首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1719篇
  免费   24篇
  国内免费   2篇
电工技术   13篇
综合类   2篇
化学工业   409篇
金属工艺   11篇
机械仪表   15篇
建筑科学   97篇
能源动力   64篇
轻工业   159篇
水利工程   10篇
石油天然气   1篇
无线电   154篇
一般工业技术   266篇
冶金工业   148篇
原子能技术   9篇
自动化技术   387篇
  2024年   27篇
  2023年   15篇
  2022年   17篇
  2021年   40篇
  2020年   45篇
  2019年   47篇
  2018年   47篇
  2017年   42篇
  2016年   74篇
  2015年   38篇
  2014年   76篇
  2013年   103篇
  2012年   103篇
  2011年   116篇
  2010年   75篇
  2009年   81篇
  2008年   89篇
  2007年   76篇
  2006年   69篇
  2005年   73篇
  2004年   60篇
  2003年   53篇
  2002年   55篇
  2001年   29篇
  2000年   24篇
  1999年   36篇
  1998年   37篇
  1997年   28篇
  1996年   30篇
  1995年   17篇
  1994年   9篇
  1993年   8篇
  1992年   13篇
  1991年   2篇
  1990年   7篇
  1989年   7篇
  1988年   7篇
  1987年   6篇
  1986年   6篇
  1985年   6篇
  1984年   8篇
  1983年   7篇
  1982年   5篇
  1981年   7篇
  1979年   2篇
  1978年   2篇
  1977年   3篇
  1976年   6篇
  1975年   3篇
  1963年   2篇
排序方式: 共有1745条查询结果,搜索用时 0 毫秒
101.
102.
At frequencies beyond 1 GHz, every component of the IC package contributes to the RF performance, whether required or not. In this work, we study the effects of packaging materials namely, the substrate and the globtop/underfill material on RF performance. We have measured interconnects on two area-array CSPs, the ball grid array and the polymer stud grid array using IMEC’s MCM-D technology. The measurements on the package interconnect show that the losses in the package substrate material account for about 50% of the total losses at 1.8 GHz and this drops to less than 20% at 5.2 GHz. The losses due to impedance mismatch dominate the losses especially below 10 GHz and considerable improvement in performance cannot be obtained by using an improved/expensive substrate. The other study is about the influence of globtop/underfill materials on wirebonds (through 3D EM simulations) as well as on standard 50 Ω MCM-D transmission lines (through experiments). While a higher value of dielectric constant of the globtop/underfill material is better on wirebonds, the influence of loss tangent is felt only above values of 0.1. The influence of seven different globtop/undefill materials on 50 Ω transmission lines has been used to extract their dielectric constant and loss tangent values at 30 GHz. These results are very valuable since one can hardly find the properties of globtop/underfill materials beyond 1 GHz.  相似文献   
103.
The notion of pseudorandomness is the theoretical foundation on which to consider the soundness of a basic structure used in some block ciphers. We examine the pseudorandomness of the block cipher KASUMI, which will be used in the next‐generation cellular phones. First, we prove that the four‐round unbalanced MISTY‐type transformation is pseudorandom in order to illustrate the pseudorandomness of the inside round function FI of KASUMI under an adaptive distinguisher model. Second, we show that the three‐round KASUMI‐like structure is not pseudorandom but the four‐round KASUMI‐like structure is pseudorandom under a non‐adaptive distinguisher model.  相似文献   
104.
With the increasing number of processor cores available in modern computing architectures, task or data parallelism is required to maximally exploit the available hardware and achieve optimal processing speed. Current state-of-the-art data-parallel processing methods for decoding image and video bitstreams are limited in parallelism by dependencies introduced by the coding tools and the number of synchronization points introduced by these dependencies, only allowing task or coarse-grain data parallelism. In particular, entropy decoding and data prediction are bottleneck coding tools for parallel image and video decoding. We propose a new data-parallel processing scheme for block-based intra sample and coefficient prediction that allows fine-grain parallelism and is suitable for integration in current and future state-of-the-art image and video codecs. Our prediction scheme enables maximum concurrency, independent of slice or tile configuration, while minimizing synchronization points. This paper describes our data-parallel processing scheme for one- and two-dimensional prediction and investigates its application to block-based image and video codecs using JPEG XR and H.264/AVC Intra as a starting point. We show how our scheme enables faster decoding than the state-of-the-art wavefront method with speedup factors of up to 21.5 and 7.9 for JPEG XR and H.264/AVC Intra coding tools respectively. Using the H.264/AVC Intra coding tool, we discuss the requirements of the algorithm and the impact on decoded image quality when these requirements are not met. Finally, we discuss the impact on coding rate in order to allow for optimal parallel intra decoding.  相似文献   
105.
