全文获取类型
收费全文 | 3513篇 |
免费 | 1016篇 |
国内免费 | 74篇 |
专业分类
化学 | 28篇 |
力学 | 90篇 |
综合类 | 30篇 |
数学 | 564篇 |
物理学 | 1293篇 |
无线电 | 2598篇 |
出版年
2024年 | 11篇 |
2023年 | 44篇 |
2022年 | 61篇 |
2021年 | 76篇 |
2020年 | 83篇 |
2019年 | 45篇 |
2018年 | 67篇 |
2017年 | 112篇 |
2016年 | 138篇 |
2015年 | 152篇 |
2014年 | 284篇 |
2013年 | 271篇 |
2012年 | 347篇 |
2011年 | 357篇 |
2010年 | 305篇 |
2009年 | 266篇 |
2008年 | 340篇 |
2007年 | 334篇 |
2006年 | 250篇 |
2005年 | 209篇 |
2004年 | 172篇 |
2003年 | 177篇 |
2002年 | 119篇 |
2001年 | 95篇 |
2000年 | 59篇 |
1999年 | 50篇 |
1998年 | 37篇 |
1997年 | 36篇 |
1996年 | 24篇 |
1995年 | 25篇 |
1994年 | 12篇 |
1993年 | 8篇 |
1992年 | 3篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1983年 | 6篇 |
1982年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有4603条查询结果,搜索用时 0 毫秒
31.
A protocol for multipartite quantum clock synchronization is performed under the influence of Unruh thermal noise. The dynamics of multipartite quantum system consisting of Unruh–DeWitt detectors when one of the detectors is accelerated are obtained. To estimate the time difference between the clocks, the time probability is calculated and how the probability is influenced by the Unruh thermal noise and other factors is analyzed. It is shown that both relativistic motion and interaction between the atom and the external scalar field affect the choice of optimal number of excited atoms in the initial state, which leads to a higher clock adjustment accuracy. Time probabilities for different types of initial states approach the same value in the limit of infinite acceleration, while tend to different minimums with increasing number of atoms. In addition, the accuracy of clock synchronization using a pair of entangled clocks in two‐party system is always higher than in a multipartite system, while the optimal Z‐type multipartite initial state always performs better than the W‐type state. 相似文献
32.
Study on autonomous navigation based on pulsar timing model 总被引:1,自引:0,他引:1
The basic principle of pulsar timing model was introduced, and the general relativistic corrections were analyzed when pulse
time of arrival (TOA) was transferred to coordinate TOA at the Solar System Barycentre. Based on the shifting, an iterative
method of autonomous position determination for spacecraft was developed. Accordingly, the linear form of the position offset
equation was evolved. Using the initial estimated value of spacecraft’s position as the input of pulsar timing equation, through
calculation of the offset between measured or transferred and predicted TOA, the position offset can be solved by Least Squares.
At last, the main error sources including modeling error and parameters error were discussed.
Supported by the National Defence Laboratory Foundation of China (Grant No. 9140C3601010901) and Science Foundation of Shaanxi
Province (Grant No. 2007F12) and the Technology Specialism Foundation of Shaanxi Education Department of Shaanxi Province
(Grant No. 07JK332), and the Innovative Research Plan of Xi’an University of Technology (Grant No. 105-210714) 相似文献
33.
In this paper, the issue of finite-time lag synchronization of coupled reaction–diffusion systems with time-varying delay (CRDSTD) is considered. A periodically intermittent controller is designed such that drive system and corresponding response system can achieve finite-time lag synchronization. By using graph theory and Lyapunov method, two sufficient criteria are presented to guarantee the finite-time lag synchronization of CRDSTD. Moreover, the time of achieving lag synchronization of CRDSTD is estimated. Finally, a numerical example is given to show the effectiveness of the proposed results. 相似文献
34.
35.
本文研究了带非线性信号连接的两个复杂网络间的同步问题,引入非线性耦合参数α来调节两个复杂网络的同步.若耦合参数不能保证网络达到外部同步,这里我们提出了一种自适应同步方式,通过此方式可以使两个复杂网络达到同步,最后通过简单的数值算例来阐述得到的理论结果,包括网络具有相同和不相同的拓扑结构两种情形. 相似文献
36.
37.
38.
为考察大一学生化学实验室安全基础知识,对天津理工大学化学化工学院大一学生警示标识、危险化学品性质、废弃物处理及意外处置等安全知识进行问卷调查。结果表明:60.4%的学生将易燃标识与氧化剂标识混淆;在危险化学品性质和酸/碱撒漏处理方面有待加强。基于以上结果,在后续安全教育过程中,普及GHS标识及MSDS,对相关知识进行针对性的查漏补缺;充分利用线上资源,弥补线下教育因时间有限、容量有限导致的不足。 相似文献
39.
40.