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   159篇
  免费   4篇
  国内免费   1篇
化学   68篇
力学   3篇
数学   38篇
物理学   29篇
无线电   26篇
  2022年   1篇
  2021年   2篇
  2020年   1篇
  2019年   4篇
  2018年   1篇
  2017年   1篇
  2016年   4篇
  2015年   5篇
  2014年   8篇
  2013年   6篇
  2012年   7篇
  2011年   9篇
  2010年   8篇
  2009年   4篇
  2008年   17篇
  2007年   10篇
  2006年   11篇
  2005年   6篇
  2004年   14篇
  2003年   9篇
  2002年   5篇
  2001年   3篇
  2000年   3篇
  1999年   5篇
  1998年   2篇
  1997年   1篇
  1996年   5篇
  1994年   4篇
  1991年   2篇
  1990年   1篇
  1988年   1篇
  1981年   1篇
  1979年   1篇
  1970年   2篇
排序方式: 共有164条查询结果,搜索用时 15 毫秒
101.
We examine the properties of the recently introduced degrees of coherence regarding the phase correlations of the optical field. It is seen that some of these quantities are straightforwardly related to the limits of complete dependence and complete independence of phases, which were used as the extremes of complete coherence and complete incoherence by Zernike in 1938. Certain other coherence measures are not in agreement with these limits in all situations. Our results elucidate the physical meaning of coherence in electromagnetic fields.  相似文献   
102.
Bertrand, Charon, Hudry and Lobstein studied, in their paper in 2004 [1], r-locating–dominating codes in paths Pn. They conjectured that if r≥2 is a fixed integer, then the smallest cardinality of an r-locating–dominating code in Pn, denoted by , satisfies for infinitely many values of n. We prove that this conjecture holds. In fact, we show a stronger result saying that for any r≥3 we have for all nnr when nr is large enough. In addition, we solve a conjecture on location–domination with segments of even length in the infinite path.  相似文献   
103.
104.
Hierarchic structure and anomalous diffusion on submicrometer scale were introduced into an artificial cell membrane, and the spatiotemporal dependence of lipid diffusion was visualized on nanostructured oxide surfaces. We observed the lipid diffusion in supported lipid bilayers (SLBs) on step-and-terrace TiO(2)(100) and amorphous SiO(2)/Si surfaces by single molecule tracking (SMT) method. The SMT at the time resolution of 500 μs to 30 ms achieved observation of the lipid diffusion over the spatial and temporal ranges of 100 nm/millisecond to 1 μm/second. The temporal dependence of the diffusion coefficient in the SLB on TiO(2)(100) showed that the crossover from anomalous diffusion to random diffusion occurred around 10 ms. The surface fine architecture on substrates will be applicable to induce hierarchic structures on the order of 100 nm or less, which correspond to the microcompartment size in vivo.  相似文献   
105.
An integrated receiver consisting of RF front ends, analog baseband (BB) chain with an analog to digital converter (ADC) for a synthetic aperture radar (SAR) implemented in 130 nm CMOS technology is presented in this paper. The circuits are integrated on a single chip with a size of 10.88 mm2. The RF front end consists of three parallel signal channel intended for L, C and X-band of the SAR receiver. The BB is selectable between 50 and 160 MHz bandwidths through switches. The ADC has selectable modes of 5, 6, 7 and 8 bits via control switches. The receiver has a nominal gain of 40 and 37 dB and noise figure of 11 and 13.5 dB for 160 MHz BB filter at room temperature for L-band and C-band, respectively. The circuits, which use a 1.2 V supply voltage, dissipate maximum power of 650 mW with 50 MHz BB and 8 bit mode ADC, and maximum power of 800 mW with 160 MHz BB and 8 bit mode ADC.  相似文献   
106.
We study a problem considered originally by A. Markov in 1947: Given two finitely generated matrix semigroups, determine whether or not they contain a common element. This problem was proved undecidable by Markov for 4 x 4 matrices, even in a very restrict form, and for 3 x 3 matrices by Krom in 1981. Here we give a new proof in the 3 x 3 case which gives undecidability in an almost as restricted form as the result of Markov.  相似文献   
107.
108.
Annals of Operations Research - In a typical decision-making process, preference elicitation methods require a priori knowledge about the desired outcomes. It is expected that the decision maker...  相似文献   
109.
The design of photoluminescent molecular probes for the selective recognition of anions is a major challenge for the development of optical chemical sensors. The reversible binding of anions to lanthanide centers is one promising option for the realization of anion sensors, because it leads in some cases to a strong luminescence increase by the replacement of quenching water molecules. Yet, it is an open problem to gain control of the sensitivity and selectivity of the luminescence response. Primarily, the selective detection of (poly)phosphate species such as nucleotides has emerged as a demanding task, because they are involved in many biological processes and enzymatic reactions. We designed a series of pyridyl‐based multidentate europium complexes (seven‐, six‐, and five‐dentate) including sensitizing chromophores and studied their luminescence intensity and lifetime responses to different (poly)phosphates (adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), cyclic adenosine monophosphate (cAMP), pyrophosphate, and phosphate anions), and carboxyanions (citrate, malate, oxalacetate, succinate, α‐ketoglutarate, pyruvate, oxalate, carbonate). The results reveal that the number of free coordination sites has a significant impact on the sensitivity and selectivity of the response. Because of its reversibility, the lanthanide probes can be applied to monitor the activity of ATP‐consuming enzymes such ATPases and apyrases, which is demonstrated by means of the five‐dentate complex.  相似文献   
110.
Evolving video coding standards demand functional flexibility for implementations, not only at design time but also after fabrication. This paper presents a System-on-Chip design approach with a feasible combination of performance, scalability, programmability, area efficiency, and design time effort for a video encoder. The encoder is based on a homogeneous master-slave processor architecture. Each slave encodes a part of the frame in the Single Program Multiple Data (SPMD) data parallel model. Both shared and distributed memory architectures are presented. Design effort is reduced by identical program codes, automated assembly of software and hardware modules independent of the number and type of processors, as well as our flexible on-chip communication network called Heterogeneous IP Block Interconnection (HIBI). A case study implementation with two to ten simple ARM7 processors, 32-bit HIBI bus and non-optimized processor-independent software gives the performance from 6 to 53 fps for QCIF. The whole encoder area ranges from 173 to 770 kgates excluding the memories. The relation scales reasonably well to systems with more powerful processors and optimized code. The optimization of the communication network shows that with more than six slaves even a serial HIBI connection with 100 MHz speed is feasible. HIBI and the parallelization approach allow exploration and optimization of the communication both at the application and architecture layers. Tero Kangas, MSc ’01, Tampere University of Technology (TUT). Since 1999 he has been working as a research scientist in the Institute of Digital and Computer Systems (DCS) at TUT. Currently he is working towards his PhD degree and his main research topics are system architectures and SoC design methodologies in multimedia applications. Kimmo Kuusilinna, PhD ’01, TUT. His main research interests include system-level design and verification, interconnection networks, and parallel memories. Currently he is working as a senior research engineer at the Nokia Research Center. Timo D. H?m?l?inen, MSc ’93, PhD ’97, TUT. He acted as a senior research scientist and project manager at TUT in 1997-2001. He was nominated to full professor at TUT/Institute of Digital and Computer Systems in 2001. He heads the DACI research group that focuses on three main lines: wireless local area networking and wireless sensor networks, high-performance DSP/HW based video encoding, and interconnection networks with design flow tools for heterogeneous SoC platforms.  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