全文获取类型
收费全文 | 3369篇 |
免费 | 240篇 |
国内免费 | 24篇 |
学科分类
工业技术 | 3633篇 |
出版年
2023年 | 16篇 |
2022年 | 27篇 |
2021年 | 62篇 |
2020年 | 45篇 |
2019年 | 68篇 |
2018年 | 90篇 |
2017年 | 156篇 |
2016年 | 82篇 |
2015年 | 74篇 |
2014年 | 120篇 |
2013年 | 235篇 |
2012年 | 177篇 |
2011年 | 250篇 |
2010年 | 173篇 |
2009年 | 175篇 |
2008年 | 152篇 |
2007年 | 135篇 |
2006年 | 133篇 |
2005年 | 154篇 |
2004年 | 148篇 |
2003年 | 106篇 |
2002年 | 93篇 |
2001年 | 76篇 |
2000年 | 77篇 |
1999年 | 71篇 |
1998年 | 98篇 |
1997年 | 74篇 |
1996年 | 61篇 |
1995年 | 40篇 |
1994年 | 52篇 |
1993年 | 64篇 |
1992年 | 49篇 |
1991年 | 33篇 |
1990年 | 13篇 |
1989年 | 33篇 |
1988年 | 21篇 |
1987年 | 27篇 |
1986年 | 17篇 |
1985年 | 15篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 10篇 |
1981年 | 12篇 |
1980年 | 17篇 |
1979年 | 10篇 |
1978年 | 9篇 |
1977年 | 10篇 |
1976年 | 8篇 |
1975年 | 8篇 |
1970年 | 10篇 |
排序方式: 共有3633条查询结果,搜索用时 640 毫秒
41.
A modified CIECAM02 colour appearance model, named CIECAM02‐m2, is proposed to enable CIECAM02 to predict the simultaneous contrast effect. The structure of the CIECAM02‐m2 is a development from CIECAM02, and contains two different procedures for modifying the reference white; one is for lightness and the other is for hue. The model was tested using a data set accumulated in this study and the LUTCHI data. The CV values for three colour attributes between predictions and experimental data were used to evaluate the accuracy of the model. The low CV values obtained show the performance of the CIECAM02‐m2 model to predict the simultaneous contrast effect satisfactorily. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 121 – 129, 2007 相似文献
42.
Chin E. Lin Jong-Bi Wei Ching-Lien Huang Chi-Jen Huang 《IEEE transactions on magnetics》1989,25(3):2706-2712
A simplified analytical expression in polynomial form to determine the transformer saturation and hysteresis characteristics without field test data is presented. Higher-order approximations are simulated for comparison with transformers of various capacities. The results are compared with experiments and simulations and show very good agreement. It is possible to determine accurate transformer saturation and hysteresis characteristics with this simplified procedure 相似文献
43.
A. Chin 《Algorithmica》1994,12(2-3):170-181
Consider the problem of efficiently simulating the shared-memory parallel random access machine (PRAM) model on massively parallel architectures with physically distributed memory. To prevent network congestion and memory bank contention, it may be advantageous to hash the shared memory address space. The decision on whether or not to use hashing depends on (1) the communication latency in the network and (2) the locality of memory accesses in the algorithm.We relate this decision directly to algorithmic issues by studying the complexity of hashing in the Block PRAM model of Aggarwal, Chandra, and Snir, a shared-memory model of parallel computation which accounts for communication locality. For this model, we exhibit a universal family of hash functions having optimal locality. The complexity of applying these hash functions to the shared address space of the Block PRAM (i.e., by permuting data elements) is asymptotically equivalent to the complexity of performing a square matrix transpose, and this result is best possible for all pairwise independent universal hash families. These complexity bounds provide theoretical evidence that hashing and randomized routing need not destroy communication locality, addressing an open question of Valiant.This work was started when the author was a student at Oxford University, supported by a National Science Foundation Graduate Fellowship and a Rhodes Scholarship. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author and do not necessarily reflect the views of the National Science Foundation or the Rhodes Trust. 相似文献
44.
45.
Su Chen Beng Chin Ooi Zhenjie Zhang 《The VLDB Journal The International Journal on Very Large Data Bases》2012,21(2):265-286
In the last decade, spatio-temporal database research focuses on the design of effective and efficient indexing structures
in support of location-based queries such as predictive range queries and nearest neighbor queries. While a variety of indexing
techniques have been proposed to accelerate the processing of updates and queries, not much attention has been paid to the
updating protocol, which is another important factor affecting the system performance. In this paper, we propose a generic
and adaptive updating protocol for moving object databases with less number of updates between objects and the database server,
thereby reducing the overall workload of the system. In contrast to the approach adopted by most conventional moving object
database systems where the exact locations and velocities last disclosed are used to predict their motions, we propose the
concept of Spatio-temporal safe region to approximate possible future locations. Spatio-temporal safe regions provide larger space of tolerance for moving objects,
freeing them from location and velocity updates as long as the errors remain predictable in the database. To answer predictive
queries accurately, the server is allowed to probe the latest status of objects when their safe regions are inadequate in
returning the exact query results. Spatio-temporal safe regions are calculated and optimized by the database server with two
contradictory objectives: reducing update workload while guaranteeing query accuracy and efficiency. To achieve this, we propose
a cost model that estimates the composition of active and passive updates based on historical motion records and query distribution.
