全文获取类型
收费全文 | 153551篇 |
免费 | 16440篇 |
国内免费 | 9486篇 |
专业分类
电工技术 | 12030篇 |
技术理论 | 6篇 |
综合类 | 12163篇 |
化学工业 | 22484篇 |
金属工艺 | 9343篇 |
机械仪表 | 10752篇 |
建筑科学 | 12875篇 |
矿业工程 | 5333篇 |
能源动力 | 4332篇 |
轻工业 | 10528篇 |
水利工程 | 3568篇 |
石油天然气 | 7628篇 |
武器工业 | 1778篇 |
无线电 | 18992篇 |
一般工业技术 | 16007篇 |
冶金工业 | 6050篇 |
原子能技术 | 1976篇 |
自动化技术 | 23632篇 |
出版年
2024年 | 673篇 |
2023年 | 2402篇 |
2022年 | 5165篇 |
2021年 | 7321篇 |
2020年 | 5394篇 |
2019年 | 4176篇 |
2018年 | 4687篇 |
2017年 | 5214篇 |
2016年 | 4705篇 |
2015年 | 7287篇 |
2014年 | 8979篇 |
2013年 | 10531篇 |
2012年 | 12327篇 |
2011年 | 12928篇 |
2010年 | 11759篇 |
2009年 | 11224篇 |
2008年 | 10685篇 |
2007年 | 9972篇 |
2006年 | 8853篇 |
2005年 | 7358篇 |
2004年 | 4887篇 |
2003年 | 3734篇 |
2002年 | 3442篇 |
2001年 | 2879篇 |
2000年 | 2437篇 |
1999年 | 2277篇 |
1998年 | 1489篇 |
1997年 | 1328篇 |
1996年 | 1156篇 |
1995年 | 956篇 |
1994年 | 773篇 |
1993年 | 550篇 |
1992年 | 418篇 |
1991年 | 345篇 |
1990年 | 268篇 |
1989年 | 224篇 |
1988年 | 180篇 |
1987年 | 107篇 |
1986年 | 92篇 |
1985年 | 40篇 |
1984年 | 36篇 |
1983年 | 16篇 |
1982年 | 33篇 |
1981年 | 25篇 |
1980年 | 40篇 |
1979年 | 24篇 |
1978年 | 10篇 |
1976年 | 9篇 |
1959年 | 18篇 |
1951年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
介绍了PET熔体长距离输送工艺流程,重点分析易对PET熔体输送带来不利影响的因素,如熔体压力降、停留时间、管道粗糙度、焊缝品质等,并针对熔体输送的不利因素,提出了相应的解决方案,对熔体直纺设计、实践提供必要的参考。 相似文献
82.
以2,6-二甲基苯胺为原料,通过重氮化反应制备2,6-二甲基苯腈,经水蒸汽蒸馏法提纯后,采用75%硫酸酸化,再经酸碱法对产物进行脱色和纯化得产物2,6-二甲基苯甲酸,总收率68.4%。工艺简单、操作安全、适合工业化生产。 相似文献
83.
84.
Yong Pan Chen Zhu Wen Bin Zeng Pei Fu Chi Chen Bao Ming Xu Zhong Feng Gao 《Chembiochem : a European journal of chemical biology》2021,22(24):3431-3436
Rapid and sensitive point-of-care testing (POCT) is an extremely critical mission in practical applications, especially for rigorous military medicine, home health care, and in the third world. Here, we report a visual POCT method for adenosine triphosphate (ATP) detection based on Taylor rising in the corner of quadratic geometries between two rod surfaces. We discuss the principle of Taylor rising, demonstrating that it is significantly influenced by contact angle, surface tension, and density of the sample, which are controlled by ATP-dependent rolling circle amplification (RCA). In the presence of ATP, RCA reaction effectively suppresses Taylor-rising behavior, due to the increased contact angle, density, and decreased surface tension. Without addition of ATP, untriggered RCA reaction is favorable for Taylor rising, resulting in a significant height. With this proposed method, visual sensitive detection of ATP without the aid of other instruments is realized with only a 5 μL droplet, which has good selectivity and a low detection limit (17 nM). Importantly, this visual method provides a promising POCT tool for user-friendly molecular diagnostics. 相似文献
85.
