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   10557篇
  免费   741篇
  国内免费   17篇
电工技术   120篇
综合类   3篇
化学工业   2481篇
金属工艺   319篇
机械仪表   382篇
建筑科学   360篇
矿业工程   26篇
能源动力   423篇
轻工业   1270篇
水利工程   72篇
石油天然气   51篇
无线电   1238篇
一般工业技术   2307篇
冶金工业   521篇
原子能技术   72篇
自动化技术   1670篇
  2024年   42篇
  2023年   103篇
  2022年   169篇
  2021年   351篇
  2020年   313篇
  2019年   257篇
  2018年   478篇
  2017年   482篇
  2016年   565篇
  2015年   359篇
  2014年   490篇
  2013年   983篇
  2012年   619篇
  2011年   749篇
  2010年   573篇
  2009年   643篇
  2008年   553篇
  2007年   484篇
  2006年   380篇
  2005年   268篇
  2004年   250篇
  2003年   228篇
  2002年   198篇
  2001年   151篇
  2000年   144篇
  1999年   106篇
  1998年   211篇
  1997年   160篇
  1996年   127篇
  1995年   96篇
  1994年   91篇
  1993年   80篇
  1992年   51篇
  1991年   64篇
  1990年   35篇
  1989年   45篇
  1988年   35篇
  1987年   17篇
  1986年   23篇
  1985年   31篇
  1984年   27篇
  1983年   29篇
  1982年   34篇
  1981年   23篇
  1980年   24篇
  1979年   26篇
  1978年   17篇
  1977年   18篇
  1976年   21篇
  1974年   16篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
A new physical and continuous BSIM (Berkeley Short-Channel IGFET Model) I-V model in BSIM3v3 is presented for circuit simulation. Including the major physical effects in state-of-the art MOS devices, the model describes current characteristics from subthreshold to strong inversion as well as from the linear to the saturation operating regions with a single I-V expression, and guarantees the continuities of Ids, conductances and their derivatives throughout all Vgs, Vds, and Tbs, bias conditions. Compared with the previous BSIM models, the improved model continuity enhances the convergence property of the circuit simulators. Furthermore, the model accuracy has also been enhanced by including the dependencies of geometry and bias of parasitic series resistances, narrow width, bulk charge, and DIBL effects. The new model has the extensive built-in dependencies of important dimensional and processing parameters (e.g., channel length, width, gate oxide thickness, junction depth, substrate doping concentration, etc.). It allows users to accurately describe the MOSFET characteristics over a wide range of channel lengths and widths for various technologies, and is attractive for statistical modeling. The model has been implemented in the circuit simulators such as Spectre, Hspice, SmartSpice, Spice3e2, and so on  相似文献   
102.
Shallow junctions are formed in crystalline Si by low-energy ion implantation of B+, P+, or As+ species accompanied by electrical activation of dopants by rapid thermal annealing and the special case of spike annealing. Diffusion depths were determined by secondary ion-mass spectroscopy (SIMS). Electrical activation was characterized by sheet resistance, Hall coefficient, and reverse-bias diode-leakage measurements. The B+ and P+ species exhibit transient-enhanced diffusion (TED) caused by transient excess populations of Si interstitials. The electrically activated fraction of implanted dopants depends mainly on the temperature for B+ species, while for P+ species, it depends on both temperature and P+ dose. The relatively small amount of diffusion associated with As+ implants is favorable for shallow-junction formation with spike annealing.  相似文献   
103.
The purpose of this paper is to present a methodology and tools for the design and test of an EN298 compliant ASIC chip for a safety-critical gas burner control system. Safe operation, as far as the critical variable is concerned, is guaranteed in the presence of two simultaneous faults. Emphasis is put on circumventing methodology, EDA (Electronic Design Automation) and foundry limitations and on product certification requirements.  相似文献   
104.
There have been several studies that jointly use audio, lip intensity, and lip geometry information for speaker identification and speech-reading applications. This paper proposes using explicit lip motion information, instead of or in addition to lip intensity and/or geometry information, for speaker identification and speech-reading within a unified feature selection and discrimination analysis framework, and addresses two important issues: 1) Is using explicit lip motion information useful, and, 2) if so, what are the best lip motion features for these two applications? The best lip motion features for speaker identification are considered to be those that result in the highest discrimination of individual speakers in a population, whereas for speech-reading, the best features are those providing the highest phoneme/word/phrase recognition rate. Several lip motion feature candidates have been considered including dense motion features within a bounding box about the lip, lip contour motion features, and combination of these with lip shape features. Furthermore, a novel two-stage, spatial, and temporal discrimination analysis is introduced to select the best lip motion features for speaker identification and speech-reading applications. Experimental results using an hidden-Markov-model-based recognition system indicate that using explicit lip motion information provides additional performance gains in both applications, and lip motion features prove more valuable in the case of speech-reading application.  相似文献   
105.
