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   215篇
  免费   14篇
化学   135篇
晶体学   1篇
力学   5篇
数学   41篇
物理学   47篇
  2023年   7篇
  2022年   2篇
  2021年   6篇
  2020年   4篇
  2019年   7篇
  2018年   4篇
  2017年   2篇
  2016年   4篇
  2015年   12篇
  2014年   10篇
  2013年   7篇
  2012年   16篇
  2011年   20篇
  2010年   15篇
  2009年   7篇
  2008年   10篇
  2007年   9篇
  2006年   12篇
  2005年   7篇
  2004年   8篇
  2003年   5篇
  2002年   9篇
  2001年   2篇
  2000年   6篇
  1999年   1篇
  1998年   3篇
  1997年   3篇
  1996年   2篇
  1995年   3篇
  1994年   1篇
  1993年   3篇
  1992年   1篇
  1984年   2篇
  1983年   2篇
  1981年   3篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
  1977年   3篇
  1974年   1篇
  1904年   1篇
  1889年   1篇
  1886年   2篇
  1884年   2篇
  1883年   1篇
排序方式: 共有229条查询结果,搜索用时 15 毫秒
31.
We consider a family of one-dimensional diffusions, in dynamical Wiener mediums, which are random perturbations of the Ornstein–Uhlenbeck diffusion process. We prove quenched and annealed convergences in distribution and under weigh-ted total variation norms. We find two kind of stationary probability measures, which are either the standard normal distribution or a quasi-invariant measure, depending on the environment, and which is naturally connected to a random dynamical system. We apply these results to the study of a model of time-inhomogeneous Brox’s diffusions, which generalizes the diffusion studied by Brox (Ann Probab 14(4):1206–1218, 1986) and those investigated by Gradinaru and Offret (Ann Inst Henri Poincaré Probab Stat, 2011). We point out two distinct diffusive behaviours and we give the speed of convergences in the quenched situations.  相似文献   
32.
We present a study of thermal conductivity in the normal state of the heavy-fermion superconductor URu2Si2. Ordering at 18 K leads to a steep increase in thermal conductivity and (in contrast with all other cases of magnetic ordering in heavy-fermion compounds) to an enhancement of the Lorenz number. By linking this observation to several other previously reported features, we conclude that most of the carriers disappear in the ordered state and this leads to a drastic increase in both the phononic and electronic mean free path.  相似文献   
33.
Given a target contained in a constrained set and an impulse control system governing the evolutions of runs or executions, that are hybrids of continuous and discrete evolutions, this paper studies and provides several characterizations of the capture basin of the target viable in the constrained set. It is the subset of initial runs from which start at least one run viable in the constrained set until it reaches the target in finite time. It also provides algorithms and regulation rules governing the runs that reach the targets while obeying state constraints.  相似文献   
34.
We prove the existence of global set-valued solutions to the Cauchy problem for partial differential equations and inclusions, with either single-valued or set-valued initial conditions. The method is based on the equivalence between this problem and problem of finding viability tubes of the associated characteristic system of ordinary differential equations. As an application we construct the value function of the Mayer problem arising in control theory. Received August 25, 1995  相似文献   
35.
We have carried out a comparative study of the thermal conductivity of two rectangular single crystals: a niobium sample and a detwinned YBCO. Thermal conductivity was measured as a function of the relative orientation of the crystaline axes and a magnetic field applied parallel to the sample plane. Different angular variations, two-fold for Nb and four-fold for YBCO, were observed in the two case. We discuss the microscopic effects related to the gap structure which are at the origin of this qualitative difference in the behavior of thermal conductivity in these two superconductors.  相似文献   
36.
Voltage-sensitive blockage by ADP, ATP and phytate (IP6) demonstrates that active-site contraction toward the middle of newly synthesized rigid-rod beta-barrels provides a general strategy to rationally create and modulate the voltage sensitivity (and to increase the efficiency) of molecular recognition by synthetic multifunctional pores.  相似文献   
37.
We prove that if X1,…,Xn (n>1) are self-adjoints in a W-probability space with finite non-microstates free Fisher information, then the von Neumann algebra W(X1,…,Xn) they generate doesn't have property Γ (especially is not amenable). This is an analog of a well-known result of Voiculescu for microstates free entropy. We also prove factoriality under finite non-microstates entropy.  相似文献   
38.
The advent of techniques to measure velocities of “GPS equipped vehicles” using satellite technology, replacing the density of the road traffic sensors, motivates and justifies the revision of conceptual, mathematical algorithms and software based models. This paper summarizes studies on the traffic evolutions achieving the minimum of a congestion function controlled “macroscopic traffic velocities” called “celerities” instead of founding traffic regulation on the measures of traffic densities. The flux valued function is the Fenchel transform of the fundamental diagram and is a convex decreasing function. We use the properties of capture basins investigated in viability theory, specifically a Lax-Hopf formula characterizing them and the “Max-Plus” morphism of capture basins for deriving the statements proved in this paper. Traffic conditions involve as well boundary conditions or conditions on trajectories inside the domain.  相似文献   
39.
We present a method for measuring the nuclear anapole in a string of francium isotopes. The anapole is a parity non-conserving electromagnetic moment that enables parity-forbidden transitions between ground state hyperfine levels of an atom. The experiment is run by the FrPNC collaboration and relies on a beam of artificially-produced francium from the ISAC facility at TRIUMF.  相似文献   
40.
New heterocyclic diradicaloids based on boron and nitrogen-doped polycyclic systems with open-shell ground-states are obtained via concomitant structural and quinoidal extensions, thus allowing to merge the best of both design strategies. A combination of experimental characterization and theoretical calculations have helped disclose their electronic structure, as well as rationalize their associated magnetic and photophysical properties, spanning the chemical space of available molecular templates for cutting-edge applications in organic electronics and spintronics.  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