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   1902篇
  免费   75篇
  国内免费   9篇
电工技术   47篇
综合类   1篇
化学工业   338篇
金属工艺   42篇
机械仪表   43篇
建筑科学   33篇
矿业工程   4篇
能源动力   83篇
轻工业   98篇
水利工程   14篇
石油天然气   8篇
无线电   367篇
一般工业技术   388篇
冶金工业   217篇
原子能技术   11篇
自动化技术   292篇
  2024年   8篇
  2023年   23篇
  2022年   47篇
  2021年   90篇
  2020年   59篇
  2019年   74篇
  2018年   80篇
  2017年   70篇
  2016年   83篇
  2015年   36篇
  2014年   68篇
  2013年   144篇
  2012年   73篇
  2011年   73篇
  2010年   69篇
  2009年   76篇
  2008年   62篇
  2007年   64篇
  2006年   66篇
  2005年   44篇
  2004年   36篇
  2003年   28篇
  2002年   43篇
  2001年   30篇
  2000年   24篇
  1999年   39篇
  1998年   56篇
  1997年   43篇
  1996年   46篇
  1995年   32篇
  1994年   26篇
  1993年   25篇
  1992年   23篇
  1991年   25篇
  1990年   12篇
  1989年   22篇
  1988年   15篇
  1987年   21篇
  1986年   13篇
  1985年   13篇
  1984年   13篇
  1983年   12篇
  1982年   11篇
  1981年   7篇
  1980年   10篇
  1978年   8篇
  1977年   5篇
  1976年   10篇
  1974年   6篇
  1971年   4篇
排序方式: 共有1986条查询结果,搜索用时 15 毫秒
871.
Computational intelligence techniques have widespread applications in the field of engineering process optimization, which typically comprises of multiple conflicting objectives. An efficient hybrid algorithm for solving multi-objective optimization, based on particle swarm optimization (PSO) and artificial bee colony optimization (ABCO) has been proposed in this paper. The novelty of this algorithm lies in allocating random initial solutions to the scout bees in the ABCO phase which are subsequently optimized in the PSO phase with respect to the velocity vector. The last phase involves loyalty decision-making for the uncommitted bees based on the waggle dance phase of ABCO. This procedure continues for multiple generations yielding optimum results. The algorithm is applied to a real life problem of intercity route optimization comprising of conflicting objectives like minimization of travel cost, maximization of the number of tourist spots visited and minimization of the deviation from desired tour duration. Solutions have been obtained using both pareto optimality and the classical weighted sum technique. The proposed algorithm, when compared analytically and graphically with the existing ABCO algorithm, has displayed consistently better performance for fitness values as well as for standard benchmark functions and performance metrics for convergence and coverage.  相似文献   
872.

The state of the art trust management techniques especially designed for wireless sensor network, are not well suited due to less battery power and less memory of sensor nodes. In this work, we propose a fuzzy based hierarchical trust management scheme which includes direct trust calculation on real time past experience and credit based calculation and indirect trust calculation on peer recommendation. In this scheme cluster head and base station maintains constructive knowledge table based on fuzzy logic which reduces memory and communication overhead. As a whole the scheme reduces the communication overhead, computational time and memory utilization because it deals with decision rather than data compare to other existing schemes.

  相似文献   
873.
The next generation of sensors requires a simple yet compact lab on chip-based precise optical detection mechanism where data interpretation can be achieved with minimum effort. Hereby, cost-efficient strategies of manufacturing both propagating surface plasmon polariton (SPP) and localized surface plasmon resonance (LSPR) sensors on flexible platforms are explored via mechanical instabilities and oblique-angled metal evaporation. Centimeter scaled dielectric grating structures produced by plasma oxidation of pre-stressed polydimethylsiloxane film have comprised the substrates, thus imparting inherent flexibility. Subsequently, both continuous and discontinuous 1D-metallic lattices are obtained via vapor deposition of gold at different angles. The optical isotropy (gold surface-grating) and anisotropy (gold edge-grating) are distinctly observed as a difference between forward and backward diffraction efficiencies, backed by analytical correlation to the observed orders. Supported with electromagnetic modeling, the SPP and LSPR excitations are experimentally characterized under reflectance and transmittance measurements, along with a demonstration of their sensing capabilities. The LSPR supported flexible sensor provides superiority in terms of sensitivity, which is investigated under mechanical deformations to exhibit consistency of the resonant wavelength. Such consistency is strategically unraveled via “finite element method” based approaches, thus providing a new paradigm of cost-efficient, large-scaled flexible sensors.  相似文献   
874.

