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   1086篇
  免费   49篇
  国内免费   26篇
化学   625篇
晶体学   9篇
力学   9篇
综合类   1篇
数学   12篇
物理学   144篇
无线电   361篇
  2024年   1篇
  2023年   5篇
  2022年   13篇
  2021年   8篇
  2020年   5篇
  2019年   9篇
  2018年   7篇
  2017年   3篇
  2016年   34篇
  2015年   37篇
  2014年   72篇
  2013年   45篇
  2012年   159篇
  2011年   120篇
  2010年   104篇
  2009年   100篇
  2008年   94篇
  2007年   63篇
  2006年   60篇
  2005年   62篇
  2004年   54篇
  2003年   49篇
  2002年   11篇
  2001年   9篇
  2000年   9篇
  1999年   3篇
  1998年   5篇
  1997年   4篇
  1996年   4篇
  1995年   3篇
  1994年   3篇
  1993年   1篇
  1992年   3篇
  1990年   1篇
  1989年   1篇
排序方式: 共有1161条查询结果,搜索用时 31 毫秒
71.
This paper proposes a SPICE model development methodology for quantum-dot cellular automata (QCA) cells and presents a SPICE model for QCA cells. The model is validated by simulating the basic logic gates such as inverter and majority voter. The proposed model makes it possible to design and simulate QCA combinational circuits and hybrid circuits of QCA and other NANO devices using SPICE. In the second half part of the paper, SET and QCA co-design methodology is proposed and SET is used as a readout interface of the QCA cell array. The SET and QCA hybrid circuit is a promising nano-scale solution.  相似文献   
72.
A complete low-power high-voltage driver for a 80×104 passive-matrix bistable LCD is integrated in a 0.7 μm CMOS smart-power technology. It features 100 V driving capability on all row and column outputs and comprises all necessary digitally programmable high-voltage generators and multiplexers to synthesize the required complex high-voltage waveforms from a 3 V battery. An original level-shifter design for the high-voltage multiplexers and a dedicated architecture for the programmable high-voltage generators yield an extremely low internal power consumption below 10 mW for the entire driver chip.  相似文献   
73.
Dy3+-doped NaGd(WO4)2 crystal with sizes of about Φ20×40 mm2 was grown by the Czochralski technique along the (0 0 1) orientation. Polarized absorption spectra, fluorescence spectra, and fluorescence decay curve of Dy3+-doped NaGd(WO4)2 have been recorded at room temperature. Based on the Judd-Ofelt (J-O) theory, the intensity parameters from the measured line strengths were evaluated. The J-O parameters were used to predict radiative transition probabilities, radiative lifetimes and branching ratios for various excited levels of Dy3+-doped NaGd(WO4)2 crystal. The luminescent quantum efficiency of the 4F9/2 level was determined to be approximately 63% for this material. The emission cross-section of the 4F9/26H13/2 transition was estimated by using the Füchtbauer-Ladengurg method.  相似文献   
74.
Good quality crystals ZnWO4 activated with Er3+ have been grown by means of Czochralski method and characterized using optical spectroscopy techniques. XRD, absorption spectra, fluorescence spectrum are presented and the Judd-Ofelt intensity parameters Ω2, Ω4, and Ω6 are obtained to be 6.76×10-20, 0.37×10-20, and 0.50×10-20 cm2, respectively. Along crystallographic axes, refractive indices are presented. The fluorescence decay time of the 4I13/2 level has also been investigated and shows an exponential behavior with a lifetime value of 5.52 ms. The crystal is potentially used for green and infrared eye-safe lasers.  相似文献   
75.
Analog implementations of digital error control decoders, generally referred to as analog decoding, have recently been proposed as an energy and area competitive methodology. Despite several successful implementations of small analog error control decoders, little is currently known about how this methodology scales to smaller process technologies and copes with the non-idealities of nano-scale transistor sizing. A comprehensive analysis of the potential of sub-threshold analog decoding is examined in this paper. It is shown that mismatch effects dominated by threshold mismatch impose firm lower limits on the sizes of transistors. The effect of various forms of leakage currents is also investigated and minimal leakage current to normalizing currents are found using density evolution and control simulations. Finally, the convergence speed of analog decoders is examined via a density evolution approach. The results are compiled and predictions are given which show that process scaling below 90 nm processes brings no advantages, and, in some cases, may even degrade performance or increase required resources.  相似文献   
76.
