全文获取类型
收费全文 | 26757篇 |
免费 | 2528篇 |
国内免费 | 1757篇 |
专业分类
电工技术 | 1149篇 |
综合类 | 1881篇 |
化学工业 | 3908篇 |
金属工艺 | 2682篇 |
机械仪表 | 997篇 |
建筑科学 | 2491篇 |
矿业工程 | 950篇 |
能源动力 | 1809篇 |
轻工业 | 995篇 |
水利工程 | 766篇 |
石油天然气 | 1702篇 |
武器工业 | 169篇 |
无线电 | 4245篇 |
一般工业技术 | 3730篇 |
冶金工业 | 759篇 |
原子能技术 | 568篇 |
自动化技术 | 2241篇 |
出版年
2024年 | 109篇 |
2023年 | 552篇 |
2022年 | 776篇 |
2021年 | 989篇 |
2020年 | 942篇 |
2019年 | 883篇 |
2018年 | 755篇 |
2017年 | 974篇 |
2016年 | 949篇 |
2015年 | 977篇 |
2014年 | 1437篇 |
2013年 | 1600篇 |
2012年 | 1801篇 |
2011年 | 2055篇 |
2010年 | 1526篇 |
2009年 | 1603篇 |
2008年 | 1535篇 |
2007年 | 1651篇 |
2006年 | 1599篇 |
2005年 | 1317篇 |
2004年 | 1143篇 |
2003年 | 1042篇 |
2002年 | 853篇 |
2001年 | 787篇 |
2000年 | 649篇 |
1999年 | 497篇 |
1998年 | 375篇 |
1997年 | 346篇 |
1996年 | 260篇 |
1995年 | 213篇 |
1994年 | 165篇 |
1993年 | 166篇 |
1992年 | 135篇 |
1991年 | 87篇 |
1990年 | 71篇 |
1989年 | 60篇 |
1988年 | 41篇 |
1987年 | 26篇 |
1986年 | 16篇 |
1985年 | 11篇 |
1984年 | 10篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 14篇 |
1980年 | 3篇 |
1979年 | 8篇 |
1976年 | 3篇 |
1959年 | 4篇 |
1958年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 859 毫秒
61.
Electrochemical investigations on low-Si alloyed steels with Si content ranging from 0.25 to 3.2 wt.% were carried out in a 0.1 M NaCl borate-buffered solution (pH 8.4) in reducing conditions at 90 °C. Silicon as an alloying element was proved to degrade at first the steel ability to passivate. For longer immersion times, protective effects developed more efficiently on the steel containing 3.2 wt.% silicon. Passive layers electrochemically formed in the transpassive domain on the steel containing 3.2% Si were shown to be significantly different from those grown at rest potential. 相似文献
62.
描述了ZnSxSe1-x光盲紫外液晶光阀的结构和工作原理 ,并从器件的电学模型出发 ,着重讨论了整体器件对ZnSxSe1-x光敏层的特殊要求。采用分子束外延技术在ITO导电玻璃上制备了具有 (111)面定向生长结构的ZnSxSe1-x多晶薄膜 ,通过控制反应时的生长参数 ,制备出了符合器件设计要求的光敏层薄膜。室温下 ,该薄膜的紫外 /可见光响应对比度大于10 3 ;响应波长截止边可通过控制薄膜中的Se组分 ,在 (36 0~ 4 10 )nm范围内连续可调 ;薄膜的暗电阻率在 (4 32× 10 9~ 2 0 3×10 11)Ω·m之间 ,并随着晶粒的增大而减小 ;在液晶光阀工作的低频段 (<2 0 0Hz) ,其光 /暗阻抗比在 0 2 2~ 0 36之间。 相似文献
63.
64.
Roberto Leoni Bruno Buonomo Gabriella Castellano Francesco Mattioli Guido Torrioli Luciana Di Gaspare Florestano Evangelisti 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2004,520(1-3):44-47
We discuss the performance, of a normal metal hot electron bolometer (NHEB) that we have measured at 0.3 K. We found that the noise equivalent power was limited by the amplifier noise. To improve the NHEB power response and to make it more robust and reliable we propose to substitute the normal metal with heavily doped silicon. The heavily doped silicon behaves like a metal with lower carrier concentration and has a smaller electron–phonon thermal coupling. We have fabricated superconductor-doped silicon-superconductor contacts (S-Sm-S) and we have used them as thermometers and coolers. 相似文献
65.
Photoluminescence features in a commercial grade cured DGEBA-based epoxy resin have been investigated with as objective to determine which of the material compounds are responsible for cured resin emissions. The origin of the bands has been approached by considering photoluminescence of base resin and hardener taken separately, of their mixture, and in the course of curing. Most of the bands observed in the cured resin could be interpreted based on those found in the components taken separately. Fluorescence of the cured resin appears dominated by two broad bands that are characteristic of the hardener and exhibits a blue shift by up to 30 nm in the course of curing which could be used for cure monitoring purpose of the investigated system. Fluorescence of the base resin is clearly detected in the resin cured with tertiary amine as catalyser. However, it is very weak if the catalyser is not added. Two phosphorescence processes have been isolated in the cured resin, one of them being related to the base resin. Finally, a chemiluminescence spectrum has been recorded in the course of curing, which has been related to either curing-related reactions or to an oxidation process. 相似文献
66.
Farzaneh Fayazpour Bart Lucas Roosmarijn E. Vandenbroucke Stefaan Derveaux Jan Tavernier Sam Lievens Joseph Demeester Stefaan C. De Smedt 《Advanced functional materials》2008,18(18):2716-2723
To obtain more biologically relevant data there is a growing interest in the use of living cells for assaying the biological activity of unknown chemical compounds. Density ‘multiplex’ cell‐based assays, where different cell types are mixed in one well and simultaneously investigated upon exposure to a certain compound are beginning to emerge. To be able to identify the cells they should be attached to microscopic carriers that are encoded. This paper investigates how digitally encoded microparticles can be loaded with cells while keeping the digital code in the microcarriers readable. It turns out that coating the surface of the encoded microcarriers with polyelectrolytes using the layer‐by‐layer (LbL) approach provides the microcarriers with a ‘highly functional’ surface. The polyelectrolyte layer allows the growth of the cells, allows the orientation of the cell loaded microcarriers in a magnetic field, and does not hamper the reading of the code. It has further been shown that the cells growing on the polyelectrolyte layer can become transduced by adenoviral particles hosted by the polyelectrolyte layer. It is concluded that the digitally encoded microparticles are promising materials for use in biomedical and pharmaceutical in‐vitro research where cells are used as tools. 相似文献
67.
68.
苏里格低渗强非均质性气田开发技术对策探讨 总被引:29,自引:2,他引:27
鄂尔多斯盆地苏里格气田储集层具有低渗、强非均质性、中强压敏的特点,气井产能低,稳产期短。根据单井模拟及生产动态分析,气井低产量生产可以降低压敏效应的影响,加强气井低产量生产阶段的管理,有利于合理利用地层能量,提高井控外围低渗区储量动用程度;分层压裂、多层合采可以在纵向上充分动用气井控制储量,增加气井最终累计产气量和稳产时间;地质研究与地震相结合,是提高储集层预测精度和钻井成功率的技术关键;降低成本,争取优惠政策也是提高经济效益的有效途径。 相似文献
69.
首先说明西方国家通信网近年发展变迁情况,然后对IP与WDM的结合使用、光数据网的发展、密集波分多路的应用和光网中通路的保护4个主要方面作了具体说明。 相似文献
70.