全文获取类型
收费全文 | 2284篇 |
免费 | 270篇 |
国内免费 | 108篇 |
专业分类
电工技术 | 49篇 |
综合类 | 176篇 |
化学工业 | 251篇 |
金属工艺 | 144篇 |
机械仪表 | 82篇 |
建筑科学 | 319篇 |
矿业工程 | 94篇 |
能源动力 | 137篇 |
轻工业 | 54篇 |
水利工程 | 123篇 |
石油天然气 | 168篇 |
武器工业 | 7篇 |
无线电 | 360篇 |
一般工业技术 | 474篇 |
冶金工业 | 52篇 |
原子能技术 | 25篇 |
自动化技术 | 147篇 |
出版年
2024年 | 9篇 |
2023年 | 79篇 |
2022年 | 40篇 |
2021年 | 70篇 |
2020年 | 88篇 |
2019年 | 90篇 |
2018年 | 81篇 |
2017年 | 81篇 |
2016年 | 81篇 |
2015年 | 97篇 |
2014年 | 129篇 |
2013年 | 143篇 |
2012年 | 142篇 |
2011年 | 159篇 |
2010年 | 114篇 |
2009年 | 124篇 |
2008年 | 134篇 |
2007年 | 142篇 |
2006年 | 133篇 |
2005年 | 96篇 |
2004年 | 100篇 |
2003年 | 75篇 |
2002年 | 70篇 |
2001年 | 42篇 |
2000年 | 45篇 |
1999年 | 55篇 |
1998年 | 43篇 |
1997年 | 37篇 |
1996年 | 25篇 |
1995年 | 15篇 |
1994年 | 22篇 |
1993年 | 16篇 |
1992年 | 18篇 |
1991年 | 12篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有2662条查询结果,搜索用时 31 毫秒
51.
High‐Performance Polymer Tandem Solar Cells Employing a New n‐Type Conjugated Polymer as an Interconnecting Layer 下载免费PDF全文
52.
The formation of all‐organic dual spin valves (DSVs) with three organic spin‐selective layers, that is, spin‐injection, spin‐detection, and an additional spin‐filtering layer at the intermediate, is reported. As spin‐selective layers, manganese‐ and cobalt phthalocyanines, which are well‐known single‐molecule magnets, are used in their immobilized forms, so that all‐organic DSVs can be prefabricated for characterization. The three spin‐selective layers have provided four configurations with at most two spin‐flip interfaces enforcing spin‐flipping at the two nonmagnetic organic spacer layers, for which copper phthalocyanine is used. Since a couple of the four configurations have exhibited similar resistivities, the degeneracy in the resistive‐states is broken through asymmetric spin‐injection and spin‐detection layers and also through asymmetric thickness of the nonmagnetic spacer layers. When both the spin‐flip interfaces are made operative independently, a 2‐bit logic with four distinct resistive states can be achieved. 相似文献
53.
The corrosion behavior of 2A02 Al alloy under simulated marine atmospheric environment has been studied using mass-gain, scanning electron microscope/energy dispersive spectroscopy (SEM/EDS), laser scanning confocal microscopy, X-ray diffraction spectroscopy and localized electrochemical methods. The results demonstrate that the relationship between the corrosion induced mass-gain and the corrosion time is in accordance with the power rule. The mass-gain increases gradually during the corrosion time, while the corrosion rate decreases. With ongoing of the corrosion, corrosion products film changed from a porous to a compact structure. The various spectroscopic data show that the corrosion products films composed mainly of Al(OH)3, Al2O3 and AlCl3. The electrochemical corrosion behavior of the 2A02 Al alloy was studied by electrochemical impedance spectroscopy (EIS). 相似文献
54.
研究了并行多层快速多极子算法(MLFMA)的分布层,提出了一种衡量其负载不均衡程度的方法,并在此基础上提出了分布树的一种新的构造算法。通过预先估算按分布层的不同层均分所得分布层的负载不均衡度,选取了一种负载不均衡度较小的方法来构造分布树。实验结果表明,该算法相比传统的按分布层的最细层均分所得分布树的算法,能更为有效地提高整个多层快速多极子算法的并行效率。 相似文献
55.