77.
Heterogeneous reconfigurable systems provide drastically higher performance and lower power consumption than traditional CPU-centric systems. Moreover, they do it at much lower costs and shorter times to market than non-reconfigurable hardware solutions. They also provide the flexibility that is often required for the engineering of modern robust and adaptive systems. Due to their heterogeneity, flexibility and potential for highly optimized application-specific instantiation, reconfigurable systems are adequate for a very broad class of applications across different industry sectors. What prevents the reconfigurable system paradigm from a broad proliferation is the lack of adequate development methodologies and electronics design tools for this kind of systems. The ideal would be a seamless compilation of a high-level computation process specification into an optimized mixture of machine code executed on traditional CPU-centric processors and on the application-specific decentralized parallel data-flow-dominated reconfigurable processors and hardware accelerators. Although much research and development in this direction was recently performed, the adequate methodologies and tools necessary to implement this compilation process as an effective and efficient hardware/software co-synthesis flow are unfortunately not yet in place. This paper focuses on the recent developments and development trends in the design methods and synthesis tools for reconfigurable systems. Reconfigurable system synthesis performs two basic tasks: system structure construction and application process mapping on the structure. It is thus more complex than standard (multi-)processor-based system synthesis for software-programmable systems that only involves application mapping. The system structure construction may involve the macro-architecture synthesis, the micro-architecture synthesis, and the actual hardware synthesis. Also, the application process mapping can be more complicated and dynamic in reconfigurable systems. This paper reviews the recent methods and tools for the macro- and micro-architecture synthesis, and for the application mapping of reconfigurable systems. It puts much attention to the relevant and currently hot topic of (re-)configurable application-specific instruction set processors (ASIP) synthesis, and specifically, ASIP instruction set extension. It also discusses the methods and tools for reconfigurable systems involving CPU-centric processors collaborating with reconfigurable hardware sub-systems, for which the main problem is to decide which computation processes should be implemented in software and which in hardware, but the hardware/software partitioning has to account for the hardware sharing by different computation processes and for the reconfiguration processes. The reconfigurable system area is a very promising, but quite a new field, with many open research and development topics. The paper reviews some of the future trends in the reconfigurable system development methods and tools. Finally, the discussion of the paper is summarized and concluded.  相似文献   
78.
A voltage-mode Multiphase Sinusoidal Oscillator realized using Second Generation Current Conveyors and only grounded passive elements is introduced in this paper. The proposed topology is suitable for realizing oscillators with both odd and even number of phases without modifying the core of the topology. Only non-inverting Current Conveyors are required for the construction of the oscillator's topology and this is a benefit from the discrete component implementation point of view. The behavior of the proposed topology has been evaluated, through experimental results, in the cases of three and six-phase oscillators.  相似文献   
79.
80.
One of the most critical challenges in today's CMOS VLSI design is the lack of predictability in chip performance at design stage. One of the process variabilities comes from the voltage drop variations in on-chip power distribution networks. In this paper, we present a novel analysis approach for computing voltage drops of large power grid networks under process variations. The new algorithm is very efficient and scalable for huge networks with a large number of variational variables. This approach, called variational extended truncated balanced realization (varETBR), is based on model order reduction techniques to reduce the circuit matrices before the variational simulation. It performs the parameterized reduction on the original system using variation-bearing subspaces. After the reduction, Monte Carlo based statistical simulation is performed on the reduced system and the statistical responses of the original system are obtained thereafter. varETBR calculates variational response Grammians by Monte Carlo based numerical integration considering both system and input source variations in generating the projection subspace. varETBR is very scalable for the number of variables and flexible for different variational distributions and ranges as demonstrated in experimental results. Experimental results, on a number of IBM benchmark circuits up to 1.6 million nodes, show that the varETBR can be 1900X faster than the Monte Carlo method and is much more scalable than one of the recently proposed approaches.  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