全文获取类型
收费全文 | 11307篇 |
免费 | 520篇 |
国内免费 | 670篇 |
专业分类
电工技术 | 101篇 |
综合类 | 454篇 |
化学工业 | 959篇 |
金属工艺 | 5005篇 |
机械仪表 | 331篇 |
建筑科学 | 36篇 |
矿业工程 | 120篇 |
能源动力 | 456篇 |
轻工业 | 14篇 |
水利工程 | 1篇 |
石油天然气 | 14篇 |
武器工业 | 75篇 |
无线电 | 294篇 |
一般工业技术 | 3347篇 |
冶金工业 | 991篇 |
原子能技术 | 150篇 |
自动化技术 | 149篇 |
出版年
2024年 | 33篇 |
2023年 | 225篇 |
2022年 | 192篇 |
2021年 | 381篇 |
2020年 | 357篇 |
2019年 | 352篇 |
2018年 | 311篇 |
2017年 | 329篇 |
2016年 | 264篇 |
2015年 | 282篇 |
2014年 | 459篇 |
2013年 | 790篇 |
2012年 | 513篇 |
2011年 | 984篇 |
2010年 | 570篇 |
2009年 | 704篇 |
2008年 | 623篇 |
2007年 | 630篇 |
2006年 | 629篇 |
2005年 | 507篇 |
2004年 | 505篇 |
2003年 | 449篇 |
2002年 | 316篇 |
2001年 | 263篇 |
2000年 | 255篇 |
1999年 | 232篇 |
1998年 | 179篇 |
1997年 | 211篇 |
1996年 | 134篇 |
1995年 | 144篇 |
1994年 | 114篇 |
1993年 | 89篇 |
1992年 | 79篇 |
1991年 | 57篇 |
1990年 | 52篇 |
1989年 | 45篇 |
1988年 | 27篇 |
1987年 | 30篇 |
1986年 | 31篇 |
1985年 | 16篇 |
1984年 | 22篇 |
1983年 | 18篇 |
1982年 | 21篇 |
1981年 | 15篇 |
1980年 | 14篇 |
1979年 | 9篇 |
1978年 | 14篇 |
1977年 | 5篇 |
1976年 | 7篇 |
1975年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
铝合金化学镀镍工艺研究与应用 总被引:6,自引:0,他引:6
报道一种在铝合金元件上实施化学镀镍的工艺方法。该方法包括在改进的锌酸 溶液中经二闪浸锌处理后,以碱性化学镀镍作底层,然后进行酸性化学镀镍,能在铝合金(LY12cz、LD31等)表面获得光亮的、具有优异附着力和良好的防腐蚀性能及其综合物理、化学特性的化学镀镍(Ni-P)层。 相似文献
102.
Magnetically hard CoPtP (up to 40 μm thickness) films for MEMS application were deposited from citrate electrolyte and considered in terms of their composition, structure, magnetic characteristics and deposition conditions. Films containing 83-92 at.% (a/o) Co were deposited in the presence of NaH2PO2 in the electrolyte, with current efficiency of about 20% (deposition rate 10-12 μm/h). Coercivity 2.7-2.8 kOe and remanence 3.0 kG were achieved magnetizing in the direction normal to the film plane. According to XRD analysis, films seem to consist of hexagonal phase of CoPt solid solutions. Current efficiency, composition and morphology of the films, as well as their magnetic characteristics, were influenced by the electrolyte prehistory and total charge passed through the electrolyte in previous operation. 相似文献
103.
Xuejie Gao Xiaofei Yang Ming Jiang Matthew Zheng Yang Zhao Ruying Li Wenfeng Ren Huan Huang Runcang Sun Jiantao Wang Chandra Veer Singh Xueliang Sun 《Advanced functional materials》2023,33(7):2209715
All-solid-state Li batteries (ASSLBs) with solid-polymer electrolytes are considered promising battery systems to achieve improved safety and high energy density. However, Li dendrite formation at the Li anode under high charging current density/capacity has limited their development. To tackle the issue, Li-metal alloying has been proposed as an alternative strategy to suppress Li dendrite growth in ASSLBs. One drawback of alloying is the relatively lower operating cell voltages, which will inevitably lower energy density compared to cells with pure Li anode. Herein, a Li-rich Li13In3 alloy electrode (LiRLIA) is proposed, where the Li13In3 alloy scaffold guides Li nucleation and hinders Li dendrite formation. Meanwhile, the free Li can recover Li's potential and facilitate fast charge transfer kinetics to realize high-energy-density ASSLBs. Benefitting from the stronger adsorption energy and lower diffusion energy barrier of Li on a Li13In3 substrate, Li prefers to deposit in the 3D Li13In3 scaffold selectively. Therefore, the Li–Li symmetric cell constructed with LiRLIA can operate at a high current density/capacity of 5 mA cm−2/5 mAh cm−2 for almost 1000 h. 相似文献
104.
105.
The influence of yttrium on oxide scale growth and adherence 总被引:5,自引:0,他引:5
Alloys and coatings for high-temperature service are designed to form selectively chromia scales, alumina scales, or, to a limited extent, silica scales upon exposure to the environment. For such oxide scales to be protective, they should be both slow growing and adherent. It turns out that the addition of yttrium to such alloys can often impart both characteristics to the oxide scale. However, the actual operating mechanisms continue to be a matter of controversy among researchers in the area of oxidation. In the present study, the growth and adherence of alumina and chromia scales on alloys containing yttrium, either as an oxide dispersion or as an intermetallic phase, have been investigated in conjunction with detailed oxide scale characterization using the techniques of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and secondary ion mass spectrometry (SIMS). The results of the study are used for critical assessment of the proposed mechanisms, especially the more recent ones, and to suggest some new mechanisms for adherence. 相似文献
106.
The surfaces of air-oxidized Pd-15Rh alloys have been examined by X-ray photoelectron spectroscopy (XPS) and by Raman spectroscopy. The XPS results indicate that the near-surface region of samples oxidized in the temperature range 1075 to 1125 K contains Pd in both the +2 and +1 oxidation states and Rh in the +3 oxidation state. The ratio of Pd (I) to Rh (III) is found to be 11. Raman spectra confirm that two Pd-containing phases, PdO and PdRhO2, are present in the near-surface region and eliminate the possibility that Rh2O3 is present. Also, a resonant Raman effect is observed in anhydrous PdO for exciting wavelengths in the vicinity of 500 nm. 相似文献
107.
108.
用液态快淬法制备非晶合金条带时,通过加入15—30%的B与Si等类金属含量是形成非晶状态的必要条件。但是,由于Si与B等类金属元素的加入,使非晶态合金的磁性受到明显的影响。本文实验研究了Si与B含量间的相对变化对(Fe_(80)Ni_(20))_(78)Si_(22-x)B_x合金的饱和磁矩、平均原子磁矩与Curie温度的影响关系。利用电子转移模型与分子场近似理论定性的解释了(Fe_(80)Ni_(20))_(78)-Si_(22-x)B_x合金的磁矩(M_s)与Curie温度(T_c)随 相似文献
109.
110.