全文获取类型
收费全文 | 290983篇 |
免费 | 6901篇 |
国内免费 | 1826篇 |
专业分类
电工技术 | 5612篇 |
技术理论 | 5篇 |
综合类 | 1160篇 |
化学工业 | 48266篇 |
金属工艺 | 11523篇 |
机械仪表 | 8372篇 |
建筑科学 | 7546篇 |
矿业工程 | 1727篇 |
能源动力 | 6249篇 |
轻工业 | 31825篇 |
水利工程 | 3240篇 |
石油天然气 | 6084篇 |
武器工业 | 246篇 |
无线电 | 29041篇 |
一般工业技术 | 54268篇 |
冶金工业 | 53542篇 |
原子能技术 | 5708篇 |
自动化技术 | 25296篇 |
出版年
2021年 | 3306篇 |
2020年 | 2433篇 |
2019年 | 2950篇 |
2018年 | 4760篇 |
2017年 | 4679篇 |
2016年 | 5061篇 |
2015年 | 3879篇 |
2014年 | 5833篇 |
2013年 | 14018篇 |
2012年 | 9625篇 |
2011年 | 11948篇 |
2010年 | 9662篇 |
2009年 | 9987篇 |
2008年 | 10803篇 |
2007年 | 10746篇 |
2006年 | 9250篇 |
2005年 | 8062篇 |
2004年 | 7314篇 |
2003年 | 6793篇 |
2002年 | 6714篇 |
2001年 | 6671篇 |
2000年 | 6218篇 |
1999年 | 6235篇 |
1998年 | 14976篇 |
1997年 | 10934篇 |
1996年 | 8131篇 |
1995年 | 6003篇 |
1994年 | 5448篇 |
1993年 | 5349篇 |
1992年 | 4070篇 |
1991年 | 3865篇 |
1990年 | 3912篇 |
1989年 | 3870篇 |
1988年 | 3642篇 |
1987年 | 3115篇 |
1986年 | 3140篇 |
1985年 | 3501篇 |
1984年 | 3391篇 |
1983年 | 3123篇 |
1982年 | 2762篇 |
1981年 | 3001篇 |
1980年 | 2730篇 |
1979年 | 2882篇 |
1978年 | 2780篇 |
1977年 | 2999篇 |
1976年 | 3985篇 |
1975年 | 2499篇 |
1974年 | 2326篇 |
1973年 | 2362篇 |
1972年 | 1991篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
Thin Film Thermoelectric Metal–Organic Framework with High Seebeck Coefficient and Low Thermal Conductivity
下载免费PDF全文
![点击此处可从《Advanced materials (Deerfield Beach, Fla.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
94.
Spinel LiSr0·1Cr0·1Mn1·8O4 was synthesised by high temperature solid state method in order to enhance the electrochemical performance. The LiSr0·1Cr0·1Mn1·8O4 (LSCMO) materials were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical tests. The XRD and SEM studies confirm that LSCMO had spinel crystal structure with a space group of Fd3m, and the particle of LSCMO shows irregular shape. The cyclic voltammetry data illustrated that the heavy current charge–discharge performance of LMO was improved by Sr2+ and Cr3+ doping. The galvanostatic charge–discharge of LSCMO cathode materials was measured at 1, 5, 10 and 20 C. The results indicated that LSCMO improved the capacity retention. 相似文献
95.
Catalysis Letters - In this work we studied the reactivity of the Trifluoroacetic acid hydroxylamine system in the one step salt free synthesis of amides from ketones. A particular regards was paid... 相似文献
96.
97.
Rodríguez-Pérez Ángel Mariano Pérez-Calañas Cinta Pulido-Calvo Inmaculada 《Water Resources Management》2021,35(6):1977-1990
Water Resources Management - This paper aims to evaluate the possibility of using non-utilized hydraulic energy in urban water distribution systems. For this purpose, the viability and possible... 相似文献
98.
Russian Journal of Nondestructive Testing - The possibility of approaching the problems of testing the regularities of elastoplastic deformation of 20GL steel by the method of analyzing the... 相似文献
99.
Zhang Xi Wang Xianhai Zhao Hongke Ordóñez de Pablos Patricia Sun Yongqiang Xiong Hui 《Scientometrics》2019,119(3):1311-1344
Scientometrics - Altmetrics indices are increasingly applied to measure scholarly influence in recent years because they can reflect the influence of research outputs more timely comparing with... 相似文献
100.
Fabíola Azanha de Carvalho Amanda Aleixo Moreira André Luiz Martinez de Oliveira Fabio Yamashita 《应用聚合物科学杂志》2021,138(28):50667
Neat poly (lactic acid) (PLA) and PLA/cassava bagasse (CB) composites were used to produce seedling tubes by extrusion and injection molding. The tubes were buried in simulated soil, and their biodegradation was investigated by weight loss, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). After 180 days, the composites' biodegradation was higher than neat PLA material, and the higher the CB content, the higher the biodegradation, which caused fissures and voids in the material. The biodegradation of PLA/CB composites increased the phosphorus content in the soil after 180 days. Composites of PLA with CB, an abundant agro-industrial residue in Brazil, are promising because they can reduce the environmental impact due to CB's proper destination, and the composites' costs and biodegradation are faster than pure PLA material. Both the faster biodegradation of the tube and the higher P content are advantageous for seedling tubes. 相似文献