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   2217篇
  免费   122篇
  国内免费   19篇
电工技术   47篇
综合类   9篇
化学工业   499篇
金属工艺   43篇
机械仪表   72篇
建筑科学   76篇
矿业工程   7篇
能源动力   189篇
轻工业   216篇
水利工程   13篇
石油天然气   29篇
无线电   267篇
一般工业技术   399篇
冶金工业   132篇
原子能技术   18篇
自动化技术   342篇
  2024年   9篇
  2023年   54篇
  2022年   115篇
  2021年   144篇
  2020年   118篇
  2019年   121篇
  2018年   141篇
  2017年   117篇
  2016年   113篇
  2015年   58篇
  2014年   105篇
  2013年   195篇
  2012年   137篇
  2011年   151篇
  2010年   101篇
  2009年   107篇
  2008年   85篇
  2007年   62篇
  2006年   37篇
  2005年   26篇
  2004年   27篇
  2003年   25篇
  2002年   23篇
  2001年   26篇
  2000年   17篇
  1999年   21篇
  1998年   35篇
  1997年   28篇
  1996年   24篇
  1995年   22篇
  1994年   18篇
  1993年   4篇
  1992年   11篇
  1991年   7篇
  1990年   8篇
  1989年   4篇
  1988年   5篇
  1987年   4篇
  1986年   6篇
  1985年   10篇
  1984年   8篇
  1983年   9篇
  1982年   5篇
  1981年   1篇
  1980年   1篇
  1978年   4篇
  1977年   4篇
  1976年   4篇
  1970年   1篇
排序方式: 共有2358条查询结果,搜索用时 15 毫秒
1.
2.
Individually, photoredox catalysis (PC) and photodynamic therapy (PDT) are well-established concepts that have experienced a remarkable resurgence in recent years, leading to significant progress in organic synthesis for PC and clinical approval of anticancer drugs for PDT. But, very recently, new photoredox catalyst systems based on Ir(III) and Ru(II) complexes have garnered significant interest because they can simultaneously be used as PDT agents apart from their demonstrated PC activity. This highlight discusses the unique PC behavior of emerging Ir(III)- and Ru(II)-based systems while also examining their potential PDT activity in cancer treatment.  相似文献   
3.
Neural Computing and Applications - This study presents the design of a tenth-order multiple feedback Chebyshev low-pass filter (MF-C-LPF). Component selection and gain calculation of filters are...  相似文献   
4.
5.
6.
Vadde  Kiran  Çam  Hasan 《Telecommunication Systems》2004,25(3-4):417-431
OVSF codes are used as channelization codes in WCDMA. Due to code blocking property of OVSF codes, the bandwidth available in the system is severely limited. Code reassignments mitigate the impact of the blocking property at the expense of causing delays and decreasing the throughput of the system. Nonblocking OVSF (NOVSF) codes have been proposed to alleviate the adverse effect of code reassignments. This paper presents a code assignment algorithm for NOVSF codes, which does not require any code reassignments. Simulation results show that NOVSF codes achieve better throughput than OVSF codes, even though code reassignments are allowed in the assignments of OVSF codes.  相似文献   
7.
On the synergy between electrical and photonic switching   总被引:1,自引:0,他引:1  
This article focuses on the values of electrical switching vs. photonic switching in the context of telecom transport networks. In particular, we show that the requirement of providing agility at the optical layer in the face of traffic forecast uncertainties is served better through photonic switching. On the other hand, some of the network-level functions, such as fast protection, subwavelength aggregation, and flexible client connectivity, require electrical switching. We further argue that additional values are achieved with hybrid photonic and electrical switching, which do not exist when either of these options is used in isolation.  相似文献   
8.
A novel method for parameter estimation of minimum-phase autoregressive moving average (ARMA) systems in noise is presented. The ARMA parameters are estimated using a damped sinusoidal model representation of the autocorrelation function of the noise-free ARMA signal. The AR parameters are obtained directly from the estimates of the damped sinusoidal model parameters with guaranteed stability. The MA parameters are estimated using a correlation matching technique. Simulation results show that the proposed method can estimate the ARMA parameters with better accuracy as compared to other reported methods, in particular for low SNRs.  相似文献   
9.
Channel-optimized vector quantization (COVQ) has proven to be an effective joint source-channel coding technique that makes the underlying quantizer robust to channel noise. Unfortunately, COVQ retains the high encoding complexity of the standard vector quantizer (VQ) for medium-to-high quantization dimensions and moderate-to-good channel conditions. A technique called sample adaptive product quantization (SAPQ) was recently introduced by Kim and Shroff to reduce the complexity of the VQ while achieving comparable distortions. In this letter, we generalize the design of SAPQ for the case of memoryless noisy channels by optimizing the quantizer with respect to both source and channel statistics. Numerical results demonstrate that the channel-optimized SAPQ (COSAPQ) achieves comparable performance to the COVQ (within 0.2 dB), while maintaining considerably lower encoding complexity (up to half of that of COVQ) and storage requirements. Robustness of the COSAPQ system against channel mismatch is also examined.  相似文献   
10.
The effects of addition of κ-carrageenan to solutions containing 40% (w/w) sugar substitute on the rheological properties of these systems were investigated at 25 °C using a rotational viscometer at rotational speeds of 6, 12, 30, and 60 rev min−1. The flow behaviour of the solutions was adequately described by the power law model with or without yield stress. The consistency index ( K ) and the flow behaviour index ( n ) were determined from shear stress vs. shear rate data. The flow parameters of the solutions depended on the carrageenan concentration. The apparent viscosities of the systems decreased with increasing shear rate, indicating pseudoplastic behaviour. The final carrageenan concentration was found to be an effective factor controlling the degree of sliminess of the model food systems studied.  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