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   8147篇
  免费   360篇
  国内免费   53篇
电工技术   216篇
综合类   20篇
化学工业   1791篇
金属工艺   167篇
机械仪表   207篇
建筑科学   249篇
矿业工程   9篇
能源动力   534篇
轻工业   804篇
水利工程   91篇
石油天然气   157篇
武器工业   4篇
无线电   1006篇
一般工业技术   1427篇
冶金工业   489篇
原子能技术   84篇
自动化技术   1305篇
  2024年   19篇
  2023年   187篇
  2022年   434篇
  2021年   550篇
  2020年   388篇
  2019年   397篇
  2018年   499篇
  2017年   350篇
  2016年   399篇
  2015年   246篇
  2014年   379篇
  2013年   628篇
  2012年   414篇
  2011年   479篇
  2010年   306篇
  2009年   282篇
  2008年   250篇
  2007年   226篇
  2006年   194篇
  2005年   169篇
  2004年   133篇
  2003年   110篇
  2002年   126篇
  2001年   71篇
  2000年   73篇
  1999年   80篇
  1998年   135篇
  1997年   112篇
  1996年   74篇
  1995年   85篇
  1994年   56篇
  1993年   54篇
  1992年   40篇
  1991年   23篇
  1990年   31篇
  1989年   45篇
  1988年   46篇
  1987年   31篇
  1986年   28篇
  1985年   42篇
  1984年   49篇
  1983年   41篇
  1982年   26篇
  1981年   23篇
  1980年   28篇
  1979年   23篇
  1978年   19篇
  1977年   22篇
  1976年   31篇
  1974年   16篇
排序方式: 共有8560条查询结果,搜索用时 9 毫秒
61.
Wireless Personal Communications - Semantic Web content extracting are the augmentation of the present web where the data is given in the better importance and allowing users to work close by close...  相似文献   
62.
With the technological advancement in body area sensor networks (BASNs), low cost high quality electrocardiographic (ECG) diagnosis systems have become important equipment for healthcare service providers. However, energy consumption and data security with ECG systems in BASNs are still two major challenges to tackle. In this study, we investigate the properties of compressed ECG data for energy saving as an effort to devise a selective encryption mechanism and a two-rate unequal error protection (UEP) scheme. The proposed selective encryption mechanism provides a simple and yet effective security solution for an ECG sensor-based communication platform, where only one percent of data is encrypted without compromising ECG data security. This part of the encrypted data is essential to ECG data quality due to its unequally important contribution to distortion reduction. The two-rate UEP scheme achieves a significant additional energy saving due to its unequal investment of communication energy to the outcomes of the selective encryption, and thus, it maintains a high ECG data transmission quality. Our results show the improvements in communication energy saving of about 40%, and demonstrate a higher transmission quality and security measured in terms of wavelet-based weighted percent root-mean-squared difference.  相似文献   
63.
64.
This letter presents the development and implementation of the convolutional perfectly matched layer (CPML) for the recently proposed locally 1-D finite difference time domain method LOD-FDTD. Two different examples are simulated. Their results are compared with the FDTD-PML method and it is found that the proposed method has 16 dB less reflection error at a Courant Friedrich Levy number of one.  相似文献   
65.
Mobile Networks and Applications - The original version of this article unfortunately contained a mistake in the author group section. Author Preetam Ghosh’s given name was incorrectly...  相似文献   
66.
67.
Several new solution‐processable organic semiconductors based on dendritic oligoquinolines were synthesized and were used as electron‐transport and hole‐blocking materials to realize highly efficient blue phosphorescent organic light‐emitting diodes (PhOLEDs). Various substitutions on the quinoline rings while keeping the central meta‐linked tris(quinolin‐2‐yl)benzene gave electron transport materials that combined wide energy gap (>3.3 eV), moderate electron affinity (2.55‐2.8 eV), and deep HOMO energy level (<‐6.08 eV) with electron mobility as high as 3.3 × 10?3 cm2 V?1 s?1. Polymer‐based PhOLEDs with iridium (III) bis(4,6‐(di‐fluorophenyl)pyridinato‐N,C2′)picolinate (FIrpic) blue triplet emitter and solution‐processed oligoquinolines as the electron‐transport layers (ETLs) gave luminous efficiency of 30.5 cd A?1 at a brightness of 4130 cd m?2 with an external quantum efficiency (EQE) of 16.0%. Blue PhOLEDs incorporating solution‐deposited ETLs were over two‐fold more efficient than those containing vacuum‐deposited ETLs. Atomic force microscopy imaging shows that the solution‐deposited oligoquinoline ETLs formed vertically oriented nanopillars and rough surfaces that enable good ETL/cathode contacts, eliminating the need for cathode interfacial materials (LiF, CsF). These solution‐processed blue PhOLEDs have the highest performance observed to date in polymer‐based blue PhOLEDs.  相似文献   
68.
Transponder collision problem can be significant when a large number of RFID (radio frequency identification) transponders exist in field. Most existing anti-collision algorithms can solve this problem. However, problem arises when all or part of these transponders are having identical UID (unique identification). This paper proposes a new transponder collision control algorithm to overcome overlapping that occurs among transponders with identical UID in RFID large scale deployment (e.g., in a large warehouse), so that the RFID reader can successfully identify the quantity of transponders for each particular UID with high identification accuracy. The proposed anti-collision algorithm adopts a modified version of frequency domain method by adding stochastic delays in time domain. The obtained results show that the proposed method can achieve optimum frequency bandwidth utilization and at the same time poses high identification accuracy (almost 100%) with low identification delay.  相似文献   
69.
The generation of the voltage generalized impedance converter (VGIC) circuits using a nodal admittance matrix (NAM) expansion is given in detail. Thirty-two equivalent circuits using current conveyors (CCII) or inverting current conveyors (ICCII) or a combination of both are generated. The reported circuits are suitable for realizing inductors or frequency dependent negative resistors (FDNR) using grounded passive elements. Similarly the generation of the current generalized impedance converter (CGIC) circuits published recently is reexamined and this resulted in 16 more new CGIC circuits using an alternative NAM expansion. Modification of two of the generated circuits to realize a floating inductor or floating FDNR is also given together with Spice simulation results.  相似文献   
70.
This paper presents a behavioral model that can be used to improve the manufacturability of systems based on MEMS convective sensors. This model permits to handle faults related to process scattering, taking into account not only the electrical and lateral geometrical parameters but also the influence of the cavity depth. Moreover correlations between conductive and convective phenomena are included. The model is validated with respect to FEM simulations and a very good agreement is obtained between the behavioral model and FEM results. The proposed model can then be used in system-level simulations, for instance to evaluate the impact of process scattering on the performances of the sensing part and/or to investigate different design and calibration strategies with respect to the system robustness.  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