全文获取类型
收费全文 | 45931篇 |
免费 | 5756篇 |
国内免费 | 3795篇 |
专业分类
电工技术 | 4137篇 |
综合类 | 4795篇 |
化学工业 | 5778篇 |
金属工艺 | 3070篇 |
机械仪表 | 3453篇 |
建筑科学 | 3311篇 |
矿业工程 | 1904篇 |
能源动力 | 1327篇 |
轻工业 | 5634篇 |
水利工程 | 1520篇 |
石油天然气 | 1762篇 |
武器工业 | 827篇 |
无线电 | 4708篇 |
一般工业技术 | 3975篇 |
冶金工业 | 1668篇 |
原子能技术 | 911篇 |
自动化技术 | 6702篇 |
出版年
2024年 | 308篇 |
2023年 | 922篇 |
2022年 | 2028篇 |
2021年 | 2574篇 |
2020年 | 1863篇 |
2019年 | 1326篇 |
2018年 | 1390篇 |
2017年 | 1517篇 |
2016年 | 1357篇 |
2015年 | 2221篇 |
2014年 | 2745篇 |
2013年 | 3122篇 |
2012年 | 3937篇 |
2011年 | 3964篇 |
2010年 | 3697篇 |
2009年 | 3492篇 |
2008年 | 3574篇 |
2007年 | 3575篇 |
2006年 | 3101篇 |
2005年 | 2315篇 |
2004年 | 1708篇 |
2003年 | 1138篇 |
2002年 | 1080篇 |
2001年 | 1021篇 |
2000年 | 745篇 |
1999年 | 317篇 |
1998年 | 93篇 |
1997年 | 47篇 |
1996年 | 37篇 |
1995年 | 35篇 |
1994年 | 23篇 |
1993年 | 29篇 |
1992年 | 31篇 |
1991年 | 20篇 |
1990年 | 14篇 |
1989年 | 20篇 |
1988年 | 11篇 |
1987年 | 7篇 |
1986年 | 12篇 |
1985年 | 6篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 18篇 |
1979年 | 4篇 |
1967年 | 1篇 |
1964年 | 1篇 |
1963年 | 1篇 |
1959年 | 3篇 |
1951年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
2.
纤维素和几丁质具有相似的结构,是自然界中储量丰富的两类天然多糖。经2, 2, 6, 6-四甲基哌啶氮氧化物(TEMPO)氧化修饰制备的纤维素和几丁质纳米纤维,不仅具有多糖类物质的良好亲水性、生物可降解性、生物相容性及丰富的官能团(羟基、羧基、乙酰氨基和氨基等)所带来的特定化学性质,而且还具有纳米纤维的纳米尺寸效应、大比表面积、高表面活性、高结晶度和手性液晶相结构等特点,已成为生物质纳米材料领域的研究重点之一。本文对TEMPO氧化修饰制备天然多糖纳米纤维的方法及剥离机制进行了总结,同时重点综述了TEMPO氧化修饰的天然多糖纳米纤维在薄膜、凝胶、导电、医用、电磁屏蔽及环境等复合材料的增强和功能升级等方面的研究进展,强调了纤维素和几丁质纳米纤维的官能团及纳米尺寸在复合材料中的增效机制。最后,对天然多糖纳米纤维的发展方向及其在各领域应用的机遇与挑战进行了展望。 相似文献
3.
Shuang Chen Chao Yu Zhanfang Cao Xiaoping Huang Shuai Wang Hong Zhong 《International Journal of Hydrogen Energy》2021,46(10):7037-7046
The development of efficient and stable oxygen evolution reaction (OER) catalysts is an ongoing challenge. In order to solve the problem of low oxygen evolution efficiency of the current OER catalysts, a novel material was synthesized by the incorporation of NiFeCr-LDH and MoS2, and its structural and electrochemical properties were also investigated. The introduction of MoS2 improves the electrochemical performance of NiFeCr-LDH. The polarization curve shows that the potential of composite material is only 1.50 V at a current density of 10 mA cm?2, which is far superior to commercial precious metal catalysts. In addition, the stability experiment shows that the composite material has excellent stability, and the current density has little change after 500 cycles. Furthermore, we found that some metal ions, such as Ni, Cr and Mo, exist in the form of high valence on the surface of NiFeCr-LDH@MoS2, which is also conducive to the occurrence of oxygen evolution reaction. 相似文献
4.
Cuiping Yu Shuang Sun Sihui Li Huijia Yan Henan Zou 《International Journal of Food Science & Technology》2022,57(2):1173-1185
In this study, the effect of high-intensity ultrasound (HIUS) (200 and 400 W for 0, 5, 10 and 15 min respectively) on conformational changes, physicochemical, rheological and emulsifying properties of scallop (Patinopecten yessoensis) myofibrillar protein (SMP) was investigated. HIUS-treated SMP had lower α-helix content and higher β-sheet content compared with the native SMP. HIUS treatment induced the unfolding of SMP and increased the surface hydrophobicity. The particle size of SMP decreased and the absolute zeta-potential increased after ultrasonication, which in turn increased the solubility of SMP. The conformational changes and the improvement of physicochemical properties of SMP increased the ability for SMP to lower the interfacial tension at the oil–water interface and increased the percentage of adsorbed protein. As a result, the emulsifying properties, rheological properties of SMP and storage stability of emulsions were also improved. In conclusion, HIUS treatment has future potential for improving the emulsifying properties of SMP. 相似文献
5.
6.
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
7.
8.
Lin Haicheng Huang Wantong Zhao Kun Qiao Shuang Liu Zheng Wu Jian Chen Xi Ji Shuai-Hua 《Nano Research》2020,13(1):133-137
Nano Research - The isostructural and isoelectronic transition-metal-dichalcogenides 1T-TaS2 and 1T-TaSe2 are layered materials with intricate electronic structures. Combining the molecular beam... 相似文献
10.
设备前期翻料钩摆臂角度设计错误,导致该处液压缸事故频繁,经改造后,将过渡篦条和中间过渡装置拆除。整体标高再次进行定位,实现穿孔出来的毛管直接过渡到轧机入口,无需中间翻料钩装置,以保证设备的正常运转和生产连续性。 相似文献