全文获取类型
收费全文 | 5172篇 |
免费 | 143篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 68篇 |
综合类 | 7篇 |
化学工业 | 951篇 |
金属工艺 | 118篇 |
机械仪表 | 168篇 |
建筑科学 | 132篇 |
矿业工程 | 6篇 |
能源动力 | 202篇 |
轻工业 | 282篇 |
水利工程 | 10篇 |
石油天然气 | 16篇 |
无线电 | 914篇 |
一般工业技术 | 926篇 |
冶金工业 | 529篇 |
原子能技术 | 26篇 |
自动化技术 | 971篇 |
出版年
2023年 | 27篇 |
2022年 | 95篇 |
2021年 | 131篇 |
2020年 | 39篇 |
2019年 | 63篇 |
2018年 | 77篇 |
2017年 | 80篇 |
2016年 | 102篇 |
2015年 | 107篇 |
2014年 | 148篇 |
2013年 | 429篇 |
2012年 | 264篇 |
2011年 | 352篇 |
2010年 | 295篇 |
2009年 | 347篇 |
2008年 | 287篇 |
2007年 | 254篇 |
2006年 | 209篇 |
2005年 | 168篇 |
2004年 | 148篇 |
2003年 | 140篇 |
2002年 | 110篇 |
2001年 | 108篇 |
2000年 | 77篇 |
1999年 | 95篇 |
1998年 | 217篇 |
1997年 | 148篇 |
1996年 | 130篇 |
1995年 | 85篇 |
1994年 | 96篇 |
1993年 | 87篇 |
1992年 | 56篇 |
1991年 | 37篇 |
1990年 | 38篇 |
1989年 | 36篇 |
1988年 | 36篇 |
1987年 | 19篇 |
1986年 | 18篇 |
1985年 | 15篇 |
1984年 | 16篇 |
1983年 | 10篇 |
1982年 | 17篇 |
1980年 | 9篇 |
1979年 | 20篇 |
1978年 | 12篇 |
1977年 | 11篇 |
1976年 | 9篇 |
1975年 | 9篇 |
1974年 | 8篇 |
1973年 | 9篇 |
排序方式: 共有5326条查询结果,搜索用时 15 毫秒
61.
Hua-Tsung Chen Chien-Li Chou Wei-Chin Tsai Suh-Yin Lee Bao-Shuh P. Lin 《Journal of Visual Communication and Image Representation》2012,23(5):767-781
With the dramatic growth of fandom population, a considerable amount of research efforts have been devoted to baseball video processing. However, little work focuses on the detailed follow-ups of ball hitting events. This paper proposes a HMM-based ball hitting event exploration system for broadcast baseball video. Utilizing the strictly-defined layout of the baseball field, the proposed system first detects the game-specific spatial patterns in the field, such as the field lines, the bases, the pitch mound, etc. Then, the play region—the currently camera-focused region of the baseball field is identified for frame type classification. Since the temporal patterns of presenting the game progress follow a prototypical order, we consider the classified frame types as observation symbols and recognize ball hitting events using HMM. Experiments conducted on broadcast baseball video show encouraging results in frame type classification and ball hitting event recognition. Three practical applications, including highlight clip extraction by user-designated query, storyboard construction, and similar event retrieval, are introduced to address the applicability of our system. 相似文献
62.
Archer J.W. Lai R. Grundbacher R. Barsky M. Tsai R. Reid P. 《Microwave and Wireless Components Letters, IEEE》2001,11(1):4-6
This paper describes a high-performance indium phosphide (InP) monolithic microwave integrated circuit (MMIC) amplifier, which has been developed for application in radioastronomy and imaging-array receivers. Implemented using coplanar waveguide, the six-stage amplifier exhibits 15 db gain, 10 dB input and output return loss, and low noise figure over the 180-205 GHz frequency range. Only one design pass was needed to obtain excellent agreement between the predicted and measured characteristics of the circuit, a unique achievement in this frequency band. The circuit is also the first 180-205 GHz amplifier designed for and successfully fabricated using TRW's standard 0.1-μm InP HEMT process 相似文献
63.
Chen C.-J. Ye J. Wong W.S. Lu Y.-W. Ho M.-C. Cao Y. Gassner M.J. Pease J.S. Tsai H.-S. Lee H.K. Cabot S. Sun Y. 《Electronics letters》2001,37(21):1304-1305
A robust control scheme for suppressing transients in both lumped and distributed Raman amplifiers is demonstrated. The control method uses only output power monitoring and holds gain fluctuations on surviving channels to <±0.06 dB in an experiment 相似文献
64.
