全文获取类型
收费全文 | 7620篇 |
免费 | 488篇 |
国内免费 | 174篇 |
专业分类
电工技术 | 205篇 |
综合类 | 255篇 |
化学工业 | 1464篇 |
金属工艺 | 254篇 |
机械仪表 | 221篇 |
建筑科学 | 465篇 |
矿业工程 | 143篇 |
能源动力 | 157篇 |
轻工业 | 725篇 |
水利工程 | 114篇 |
石油天然气 | 169篇 |
武器工业 | 47篇 |
无线电 | 807篇 |
一般工业技术 | 1165篇 |
冶金工业 | 1119篇 |
原子能技术 | 67篇 |
自动化技术 | 905篇 |
出版年
2024年 | 27篇 |
2023年 | 97篇 |
2022年 | 224篇 |
2021年 | 315篇 |
2020年 | 173篇 |
2019年 | 168篇 |
2018年 | 202篇 |
2017年 | 240篇 |
2016年 | 205篇 |
2015年 | 265篇 |
2014年 | 287篇 |
2013年 | 382篇 |
2012年 | 391篇 |
2011年 | 475篇 |
2010年 | 396篇 |
2009年 | 369篇 |
2008年 | 438篇 |
2007年 | 371篇 |
2006年 | 339篇 |
2005年 | 253篇 |
2004年 | 189篇 |
2003年 | 182篇 |
2002年 | 162篇 |
2001年 | 158篇 |
2000年 | 149篇 |
1999年 | 186篇 |
1998年 | 279篇 |
1997年 | 202篇 |
1996年 | 150篇 |
1995年 | 97篇 |
1994年 | 103篇 |
1993年 | 99篇 |
1992年 | 60篇 |
1991年 | 48篇 |
1990年 | 51篇 |
1989年 | 50篇 |
1988年 | 47篇 |
1987年 | 43篇 |
1986年 | 45篇 |
1985年 | 35篇 |
1984年 | 35篇 |
1983年 | 33篇 |
1982年 | 25篇 |
1981年 | 12篇 |
1980年 | 22篇 |
1979年 | 15篇 |
1978年 | 18篇 |
1977年 | 18篇 |
1976年 | 37篇 |
1974年 | 14篇 |
排序方式: 共有8282条查询结果,搜索用时 10 毫秒
61.
Novel Air Stable Organic Radical Semiconductor of Dimers of Dithienothiophene,Single Crystals,and Field‐Effect Transistors 下载免费PDF全文
62.
Researchers on organisational ambidexterity have proposed several solutions to address the potential conflicts between exploration activities and exploitation activities. Unlike simultaneous ambidexterity, sequential ambidexterity – defined as temporal switching between exploration and exploitation – has not been examined fully, and the conditions under which this temporal switching can be successful are unclear. This paper proposes the concept of temporal switching capability to better understand the process by which sequential ambidexterity is executed. In addition, we hypothesise that performance effects are contingent upon firm-specific factors: a firm’s business strategy and absorptive capacity. Utilising three sources of data – a secondary database, annual reports and a survey administered to 145 firms in the electronics industry with 10-year observations – we find support for our hypotheses. The results show that the temporal switching capability positively relates to new product performance and that business strategy type and absorptive capacity have moderating effects. The results are meaningful in both theory and practice. 相似文献
63.
Shen Lang Poudel Nirakar Gibson George N. Hou Bingya Chen Jihan Shi Haotian Guignon Ernest Page William D. Pilar Arturo Cronin Stephen B. 《Nano Research》2018,11(4):2310-2314
Nano Research - We report plasmon resonant excitation of hot electrons in a photodetector based on a metal/oxide/metal (Au/Al2O3/graphene) heterostructure. In this device, hot electrons, excited... 相似文献
64.