A method of generating modified advancing layers mesh is proposed. In this paper the mesh generation process of semi-unstructured prismatic/tetrahedral mesh is presented for relatively thin three-dimensional geometries with variable thickness, as in the case of injection molding analysis. Prismatic meshes are generated by offsetting initial surface triangular meshes. During the mesh generation process, mesh quality is efficiently improved with the use of a new node relocation method. Finally, tetrahedral meshes are automatically generated in the rest of the domain. The mesh generating capability of the proposed algorithm is demonstrated with the several practical test cases. 相似文献
56.
57.
用Java开发CORBA式应用程序 总被引:1,自引:0,他引:1
采用Java与CORBA组合方式编写客户机 /服务器应用程序 ,使其应用程序功能更强、更加灵活。这样既可允许开发者利用已有的代码保护投资 ,另一方面又可充分发挥Java编程语言的优势 ,利用JDBC获得相关信息 ,该方法将用CORBA生成一个真正的三层应用程序。 相似文献
58.
Lachezar Komitov 《Journal of the Society for Information Display》2008,16(9):919-925
Abstract— The solid‐surface/liquid‐crystal interactions, defining the field‐free alignment of the liquid crystal in conventional liquid‐crystal displays, are playing a vital role in their optical appearance and performance. Nano‐scale changes in the solid‐surface structure induced by light have been recently shown to affect the anchoring strength and the easy‐axis direction. Fine tuning of the anchoring strength is also demonstrated by nano‐structuring of the Langmuir‐Blodgett monolayer employed as liquid‐crystal alignment layers promoting homeotropic orientation. On the basis of nano‐engineering of the surface alignment properties, two novel alignment concepts have been introduced: electrically commanded surfaces (ECS) and high‐performance alignment layers (HiPAL). Nano‐structured polymers related to these concepts have been designed, synthesized, and used as materials for alignment layers in LCDs. ECS materials belong to the category of active alignment materials designed to mediate switching of the liquid crystal, whereas the HiPAL materials make possible the control of the molecular tilt angle in a broad range, from 0° to 90°, and they seem to enable the control of the anchoring strength as well. The nano‐structured alignment materials are strong candidates for implementation in a new generation of advanced liquid‐crystal displays and devices. 相似文献
59.
GIS域状图层可交换文件的C++编程转换——以ARC/INFO向MapInfo转换为例 总被引:1,自引:1,他引:0
域状图是GIS处理或操作的基本对象之一,大量复杂的域状图层靠备拓扑运算功能的GIS自动生成,编码严谨、档注完备,是单机和网络上数据分析可视化应用急需的信息源。为了信息共享,不同GIS平台之间,GIS与GIS应用软件之间常进行可交换文件的格式转换,以ARC/INFO向MapInfo文件转换为例,通过简析它们相应的文件结构,简介了C++环境下的数据转换编程思路、流程、相关的数据结构和解决方法,为日常办公电子表格应用中的区域状图层或图件自动插入奠定了基础。 相似文献
60.
Study of Nano-Porous Silicon with Low Thermal Conductivity as Thermal Insulating Material 总被引:1,自引:0,他引:1
V. Lysenko Ph. Roussel B. Remaki G. Delhomme A. Dittmar D. Barbier V. Strikha C. Martelet 《Journal of Porous Materials》2000,7(1-3):177-182
Recently discovered phenomenon of extremely low thermal conductivity of nano-porous silicon (nano-PS) is discussed in detail. A theoretical model describing specific mechanisms of heat transport in as-prepared and oxidized nano-PS layers is described. The theoretical estimations are in a good agreement with experimental data obtained earlier. The low thermal conductivity values allow to use this promising material as thermal insulator in microsensors and microsystems. To ensure an efficient thermal isolation, a nano-PS layer has to be as thick as possible and mechanically stable. We describe here the procedures to form thick (up to 200 m) and stable nano-PS layers. Distribution of Si oxidized fraction along the layer thickness after thermal oxidation in dry O2 atmosphere at 300°C during 1 h is studied. 相似文献