全文获取类型
收费全文 | 2032篇 |
免费 | 201篇 |
国内免费 | 131篇 |
专业分类
电工技术 | 39篇 |
综合类 | 105篇 |
化学工业 | 473篇 |
金属工艺 | 453篇 |
机械仪表 | 36篇 |
建筑科学 | 14篇 |
矿业工程 | 48篇 |
能源动力 | 129篇 |
轻工业 | 43篇 |
石油天然气 | 18篇 |
武器工业 | 7篇 |
无线电 | 303篇 |
一般工业技术 | 522篇 |
冶金工业 | 100篇 |
原子能技术 | 34篇 |
自动化技术 | 40篇 |
出版年
2024年 | 2篇 |
2023年 | 45篇 |
2022年 | 58篇 |
2021年 | 80篇 |
2020年 | 77篇 |
2019年 | 74篇 |
2018年 | 76篇 |
2017年 | 90篇 |
2016年 | 89篇 |
2015年 | 94篇 |
2014年 | 118篇 |
2013年 | 118篇 |
2012年 | 122篇 |
2011年 | 171篇 |
2010年 | 123篇 |
2009年 | 146篇 |
2008年 | 84篇 |
2007年 | 135篇 |
2006年 | 105篇 |
2005年 | 84篇 |
2004年 | 64篇 |
2003年 | 85篇 |
2002年 | 71篇 |
2001年 | 45篇 |
2000年 | 49篇 |
1999年 | 25篇 |
1998年 | 39篇 |
1997年 | 22篇 |
1996年 | 18篇 |
1995年 | 14篇 |
1994年 | 11篇 |
1993年 | 6篇 |
1992年 | 8篇 |
1991年 | 7篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1987年 | 1篇 |
1984年 | 2篇 |
1979年 | 2篇 |
排序方式: 共有2364条查询结果,搜索用时 46 毫秒
51.
《Calphad》2014
Using MHTC 96 Setaram high temperature drop calorimeter, partial and integral enthalpies of mixing of liquid alloys were determined in the Ag–Ga, Cu–Ga and in the ternary Ag–Cu–Ga system. The ternary alloys were investigated along two cross-sections at two different temperatures: 1128 K and 1273 K, respectively. Experimental data were used to find ternary interaction parameters by applying the Redlich–Kister–Muggianu model for substitutional solutions, and a full set of parameters describing the concentration dependence of the enthalpy of mixing was derived. The experimental data indicate that the heat of mixing in this system is slightly temperature dependent, at least in the measured temperature range. 相似文献
52.
Yuhao Yang Enzhou Liu Hongzhe Dai Limin Kang Huitong Wu Jun Fan Xiaoyun Hu Hanchen Liu 《International Journal of Hydrogen Energy》2014
TiO2-graphene (P25-GR, PG) nanocomposite was fabricated with P25 and graphite oxide through a hydrothermal method, and then Ag nanoparticles (Ag NPs) was assembled in P25-GR (Ag-P25-GR, APG) under microwave-assisted chemical reduction. The prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), transmission electron microscopy (TEM), photoluminescence spectrum (PL), UV–vis absorption spectrum (UV–vis) and Raman spectrum, respectively. The results showed that Ag NPs were well dispersed on the surface of PG with metallic state. The ternary Ag-P25-GR (APG) nanocomposites possessed the extended light absorption range and more efficient charge separation properties compared to binary P25-GR (PG). Methylene blue photodegradation experiment proved that surface plasmon resonance (SPR) phenomenon had an effect on photoreaction efficiency. The corresponding hydrogen evolution rate of APG prepared with 0.002 M AgNO3 solution was 7.6 times than pure P25 and 2.7 times than PG in the test condition. The improved photocatalytic performance can be attributed to the presence of GR and SPR effect, leading to the longer lifetime of photo-generated electron–hole pairs and faster interfacial charge transfer rate. This work indicates that the photoactivity of ternary GR-based nanocomposites is superior to the binary one. We expected our work could give a new train of thought on exploration of GR-based nanocomposites. 相似文献
53.
54.
55.
Zhou Zeyuan Yu Shuxiang Lin Yuan Zhang Ming Cai Hanhui Shang Hongtao He Wenxi 《稀有金属材料与工程》2011,40(2):215-219
Nanostructured Ag with different morphologies and structures was prepared by replacement reaction (Zn versus AgNO3). The influence of AgNO3 concentration on the growth speed, the morphology and the structure of the nanostructured Ag was investigated. Experimental results show that the growth speed, morphologies and structures of the nanostructured Ag strongly depend on AgNO3 concentration and reaction time. The growth speed is mainly dependent on the AgNO3 concentration; the higher the concentration, the faster the growth speed. When the AgNO3 concentration is 5 mmol/L, Ag fractal forms at the beginning stage, but the fractal transforms to dendrite consisting of nanoparticles and to monocrystal at last as the reaction proceeds. When the concentration is in the range of 20-100 mmol/L, the products are all Ag dendrites, but the dendrites consist of nanoparticles when the concentration is below 40 mmol/L while they are monocrystal when the concentration is above 60 mmol/L. Ag nanostructures with different morphologies and structures can be prepared by controlling AgNO3 concentration and reaction time. 相似文献
56.
57.
采用大气熔炼与形变原位复合的方法制备形变Cu-10Fe-3Ag原位复合材料。在不同温度时效6 h后,用SEM观察分析材料的显微组织;用XRD测定晶面间距的变化,分析合金元素Ag在时效过程中的行为规律和作用机制。结果表明:Ag能够促进γ-Fe在Cu基体中的时效析出,同时降低Fe纤维的热稳定性;随着时效温度的升高,形变Cu-10Fe-3Ag复合材料的硬度和导电率都是先增加后降低,在475℃时效6 h后,导电率达到58.4%IACS。合金的断口全是韧性断裂,随着时效温度的升高,韧窝变小。 相似文献
58.
59.
For development of a lead-free composite solder for advance electrical components, lead-free Sn3.5Ag0.5Cu solder was produced by mechanically mixing 0.5 wt.% TiO2 nanopowder with Sn3.5Ag0.5Cu solder. The morphology and growth kinetics of the intermetallic compounds that formed during the soldering reactions between Sn3.5Ag0.5Cu solder with intermixed TiO2 nanopowder and Cu substrates at various temperatures ranging from 250 to 325 °C were investigated. A scanning electron microscope (SEM) was used to quantify the interfacial microstructure at each processing condition. The thickness of interfacial intermetallic layers was quantitatively evaluated from SEM micrographs using imaging software. Experimental results show that a discontinuous layer of scallop-shaped Cu-Sn intermetallic compounds formed during the soldering. Kinetics analysis shows that the growth of such interfacial Cu-Sn intermetallic compounds is diffusion controlled with an activation energy of 67.72 kJ/mol. 相似文献
60.
利用扫描电子显微镜(SEM)和透射电子显微镜(TEM)研究了Sn3.8Ag0.7Cu(Sn37Pb)/Cu焊点在时效过程中的界面金属间化合物(IMC)形貌和成份。结果表明:150℃高温时效50、100、200、500h后,Sn3.8Ag0.7Cu(Sn37Pb)/Cu焊点界面IMC尺寸和厚度增加明显,IMC颗粒间的沟槽越来越小。50h时效后界面出现双层IMC结构,靠近焊料的上层为Cu6Sn5,邻近基板的下层为Cu3Sn。之后利用透射电镜观察了Sn37Pb/Ni和Sn3.8Ag0.7Cu/Ni样品焊点界面,结果显示,焊点界面清晰,IMC晶粒明显。 相似文献