Yu-Pao Tsai Cheng-Hung Ko Yi-Ping Hung Zen-Chung Shih 《IEEE transactions on image processing》2007,16(10):2607-2616
Image-based rendering has been successfully used to display 3-D objects for many applications. A well-known example is the object movie, which is an image-based 3-D object composed of a collection of 2-D images taken from many different viewpoints of a 3-D object. In order to integrate image-based 3-D objects into a chosen scene (e.g., a panorama), one has to meet a hard challenge--to efficiently and effectively remove the background from the foreground object. This problem is referred to as multiview images (MVIs) segmentation. Another task requires MVI segmentation is image-based 3-D reconstruction using multiview images. In this paper, we propose a new method for segmenting MVI, which integrates some useful algorithms, including the well-known graph-cut image segmentation and volumetric graph-cut. The main idea is to incorporate the shape prior into the image segmentation process. The shape prior introduced into every image of the MVI is extracted from the 3-D model reconstructed by using the volumetric graph cuts algorithm. Here, the constraint obtained from the discrete medial axis is adopted to improve the reconstruction algorithm. The proposed MVI segmentation process requires only a small amount of user intervention, which is to select a subset of acceptable segmentations of the MVI after the initial segmentation process. According to our experiments, the proposed method can provide not only good MVI segmentation, but also provide acceptable 3-D reconstructed models for certain less-demanding applications. 相似文献
65.
66.
Signal propagation delay on a multi-source multi-sink bidirectional bus has a dominant effect on high-performance chips. This
work presents a novel greedy algorithm that minimizes the critical propagation delay of an RLC-based bus. Based on the topology
of a multi-source multi-sink bus and the RLC delay model, the proposed algorithm inserts signal repeaters into the critical
path of the RLC-based bus and adjusts their sizes to minimize the maximal propagation delay. This procedure is repeated until
no additional improvement is needed. Several buses with various topologies are tested using the proposed algorithm in deep
submicron technologies. Experimentally, the critical delay in an RLC-based bus can be reduced dramatically by up to 62.4%
with inserted repeater sizes of 24 and execution time of 1.65 s on average. Moreover, average delay reduction, repeater sizes,
and running time for 0.18 μm technology are 5.8%, 6.4%, and 26.2%, respectively, better than those of 0.35 μm. Additionally,
the topologies of all of the RLC-based buses with inserted repeaters in deep submicron technologies are simulated using HSPICE.
The error ratio in the critical delay of a bus with inserted repeaters determined by comparison with HSPICE is 2.7% on average.
The proposed algorithm is simple and extremely practical. 相似文献
67.
Tsai JZ Cao H Tungjitkusolmun S Woo EJ Vorperian VR Webster JG 《IEEE transactions on bio-medical engineering》2000,47(1):41-48
The apparent resistance of a finite-thickness layer measured with a four-electrode plunge probe depends on the electrode insertion depth, electrode spacing, and layer thickness, as well as the resistivity ratio of an underlying layer. A physical model consisting of air, a saline solution layer, and an agar layer simulates the real situation of resistivity measurement. The saline layer represents the finite-thickness layer whose resistivity is to be measured by a plunge electrode probe, and the agar layer represents an underlying perturbing layer. A micropositioner controls the insertion depth of the four electrodes into the saline solution. With the apparent resistance measured on a semi-infinite-thickness layer of saline solution as standard, measurement results show decreasing apparent resistance and increasing error with increasing electrode insertion depth. This information is important for correct measurement of myocardial resistivity in vivo and in vitro. 相似文献
68.
Tsai JZ Will JA Vorperian VR Hubbard-van Stelle S Cao H Tungjitkusolmun S Choy YB Webster JG 《IEEE transactions on bio-medical engineering》2003,50(4):528-532
Due to rapid change of fiber orientation, it is difficult to measure myocardial impedivity separately in a longitudinal or transverse fiber direction without mutual influence in the two directions. Previously published values of the longitudinal and the transverse myocardial impedivity were derived indirectly from measurements that mixed the impedivity in all directions. Those values are questionable because the derivations were based on a simplified uniform myocardial fiber model. In this paper, a miniature rectangular tube was devised to facilitate direct measurement of myocardial impedivity in a uniform fiber direction. The average transverse-to-longitudinal ratio of the measured in vitro swine myocardial impedivity was about 1.66 from 1 Hz to 1 kHz and dropped to 1.25 at 1 MHz. The result is important for accurate modeling of the electrical property of myocardium in biomedical research of radio-frequency cardiac catheter ablation. 相似文献
69.
Fang-Biau Ueng Jun-Da Chen Shang-Chun Tsai 《Wireless Communications, IEEE Transactions on》2008,7(4):1227-1235
In this paper, we propose and analyze a new noncoherent receiver with PN code tracking for direct sequence code division multiple access (DS-CDMA) communication systems in multipath channels. We employ the decision-feedback differential detection method to detect MDPSK signals. An ";error signal"; is used to update the tap weights and the estimated code delay. Increasing the number of feedback symbols can improve the performance of the proposed noncoherent receiver. For an infinite number of feedback symbols, the optimum weight can be derived analytically, and the performance of the proposed noncoherent receiver approaches to that of the conventional coherent receiver. Simulations show good agreement with the theoretical derivation. 相似文献
70.