Because of constant growth in proportion and complexity of networks, flow analysis has become an indispensable tool for network management mechanisms. Through this resource, a traffic characterization, called digital signature of network segment using flow analysis (DSNSF), is accomplished. The models used for this purpose are the ant colony optimization metaheuristic, the Holt–Winters forecasting method and the statistical procedure, principal component analysis. The obtained DSNSF by each model is compared with the actual traffic of packets and bits and then subjected to specific evaluations in order to measure its accuracy. The experimental results show that the three methods could achieve good correlation indices and low normalized mean square error values between the DSNSF curve and the real traffic movement, indicating a good adaptability and efficiency in characterizing a network traffic segment. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
106.
Clams are widely used in the preparation of several seafood dishes but there are still a few bivalve species which have not been extensively used. Among these species is dog cockle (Glycymeris glycymeris), which is a major by-catch of surf clam (Spisula solida) fishing. However, dog cockle has a low commercial value because its texture is too tough after cooking. This study was initiated to find the best way of tenderising the meat of this species to make it suitable for human consumption. Based on preliminary trials using different tenderising products, a mixture of sodium tripolyphosphate and sodium chloride (3% and 1.5% respectively) was considered the most effective. The optimization of the processing parameters (time and temperature) was done by response surface methodology. According to the sensory analysis, objective texture evaluation and phosphate determinations the optimum conditions for the tenderisation process were an immersion time of 3 h at a temperature of 20  °C. The tenderised meat was used in the preparation of two types of canned products (light brine and a pickling sauce known as "escabeche"), which were evaluated by a taste panel and judged satisfactory.  相似文献   
107.
Bit-level systolic arrays for modular multiplication   总被引:4,自引:0,他引:4  
This paper presents bit-level cellular arrays implementing Blakley's algorithm for multiplication of twon-bit integers modulo anothern-bit integer. The semi-systolic version uses 3n(n+3) single-bit carry save adders and 2n copies of 3-bit carry look-ahead logic, and computes a pair of binary numbers (C, S) in 3n clock cycles such thatC+S[0, 2N). The carry look-ahead logic is used to estimate the sign of the partial product, which is needed during the reduction process. The final result in the correct range [0,N) can easily be obtained by computingC+S andC+S–N, and selecting the latter if it is positive; otherwise, the former is selected. We construct a localized process dependence graph of this algorithm, and introduce a systolic array containing 3nw simple adder cells. The latency of the systolic array is 6n+w–2, wherew=n/2. The systolic version does not require broadcast and can be used to efficiently compute several modular multiplications in a pipelined fashion, producing a result in every clock cycle.  相似文献   
108.
A detailed performance analysis of the least mean square (LMS) algorithm to update each stage of an adaptive Gram-Schmidt processor in interference cancelling adaptive arrays is presented. It is shown that although the number of adaptive weights in the processor is proportional to M2. the total misadjustment contributed by weight jittering is proportional to only M, where M is the size of the processor. In absolute terms, the weight jittering noises do not accumulate as would be expected, but cancel one another out and decrease in magnitude as the optimal powers become smaller from one processing stage to the next. For optimal performance, the feedback factors used in the individual LMS loops should be normalized so that the amount of misadjustment contributed and the convergence time constant are the same for all processing stages. All the weights belonging to one processing stage must be adjusted in a synchronous manner with the same input vector. This synchronous updating requirement is essential for the cancellation of the jittering noises, although in situations where the weights are adaptively updated in a time-multiplexed manner, it may appear more efficient to update each weight based on the most current inputs  相似文献   
109.
In vivo measurements of equivalent resistivities of skull (rho(skull)) and brain (rho(brain)) are performed for six subjects using an electric impedance tomography (EIT)-based method and realistic models for the head. The classical boundary element method (BEM) formulation for EIT is very time consuming. However, the application of the Sherman-Morrison formula reduces the computation time by a factor of 5. Using an optimal point distribution in the BEM model to optimize its accuracy, decreasing systematic errors of numerical origin, is important because cost functions are shallow. Results demonstrate that rho(skull)/rho(brain) is more likely to be within 20 and 50 rather than equal to the commonly accepted value of 80. The variation in rho(brain)(average = 301 omega x cm, SD = 13%) and rho(skull)(average = 12230 omega x cm, SD = 18%) is decreased by half, when compared with the results using the sphere model, showing that the correction for geometry errors is essential to obtain realistic estimations. However, a factor of 2.4 may still exist between values of rho(skull)/rho(brain) corresponding to different subjects. Earlier results show the necessity of calibrating rho(brain) and rho(skull) by measuring them in vivo for each subject, in order to decrease errors associated with the electroencephalogram inverse problem. We show that the proposed method is suited to this goal.  相似文献   
110.
Radar images can show great variability from pixel to pixel, which is an obstacle to effective processing. This variability, due to speckle created by the radar wave coherence, necessitates the use of more adapted filters. Previous studies have shown that multiresolution wavelet analysis yields better results but produces artefacts due to multiscale decomposition. This paper proposes a method that reduces these effects by introducing the fractal dimension. The resultant filter combines wavelet decomposition and variance change model based on the level of variance estimated by studying the fractal dimension of the image.  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