In this work the design of 4 bit binary to Gray code converter circuit with 8 × 4 barrel shifter has been carried out. The circuit has been designed using metal oxide semiconductor (MOS) transistor. The verification of the functionality of the circuits has been performed using Tanner-SPICE software. Power consumption and speed are the major design metrics for very large scale integrated circuit. In this work the average power consumption and gate delay analysis of 4 bit binary to Gray converter with 8 × 4 barrel shifter has been carried out using nano dimensional MOS transistor having channel length of 150 nm. Power consumption, delay analysis has been carried out for different set of supply voltage. It has been observed that power consumption of the 4 bit binary to Gray converter with 8 × 4 barrel shifter has been reduced by reducing the power supply voltage VDD. The power consumption and delay offers by the circuit is very less. At 1 V VDD, power consumption and delay are 0.15 μW and 52.7 ps respectively. Therefore the circuit is suited for low power and high speed application in the area of arithmetical, logical and telecommunication.

  相似文献   
875.

Due to the continual advancement of future generation communication systems, channel capacity is considered to be an important parameter for achieving greater signal strength by means of faster data transmission speed. Usually in multiple input multiple output (MIMO) systems, the diversity technique lessens the propagation speed significantly than the channel capacity. Using MIMO in combination with phase shift keying (PSK) modulation jointly known as MIMO–PSK systems, the present paper focuses on a novel distribution method in order to optimize the channel capacity over a Rayleigh fading channel. First, ergodic channel capacity and distribution capacity in terms of outage capacity is simulated for different MIMO–PSK configurations as well as channel conditions. Later, the channel performance of MIMO–PSK for the novel distribution conditions with antenna correlation effect is evaluated and finally the optimal channel capacity is determined.

  相似文献   
876.
Central Glass & Ceramic Research Institute, Jadavpur, Calcutta-700 032, India The observation of a high pressure polymorph of titania, originating from an anatase phase, using high energy impact vibrational ball milling (HEIVBM) is reported here for the first time. The observed polymorph conforms to the reported high pressure modified phase of titania [orthorhombic, -PbO2 (Pbcn) structure] developed by static high pressure and shock wave techniques. X-ray diffraction (XRD) and electron spin resonance (ESR) techniques are used to characterize the polymorph.  相似文献   
877.
878.
We check the decoherence dynamics of Measurement-induced Nonlocality (in short, MIN) and compare it with geometric discord for two qubit systems. There are quantum states, on which the action of dephasing channel cannot destroy MIN in finite or infinite time. We check the additive dynamics of MIN on a qubit state under two independent noise. Geometric discord also follows such additive dynamics like quantum discord. We have further compared non-Markovian evolution of MIN and geometric discord under dephasing and amplitude damping noise for pure state and it shows distinct differences between their dynamics.  相似文献   
879.
Laterite waste powder has been consolidated into building bricks using phosphoric acid as bonding agent. The bricks could be cured at low temperatures (450–500°C). Properties have been achieved comparable with those of burnt clay bricks. For example, 2·5% binder-added brick has shown superior properties such as compressive strenght of about 10 MPa, water absorption of 10% and bulk density of 1·5 g/cm3. The bonding between the laterite grains is quite strong and the brick has attained improved wear properties. These bricks showed typical microstructures (studies by SEM method) consisting of well-bonded compacted laterite particles, the determining factor towards superior properties of the finished products.  相似文献   
880.
Jute fibers were treated with 5% NaOH solution for 4 and 8 h, respectively, to study the mechanical and impact fatigue properties of jute‐reinforced vinylester resin matrix composites. Mechanical properties were enhanced in case of fiber composites treated for 4 h, where improved interfacial bonding (as evident from scanning electron microscopy [SEM]) and increased fiber strength properties contributed effectively in load transfer from the matrix to the fiber; but their superior mechanical property was not retained with fatigue, as they showed poor impact fatigue behavior. The fracture surfaces produced under a three‐point bend test and repeated impact loading were examined under SEM to study the nature of failure in the composites. In case of untreated fiber composites, interfacial debonding and extensive fiber pullout were observed, which lowered the mechanical property of the composites but improved their impact fatigue behavior. In composites treated for 4 h under repeated impact loading, interfacial debonding occurred, followed by fiber breakage, producing a sawlike structure at the fracture surface, which lowered the fatigue resistance property of the composites. The composites with fibers treated with alkali for 8 h showed maximum impact fatigue resistance. Here, interfacial debonding was at a minimum, and the fibers, being much stronger and stiffer owing to their increased crystallinity, suffered catastrophic fracture along with some microfibrillar pullout (as evident from the SEM micrographs), absorbing a lot of energy in the process, which increased the fatigue resistance property of the composites. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2588–2593, 2002  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