P. Jess U. Hubler H. P. Lang H. -J. Güntherodt K. Lüders E. V. Antipov 《Journal of Low Temperature Physics》1996,105(5-6):1243-1248
The superconducting energy gap distribution of poly crystalline HgBa2CuO4+ samples of differing oxygen doping levels (Tc = 94 K and Tc = 96 K) is determined by scanning tunneling spectroscopy (STS) using a low temperature scanning tunneling microscope (STM). From histograms of energy gap values the presence of two distinct energy gaps is inferred (1=8.5±1.6meV and 2=15.1±1.4meV). We attribute the different gaps to different crystallographic faces, implying a non-BCS electron-electron pairing mechanism. 相似文献
65.
H. P. Lang A. Erb P. Jess U. Hubler H. -J. Güntherodt 《Journal of Low Temperature Physics》1996,105(5-6):1373-1378
Very pure YBa2Cu3O7– (YBCO) single crystals grown in BaZrO3 crucibles are studied in the as-grown and the oxidized state by scanning force (SFM), friction force (FFM) and scanning tunneling microscopies (STM). The images show clean terraces with step-heights of one unit cell along YBCO(001), i.e. 1.2 nm. Only close to step edges is material contrast observed by FFM indicating traces af flux. Some crystal surfaces exhibit over-layer features, such as star-like, ribbon-like and checkerboard-like structures, which exhibit friction contrast implying the presence of different materials on the surface. Tunneling spectroscopy at 4.7 K in high vacuum reveals a superconducting energy gap of 2 26 me V. 相似文献
66.
随着网络的不断发展,传统的TCP拥塞控制机制已经不能很好地适应现有的网络环境;文中在分析了不同反馈信息的价值的基础上提出了一种新的基于路由器反馈的拥塞控制机制RSCP,部署方便,不需要额外包头;该机制创造性地提出了信号包的方法与路由器交换信息,并以公平带宽和公平剩余带宽为反馈信息,在以公平带宽为基点的基础上根据公平剩余带宽的变化调整发送速率,同时采用快速启动机制使连接能够快速达到公平带宽;仿真实验证明RSCP在单瓶颈网络中能取得高利用率、低队列长度和零丢包以及良好的收敛性能. 相似文献
67.
Haptic texture represents the fine-grained attributes of an object's surface and is related to physical characteristics such as roughness and stiffness. We introduce an interactive and mobile scanning system for the acquisition and synthesis of haptic textures that consists of a visually tracked handheld touch probe. The most novel aspect of our work is an estimation method for the contact stiffness of an object based solely on the acceleration and forces measured during stroking of its surface with the handheld probe. We establish an experimental relationship between the estimated stiffness and the contact stiffness observed during compression. We also measure the height-displacement profile of an object's surface enabling us to generate haptic textures. We show an example of mapping the textures on to a coarse surface mesh obtained with an image-based technique, but the textures may also be combined with coarse surface meshes obtained by manual modeling. 相似文献
68.
69.
70.
The emergence of the Internet as a global communication infrastructure has dramatically reduced interaction costs within and across organizations, with significant impact on inter-organizational relationships, vertical industry structures, and markets. More recently, service-oriented architectures (SOA) and Web services have introduced the next paradigm shift and foster the idea of dynamic business networks with quick connect and disconnect relationships. However, little research has systematically analyzed how companies leverage SOA to improve their inter-organizational relationships and reshape their business networks. In addition, the mature research stream on inter-organizational information systems (IOS) has not yet sufficiently considered SOA. In order to close this gap, our research seeks to improve the fundamental understanding of how SOA is applied in business networks and how it differs from prior forms of IOS. Using an exploratory research approach, we investigate 33 SOA cases to identify focus areas and patterns of SOA adoption in business networks. Our case analysis builds on a multi-dimensional classification scheme which we derived from prior literature. While our empirical findings do not confirm all promising propositions related to SOA, they underline the specific contribution of SOA compared to prior forms of IOS. We conclude by suggesting five clusters of SOA adoption in the inter-organizational domain, each of those introducing new aspects in the coordination of distributed business networks. 相似文献