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   1466篇
  免费   225篇
  国内免费   163篇
化学   565篇
晶体学   33篇
力学   67篇
综合类   12篇
数学   493篇
物理学   684篇
  2024年   2篇
  2023年   25篇
  2022年   57篇
  2021年   72篇
  2020年   67篇
  2019年   56篇
  2018年   58篇
  2017年   72篇
  2016年   73篇
  2015年   60篇
  2014年   75篇
  2013年   131篇
  2012年   77篇
  2011年   72篇
  2010年   65篇
  2009年   78篇
  2008年   100篇
  2007年   75篇
  2006年   85篇
  2005年   41篇
  2004年   37篇
  2003年   36篇
  2002年   52篇
  2001年   45篇
  2000年   45篇
  1999年   39篇
  1998年   44篇
  1997年   26篇
  1996年   28篇
  1995年   14篇
  1994年   19篇
  1993年   9篇
  1992年   15篇
  1991年   13篇
  1990年   11篇
  1989年   9篇
  1988年   8篇
  1987年   9篇
  1986年   14篇
  1985年   11篇
  1984年   8篇
  1983年   1篇
  1982年   10篇
  1981年   1篇
  1980年   2篇
  1979年   1篇
  1978年   1篇
  1977年   3篇
  1975年   1篇
  1973年   1篇
排序方式: 共有1854条查询结果,搜索用时 15 毫秒
141.
N. Mehta  S. Kumar 《哲学杂志》2013,93(9):797-806
We report the inverse Meyer–Neldel (MN) rule in the thermally activated crystallization of a hybrid composite of phenol formaldehyde using two experimental approaches. In the first experiment, the annealing time dependence of the pre-exponential factor K 0 and the activation energy of crystallization E c were studied. In the second experiment, the annealing temperature dependence of the same parameters was investigated. We observed the inverse Meyer–Neldel rule between the pre-exponential factor K 0 and the activation energy of crystallization E c in both cases.  相似文献   
142.
通过分层立方网络HCNn (n≥3)的容错性分析,从理论上探讨了分层立方网络基于比较模型的条件诊断度,并证明其条件诊断度为tc(HCNn)=3n?2,大约是传统诊断度(t(HCNn)=n+1)的3倍.  相似文献   
143.
A proof of the existence of a mixed ferromagnetic (or antiferromagnetic)-spin-glass fixed point for an Ising spin-glass model on the diamond hierarchical lattice is given.  相似文献   
144.
The density function perturbation theory (DFPT) is employed to study the linear thermal expansion and heat capacity at constant pressure (with the quasiharmonic approximation) for wurtzite GaN. The calculated results of linear thermal expansion coefficient and heat capacity at constant pressure are compared with the available experimental data in a wide temperature range. Generally these properties calculated agree well with experimental data except at high temperature, thus it suggests the thermal expansion and heat capacity can be well calculated from this first-principle approach.  相似文献   
145.
对格上Erceg式p.q.(p.)度量的注记   总被引:4,自引:0,他引:4  
本文的主要结果是大幅度地简化了Erceg引入的不分明度量的无点化定义,建立了相应的点式刻画.  相似文献   
146.
A new method and corresponding numerical procedure are introduced to estimate scaling exponents of power-law degree distribution and hierarchical clustering func tion for complex networks. This method can overcome the biased and inaccurate faults of graphical linear fitting methods commonly used in current network research. Furthermore, it is verified to have higher goodness-of-fit than graphical methods by comparing the KS (Kolmogorov-Smirnov) test statistics for 10 CNN (Connecting Nearest-Neighbor)networks.  相似文献   
147.
In this paper we prove that the equational class generated by bounded BCK‐algebras is the variety generated by the class of finite simple bounded BCK‐algebras. To obtain these results we prove that every simple algebra in the equational class generated by bounded BCK‐algebras is also a relatively simple bounded BCK‐algebra. Moreover, we show that every simple bounded BCK‐algebra can be embedded into a simple integral commutative bounded residuated lattice. We extend our main results to some richer subreducts of the class of integral commutative bounded residuated lattices and to the involutive case. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
148.
The efficiency of hierarchical matrices is based on the approximate evaluation of usual matrix operations. The introduced approximation error may, however, lead to a loss of important matrix properties. In this article we present a technique which preserves the positive definiteness of a matrix independently of the approximation quality. The importance of this technique is illustrated by an elliptic mixed boundary value problem with tiny Dirichlet part. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   
149.
We consider a linear sytem in a Banach lattice and provide a simple theorem of the alternative (or Farkas lemma) without the usual closure condition.

  相似文献   

150.
Summary A tool for analyzing spatio-temporal complex physical phenomena was recently proposed by the authors, Aubry et al. [5]. This tool consists in decomposing a spatially and temporally evolving signal into orthogonal temporal modes (temporal “structures”) and orthogonal spatial modes (spatial “structures”) which are coupled. This allows the introduction of a temporal configuration space and a spatial one which are related to each other by an isomorphism. In this paper, we show how such a tool can be used to analyze space-time bifurcations, that is, qualitative changes in both space and time as a parameter varies. The Hopf bifurcation and various spatio-temporal symmetry related bifurcations, such as bifurcations to traveling waves, are studied in detail. In particular, it is shown that symmetry-breaking bifurcations can be detected by analyzing the temporal and spatial eigenspaces of the decomposition which then lose their degeneracy, namely their invariance under the symmetry. Furthermore, we show how an extension of the theory to “quasi-symmetries” permits the treatment of nondegenerate signals and leads to an exponentially decreasing law of the energy spectrum. Examples extracted from numerically obtained solutions of the Kuramoto-Sivashinsky equation, a coupled map lattice, and fully developed turbulence are given to illustrate the theory.  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