全文获取类型
收费全文 | 5732篇 |
免费 | 1274篇 |
国内免费 | 803篇 |
专业分类
化学 | 782篇 |
晶体学 | 79篇 |
力学 | 121篇 |
综合类 | 62篇 |
数学 | 114篇 |
物理学 | 3268篇 |
综合类 | 3383篇 |
出版年
2024年 | 55篇 |
2023年 | 214篇 |
2022年 | 218篇 |
2021年 | 262篇 |
2020年 | 160篇 |
2019年 | 223篇 |
2018年 | 149篇 |
2017年 | 206篇 |
2016年 | 201篇 |
2015年 | 255篇 |
2014年 | 528篇 |
2013年 | 387篇 |
2012年 | 404篇 |
2011年 | 440篇 |
2010年 | 410篇 |
2009年 | 454篇 |
2008年 | 479篇 |
2007年 | 346篇 |
2006年 | 322篇 |
2005年 | 290篇 |
2004年 | 298篇 |
2003年 | 281篇 |
2002年 | 214篇 |
2001年 | 187篇 |
2000年 | 126篇 |
1999年 | 101篇 |
1998年 | 107篇 |
1997年 | 100篇 |
1996年 | 79篇 |
1995年 | 64篇 |
1994年 | 64篇 |
1993年 | 30篇 |
1992年 | 37篇 |
1991年 | 26篇 |
1990年 | 34篇 |
1989年 | 19篇 |
1988年 | 18篇 |
1987年 | 10篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有7809条查询结果,搜索用时 15 毫秒
51.
52.
CHENXixin JIANGGuojian XUXinsheng XUXinsheng 《声学学报:英文版》2004,23(1):88-96
An approach to the detection of underwater remote target by estimating its backscattering coefficient is presented. The key to this approach is that the echo signal is represented in state-variable model and the back-scattering coefficients of target are contained in dynamic noise of this model, thus underwater target can be detected by estimating this dynamic noise, i.e., deconvolving this model. When all noise statistics are a priori known, an optimum deconvolution algorithm based on the optimum state filter is derived, or else, an adaptive deconvolution algorithm based on the adaptive state filter of alternatively estimating the vector state and the noise statistics is developed. In the final simulation test, an echo signal with SNR equal to -6.1 dB is proceeded using the aforementioned two deconvolution algorithms, respectively, and the results demonstrate good performance of the approach. 相似文献
53.
54.
YANGHe-lin LIUZhen-lai WENDing-e XIAYing-qing LIUWu LUShu 《武汉大学学报:自然科学英文版》2005,10(3):559-561
The electromagnetic (EM) scattering by rivets on the conducting plate is studied for the first time by using electric field integral equation (EFIE) in conjunction with the moment method. The surfaces of the rivets and the plate are partitioned into triangular cells, the current distribution on the patches is represented by sub-domain type basis function, the EFIE is translated into matrix equation by the Galerkin method, then the current coefficient is obtained. The results show the properties of radar cross section (RCS) varying with the incident angle when there are rivets on the plate. 相似文献
55.
56.
57.
在当前激光核聚变实验中,中子集中在短时间内出现、且产额低。为适应这种特点,要求探测器的效率高,分辨时间短。利用闪烁中子探测器探测激光核聚变所产生的中子,能测定中子产额,记录中子能量,而且探测效率高,分辨时间短。缺点是易受γ射线、X射线的干扰。 相似文献
58.
太赫兹半导体探测器研究进展 总被引:4,自引:0,他引:4
太赫兹(THz)探测器是THz技术应用的关键器件之一.基于半导体的全固态THz量子阱探测器(THzQWIP)具有探测响应速度快、制作工艺成熟、体积小和易集成等优点.文章简要介绍了THz探测器的分类和特点,重点介绍了THzQWIP的工作原理和研究进展. 相似文献
59.
60.
Phase-Locked Fibre Array for Coherent Combination and Atmosphere Aberration Compensation 总被引:1,自引:0,他引:1 下载免费PDF全文
We report a fibre amplifier array that not only achieves coherent beam combination by compensation of phase noises of fibre amplifier, but also accomplishes correction of atmosphere aberration. It is of master-oscillatormultiple-amplifier (MOPA) configuration, which can be phase-locked by the multidither principle or heterodyne detection principle. First laboratory experiments of atmosphere aberration compensation of a three-element fibre amplifier array are reported. The atmosphere aberration is created by a phase screen in the experiment. The phase changes of the beam, which are introduced by the fibre amplifier and the phase screen, are both detected by the heterodyne detection method. Phase modulators are controlled to compensate for the phase in the three paths. No matter whether there is a phase screen producing atmosphere aberration or not, the dim dynamic interference fringes in the far field turn to a clear and stable pattern, and the peak intensity is maximized. It is indicated that the fibre amplifier array is phase-locked, and coherent combination of the three beams is achieved. It can be used not only to obtain high power fibre laser array but also in laser space communication. 相似文献