全文获取类型
收费全文 | 31131篇 |
免费 | 2386篇 |
国内免费 | 1167篇 |
专业分类
电工技术 | 1543篇 |
技术理论 | 2篇 |
综合类 | 1762篇 |
化学工业 | 5318篇 |
金属工艺 | 1936篇 |
机械仪表 | 2083篇 |
建筑科学 | 2432篇 |
矿业工程 | 1051篇 |
能源动力 | 824篇 |
轻工业 | 1790篇 |
水利工程 | 543篇 |
石油天然气 | 2122篇 |
武器工业 | 221篇 |
无线电 | 3317篇 |
一般工业技术 | 3837篇 |
冶金工业 | 1656篇 |
原子能技术 | 369篇 |
自动化技术 | 3878篇 |
出版年
2024年 | 124篇 |
2023年 | 579篇 |
2022年 | 939篇 |
2021年 | 1296篇 |
2020年 | 1064篇 |
2019年 | 808篇 |
2018年 | 995篇 |
2017年 | 996篇 |
2016年 | 959篇 |
2015年 | 1202篇 |
2014年 | 1490篇 |
2013年 | 1853篇 |
2012年 | 1948篇 |
2011年 | 1990篇 |
2010年 | 1780篇 |
2009年 | 1756篇 |
2008年 | 1626篇 |
2007年 | 1592篇 |
2006年 | 1732篇 |
2005年 | 1411篇 |
2004年 | 917篇 |
2003年 | 870篇 |
2002年 | 774篇 |
2001年 | 648篇 |
2000年 | 678篇 |
1999年 | 822篇 |
1998年 | 701篇 |
1997年 | 633篇 |
1996年 | 562篇 |
1995年 | 461篇 |
1994年 | 358篇 |
1993年 | 266篇 |
1992年 | 196篇 |
1991年 | 159篇 |
1990年 | 116篇 |
1989年 | 100篇 |
1988年 | 80篇 |
1987年 | 51篇 |
1986年 | 50篇 |
1985年 | 24篇 |
1984年 | 23篇 |
1983年 | 16篇 |
1982年 | 18篇 |
1981年 | 12篇 |
1980年 | 7篇 |
1979年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
Hechun Cao Hui Zheng Lining Fan Zifeng Cheng Jianwei Zhou Qiong Wu Peng Zheng Liang Zheng Yang Zhang 《International Journal of Applied Ceramic Technology》2020,17(2):813-822
In this study, yttrium iron garnet co-doped with Zn and Zr atoms with a chemical formula Y3ZnxZrxFe(5−2x)O12 (x = 0.0-0.3) has been successfully prepared by the solid-state reaction method. The effects of doping concentration on the microstructure, crystal structure, magnetic properties, and dielectric properties of Y3ZnxZrxFe(5−2x)O12 were investigated. The microstructure analysis indicates that co-doping of YIG with Zn and Zr can effectively reduce the grain size of the ceramic. The crystal structure results reveal that the doping concentration of Zn–Zr has substantial influence on the lattice parameters of YIG, such as, increases the lattice constant, crystal cell size, and interplanar spacing. However, the second phase of ZrO2 appears once x ≥ 0.15. Additionally, the dielectric properties of YIG ferrite can be regulated using this Zn–Zr co-doping method. Zn–Zr co-doping can improve the dielectric stability and reduce the dielectric loss at high temperature. The magnetization measurement shows that the saturation magnetization is stabilized at x < 0.15, and the magnetic loss is decreased with the increase in the doping concentration. Overall, the findings show that the ceramic with x = 0.1 exhibits better properties included high saturation magnetization (24.607 emu/g), low magnetic loss (0.0025 @ 1 MHz), and relatively low dielectric loss (496 @ 400°C). 相似文献
14.
15.
Y S Cao C M Ang K S Raajeevan A K Kiran K C Lai S W Ng I Zulkifli Y L Wah 《Water science and technology》2006,54(8):237-246
This paper analyses the performance of the anaerobic selector (A/O process) in a full-scale activated sludge process receiving mostly industrial sewage discharge (> 60%) in Singapore. In addition to the sludge settleability, enhanced biological phosphorus removal (EBPR) was studied. The sludge volume index (SVI) reduced from 200 to 80 ml g(-1) and foaming was suppressed significantly, indicating the effectiveness of the anaerobic selector in improving sludge settleability. The phosphorus removal efficiency was 66%, and 7.5 mg HAc-COD was consumed per mg PO4(3-) -P removed. In the anaerobic compartment, 31% of the SCOD and 73% of the acetic acid in the settled sewage were removed with PO4(3-) -P release of 14.1 mg PO4(3-)-P l(-1). The linear correlation between PO4(3-) -P release in the anaerobic compartment and PO4(3-) -P uptake in the aerobic compartment indicates that there is about 0.8 mg PO4(3-) -P release in the anaerobic compartment per mg PO34(3-) -P uptake in the aerobic compartment. The fates of volatile fatty acids (VFAs) and its short chain acids (SCAs) in the process were studied and discussed. 相似文献
16.
可控震源控制系统(包括编码器和译码器)的系统时钟频率的精度是影响可控震源振动质量的一个重要因素.文章描述了先进Ⅲ控制系统时钟调整,介绍了保证该系统时钟的精度的具体方法. 相似文献
17.
在阐述客户服务意义的基础上,提出对中国石化成品油销售企业客户服务体系建设的建议,即建立以客户为尊的服务理念;建设特色企业文化;完善员工服务体系;注重细节,提高服务质量;整合现有客户体系资源,拓展服务功能。 相似文献
18.
19.
Xiang Cao Sheng Zhong 《Communications Letters, IEEE》2006,10(8):580-581
Lin et al., (2003) proposed a remote user authentication scheme for multi-server architecture. In this paper, we breaks this scheme by giving an attack. Our attack allows an adversary to impersonate any user in the system, as long as a single authentication message of that user is observed. 相似文献
20.
Commercial purity aluminum (99.5%) was fabricated by equal channel angular pressing (ECAP) up to total accumulated strains of approx. 10. The annealing behavior of material deformed to total strains of approx. 1 and 10 was investigated, using heat treatments of 2 h at various temperatures from 100 to 500 °C. The microstructure of the annealed materials was characterized using the electron back-scatter pattern technique. A number of parameters were determined including the distribution and average values of both the boundary spacings and misorientations. For samples deformed to a total strain of 1, annealing resulted in discontinuous recrystallization. For samples deformed to a total strain of 10, annealing resulted in microstructures exhibiting characteristics of both uniform coarsening and, in a number of places, of discontinuous recrystallization. An attempt was made, based on the boundary spacing distributions, to separate these two components. The grain size after annealing was still however small, being just 6.4 μm after 2 h at 300 °C. 相似文献