全文获取类型
收费全文 | 17961篇 |
免费 | 1169篇 |
国内免费 | 827篇 |
专业分类
电工技术 | 378篇 |
综合类 | 556篇 |
化学工业 | 3892篇 |
金属工艺 | 1879篇 |
机械仪表 | 688篇 |
建筑科学 | 136篇 |
矿业工程 | 86篇 |
能源动力 | 945篇 |
轻工业 | 684篇 |
水利工程 | 11篇 |
石油天然气 | 99篇 |
武器工业 | 29篇 |
无线电 | 2969篇 |
一般工业技术 | 6877篇 |
冶金工业 | 269篇 |
原子能技术 | 155篇 |
自动化技术 | 304篇 |
出版年
2024年 | 33篇 |
2023年 | 197篇 |
2022年 | 167篇 |
2021年 | 324篇 |
2020年 | 314篇 |
2019年 | 337篇 |
2018年 | 402篇 |
2017年 | 493篇 |
2016年 | 498篇 |
2015年 | 551篇 |
2014年 | 709篇 |
2013年 | 1118篇 |
2012年 | 1075篇 |
2011年 | 1726篇 |
2010年 | 1244篇 |
2009年 | 1276篇 |
2008年 | 1161篇 |
2007年 | 1234篇 |
2006年 | 1082篇 |
2005年 | 781篇 |
2004年 | 782篇 |
2003年 | 685篇 |
2002年 | 658篇 |
2001年 | 520篇 |
2000年 | 438篇 |
1999年 | 361篇 |
1998年 | 328篇 |
1997年 | 285篇 |
1996年 | 195篇 |
1995年 | 177篇 |
1994年 | 146篇 |
1993年 | 111篇 |
1992年 | 122篇 |
1991年 | 107篇 |
1990年 | 73篇 |
1989年 | 46篇 |
1988年 | 36篇 |
1987年 | 29篇 |
1986年 | 24篇 |
1985年 | 25篇 |
1984年 | 15篇 |
1983年 | 9篇 |
1982年 | 11篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1976年 | 7篇 |
1975年 | 7篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
82.
S Kasiviswanathan P S Asoka Kumar B K Mathur K L Chopra 《Bulletin of Materials Science》1996,19(2):411-416
Surface structure of thin silver films (200 Å) on two technologically important films, indium tin oxide (ITO) and aluminium oxide, has been studied using scanning tunneling microscope. ITO films were prepared by reactive electron beam evaporation. Aluminium oxide films were prepared by oxidizing 2000 Å thick aluminium films evaporated on to H2 terminated single crystal silicon substrates. The surface structure of silver on ITO and aluminium oxide appeared to be same and was characteristic of Stranski-Krastanov type. The observed asymmetry in the island shape was attributed to the anisotropic nature of the strain fields surrounding the nucleation centres. 相似文献
83.
含淀粉聚乙烯膜的时控光降解研究 总被引:2,自引:0,他引:2
使用复合光降解剂,得到了可光降解的生物降解膜。对膜的光降解进行了考察,并对影响光降解的因素进行了讨论,结果表明,我们所制得的膜是一种较好的时控光降解膜。 相似文献
84.
A. Benati M.A. Butturi C. Capperdoni M.C. Carotta G. Martinelli M. Merli L. Passari G. Sartori R. Van Steenwinkel G.M. Youssef 《Solar Energy Materials & Solar Cells》1996,43(2):183
The newly developed ingot growing techniques, as the three-grain and the columnar multigrain ingot processes, are now offering the possibility of slicing thinner wafers (≤ 100 μm). In this paper we present the results obtained on p type large area (≥ 100 cm2) and 100 μm thick wafers by using both conventional and reverse cell manufacturing technologies.The conventional cells are provided with aluminium or boron BSF plus screen-printed silver mirror or a silver-aluminium net; the reverse cells have a FSF and the deep back junction completely covered by a screen-printed or CVD silver layer.The constructing parameters have been chosen on the base of one and two dimensions modeling and both raw material and devices have been completely characterized.This work shows that very thin wafers do not introduce serious problems for the conventional manufacturing of solar cells. The efficiencies of the normal and of the reverse cells are found to be comparable and are of the same order than those of thicker cells, however at a significant lower cost. The main obtained result has to be related to the demonstration of a cell manufacturing feasibility starting from very thin wafers. 相似文献
85.
