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   608篇
  免费   102篇
  国内免费   43篇
化学   195篇
晶体学   2篇
力学   55篇
综合类   8篇
数学   261篇
物理学   232篇
  2024年   5篇
  2023年   14篇
  2022年   33篇
  2021年   34篇
  2020年   45篇
  2019年   45篇
  2018年   28篇
  2017年   21篇
  2016年   33篇
  2015年   23篇
  2014年   24篇
  2013年   42篇
  2012年   24篇
  2011年   24篇
  2010年   27篇
  2009年   19篇
  2008年   39篇
  2007年   21篇
  2006年   23篇
  2005年   19篇
  2004年   28篇
  2003年   18篇
  2002年   17篇
  2001年   13篇
  2000年   12篇
  1999年   13篇
  1998年   14篇
  1997年   11篇
  1996年   7篇
  1995年   13篇
  1994年   6篇
  1993年   6篇
  1992年   9篇
  1991年   10篇
  1990年   8篇
  1988年   1篇
  1987年   4篇
  1986年   4篇
  1985年   1篇
  1984年   4篇
  1983年   1篇
  1982年   3篇
  1981年   4篇
  1979年   1篇
  1977年   1篇
  1973年   1篇
排序方式: 共有753条查询结果,搜索用时 7 毫秒
511.
一类非线性时滞系统概周期解的存在唯一性   总被引:2,自引:0,他引:2  
冯春华 《数学杂志》2004,24(4):406-410
应用Liapunov,泛函,研究了一类时滞系统概周期解的存在唯一性,得到了保证系统存在唯一概周期解的一组充分条件.  相似文献   
512.
Mu-Zhen Li 《中国物理 B》2021,30(12):123302-123302
Thermally activated delayed fluorescence (TADF) molecules have attracted great attention as high efficient luminescent materials. Most of TADF molecules possess small energy gap between the first singlet excited state (S1) and the first triplet excited state (T1) to favor the up-conversion from T1 to S1. In this paper, a new TADF generation mechanism is revealed based on theoretical simulation. By systematic study of the light-emitting properties of SOBF-OMe in both toluene and in aggregation state, we find that the single SOBF-OMe could not realize TADF emission due to large energy gap as well as small up-conversion rates between S1 and T1. Through analysis of dimers, we find that dimers with intermolecular hydrogen bond (H-bond) are responsible for the generation of TADF, since smaller energy gap between S1 and T1 is found and the emission wavelength is in good agreement with experimental counterpart. The emission properties of SOBF-H are also studied for comparison, which reflect the important role of H-bond. Our theoretical results agree ith experimental results well and confirm the mechanism of H-bond induced TADF.  相似文献   
513.
冯玉玲  沈柯 《中国物理 B》2008,17(1):111-116
The resistively-capacitively-inductively-shunted (RCL-shunted) Josephson junction (RCLSJJ) shows chaotic behaviour under some parameter conditions. Here a scheme for controlling chaos in the RCLSJJ is presented based on the linear feedback theory. Numerical simulations show that this scheme can be effectively used to control chaotic states in this junction into stable periodic states. Moreover, the different stable period states with different period numbers can be obtained by appropriately adjusting the feedback intensity and delay time without any pre-knowledge of this system required.  相似文献   
514.
关于B值随机元随机指标和的矩的讨论   总被引:1,自引:0,他引:1  
在本文中,我们研究停止时间N的矩、B值随机元X_n的矩以及{X_n,n≥1}的随机指标和S_N的矩之间的关系。特别,在赋予Banach空间以某些特定的几何性质,例如假设B为p-阶光滑空间、q-凸空间及Hilbert空间的情形下,讨论了上述各种矩之间的关系。  相似文献   
515.
Minimum Renyi’s pseudodistance estimators (MRPEs) enjoy good robustness properties without a significant loss of efficiency in general statistical models, and, in particular, for linear regression models (LRMs). In this line, Castilla et al. considered robust Wald-type test statistics in LRMs based on these MRPEs. In this paper, we extend the theory of MRPEs to Generalized Linear Models (GLMs) using independent and nonidentically distributed observations (INIDO). We derive asymptotic properties of the proposed estimators and analyze their influence function to asses their robustness properties. Additionally, we define robust Wald-type test statistics for testing linear hypothesis and theoretically study their asymptotic distribution, as well as their influence function. The performance of the proposed MRPEs and Wald-type test statistics are empirically examined for the Poisson Regression models through a simulation study, focusing on their robustness properties. We finally test the proposed methods in a real dataset related to the treatment of epilepsy, illustrating the superior performance of the robust MRPEs as well as Wald-type tests.  相似文献   
516.
The anomalous diffraction theory (ADT) that is originally introduced by van de Hulst (Light scattering by small particles, Wiley, New York, 1957), is often highly simplified so that the extinction and absorption efficiencies of randomly oriented particles are determined by the ratio of particle volume to the projected area. In this work, we compare the simplified ADT and the original one for randomly oriented particles with different shapes. Significant differences are found in both extinction and absorption efficiencies.  相似文献   
517.
In this paper, we propose a memory state feedback model predictive control (MPC) law for a discrete-time uncertain state delayed system with input constraints. The model uncertainty is assumed to be polytopic, and the delay is assumed to be unknown, but with a known upper bound. We derive a sufficient condition for cost monotonicity in terms of LMI, which can be easily solved by an efficient convex optimization algorithm. A delayed state dependent quadratic function with an estimated delay index is considered for incorporating MPC problem formulation. The MPC problem is formulated to minimize the upper bound of infinite horizon cost that satisfies the sufficient conditions. Therefore, a less conservative sufficient conditions in terms of linear matrix inequality (LMI) can be derived to design a more robust MPC algorithm. A numerical example is included to illustrate the effectiveness of the proposed method.  相似文献   
518.
本文通过积分检验, 刻画了不同分布的$\varphi$-混合序列后置和的极限结果,并由此导出了它们的Chover型重对数律,推广和改进了已有的结果.  相似文献   
519.
Various first-order and second-order sufficient conditions of optimality for nonlinear optimal control problems with delayed argument are formulated. The functions involved are not required to be convex. Second-order sufficient conditions are shown to be related to the existence of solutions of a Riccati-type matrix differential inequality. Their relation with the second variation is discussed.The authors are indebted to an anonymous referee for valuable suggestions that lead to various improvements in the paper.  相似文献   
520.
应用锥不动点定理研究了一类时滞微分方程周期解的存在性问题,建立了该系统具有至少一个正周期解的充分条件.  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