全文获取类型
收费全文 | 3226篇 |
免费 | 130篇 |
国内免费 | 35篇 |
专业分类
电工技术 | 52篇 |
综合类 | 59篇 |
化学工业 | 557篇 |
金属工艺 | 109篇 |
机械仪表 | 100篇 |
建筑科学 | 86篇 |
矿业工程 | 10篇 |
能源动力 | 146篇 |
轻工业 | 190篇 |
水利工程 | 15篇 |
石油天然气 | 15篇 |
武器工业 | 2篇 |
无线电 | 470篇 |
一般工业技术 | 706篇 |
冶金工业 | 401篇 |
原子能技术 | 15篇 |
自动化技术 | 458篇 |
出版年
2023年 | 23篇 |
2022年 | 54篇 |
2021年 | 71篇 |
2020年 | 39篇 |
2019年 | 43篇 |
2018年 | 52篇 |
2017年 | 58篇 |
2016年 | 66篇 |
2015年 | 50篇 |
2014年 | 90篇 |
2013年 | 244篇 |
2012年 | 176篇 |
2011年 | 184篇 |
2010年 | 149篇 |
2009年 | 173篇 |
2008年 | 150篇 |
2007年 | 139篇 |
2006年 | 152篇 |
2005年 | 113篇 |
2004年 | 98篇 |
2003年 | 81篇 |
2002年 | 72篇 |
2001年 | 69篇 |
2000年 | 69篇 |
1999年 | 74篇 |
1998年 | 112篇 |
1997年 | 101篇 |
1996年 | 116篇 |
1995年 | 70篇 |
1994年 | 63篇 |
1993年 | 51篇 |
1992年 | 45篇 |
1991年 | 36篇 |
1990年 | 33篇 |
1989年 | 39篇 |
1988年 | 36篇 |
1987年 | 25篇 |
1986年 | 30篇 |
1985年 | 16篇 |
1984年 | 12篇 |
1983年 | 12篇 |
1982年 | 15篇 |
1981年 | 19篇 |
1980年 | 9篇 |
1979年 | 12篇 |
1977年 | 12篇 |
1976年 | 15篇 |
1975年 | 5篇 |
1972年 | 6篇 |
1970年 | 2篇 |
排序方式: 共有3391条查询结果,搜索用时 15 毫秒
51.
Chou W. Gray R.M. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1991,37(3):500-513
The spectrum of the quantization error in a dithered sigma-delta modulator is derived under the constraint that the dithering signal does not cause overload. The results apply to DC, sinusoidal, and more general quasi-stationary signals. It is shown in the case of a simple sigma-delta modulation that no-overload dithering can smooth the error spectrum and can make the quantization error asymptotically uncorrelated with the input. It does not, however, make the quantization error white. In the case of multistage sigma-delta modulation with the appropriate dithering, the quantization error becomes white, even for a system with only two stages. The signal-to-quantization-noise ratio (SQNR) is derived for sigma-delta and multistage sigma-delta oversampled analog-to-digital conversion with additive dithering. Simulation results, are presented to support the theoretical analysis.<> 相似文献
52.
Jiun‐Wei Horng Chun‐Li Hou Chun‐Ming Chang Hung‐Pin Chou Chun‐Ta Lin Yao‐Hsin Wen 《ETRI Journal》2006,28(4):486-494
Two current‐mode and/or voltage‐mode quadrature oscillator circuits each using one fully‐differential second‐generation current conveyor (FDCCII), two grounded capacitors, and two (or three) grounded resistors are presented. In the proposed circuits, the current‐mode quadrature signals have the advantage of high‐output impedance. The oscillation conditions and oscillation frequencies are orthogonally (or independently) controllable. The current‐mode and voltage‐mode quadrature signals can be simultaneously obtained from the second proposed circuit. The use of only grounded capacitors and resistors makes the proposed circuits ideal for integrated circuit implementation. Simulation results are also included. 相似文献
53.
Yu Jiang Chou Chun Tung Yang Zhongkai Du Xu Wang Tai 《电子科学学刊(英文版)》2006,23(5):798-800
I. Introduction Streaming media has been widely used over the Internet in recent years. However, the growing use in streaming media, which generally has large size, can have a significant impact on the user perceived latency and network congestion. A popular approach to reduce the response time and backbone bandwidth consumption is to deploy proxy caches at the edge of the Internet. Due to the large size and different popularity for different part of the streaming video, it is not practical … 相似文献
54.
