全文获取类型
收费全文 | 59063篇 |
免费 | 6000篇 |
国内免费 | 2812篇 |
专业分类
电工技术 | 749篇 |
技术理论 | 4篇 |
综合类 | 3629篇 |
化学工业 | 29624篇 |
金属工艺 | 2187篇 |
机械仪表 | 1116篇 |
建筑科学 | 1611篇 |
矿业工程 | 736篇 |
能源动力 | 1416篇 |
轻工业 | 3458篇 |
水利工程 | 296篇 |
石油天然气 | 3254篇 |
武器工业 | 1372篇 |
无线电 | 4964篇 |
一般工业技术 | 9511篇 |
冶金工业 | 1152篇 |
原子能技术 | 358篇 |
自动化技术 | 2438篇 |
出版年
2024年 | 101篇 |
2023年 | 1047篇 |
2022年 | 946篇 |
2021年 | 1714篇 |
2020年 | 1753篇 |
2019年 | 1711篇 |
2018年 | 1611篇 |
2017年 | 1834篇 |
2016年 | 2063篇 |
2015年 | 2197篇 |
2014年 | 3467篇 |
2013年 | 3390篇 |
2012年 | 4051篇 |
2011年 | 4696篇 |
2010年 | 3568篇 |
2009年 | 3780篇 |
2008年 | 3139篇 |
2007年 | 4036篇 |
2006年 | 3658篇 |
2005年 | 3274篇 |
2004年 | 2660篇 |
2003年 | 2429篇 |
2002年 | 2012篇 |
2001年 | 1681篇 |
2000年 | 1469篇 |
1999年 | 1117篇 |
1998年 | 874篇 |
1997年 | 672篇 |
1996年 | 551篇 |
1995年 | 474篇 |
1994年 | 425篇 |
1993年 | 317篇 |
1992年 | 283篇 |
1991年 | 188篇 |
1990年 | 152篇 |
1989年 | 103篇 |
1988年 | 65篇 |
1987年 | 65篇 |
1986年 | 43篇 |
1985年 | 49篇 |
1984年 | 43篇 |
1983年 | 32篇 |
1982年 | 29篇 |
1981年 | 16篇 |
1980年 | 15篇 |
1979年 | 20篇 |
1978年 | 11篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1951年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 20 毫秒
101.
A.L. Pan H.G. ZhengZ.P. Yang F.X. Liu Z.J. Ding Y.T. Qian 《Materials Research Bulletin》2003,38(5):789-796
Small Ag particles or clusters dispersed mesoporous SiO2 composite films were prepared by a new method: First the matrix SiO2 films were prepared by sol-gel process combined with the dip-coating technique, then they were soaked in AgNO3 solutions followed by irradiation of γ-ray at room temperature and in ambient pressure. The structures of these films were examined by X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), and optical absorption spectroscopy. It has been shown that the Ag particles grown within the porous SiO2 films are very small, and they are isolated and dispersed from each other with very narrow size distributions. With increasing the soaking concentration and an additional annealing, an opposite peakshift effect of the surface plasmon resonance (SPR) was observed in the optical absorption measurements. 相似文献
102.
103.
P. CRISP T.J. WICKS D. BRUER E.S. SCOTT 《Australian Journal of Grape and Wine Research》2006,12(3):203-211
Grapevine powdery mildew ( Erysiphe necator) affects grape yield and fruit quality worldwide. Managers of conventional vineyards rely mainly on synthetic fungicides and sulfur to control powdery mildew, while in organic vineyards sulfur is the main control agent, often in rotation with canola-based oils, bicarbonates and biological control agents. The efficacy of those materials has not been evaluated critically under field conditions in Australia. Accordingly, a range of materials showing most promise in previous greenhouse trials (Crisp et al. 2006 Australian Journal of Grape and Wine Research 12 , pp. 192–202) were assessed via field trials in commercial vineyards. Applications of either milk or whey (alone, or mixed with a canola oil-based product), as well as applications of potassium bicarbonate (commercial formulation), all reduced the severity of powdery mildew compared with untreated vines. Eight applications of a 1:10 dilution of milk, 45 g/L whey powder or programs comprising rotations of potassium bicarbonate plus oil and whey, applied at 10–14 day intervals, reduced the severity of powdery mildew to levels not significantly different from that on vines sprayed with sulfur (wettable powder, 3–6 g/L). However, the relative control of powdery mildew by the test materials in field trials was dependent on the susceptibility of the grapevine cultivar and the extent of spray coverage achieved. In vineyards where highly susceptible cultivars were planted, and spray coverage was compromised, the resultant control of powdery mildew was reduced; and sometimes to commercially unacceptable levels. 相似文献
104.
