全文获取类型
收费全文 | 70023篇 |
免费 | 5974篇 |
国内免费 | 3136篇 |
专业分类
电工技术 | 4072篇 |
技术理论 | 7篇 |
综合类 | 4618篇 |
化学工业 | 12068篇 |
金属工艺 | 4021篇 |
机械仪表 | 4295篇 |
建筑科学 | 5871篇 |
矿业工程 | 1971篇 |
能源动力 | 2003篇 |
轻工业 | 4705篇 |
水利工程 | 1340篇 |
石油天然气 | 4943篇 |
武器工业 | 498篇 |
无线电 | 7568篇 |
一般工业技术 | 8627篇 |
冶金工业 | 3307篇 |
原子能技术 | 764篇 |
自动化技术 | 8455篇 |
出版年
2024年 | 258篇 |
2023年 | 1147篇 |
2022年 | 1928篇 |
2021年 | 2695篇 |
2020年 | 2124篇 |
2019年 | 1821篇 |
2018年 | 2030篇 |
2017年 | 2317篇 |
2016年 | 2074篇 |
2015年 | 2637篇 |
2014年 | 3525篇 |
2013年 | 4066篇 |
2012年 | 4537篇 |
2011年 | 4871篇 |
2010年 | 4293篇 |
2009年 | 4047篇 |
2008年 | 3923篇 |
2007年 | 3843篇 |
2006年 | 3858篇 |
2005年 | 3348篇 |
2004年 | 2264篇 |
2003年 | 2050篇 |
2002年 | 1810篇 |
2001年 | 1727篇 |
2000年 | 1787篇 |
1999年 | 1939篇 |
1998年 | 1482篇 |
1997年 | 1256篇 |
1996年 | 1125篇 |
1995年 | 988篇 |
1994年 | 813篇 |
1993年 | 586篇 |
1992年 | 459篇 |
1991年 | 352篇 |
1990年 | 325篇 |
1989年 | 230篇 |
1988年 | 179篇 |
1987年 | 109篇 |
1986年 | 105篇 |
1985年 | 60篇 |
1984年 | 41篇 |
1983年 | 26篇 |
1982年 | 34篇 |
1981年 | 22篇 |
1980年 | 13篇 |
1979年 | 3篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1959年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Bin Feng Xin Jiang Guisheng Zou Wengan Wang Tianming Sun Heng Yang Guanlei Zhao Mingye Dong Yu Xiao Hongwei Zhu Lei Liu 《Advanced functional materials》2021,31(29):2102359
The realization of liquid metal-based wearable systems will be a milestone toward high-performance, integrated electronic skin. However, despite the revolutionary progress achieved in many other components of electronic skin, liquid metal-based flexible sensors still suffer from poor sensitivity due to the insufficient resistance change of liquid metal to deformation. Herein, a nacre-inspired architecture composed of a biphasic pattern (liquid metal with Cr/Cu underlayer) as “bricks” and strain-sensitive Ag film as “mortar” is developed, which breaks the long-standing sensitivity bottleneck of liquid metal-based electronic skin. With 2 orders of magnitude of sensitivity amplification while maintaining wide (>85%) working range, for the first time, liquid metal-based strain sensors rival the state-of-art counterparts. This liquid metal composite features spatially regulated cracking behavior. On the one hand, hard Cr cells locally modulate the strain distribution, which avoids premature cut-through cracks and prolongs the defect propagation in the adjacent Ag film. On the other hand, the separated liquid metal cells prevent unfavorable continuous liquid-metal paths and create crack-free regions during strain. Demonstrated in diverse scenarios, the proposed design concept may spark more applications of ultrasensitive liquid metal-based electronic skins, and reveals a pathway for sensor development via crack engineering. 相似文献
12.
为探讨剪跨比对无腹筋UHPC梁抗剪承载力的影响,文中采用ABAQUS有限元软件,以剪跨比为主要参数,对3种不同剪跨比的无腹筋UHPC简支梁的抗剪承载力进行数值分析,与试验结果相比较,吻合较好。在此基础上,考虑不同的剪跨比进行参数分析,结果表明:随着剪跨比的增大,无腹筋UHPC梁的抗剪承载力降低,且降低速率逐渐减小;剪跨比越大,纵筋配筋率对抗剪承载力的提高幅度越小。文中采用的有限元分析方法为无腹筋UHPC梁的抗剪承载力设计和计算提供参考。 相似文献
13.
14.
15.
16.
17.
Colour remains one of the key factors in presenting an object and, consequently, has been widely applied in retrieval of images based on their visual contents. However, a colour appearance changes with the change of viewing surroundings, the phenomenon that has not been paid attention yet while performing colour‐based image retrieval. To comprehend this effect, in this article, a chromatic contrast model, CAMcc, is developed for the application of retrieval of colour intensive images, cementing the gap that most of existing colour models lack to fill by taking simultaneous colour contrast into account. Subsequently, the model is applied to the retrieval task on a collection of museum wallpapers of colour‐rich images. In comparison with current popular colour models including CIECAM02, HSI and RGB, with respect to both foreground and background colours, CAMcc appears to outperform the others with retrieved results being closer to query images. In addition, CAMcc focuses more on foreground colours, especially by maintaining the balance between both foreground and background colours, while the rest of existing models take on dominant colours that are perceived the most, usually background tones. Significantly, the contribution of the investigation lies in not only the improvement of the accuracy of colour‐based image retrieval but also the development of colour contrast model that warrants an important place in colour and computer vision theory, leading to deciphering the insight of this age‐old topic of chromatic contrast in colour science. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 361–373, 2015 相似文献
18.
19.
20.
Dongdong Ji Zheng Liu Bailing Jiang Xiaofei Luo 《International Journal of Hydrogen Energy》2021,46(27):13960-13970
The evaluation of cell's weatherability is of practical interest. To further improve the soluble lead flow battery's weatherability, physiochemical properties of electrolytes containing fluoborate, perchlorate, methanesulfonate and trifluoromethanesulfonate are investigated from ?60 to 50 °C. Activities of CF3SO3H and HClO4 are poor in trifluoromethanesulfonate and perchlorate solutions due to common anion effect. The solubility of lead salt can be improved by increasing temperature, but worsened by increasing acid's content. With the temperature increasing, the conductivity is enhanced, and the viscosity is lowered for four solutions. The same results have been found by increasing acid's content except for CF3SO3H. The high energy efficiency can be achieved for cells over ?40–0 °C using fluoborate and perchlorate solutions, 73.2% at ?40 °C and 78.1% at ?30 °C respectively. Over the temperature range of 20–50 °C, the cells with methanesulfonate and trifluoromethanesulfonate solutions have good performance, 77.4% and 73.7% at 50 °C respectively. 相似文献