For building an optical access network, we propose some new hybrid WDM/TDM passive optical network (PON) architectures that use wavelength selective switches (WSSs) at the remote node to improve flexibility, data security and power budget. Through simulations we demonstrate that the switching capabilities of a WSS can provide additional gains in terms of wavelength usage by a better statistical multiplexing. Several WSS-based hybrid WDM/TDM PON variants are proposed and assessed. These architectures are also compared with the more commonly used hybrid WDM/TDM PONs consisting of power splitters and/or arrayed wavelength gratings (AWGs), in terms of cost and power budget.  相似文献   
106.
The notion of fuzzy set cardinality is examined. Zadeh's suggested measure of fuzzy cardinality, the sigma-count, is adopted and shown to generalize classical counting measure. This allows many combinatorial structures and counting techniques to be fuzzified, and hence used in knowledge representation and pattern recognition models. A fuzzy set review is found in the Appendix.  相似文献   
107.
Incineration processes are critical for the environment. SO2 and NOX removal with processes is nowadays commonplace. Up to now, heavy metal were recovered via precipitation. The alternative use of liquid ion exchange techniques offers an easy re-use of the heavy metals, which are obtained as concentrates. A separation process is described, starting from laboratory experiments and ending with pilot plant field tests. A cost comparison for extraction, permeation and precipitation gives the scope of the necessary expenses for such environmentally controlled processes.  相似文献   
108.
The high viscosity of thermoplastic matrices hampers fiber impregnation. This problem can be overcome by using low viscous polymeric precursors such as cyclic butylene terephthalate (CBT® resins), which polymerize to form a thermoplastic matrix. This allows thermoset production techniques, like resin transfer molding (RTM), to be used for the production of textile reinforced thermoplastics. Due to the processing route and more specifically the time-temperature profile, inherent to the RTM process, the crystallites of the matrix consist out of well-defined, thick and well-oriented crystal lamellae. Together with a high overall degree of crystallinity and a low density of tie molecules, these large and perfect crystals cause polymer brittleness. Matrix brittleness lowers the transverse strength of unidirectional composites to below the matrix strength, but leaves the mechanical properties in the fiber direction unaffected. Although not a valid option for the RTM production route, crystallization from a truly random melt and at a sufficiently high cooling rate would substantially improve the ductility.  相似文献   
109.
Organizing for innovation does not present itself as a straightforward exercise. The complexities entailed when implementing an innovation strategy can be related directly to the multitude of objectives it comprises. Recently, several scholars have advanced the notions of semi‐ or quasi‐structures and ambidextrous organizations to handle these multiple requirements. These organizational forms imply the simultaneous presence of different activities, exhibiting differences in technology and market maturation. As a consequence, financial returns will reflect this diversified resource allocation pattern. Moreover, as higher levels of complexity are being introduced; ambidextrous organizations will encounter additional, organizational, costs. Compared to organizations that focus on the most profitable part of the portfolio, ambidextrous organizations – ceteris paribus – tend to be inferior in terms of financial returns. Within this contribution we explore under which conditions ambidextrous organizations can outperform focused firms; considered a prerequisite for their sustainability. In order to do so, we develop an analytical framework depicting the differential value dynamics, focused and ambidextrous firms can enact. Our findings reveal the relevancy of adopting extended time frames as well as introducing interface management practices aimed at cross‐fertilization. Finally, the synergetic potential of (underlying) technologies comes to the forefront as necessary in order for ambidextrous organizations to become sustainable.  相似文献   
110.
This paper discusses the possibility of a spatial hierarchy of innovation and growth dynamics in Europe. A spatial hierarchy is understood as a geographical clustering of regions, where important differences exist in terms of innovation and growth dynamics between the clusters. The literature on regional growth and innovation is briefly scanned. After this, a database on European regional growth and innovation dynamics is presented. Spatial correlation analysis and spatial principal components analysis are used to explore the possibility of a spatial hierarchy in Europe. The results point to a hierarchy consisting of four groups: South Europe, East Europe, and two groups in West and North Europe. Growth and innovation performance in these clusters are discussed, and some policy conclusions are drawn.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号