105.
106.
107.
108.
Electro-organic synthesis without supporting electrolyte: Possibilities of solid polymer electrolyte technology 总被引:1,自引:0,他引:1
J. Jörissen 《Journal of Applied Electrochemistry》2003,33(10):969-977
The application of ion exchange membranes as solid polymer electrolytes (SPE) in fuel cells is state-of-the-art. This technology needs no supporting electrolyte; consequently it can be applied for electro-organic syntheses in order to save process steps. In this case the process is not predetermined to a maximized energy efficiency so that the selection of the cell design, of the electrode materials and of the operating conditions can be focused on a high selectivity of the electrode reactions. The electro-osmotic stream, which is caused by the solvation shells of the ions during their migration through the membrane, and hence is a typical property of SPE technology, has a significant effect on the electrode reactions. It generates enhanced mass transfer at the electrodes, which is beneficial for reaction selectivity. It can be influenced by the choice of, and possibly by the preparation of, the membrane. An additional remarkable advantage of SPE technology is the exceptional long durability of oxide coated electrodes. By combination of several process engineering methods stable operation of SPE cells has been realized, even for examples of non-aqueous reaction systems. Experiments up to 6000 h duration and in cells of up to 250 cm2 membrane area show the potential for industrial application. 相似文献
109.
不同表面预处理对有机电致发光显示器性能的影响 总被引:1,自引:1,他引:0
从生产角度研究了基板表面的预处理工艺对OLED性能的影响,分别用UVOzone、氧Plasma以及两者相结合的方式对基板进行表面处理,并按照生产工艺制作器件,从接触角、方阻以及光电特性等测试结果对各种表面处理的样品进行比较。结果表明以上处理都改善了器件性能,不同程度提高了器件的清洁度、亮度和发光效率,其中UVOzone和氧Plasma结合的方式处理效果最为显著,器件在10V时亮度达到79920cd/m2,比其他两种处理方式亮度提高约25%。 相似文献
110.
Organic solar cells are a promising route towards large‐area and low‐price photovoltaic systems. The devices are composed of at least two layers: the hole‐transport layer and the electron‐transport layer. The light absorption can occur in one or both layers. At the interface of the layers the excitons are separated into charge carriers, and every layer deals with one type of carrier. Higher efficiencies of the separation process can be obtained by using a mixed layer containing both materials to obtain a very high interface area. Although the structure of the mixed layers used plays a crucial role for the device performance, until now the morphologies have not been elucidated. In order to correlate physical and optical findings with structure and morphology for the materials in question, electron microscopy experiments were performed on the single components as well as on the layer systems. The conventional electron microscope is a poor phase microscope. As consequence, weak‐phase objects like organic molecules have to be stained or imaged under strong defocus to produce an observable contrast. Artifacts caused by chemical staining and the appearance of Fresnel diffraction using the defocus technique represent the main problems of conventional microscopy. These artifacts can be avoided using electron holography. Holograms of ultrathin sections of thin layers composed of organic dye molecules were recorded. Subsequently, the phase images were reconstructed. In this manner, we succeeded in obtaining high‐contrast electron micrographs without applying staining or defocus. In addition, holograms of crystalline C60 and zinc phthalocyanine were successfully recorded. Holography has been shown to be a useful tool to image beam‐sensitive and weak‐phase objects without artifacts. 相似文献