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   6987篇
  免费   214篇
  国内免费   48篇
电工技术   99篇
综合类   80篇
化学工业   1738篇
金属工艺   141篇
机械仪表   180篇
建筑科学   250篇
矿业工程   17篇
能源动力   322篇
轻工业   958篇
水利工程   74篇
石油天然气   72篇
武器工业   2篇
无线电   541篇
一般工业技术   960篇
冶金工业   502篇
原子能技术   30篇
自动化技术   1283篇
  2024年   41篇
  2023年   104篇
  2022年   199篇
  2021年   292篇
  2020年   214篇
  2019年   232篇
  2018年   213篇
  2017年   188篇
  2016年   239篇
  2015年   197篇
  2014年   260篇
  2013年   536篇
  2012年   392篇
  2011年   555篇
  2010年   349篇
  2009年   358篇
  2008年   368篇
  2007年   300篇
  2006年   270篇
  2005年   189篇
  2004年   211篇
  2003年   190篇
  2002年   185篇
  2001年   156篇
  2000年   117篇
  1999年   94篇
  1998年   181篇
  1997年   112篇
  1996年   88篇
  1995年   77篇
  1994年   46篇
  1993年   47篇
  1992年   28篇
  1991年   26篇
  1990年   23篇
  1989年   18篇
  1988年   11篇
  1987年   14篇
  1986年   12篇
  1985年   16篇
  1984年   9篇
  1983年   6篇
  1982年   11篇
  1981年   10篇
  1980年   9篇
  1979年   6篇
  1978年   6篇
  1977年   8篇
  1976年   13篇
  1975年   5篇
排序方式: 共有7249条查询结果,搜索用时 15 毫秒
51.
The aim of this study was to assess whether independent component analysis (ICA) could be valuable to remove power line noise, cardiac, and ocular artifacts from magnetoencephalogram (MEG) background activity. The MEGs were recorded from 11 subjects with a 148-channel whole-head magnetometer. We used a statistical criterion to estimate the number of independent components. Then, a robust ICA algorithm decomposed the MEG epochs and several methods were applied to detect those artifacts. The whole process had been previously tested on synthetic data. We found that the line noise components could be easily detected by their frequency spectrum. In addition, the ocular artifacts could be identified by their frequency characteristics and scalp topography. Moreover, the cardiac artifact was better recognized by its skewness value than by its kurtosis one. Finally, the MEG signals were compared before and after artifact rejection to evaluate our method.  相似文献   
52.
A novel technique for operating MOS Translinear loops at very low supply voltages is described, based on the use of Flipped Voltage Followers for biasing the loops. The resulting topologies, suited to standard CMOS processes, can be successfully applied to a varied repertory of low-voltage analog circuits, such as squarers, multipliers, filters, oscillators, and RMS-DC converters. Measurement results for a geometric-mean and a squarer/divider circuit demonstrate on silicon the usefulness of this technique.  相似文献   
53.
The uplink capacity and the interference statistics (mean and variance) of the sectors of the cigar-shaped W-CDMA microcell are studied. A model with eighteen sectors is used to analyze the uplink. The microcells are assumed to exist in a long tunnel with at least nine base stations. The hybrid model of propagation is used in the calculations. The capacity and the interference statistics of the sectors are studied in terms of the most important parameters: sector radius, specific attenuation factor, antenna sidelobe levels, bend losses and the power control standard deviation error.  相似文献   
54.
This article presents the first results of our study and experimentation with the new IPv6 IX-based address assignment model and its deployment in IXs where peering is organized around route servers. An IX model that identifies where the new IX customers can be located and how services like provider choice or multihoming can be offered is proposed. The article also describes the emulation environment that has been developed to easily create and experiment with complex IX scenarios without involving setup of costly configurations made of several pieces of equipment. This work has been carried out in the context of the European Union funded project Euro6IX.  相似文献   
55.
For the past few decades there has been tremendous innovation and development of Terahertz (THz) science and imaging. In particular, the technique of 3-D computed tomography has been adapted from the X-Ray to the THz range. However, the finite refractive index of materials in the THz range can severally refract probing THz beams during the acquisition of tomography data. Due to Fresnel reflection power losses at the boundaries as well as steering of the THz beam through the sample, refractive effects lead to anomalously high local attenuation coefficients near the material boundaries of a reconstructed image. These boundary phenomena can dominate the reconstructed THz-CT images making it difficult to distinguish structural defect(s) inside the material. In this paper an algorithm has been developed to remove the effects of refraction in THz-CT reconstructed images. The algorithm is successfully implemented on cylindrical shaped objects.  相似文献   
56.
This paper presents a novel two-stage comb decimator with the improved magnitude characteristic. Simple multiplierless corrector filters, which are designed using the frequency sampling and IFIR methods, are introduced. The proposed filters compensate the comb passband droop in the wideband passband region and increase the attenuations in the folding bands. Using the multirate identity the filters may be moved to a lower rate. The filter design depends only on the number of the cascaded comb filters and do not depend on the decimation factor M.  相似文献   
57.
Stable droplets and dark-ring cavity solitons in nonlinear optical devices   总被引:1,自引:0,他引:1  
Two kinds of cavity solitons, stable circular domain walls (droplets) and dark-ring cavity solitons, are presented in models of vectorial Kerr resonators and degenerate optical parametric oscillators. These structures are universal in systems with two equivalent homogeneous states and are found for parameter values close to those of a modulational instability of a flat front. Stable droplets owe their existence to curvature effects and, therefore, they are not present in one-dimensional systems. We show that stable droplets nucleate out of dark-ring cavity solitons and that in some systems there are regimes in which they coexist.  相似文献   
58.
On the algebraic structure of quasi-cyclic codes .I. Finite fields   总被引:5,自引:0,他引:5  
A new algebraic approach to quasi-cyclic codes is introduced. The key idea is to regard a quasi-cyclic code over a field as a linear code over an auxiliary ring. By the use of the Chinese remainder theorem (CRT), or of the discrete Fourier transform (DFT), that ring can be decomposed into a direct product of fields. That ring decomposition in turn yields a code construction from codes of lower lengths which turns out to be in some cases the celebrated squaring and cubing constructions and in other cases the (u+υ|u-υ) and Vandermonde constructions. All binary extended quadratic residue codes of length a multiple of three are shown to be attainable by the cubing construction. Quinting and septing constructions are introduced. Other results made possible by the ring decomposition are a characterization of self-dual quasi-cyclic codes, and a trace representation that generalizes that of cyclic codes  相似文献   
59.
吴蔚华  孙三  陈宇 《电视技术》2021,45(6):119-121,125
在介绍8K超高清显示系统技术现状的基础上,详细介绍8K超高清复合测试图的参数指标、关键要素及测试内容,研究8K超高清显示设备的关键光学指标的测量方法.  相似文献   
60.
We investigate the ability to derive meaningful information from decompressed imaging spectrometer data. Hyperspectral images are compressed with near-lossless and lossy coding methods. Linear prediction between the bands is used in both cases. Each band is predicted by a previously transmitted band. The residual is formed by subtracting the prediction from the original data and then is compressed either with a near-lossless bit-plane coder or with the lossy JPEG2000 algorithm. We study the effects of these two types of compression on hyperspectral image processing such as mineral and vegetation content classification using whole- and mixed pixel analysis techniques. The results presented in this paper indicate that an efficient lossy coder outperforms near-lossless method in terms of its impact on final hyperspectral data applications.  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