86.
Sumeng Wei Yuling Yang Xiao Feng Shanshan Li Lei Zhou Jingyu Wang Xiaozhi Tang 《International Journal of Food Science & Technology》2020,55(7):2691-2699
Structures and properties of myofibrillar protein gel prepared at different power (300–800 W) were evaluated. Amino acid analysis demonstrated that changes in microwave power did not alter primary structure of gel. However, an increase in microwave power could change higher structures of gel. As microwave power increased, α-helix content decreased and β-sheet content increased. Increased microwave power probably facilitated protein to unfold and expose the internal groups, causing surface hydrophobicity and the formation of disulphide bonds were enhanced, which indicated changes in tertiary and quaternary structures of protein. At 500 W, gel had the best ultrastructure where surface morphology, springiness and water holding capacity reached the optimum. Our findings suggested that microwave at an appropriate power (500 W) could change higher structures of myofibrillar protein gel to achieve desired processing and quality protein gel characteristics. 相似文献
87.
Yanlong Shi Xiaojuan Feng Haiyu Guan Jiahua Zhang Zhongai Hu 《International Journal of Hydrogen Energy》2021,46(12):8557-8566
Constructing high-efficient and nonprecious electrocatalysts is of primary importance for improving the efficiency of water splitting. Herein, a novel sunflower plate-like NiFe2O4/CoNi–S nanosheet heterostructure was fabricated via facile hydrothermal and electrodeposition methods. The as-fabricated NiFe2O4/CoNi–S heterostructure array exhibits remarkable bifunctional catalytic activity and stability toward oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline media. It presents a small overpotential of 219 mV and 149 mV for OER and HER, respectively, to produce a current density of 10 mA cm?2. More significantly, when the obtained electrodes are used as both the cathode and anode in an electrolyzer, a voltage of 1.57 V is gained at 10 mA cm?2, with superior stability for 72 h. Such outstanding properties are ascribed to: the 3D porous network structure, which exposes more active sites and accelerates mass transfer and gas bubble emission; the high conductivity of CoNi–S, which provides faster charge transport and thus promotes the electrocatalytic reaction of the composites; and the effective interface engineering between NiFe2O4 (excellent performance for OER) and CoNi–S (high activity for HER), which leads to a shorter transport pathway and thus expedites electron transfer. This work provides a new strategy for designing efficient and inexpensive electrocatalysts for water splitting. 相似文献
88.
89.
90.
Li Lei Limin Li Shasha Wang Gaoyang Zhao Yoshifumi Oshima Yang Ren Lei Zhao Lihua Jin Yao Wang Chengshan Li Pingxiang Zhang 《Journal of the European Ceramic Society》2018,38(14):4694-4700
Highly (100)-oriented Ce1-x(Y0.2Zr0.8)xOδ (CYZO) films were prepared on biaxially textured NiW substrates by a chemical solution deposition approach using metal inorganic salts as starting materials. It has been found that both the preferential orientation and surface roughness of CYZO films decrease gradually with increasing of the doping percentage of Y3+ and Zr4+ ions. The epitaxial growth relationship of (220)CYZO//(200)NiW and [00?l]CYZO//[001]NiW was demonstrated by XRD texture measurement as well as atomic resolution STEM observation. XRD, Raman and XPS spectra results indicate that Y3+ and Zr4+ ions were indeed introduced into CeO2 lattice to substitute Ce4+ ions and form cubic fluorite CYZO solid solution. Moreover, CeO2 buffer layer can be endowed a strong enough capability to prevent element diffusion through co-doping of yttrium and zirconium, provided that an optimal doping ratio of them is adopted. This will provide a new approach to fabricating strong-barrier single buffer layer for coated conductor. 相似文献