扫描电子显微研究表明,化学汽相沉积的金刚石薄膜中晶粒大小比较均匀。但随着沉积时间和薄膜厚度的增加,晶粒逐渐变大,且每一层内,存在少量的大金刚石颗粒,讨论了晶粒尺寸变化和大晶粒形成的原因和机制。 相似文献
86.
The use of thin film grids coated on surfaces is described in relation to the determination of deformations in doubly curved shells. The technique is called the coating film moiré interference method and employs a laser holographic approach. 相似文献
87.
Fusae Nakanishi 《Polymer International》1992,27(3):237-241
Preparation of photoreactive Langmuir-Blodgett (LB) films was carried out using polymers/oligomers prepared from long-chain dialkyl esters of di-and tetra-olefins and having cyclobutane rings in the main chain. These polymers/oligomers formed stable monolayers on a water surface when mixed with arachidic acid. These monolayers could be deposited onto a substrate successfully forming Y-type films. The oligomer LB films were polymerized on irradiation. The polymer LB films showed a photo-reversible process between polymers and oligomers, depending on wavelength of the irradiating light. On the basis of spectral data and molecular weight change, this behaviour was found to be caused by cleavage and formation of cyclobutane rings. 相似文献
88.
Poly(N-vinyl-carbazole) (PVK) thin films doped with bromine has been studied by scanning electron microscopy, X-ray diffraction, infrared absorption, X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR), optical transmission (visible, near ultra violet) and conductivity measurements. The polymer has been doped at room temperature and at 373 K. It is shown by ESR, XPS and optical measurements that a charge transfer complex (CT-complex) is formed between PVK and Br. However, if some bromine acts as dopant of the polymer there is another bromine contribution, which corresponds to bromine covalently bonded to PVK and some only adsorbed. It is also shown by ESR that there is not only polymer doping by bromine but also some partial polymer degradation. Therefore, it can be said that the optimum doping condition of PVK thin films with bromine has been shown to be room temperature post-doping. 相似文献
89.
M. Saaoudi E. Chassaing M. Cherkaoui M. Ebntouhami 《Journal of Applied Electrochemistry》2002,32(12):1331-1336
Electroless NiP films, with 12 to 16 wt % P, were deposited from a moderately acid solution. Thermogravimetric analysis indicates the presence of occluded hydrogen in the layers, which desorbs upon heating. The amount of incorporated hydrogen decreases when the pH of the solution or the nickel sulfate concentration is increased; by contrast it increases with hypophosphite concentration. Cyclic voltammetry, using an electrochemical quartz crystal microbalance, confirms the existence of parasitic reactions, namely the reduction of protons of the solvent during the cathodic process and oxidation of hydrogen during the dissolution of the layers. This behaviour is in qualitative agreement with the proposed reaction scheme. 相似文献
90.
GaN buffer and main layers were grown by the conventional hydride vapor phase epitaxy technique using GaCl3 consecutively. The deposited buffer layers were investigated by atomic force microscopy and X-ray analysis. To examine the behavior of the buffer layers at main layer growth temperature, heat treatment was conducted at 900°C. Based on the results of the buffer layer study, GaN thick films were grown at 1050°C. Optimum deposition conditions of buffer layer from the buffer and main layer studies generally coincided. On the φ scanning pattern, the GaN films grown on (0001) Al2 O3 were single-crystalline. Band-edge emission dominated photoluminescence was observed at room temperature. 相似文献