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   188821篇
  免费   31737篇
  国内免费   19366篇
化学   127007篇
晶体学   2035篇
力学   12925篇
综合类   1122篇
数学   23587篇
物理学   73248篇
  2024年   393篇
  2023年   3488篇
  2022年   5270篇
  2021年   6285篇
  2020年   7325篇
  2019年   6966篇
  2018年   6212篇
  2017年   5678篇
  2016年   8900篇
  2015年   8394篇
  2014年   10361篇
  2013年   13732篇
  2012年   16684篇
  2011年   17406篇
  2010年   11780篇
  2009年   11309篇
  2008年   12237篇
  2007年   11088篇
  2006年   10211篇
  2005年   8580篇
  2004年   6566篇
  2003年   5184篇
  2002年   4860篇
  2001年   4030篇
  2000年   3565篇
  1999年   4035篇
  1998年   3545篇
  1997年   3361篇
  1996年   3494篇
  1995年   2964篇
  1994年   2703篇
  1993年   2220篇
  1992年   2029篇
  1991年   1828篇
  1990年   1471篇
  1989年   1112篇
  1988年   875篇
  1987年   711篇
  1986年   709篇
  1985年   586篇
  1984年   411篇
  1983年   289篇
  1982年   257篇
  1981年   184篇
  1980年   123篇
  1979年   54篇
  1976年   41篇
  1975年   39篇
  1974年   51篇
  1957年   53篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Annals of the Institute of Statistical Mathematics - In this paper, a model averaging approach is developed for the linear regression models with response missing at random. It is shown that the...  相似文献   
42.
Xu  Mengtao  Li  Changyou  Sun  Yang  Yang  Tianzhi  Zhang  Hongzhuang  Liu  Zhendong  Liu  Haiyang  Li  Zhenyuan  Zhang  Yimin 《Nonlinear dynamics》2021,105(4):3061-3092
Nonlinear Dynamics - Investigation of the dynamic characteristics of linear guideway is essential for enhancing structural performance of machine tools. However, few mechanical models are...  相似文献   
43.
International Journal of Theoretical Physics - The Majorana representation, which provides an intuitive way to represent the quantum state by stars on the Bloch sphere, has drawn considerable...  相似文献   
44.
Acridone as a new kind of visible light photocatalyst has been developed to catalyze metal free atom transfer radical polymerization (ATRP). The photocatalyst possess low excited state potential as can undergo an oxidative quenching pathway to initiate ATRP of vinyl monomers. Kinetic study and light on/off reaction demonstrate the “living”/controlled nature of the polymerization by light. Block copolymers can be achieved by using PMMA as macroinitiator to reinitiate polymerization of other vinyl monomers, which shows highly preserved Br chain-end functionality in the synthesized polymers. Moreover, the polymerization can be conducted under air atmosphere as most photocatalysts need anaerobic condition, which may give inspiration of further application of this kind of photocatalyst.  相似文献   
45.

We study the Bell nonlocality of high dimensional quantum systems based on quantum entanglement. A quantitative relationship between the maximal expectation value B of Bell operators and the quantum entanglement concurrence C is obtained for even dimension pure states, with the upper and lower bounds of B governed by C.

  相似文献   
46.
Gao  Zhigen  Guo  Jianhua  Ma  Yanyuan 《中国科学 数学(英文版)》2021,64(8):1905-1916
Science China Mathematics - Linear factor models are familiar tools used in many fields. Several pioneering literatures established foundational theoretical results of the quasi-maximum likelihood...  相似文献   
47.
The chiral phase transition and equation of state are studied within a novel self-consistent mean-field approximation of the two-flavor Nambu-Jona-Lasinio model. In this newly developed model, modifications to the chemical μ and chiral chemical \begin{document}$\mu_5$\end{document} potentials are naturally included by introducing vector and axial-vector channels from Fierz-transformed Lagrangian to the standard Lagrangian. In the proper-time scheme, the chiral phase transition is a crossover in the \begin{document}$T-\mu$\end{document} plane. However, when \begin{document}$\mu_5$\end{document} is incorporated, our study demonstrates that a first order phase transition may emerge. Furthermore, the chiral imbalance will soften the equation of state of quark matter. The mass-radius relationship and tidal deformability of quark stars are calculated. The maximum mass and radius decrease as \begin{document}$\mu_5$\end{document} increases. Our study also indicates that the vector and axial-vector channels exhibit an opposite influence on the equation of state.  相似文献   
48.
Herein, we successfully construct the 3D biocompatible graphene through crosslinking 2D graphene nanosheet onto carbon fiber paper with poly(diallyldimethylammonium chloride) (PDDA) as anode of the alcohol biofuel cell. Compared with the bioanode without 3D graphene, the current density and output power of PDDA-graphene-ADH bioanode is increased by 23 % and 41 % at a high concentration of ethanol at pH 8.9, suggesting the stabilization role of graphene in enzyme loading. The study provides us a deep analysis on structures and performances of the bioanode incl. electrochemistry, X-ray photoelectron spectra, and atomic force microscopy images, which is significant to develop the new methods to construct 3D porous electrodes in energy conversion device.  相似文献   
49.
Journal of Mathematical Chemistry - The analytical solutions of an asymmetric double well potential $$V(x)=a\, x^2-b\, x^3+c\, x^4$$ are found to be a triconfluent Heun function $$H_{T}(\alpha ,...  相似文献   
50.
Cao  Xiangyang  Zhang  Chenghui  Zhao  Daduan  Li  Yan 《Nonlinear dynamics》2022,107(4):3557-3572
Nonlinear Dynamics - This paper investigates the guaranteed cost positive consensus for linear multi-agent systems (MASs) with multiple time-varying delays and switching topologies. First,...  相似文献   
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