全文获取类型
收费全文 | 358076篇 |
免费 | 21372篇 |
国内免费 | 16053篇 |
专业分类
化学 | 177393篇 |
晶体学 | 4444篇 |
力学 | 16624篇 |
综合类 | 687篇 |
数学 | 33864篇 |
物理学 | 103354篇 |
无线电 | 59135篇 |
出版年
2023年 | 3385篇 |
2022年 | 5598篇 |
2021年 | 7377篇 |
2020年 | 7361篇 |
2019年 | 7678篇 |
2018年 | 8154篇 |
2017年 | 8063篇 |
2016年 | 11011篇 |
2015年 | 8733篇 |
2014年 | 12182篇 |
2013年 | 18651篇 |
2012年 | 18617篇 |
2011年 | 19719篇 |
2010年 | 15148篇 |
2009年 | 15587篇 |
2008年 | 17209篇 |
2007年 | 16232篇 |
2006年 | 14831篇 |
2005年 | 13110篇 |
2004年 | 11208篇 |
2003年 | 10065篇 |
2002年 | 9870篇 |
2001年 | 9713篇 |
2000年 | 7829篇 |
1999年 | 6833篇 |
1998年 | 5836篇 |
1997年 | 5614篇 |
1996年 | 5277篇 |
1995年 | 4600篇 |
1994年 | 4449篇 |
1993年 | 4077篇 |
1992年 | 4233篇 |
1991年 | 4161篇 |
1990年 | 3870篇 |
1989年 | 3657篇 |
1988年 | 3432篇 |
1987年 | 3158篇 |
1986年 | 2976篇 |
1985年 | 3629篇 |
1984年 | 3559篇 |
1983年 | 2950篇 |
1982年 | 2832篇 |
1981年 | 2753篇 |
1979年 | 2851篇 |
1978年 | 2811篇 |
1977年 | 3002篇 |
1976年 | 2999篇 |
1975年 | 2765篇 |
1974年 | 2692篇 |
1973年 | 2825篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
In this article, we construct and analyze a residual-based a posteriori error estimator for a quadratic finite volume method (FVM) for solving nonlinear elliptic partial differential equations with homogeneous Dirichlet boundary conditions. We shall prove that the a posteriori error estimator yields the global upper and local lower bounds for the norm error of the FVM. So that the a posteriori error estimator is equivalent to the true error in a certain sense. Numerical experiments are performed to illustrate the theoretical results. 相似文献
2.
3.
Shunkang Liu 《Journal of Infrared, Millimeter and Terahertz Waves》2003,24(5):629-638
The pill-box and block RF windows for millimeter wave (MMW) tubes are presented. The pill-box window is suitable for broadband MMW tubes. And the block window can be used for high power tubes in short MMW. The equivalent circuits for two windows are given. To reach better match characteristics in wider operating bandwidth, the optimum design methods for pill-box and block window in MMW tubes are described in this paper. The testing results show that the theoretic computation is fast and useful accuracy. The design methods possess references value to designer for MMW tubes. 相似文献
4.
5.
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
6.
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
7.
8.
Kontogiannopoulos N. Psychalinos C. 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2006,53(12):1373-1377
In this brief, the well-known switched-current (SI) filtering technique is revisited using the concept of the square-root domain (SRD) filtering. It is proved that SI filters are a subclass of the SRD filters, where sampled-data signal processing is performed. This is achieved by considering typical lossless and lossy SRD sampled-data integrator configurations, using a set of complementary SRD operators which are based on the quadratic I-V relationship of MOS transistor operated in the saturation. Circuit examples are given, where linear-domain integrator and third-order filter configurations were derived using appropriate SRD sampled-data building blocks 相似文献
9.
V. N. Logozinskii 《Journal of Communications Technology and Electronics》2006,51(7):836-840
Optical phase nonreciprocity is found to appear in fiber-optic gyroscopes as a result of a magnetically induced distortion of a propagating fiber mode. It is shown that this nonreciprocity places a limitation on the magnetic stability of a gyroscope. 相似文献
10.
M. N. Levin A. V. Tatarintsev V. A. Makarenko V. R. Gitlin 《Russian Microelectronics》2006,35(5):329-336
A model is formulated that describes how radiation-induced charge accumulates in the gate oxide of a MOS structure and how it decays through tunneling and thermal emission. The model is used in a numerical analysis of the x-ray or UV adjustment of threshold voltage in MOS-circuit manufacture. The limits of this process technique are evaluated. 相似文献