More system performance improvements can be obtained by cutting more updates from the clients, when the users of system are
comfortable with incomplete but accuracy bounded query results. We have conducted extensive experiments to evaluate our proposal
on a variety of popular indexing structures. The results confirm the viability, robustness, accuracy and efficiency of our
proposed protocol. 相似文献
46.
Faa‐Jeng Lin Jonq‐Chin Hwang Kuang‐Hsiung Tan Zong‐Han Lu Yung‐Ruei Chang 《Asian journal of control》2012,14(3):768-783
An intelligent control for a stand‐alone doubly‐fed induction generator (DFIG) system using a proportional‐integral‐derivative neural network (PIDNN) is proposed in this study. This system can be applied as a stand‐alone power supply system or as the emergency power system when the electricity grid fails for all sub‐synchronous, synchronous, and super‐synchronous conditions. The rotor side converter is controlled using field‐oriented control to produce 3‐phase stator voltages with constant magnitude and frequency at different rotor speeds. Moreover, the grid side converter, which is also controlled using field‐oriented control, is primarily implemented to maintain the magnitude of the DC‐link voltage. Furthermore, the intelligent PIDNN controller is proposed for both the rotor and grid side converters to improve the transient and steady‐state responses of the DFIG system for different operating conditions. Both the network structure and online learning algorithm are introduced in detail. Finally, the feasibility of the proposed control scheme is verified through experimentation. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society 相似文献
47.
An improved version of Afek and Gafni's synchronous algorithm for distributed election in complete networks is given and anO(n) expected message complexity is shown.
M.Y. Chan received her Ph.D. in 1988 from the University of Hong Kong, and her M.S. and B.A. degrees in computer science from the University of California, San Diego in 1980 and 1981, respectively. She is currently an Assistant Professor at the University of Texas at Dallas.
Francis Y.L. Chin (S71-M76-SM85) received the B.Sc. degree in engineering science from the University of Toronto, Toronto, Canada, in 1972, and the M.S., M.A., and Ph.D. degrees in electrical engineering and computer science from Princeton University, New Jersey, in 1974, 1975, and 1976, respectively. Since 1975, he has taught at the University of Maryland, Baltimore Country, University of California, San Diego, University of Alberta, and Chinese University of Hong Kong. He is currently Head of the Department of Computer Science, University of Hong Kong. He has served as a program co-chairman of the 1988 International Conference on Computer Processing of Chinese and Oriental Languages (Toronto) and the International Computer Science Conference '88 (Hong Kong). His current research interests include algorithm design and analysis, parallel and distributed computing. 相似文献
48.
Gordon Chin 《Journal of Infrared, Millimeter and Terahertz Waves》1987,8(10):1219-1234
An optically pumped submillimeter laser operating in the 500 μm (600 GHz) to 100 μm (3 THz) spectral range is the primary and, at present, the only available local oscillator (LO) source for laboratory and astronomical heterodyne applications for this wavelength region. A short review of the state-of-the-art of submillimeter lasers as LO sources, with an emphasis given to receiver systems designed for airborne heterodyne observations, will be presented. The characteristics and prospects for constructing a spacequalifiable laser LO system will also be given. 相似文献
49.
Given two processes, each having a total-ordered set ofn elements, we present a distributed algorithm for finding median of these 2n elements using no more than logn +O(logn) messages, but if the elements are distinct, only logn +O(1) messages will be required. The communication complexity of our algorithm is better than the previously known result which takes 2 logn messages. 相似文献
50.
Chun-Yuan Cheng Lassina Barro Shang-Ting Tsai Tai-Wei Feng Xiao-Yu Wu Che-Wei Chao Ruei-Siang Yu Ting-Yu Chin Ming Fa Hsieh 《International journal of molecular sciences》2021,22(6)
Microglia-mediated neuroinflammation is recognized to mainly contribute to the progression of neurodegenerative diseases. Epigallocatechin-3-gallate (EGCG), known as a natural antioxidant in green tea, can inhibit microglia-mediated inflammation and protect neurons but has disadvantages such as high instability and low bioavailability. We developed an EGCG liposomal formulation to improve its bioavailability and evaluated the neuroprotective activity in in vitro and in vivo neuroinflammation models. EGCG-loaded liposomes have been prepared from phosphatidylcholine (PC) or phosphatidylserine (PS) coated with or without vitamin E (VE) by hydration and membrane extrusion method. The anti-inflammatory effect has been evaluated against lipopolysaccharide (LPS)-induced BV-2 microglial cells activation and the inflammation in the substantia nigra of Sprague Dawley rats. In the cellular inflammation model, murine BV-2 microglial cells changed their morphology from normal spheroid to activated spindle shape after 24 h of induction of LPS. In the in vitro free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, EGCG scavenged 80% of DPPH within 3 min. EGCG-loaded liposomes could be phagocytized by BV-2 cells after 1 h of cell culture from cell uptake experiments. EGCG-loaded liposomes improved the production of BV-2 microglia-derived nitric oxide and TNF-α following LPS. In the in vivo Parkinsonian syndrome rat model, simultaneous intra-nigral injection of EGCG-loaded liposomes attenuated LPS-induced pro-inflammatory cytokines and restored motor impairment. We demonstrated that EGCG-loaded liposomes exert a neuroprotective effect by modulating microglia activation. EGCG extracted from green tea and loaded liposomes could be a valuable candidate for disease-modifying therapy for Parkinson’s disease (PD). 相似文献