设备停电时使用的一大限制,本文提出并设计了一种新型低压回路电阻测试仪。该仪器可在低压设备运行状态下对其回路电阻进行测量,在保证测量精度的前提下减少了设备停电率,大大提高了工作效率。 相似文献
90.
Chengxiao Zhao Zupeng Chen Run Shi Xiaofei Yang Tierui Zhang 《Advanced materials (Deerfield Beach, Fla.)》2020,32(28):1907296
With the ambition of solving the challenges of the shortage of fossil fuels and their associated environmental pollution, visible-light-driven splitting of water into hydrogen and oxygen using semiconductor photocatalysts has emerged as a promising technology to provide environmentally friendly energy vectors. Among the current library of developed photocatalysts, organic conjugated polymers present unique advantages of sufficient light-absorption efficiency, excellent stability, tunable electronic properties, and economic applicability. As a class of rising photocatalysts, organic conjugated polymers offer high flexibility in tuning the framework of the backbone and porosity to fulfill the requirements for photocatalytic applications. In the past decade, significant progress has been made in visible-light-driven water splitting employing organic conjugated polymers. The recent development of the structural design principles of organic conjugated polymers (including linear, crosslinked, and supramolecular self-assembled polymers) toward efficient photocatalytic hydrogen evolution, oxygen evolution, and overall water splitting is described, thus providing a comprehensive reference for the field. Finally, current challenges and perspectives are also discussed. 相似文献