Traditional wireless communications only utilize fixed-rate multicast and broadcast. In other words, only the most robust
modulation and coding scheme can be applied for data transmission. Such a scheme fails to sufficiently exploit the potential
gains of multicast and broadcast, resulting in bandwidth waste. To overcome such a problem, investigating the rate adaptation
of multicast and broadcast wireless systems is the primary task. Unlike the traditional wireless systems, this paper presents
an analytical model with rate adaptation for both multicast and broadcast. Adaptive modulation and coding are applied to achieve
rate adaptation. We construct a stochastic model by using Finite State Markov chains for the multicast broadcast system modeling.
The model’s outputs are shown to approximate to the results of our system level simulations. The model derives the performance
of rate adaptation in multicast and broadcast. With the deduced modeling results, we can predict the system throughput providing
the channel states, and the modulation and coding schemes variations. 相似文献
55.
Wireless mesh networks have become a promising means to provide low-cost broadband access. Many WMN applications require broadcasting data (IPTV etc.) over the WMN. This article studies how efficient data broadcast, measured in terms of broadcast latency, can be realized by exploiting two features of WMNs: the use of multiple transmission rates at the link layer and the use of multiple radio interfaces on each node. We demonstrate that by exploiting these features, broadcast latency can be reduced severalfold compared to the current default practice in wireless LANs of using the lowest transmission rate for broadcast traffic. We also discuss two important insights we have gained from our investigation. First, we find that when multiple radio interfaces are used, a channel assignment algorithm designed for unicast traffic may often perform poorly for broadcast flows. Second, we find that the efficiency of a transmission rate for reducing broadcast latency can be reasonably predicted by the product of the transmission rate and its coverage area. 相似文献
56.
文章以区域调度理论为基础,提出了构建城市公共自行车调度系统进行了构建,并以GSM通信技术、定位系统技术等为技术支撑,从而对系统进行了实现。 相似文献
57.
Ta-Hsin Chou Kuei-Yuan Cheng Tien-Li Chang Chia-Jen Ting Hsiu-Chen Hsu Chin-Jyi Wu Jen-Hui Tsai Tzn-Yu Huang 《Microelectronic Engineering》2009,86(4-6):628-631
The cholesteric liquid crystals display (ChLCD) is one kind of reflective liquid crystal display, the antireflective layer on its transparent conduction oxides (TCO) film is needed for good contrast and color performance. In this study, the finite difference time domain (FDTD) simulation and nanoimprinting fabrication of AR structures on the TCO film are developed. Finally, the reflectance of AR structures on TCO film is just half of the original film, and this result is useful for the reflective ChLCD product commercialized in the future. 相似文献
58.
A new full-wave analysis method, referred to as the WH/GSMT, is developed to solve multilayered planar transmission line problems. First, the scattering of an obliquely incident parallel plate mode (PPM) by a PEC half plane embedded in a multilayered isotropic dielectric substrate within a PEC parallel plate region is analyzed via the Wiener-Hopf (WH) technique. The solution is then incorporated into the generalized scattering matrix technique (GSMT) to find the (complex) propagation constant and characteristic impedance of the planar transmission lines. The lateral power leakage is taken into account rigorously in the WH/GSMT. Numerical results including the microstrip line, conductor-backed slotline, coupled microstrip lines, and antipodal finlines are presented along with a discussion of the advantages/disadvantages of this method 相似文献
59.
Nan-Chi Chou Chung-Kuan Cheng 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》1995,3(1):141-146
We propose a simulated annealing based zero-skew clock net construction algorithm that works in any routing spaces, from Manhattan to Euclidean, with the added flexibility of optimizing either the wire length or the propagation delay. We first devise an O(log n) tree grafting perturbation function to construct a zero-skew clock tree under the Elmore delay model. This tree grafting scheme is able to explore the entire solution space asymptotically. A Gauss-Seidel iteration procedure is then applied to optimize the Steiner point positions. Experimental results have shown that our algorithm can achieve substantial delay reduction and encouraging wire length minimization compared to previous works 相似文献
60.
We introduce a probabilistic computer vision technique to track monotonically advancing boundaries of objects within image sequences. Our method incorporates a novel technique for including statistical prior shape information into graph-cut based segmentation, with the aid of a majorization-minimization algorithm. Extension of segmentation from single images to image sequences then follows naturally using sequential Bayesian estimation. Our methodology is applied to two unrelated sets of real biomedical imaging data, and a set of synthetic images. Our results are shown to be superior to manual segmentation. 相似文献