全文获取类型
收费全文 | 531942篇 |
免费 | 4566篇 |
国内免费 | 1595篇 |
专业分类
化学 | 236051篇 |
晶体学 | 7473篇 |
力学 | 23621篇 |
综合类 | 17篇 |
数学 | 56796篇 |
物理学 | 150330篇 |
无线电 | 63815篇 |
出版年
2021年 | 4798篇 |
2020年 | 5130篇 |
2019年 | 5953篇 |
2018年 | 8077篇 |
2017年 | 8185篇 |
2016年 | 11232篇 |
2015年 | 5998篇 |
2014年 | 10587篇 |
2013年 | 23267篇 |
2012年 | 17817篇 |
2011年 | 21253篇 |
2010年 | 16491篇 |
2009年 | 17322篇 |
2008年 | 20844篇 |
2007年 | 21339篇 |
2006年 | 19634篇 |
2005年 | 17420篇 |
2004年 | 16288篇 |
2003年 | 14737篇 |
2002年 | 14602篇 |
2001年 | 16593篇 |
2000年 | 12889篇 |
1999年 | 10249篇 |
1998年 | 8866篇 |
1997年 | 8774篇 |
1996年 | 8028篇 |
1995年 | 7185篇 |
1994年 | 7176篇 |
1993年 | 6917篇 |
1992年 | 7552篇 |
1991年 | 7751篇 |
1990年 | 7311篇 |
1989年 | 7132篇 |
1988年 | 6714篇 |
1987年 | 6360篇 |
1986年 | 5940篇 |
1985年 | 7501篇 |
1984年 | 7619篇 |
1983年 | 6352篇 |
1982年 | 6265篇 |
1981年 | 6011篇 |
1980年 | 5706篇 |
1979年 | 6206篇 |
1978年 | 6142篇 |
1977年 | 6287篇 |
1976年 | 6249篇 |
1975年 | 5918篇 |
1974年 | 5768篇 |
1973年 | 5901篇 |
1972年 | 4312篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Note on B-splines, wavelet scaling functions, and Gabor frames 总被引:3,自引:0,他引:3
Grochenig K. Janssen A.J.E.M. Kaiblinger N. Pfander G.E. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2003,49(12):3318-3320
Let g be a continuous, compactly supported function on such that the integer translates of g constitute a partition of unity. We show that the Gabor system (g,a,b), with window g and time-shift and frequency-shift parameters a,b>0 has no lower frame bound larger than 0 if b=2,3,... and a>0. In particular, (g,a,b) is not a Gabor frame if g is a continuous, compactly supported wavelet scaling function and if b=2,3,... and a>0. We give an example for our result for the case that g=B/sub 1/, the triangle function supported by [-1,1], by showing pictures of the canonical dual corresponding to (g,a,b) where ab=1/4 and b crosses the lines N=2,3,. 相似文献
5.
de Oliveira J.C. Hosseini M. Shirmohammadi S. Malric F. Nourian S. El Saddik A. Georganas N.D. 《Multimedia, IEEE》2003,10(3):18-29
Using Java-based tools in multimedia collaborative environments accessed over the Internet can increase an application's client base. Most operating systems support Java, and its "compile once-run everywhere" architecture is easy to maintain and update. The Java-based tools presented here let users share Internet resources, including resources originally designed for single use. 相似文献
6.
Hasegawa M. Furutani S. Doki S. Okuma S. 《Industrial Electronics, IEEE Transactions on》2003,50(5):912-919
This paper proposes a method for designing a robust full-order observer for vector-controlled induction motors taking core loss into account. Although conventional research focuses on parameter identification, global stability of the identification remains questionable. Therefore, robustness against some parameters is required. This paper describes the design of a robust full-order observer which takes core loss into account, using both the gain-scheduled H/sub /spl infin// control and the linear matrix inequality technique. This design always results in a stable controller. The robustness of the proposed method against variations of resistances is evaluated by experiments. 相似文献
7.
N. P. Yeliseyeva 《Journal of Communications Technology and Electronics》2006,51(4):380-384
Rigorous analytic expressions for radiation resistance R Σ of an electric dipole are obtained for three mutually orthogonal orientations of the dipole’s axis with respect to a plane metal screen or right-angle corner of infinite dimensions. Radiation resistance R Σ of the dipole oriented arbitrarily in space is calculated and analyzed as a function of the distance from the screen. 相似文献
8.
In this letter, we introduce and investigate a new problem referred to as the All Hops Shortest Paths (AHSP) problem. The AHSP problem involves selecting, for all hop counts, the shortest paths from a given source to any other node in a network. We derive a tight lower bound on the worst-case computational complexities of the optimal comparison-based solutions to AHSP. 相似文献
9.
S.M. Savaresi F.L. Taroni F. Previdi S. Bittanti 《Mechatronics, IEEE/ASME Transactions on》2004,9(3):569-579
The problem considered in this paper is the design and tuning of the control system of a power-split continuously variable transmission (CVT) used in high-power tractors. Power-split CVTs are characterized by the combination of a traditional mechanical transmission and by a continuously-variable transmission. This guarantees, at the same time, smooth variations of the transmission-ratio and high efficiency of the overall transmission system. The control architecture of an hydrostatic power-split CVT is constituted by three main parts: 1) servo-controller on the current of the valve which drives the hydraulic transmission; 2) a servo-controller on the hydraulic transmission-ratio; and 3) a synchronizer which coordinates the hydraulic and the mechanical parts of the CVT. In this work, these three controllers are fully developed, including: design, implementation, and evaluation on an experimental system. 相似文献
10.