全文获取类型
收费全文 | 103093篇 |
免费 | 9226篇 |
国内免费 | 4097篇 |
专业分类
电工技术 | 5832篇 |
技术理论 | 2篇 |
综合类 | 4633篇 |
化学工业 | 17579篇 |
金属工艺 | 5206篇 |
机械仪表 | 7046篇 |
建筑科学 | 5466篇 |
矿业工程 | 1899篇 |
能源动力 | 3776篇 |
轻工业 | 8060篇 |
水利工程 | 1750篇 |
石油天然气 | 2663篇 |
武器工业 | 776篇 |
无线电 | 14926篇 |
一般工业技术 | 15892篇 |
冶金工业 | 5777篇 |
原子能技术 | 1504篇 |
自动化技术 | 13629篇 |
出版年
2024年 | 261篇 |
2023年 | 1442篇 |
2022年 | 2402篇 |
2021年 | 4282篇 |
2020年 | 3039篇 |
2019年 | 2740篇 |
2018年 | 3135篇 |
2017年 | 3317篇 |
2016年 | 3531篇 |
2015年 | 3949篇 |
2014年 | 5416篇 |
2013年 | 6917篇 |
2012年 | 7984篇 |
2011年 | 8631篇 |
2010年 | 7140篇 |
2009年 | 7018篇 |
2008年 | 6680篇 |
2007年 | 5898篇 |
2006年 | 5389篇 |
2005年 | 4331篇 |
2004年 | 3423篇 |
2003年 | 2840篇 |
2002年 | 2619篇 |
2001年 | 2148篇 |
2000年 | 1758篇 |
1999年 | 1451篇 |
1998年 | 1893篇 |
1997年 | 1252篇 |
1996年 | 1041篇 |
1995年 | 770篇 |
1994年 | 599篇 |
1993年 | 492篇 |
1992年 | 374篇 |
1991年 | 326篇 |
1990年 | 304篇 |
1989年 | 277篇 |
1988年 | 227篇 |
1987年 | 179篇 |
1986年 | 134篇 |
1985年 | 127篇 |
1984年 | 106篇 |
1983年 | 71篇 |
1982年 | 48篇 |
1981年 | 48篇 |
1980年 | 47篇 |
1979年 | 42篇 |
1978年 | 37篇 |
1977年 | 47篇 |
1976年 | 79篇 |
1975年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
91.
92.
Although Mg alloy attracts great attention for engineering applications because of high specific strength and low density, low corrosion resistance limits its extensive use. In this study, Mg–Al–Zn–Mn alloy was treated via a laser cladding process to generate a dense and compact laser cladding layer with solid metallurgical bonding on the substrate for improving corrosion resistance, effectively hindering the corrosion pervasion into Mg alloy. The corrosion current density declined from 103 μA/cm2 for Mg alloy to 13 μA/cm2 for the laser cladding layer in NaCl aqueous solution. Moreover, the laser cladding layer was slightly corroded in comparison with Mg alloy in NaCl aqueous solution. Besides, the microhardness of the cladding layer reached a mean value of 170.5 HV, 3.1 times of Mg alloy (56.8 HV) due to the in situ formation of hardening intermetallic phases. Wear resistance of laser cladding layer was also obviously improved. These results demonstrated that the laser cladding layer obviously enhanced anticorrosion property of Mg alloy for engineering applications. 相似文献
93.
Although Mg alloy possesses high specific strength, low density, and good biocompatibility, poor corrosion resistance hinders its further applications. In the present study, an innovative protective layer against corrosion was prepared on the AZ31 Mg alloy via alkali pretreatment followed by vanillic acid treatment. The alkali pretreatment supplied –OH for the AZ31 Mg alloy surface to react with vanillic acid. The vanillic acid treatment played a crucial role in enhancing the corrosion resistance due to the excellent ability to act as a barrier and retard aqueous solution penetration, which effectively isolated the underlying Mg alloy from the corrosive environment. The corrosion current density of alkali and vanillic acid-treated Mg alloy (AZ31V) almost showed two orders of magnitude lower values in comparison with that of the AZ31 Mg alloy, and the corrosion potential of AZ31V Mg alloy increased from −1.41 to −1.25 V. The immersion tests proved that there was no occurrence of severe corrosion. Hence, the alkali pretreatment and vanillic acid treatment may represent a promising method to improve the corrosion resistance of Mg alloy. 相似文献
94.
Park Sangwon Nam Hyunbin Na Youngsang Kim Hyoungseop Moon Younghoon Kang Namhyun 《Metals and Materials International》2020,26(5):641-649
Metals and Materials International - This study investigated the influence of the initial grain size on the plastic deformation and tunnel defects that occurred from friction stir welding of... 相似文献
95.
96.
Kim Geonu Kacar Yilmaz Pistorius Petrus Christiaan 《Metallurgical and Materials Transactions B》2019,50(6):2508-2516
Metallurgical and Materials Transactions B - The concentration and chemical bonding state of carbon in direct-reduced iron (DRI) might affect DRI melting temperature and rate. The effects of carbon... 相似文献
97.
Seong‐Hee Kim 《Quality and Reliability Engineering International》2015,31(6):923-934
We present a distribution‐free tabular cumulative sum chart for monitoring the variability of an autocorrelated process. A quantity known as the asymptotic variance parameter is employed as a measure of the variability, and a distribution‐free tabular cumulative sum chart is applied to variance estimates calculated from batches of nonoverlapping samples. The proposed chart is applicable to a stationary process with a general marginal distribution and a general autocorrelation structure. It also determines control limits analytically without trial‐and‐error simulations. The performance of the proposed chart is tested on stationary processes with both normal and nonnormal marginals with various autocorrelation structures. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
98.
99.
100.
Oh Seung-Jun Yoon Jeong-Hwan Kim Si-Pom 《Journal of Mechanical Science and Technology》2021,35(3):1065-1073
Journal of Mechanical Science and Technology - In the industry, globe valves, which are commonly used to precise control the flow rate along with opening and closing flow in pipes, are technically... 相似文献