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   3765篇
  免费   308篇
  国内免费   12篇
化学   2227篇
晶体学   32篇
力学   41篇
数学   117篇
物理学   563篇
无线电   1105篇
  2024年   4篇
  2023年   46篇
  2022年   45篇
  2021年   112篇
  2020年   105篇
  2019年   124篇
  2018年   68篇
  2017年   79篇
  2016年   138篇
  2015年   144篇
  2014年   146篇
  2013年   262篇
  2012年   296篇
  2011年   296篇
  2010年   183篇
  2009年   183篇
  2008年   228篇
  2007年   212篇
  2006年   216篇
  2005年   217篇
  2004年   172篇
  2003年   161篇
  2002年   148篇
  2001年   87篇
  2000年   66篇
  1999年   69篇
  1998年   38篇
  1997年   34篇
  1996年   31篇
  1995年   16篇
  1994年   24篇
  1993年   14篇
  1992年   8篇
  1991年   13篇
  1990年   12篇
  1989年   17篇
  1988年   13篇
  1987年   6篇
  1986年   4篇
  1985年   5篇
  1984年   5篇
  1983年   8篇
  1981年   3篇
  1980年   4篇
  1979年   2篇
  1978年   4篇
  1977年   5篇
  1975年   2篇
  1974年   3篇
  1972年   2篇
排序方式: 共有4085条查询结果,搜索用时 668 毫秒
21.
22.
This paper proposes a high‐performance connection management architecture to design a common QoS framework applied to an ATM network based on the Open Distributed Processing (ODP) concept. We design the QoS framework in accordance from the RM‐ODP information and computational viewpoints. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
23.
The multiple line grid array (MLGA) interposer was recently introduced as a future high-density high-speed bonding method. In this paper, we introduce an electrical model and high-frequency characteristics of the MLGA interposer. The high-frequency electrical model was extracted from microwave S-parameter measurements up to 20 GHz as well as from fundamental microwave network analysis. For the parameter fitting process during model extraction, an optimization method was used. Several different types of MLGA interposers were designed, assembled and tested. The test vehicles contained coplanar waveguides, probing pads and an MLGA interposer structure. The height of the MLGA, the conductor shape inside the MLGA, and the dielectric insulator of the MLGA were varied. From the model, an MLGA with a height of 0.4 mm and a polymer dielectric insulator was found to have 203 pH of self inductance, 49 pH of mutual inductance with the nearest ground conductor line, and 186 fF of mutual capacitance. By reducing the height of the MLGA and by using an insulator with a lower dielectric constant, parasitic inductance and capacitance is further reduced. TDR/TDT simulation and measurement showed the validity of the extracted model parameters of the MLGA interposer. Circuit simulation based on the extracted model revealed that the MLGA interposer could be successfully used for microwave device packages up to 20 GHz and for high-speed digital device packages with a clock cycle up to 5 GHz.  相似文献   
24.
An analog front‐end circuit for ISO/IEC 14443‐compatible radio frequency identification (RFID) interrogators was designed and fabricated by using a 0.25 µm double‐poly CMOS process. The fabricated chip was operated using a 3.3 Volt single‐voltage supply. The results of this work could be provided as reusable IPs in the form of hard or firm IPs for designing single‐chip ISO/IEC 14443‐compatible RFID interrogators.  相似文献   
25.
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   
26.
Kim  J.D. Ryu  M. Kim  J. Chin  H.U. 《Electronics letters》2006,42(14):792-793
An impedance matching technique using series condensers for the power receivers of in vivo robotic capsules is proposed. The power delivery function of the condenser ratio and its optimal ratio are derived. Experimental results validate the derived function.  相似文献   
27.
We have studied the algorithm for the automatic chromatic dispersion compensation using bit error rate (BER) and Q-factor optimization for realization of dynamically reconfigurable all-optical network. We have made sure good performance using the compensation system by laboratory experiments.  相似文献   
28.
29.
Motion based object tracking with mobile camera   总被引:4,自引:0,他引:4  
An efficient algorithm which detects and tracks a moving object is proposed. The global motion energy caused by camera movement is eliminated by finding the maximal matching position with the cross-correlation value between two consecutive frames using the spiral scanning technique. The region of a moving object is segmented exactly by combining the results of the temporal derivatives and edge map from one image, and the actual centroid of the moving object is determined as the mid-point of the cumulative distribution of the projection profile of the region  相似文献   
30.
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