首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   18739篇
  免费   1182篇
  国内免费   828篇
化学   1180篇
晶体学   9篇
力学   1002篇
综合类   24篇
数学   16007篇
物理学   2527篇
  2024年   47篇
  2023年   403篇
  2022年   568篇
  2021年   765篇
  2020年   827篇
  2019年   620篇
  2018年   808篇
  2017年   852篇
  2016年   714篇
  2015年   892篇
  2014年   1359篇
  2013年   1646篇
  2012年   1474篇
  2011年   1507篇
  2010年   1217篇
  2009年   1127篇
  2008年   951篇
  2007年   840篇
  2006年   738篇
  2005年   434篇
  2004年   292篇
  2003年   315篇
  2002年   300篇
  2001年   377篇
  2000年   185篇
  1999年   289篇
  1998年   240篇
  1997年   86篇
  1996年   89篇
  1995年   46篇
  1994年   79篇
  1993年   63篇
  1992年   60篇
  1991年   54篇
  1990年   44篇
  1989年   42篇
  1988年   58篇
  1987年   39篇
  1986年   39篇
  1985年   51篇
  1984年   37篇
  1983年   25篇
  1982年   15篇
  1981年   15篇
  1980年   15篇
  1979年   10篇
  1978年   19篇
  1976年   19篇
  1975年   16篇
  1973年   7篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
International Journal of Theoretical Physics - We investigate the monogamy relations related to the concurrence, the entanglement of formation, convex-roof extended negativity, Tsallis-q...  相似文献   
3.
4.
5.
6.
A formal computation proving a new operator identity from known ones is, in principle, restricted by domains and codomains of linear operators involved, since not any two operators can be added or composed. Algebraically, identities can be modelled by noncommutative polynomials and such a formal computation proves that the polynomial corresponding to the new identity lies in the ideal generated by the polynomials corresponding to the known identities. In order to prove an operator identity, however, just proving membership of the polynomial in the ideal is not enough, since the ring of noncommutative polynomials ignores domains and codomains. We show that it suffices to additionally verify compatibility of this polynomial and of the generators of the ideal with the labelled quiver that encodes which polynomials can be realized as linear operators. Then, for every consistent representation of such a quiver in a linear category, there exists a computation in the category that proves the corresponding instance of the identity. Moreover, by assigning the same label to several edges of the quiver, the algebraic framework developed allows to model different versions of an operator by the same indeterminate in the noncommutative polynomials.  相似文献   
7.
8.
The localized electrostatic structures with dissipation due to ion-neutral collisions in a symmetric warm pair-ion plasma in the presence of non-Maxwellian population of electrons are studied. The analytical model for ion dynamics is based on fluid equations and the evolution equation is derived by using the reductive perturbation scheme in the form of a damped Korteweg-de Vries equation. The parameter regime relevant to space-based observations and laboratory plasmas is considered and time evolution of the propagating ion-acoustic soliton is discussed. The energetic-particles-driven properties of soliton for various spectral indices, dissipation, ion temperature, and density are illustrated with comparison to the thermal mode for Boltzmann distribution of electrons.  相似文献   
9.
Chenguang Ma 《中国物理 B》2021,30(12):120504-120504
A new five-dimensional fractional-order laser chaotic system (FOLCS) is constructed by incorporating complex variables and fractional calculus into a Lorentz-Haken-type laser system. Dynamical behavior of the system, circuit realization and application in pseudorandom number generators are studied. Many types of multi-stable states are discovered in the system. Interestingly, there are two types of state transition phenomena in the system, one is the chaotic state degenerates to a periodical state, and the other is the intermittent chaotic oscillation. In addition, the complexity of the system when two parameters change simultaneously is measured by the spectral entropy algorithm. Moreover, a digital circuit is design and the chaotic oscillation behaviors of the system are verified on this circuit. Finally, a pseudo-random sequence generator is designed using the FOLCS, and the statistical characteristics of the generated pseudo-random sequence are tested with the NIST-800-22. This study enriches the research on the dynamics and applications of FOLCS.  相似文献   
10.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号