全文获取类型
收费全文 | 25833篇 |
免费 | 582篇 |
国内免费 | 740篇 |
专业分类
电工技术 | 472篇 |
综合类 | 58篇 |
化学工业 | 2796篇 |
金属工艺 | 2260篇 |
机械仪表 | 1004篇 |
建筑科学 | 622篇 |
矿业工程 | 47篇 |
能源动力 | 945篇 |
轻工业 | 1294篇 |
水利工程 | 162篇 |
石油天然气 | 375篇 |
武器工业 | 5篇 |
无线电 | 3165篇 |
一般工业技术 | 7056篇 |
冶金工业 | 4290篇 |
原子能技术 | 326篇 |
自动化技术 | 2278篇 |
出版年
2023年 | 71篇 |
2022年 | 113篇 |
2021年 | 220篇 |
2020年 | 173篇 |
2019年 | 289篇 |
2018年 | 466篇 |
2017年 | 434篇 |
2016年 | 529篇 |
2015年 | 408篇 |
2014年 | 631篇 |
2013年 | 1671篇 |
2012年 | 997篇 |
2011年 | 1509篇 |
2010年 | 1188篇 |
2009年 | 1401篇 |
2008年 | 1421篇 |
2007年 | 1402篇 |
2006年 | 1240篇 |
2005年 | 1116篇 |
2004年 | 931篇 |
2003年 | 880篇 |
2002年 | 812篇 |
2001年 | 800篇 |
2000年 | 773篇 |
1999年 | 797篇 |
1998年 | 1615篇 |
1997年 | 1146篇 |
1996年 | 957篇 |
1995年 | 610篇 |
1994年 | 495篇 |
1993年 | 407篇 |
1992年 | 265篇 |
1991年 | 264篇 |
1990年 | 182篇 |
1989年 | 187篇 |
1988年 | 142篇 |
1987年 | 99篇 |
1986年 | 77篇 |
1985年 | 76篇 |
1984年 | 50篇 |
1983年 | 39篇 |
1982年 | 34篇 |
1981年 | 42篇 |
1980年 | 23篇 |
1979年 | 12篇 |
1978年 | 18篇 |
1977年 | 14篇 |
1976年 | 34篇 |
1975年 | 18篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 703 毫秒
1.
Reliable joints of Ti3SiC2 ceramic and TC11 alloy were diffusion bonded with a 50 μm thick Cu interlayer. The typical interfacial structure of the diffusion boned joint, which was dependent on the interdiffusion and chemical reactions between Al, Si and Ti atoms from the base materials and Cu interlayer, was TC11/α-Ti + β-Ti + Ti2Cu + TiCu/Ti5Si4 + TiSiCu/Cu(s, s)/Ti3SiC2. The influence of bonding temperature and time on the interfacial structure and mechanical properties of Ti3SiC2/Cu/TC11 joint was analyzed. With the increase of bonding temperature and time, the joint shear strength was gradually increased due to enhanced atomic diffusion. However, the thickness of Ti5Si4 and TiSiCu layers with high microhardness increased for a long holding time, resulting in the reduction of bonding strength. The maximum shear strength of 251 ± 6 MPa was obtained for the joint diffusion bonded at 850 °C for 60 min, and fracture primarily occurred at the diffusion layer adjacent to the Ti3SiC2 substrate. This work provided an economical and convenient solution for broadening the engineering application of Ti3SiC2 ceramic. 相似文献
2.
Quan Nguyen Minh Quoc Dat Lai Hoang Nguy Minh Minh Tu Tran Kieu Ngoc Lam Gia Uyen Le My Phung Hang Hoang Dung Nguyen Tran Diem Ai Chau Ngoc Thuc Trinh Doan 《International Journal of Food Science & Technology》2022,57(7):4507-4517
To prevent the adulteration of agricultural resources and provide a solution to enhance the green coffee bean supply chain, authentication using the near-infrared spectroscopy (NIRS) technique was investigated. Partial least square with discrimination analysis (PLS-DA) models combined with various preprocessing methods were built from NIR spectra of 153 Vietnamese green coffee samples. The model combined with the standard normal variate and the first order of derivative yielded excellent performance in predicting coffee species with the error cross-validation of 0.0261. PLS-DA model of mean centre and first-order derivative spectra also yielded good performance in verifying geographical indication of green coffee with the error of 0.0656. By contrast, the predicting abilities of post-harvest methods were poor. The overall results showed a high potential of the NIRS in online authentication practices. 相似文献
3.
4.
5.
As a solid state joining process, ultrasonic spot welding has been proven to be a promising technique for joining copper alloys. However, challenges still remain in employing ultrasonic spot welding to join copper alloys. This article comprehensively reviews the current state of ultrasonic spot welding of copper alloys with a number of critical issues including materials flow, plastic deformation, temperature distribution, vibration, relative motion, vertical displacement, interface friction coefficient, online monitoring technique, coupled with the macrostructure and microstructure, the mechanical properties and electrical conductivity. In addition, the future trends in this field are provided. 相似文献
6.
7.
8.
9.
10.
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