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   9258篇
  免费   1248篇
  国内免费   1327篇
化学   5817篇
晶体学   87篇
力学   1351篇
综合类   64篇
数学   500篇
物理学   4014篇
  2024年   23篇
  2023年   113篇
  2022年   273篇
  2021年   289篇
  2020年   385篇
  2019年   328篇
  2018年   298篇
  2017年   383篇
  2016年   396篇
  2015年   379篇
  2014年   485篇
  2013年   751篇
  2012年   603篇
  2011年   640篇
  2010年   491篇
  2009年   558篇
  2008年   518篇
  2007年   571篇
  2006年   484篇
  2005年   502篇
  2004年   424篇
  2003年   358篇
  2002年   318篇
  2001年   317篇
  2000年   246篇
  1999年   227篇
  1998年   204篇
  1997年   165篇
  1996年   149篇
  1995年   148篇
  1994年   122篇
  1993年   90篇
  1992年   79篇
  1991年   72篇
  1990年   64篇
  1989年   41篇
  1988年   47篇
  1987年   34篇
  1986年   30篇
  1985年   31篇
  1984年   31篇
  1983年   12篇
  1982年   27篇
  1981年   17篇
  1980年   17篇
  1979年   20篇
  1978年   10篇
  1977年   22篇
  1976年   14篇
  1973年   9篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
Time differential perturbed angular correlation measurements of the 133–482 keVγ-γ cascade of181Ta in Hf-doped YBa2Cu3O7−x are presented. The181Hf precurser nuclei are incorporated into the sample by thermal neutron irradiation. Two quadrupole interaction frequencies are observed in the as-irradiated sample:v Q1=161±10 MHz with intensityf 1=75%, asymmetry parameterη 1=0.32 and damping parameter Λ1=0.42, andv Q2=1108±40 MHz withf 2=25%,η 2=0.62, and Λ2=0.60. On annealing the sample in air at various temperaturesT a and quenching to room temperature,f 1 remained nearly constant forT a<600°C andv Q1 for all annealing temperatures indicating that these are insensitive to oxygen stoichiometry. This frequency is interpreted to be due to181Hf substitutingY sites. BeyondT a=600°C,f 1 increased and reached a constant value of 90% forT a=800°C. The value ofv Q2 showed a slight variation between 1086 and 1160 MHz, whilef 2 remained nearly constant at 25% forT a<600°C. This component is identified to be due to181Hf substituting Cu 1 sites in the Cu-O chains of YBCO. Above 600°Cv Q2 decreased and reached a value of 808 MHz beyond 750°C.  相似文献   
72.
高密度氩气的原子间相互作用与状态方程   总被引:5,自引:4,他引:1  
本文从高密度气体的原子间相互作用出发进行思考,在修改范德瓦耳方程的基础上,提出了一种新的适用于高密度气体的状态方程,并用以对氩气临界区的等温压缩线进行计算,结果与实验值很符合.  相似文献   
73.
The phenomenological amplitude for the reaction πN→ππN fixed by fittings to the experimental data in the energy region 0.300 ≤P Lab≤ 500 MeV/c is used for modelling the Chew–Low extrapolation and Olsson–Turner threshold approach. It is shown that the uncritical application of the former results in enermous theoretical errors, the extracted values being in fact random numbers. The results of the Olsson–Turner method are characterized by significant systematic errors coming from unknown details of the isobar physics. Received: 10 December 1997  相似文献   
74.
陈美锋 《中国物理》2006,15(12):2847-2849
A scheme is proposed for generating a three-atom maximal entanglement W state. It is based on the simultaneous nonresonant interaction of atoms with a single-mode cavity field. Our scheme is insensitive to the cavity field, so the cavity field in our scheme can be initially in thermal states.  相似文献   
75.
The aim of this paper is to present several features of the couplings occurring between radiative transfer and the kinetics of a moving dielectric. After determining how the velocity field affects the apparent thermo-optical properties of matter, the energy transport problem is investigated in instationary regime and the general form of transient radiative transfer equation inside a moving medium is built. Then, the model is applied to the particular case of turbulent flows: a system of two equations for mean and fluctuating radiative energies is presented, and the resolution of this system is finally carried out.  相似文献   
76.
Manganites of the LA1−x Ca x MnO3 family show a variety of new and poorly understood electronic, magnetic and structural effects. Here we outline a new approach recently proposed by us, where we argue that due to strong Jahn-Teller (JT) coupling with phonons the twofold degeneratee g states at the Mn sites dynamically reorganize themselves into localised, JT polaronsl with exponentially small inter-site hopping, and band-like, nonpolaronic statesb, leading to anew 2-band model for manganites which includes strong Coulomb and Hund’s couplings. We also discuss some results from a dynamical mean-field theory treatment of the model which explains quantitatively a wide variety of experimental results, including insulator-metal transitions and CMR, in terms of the influence of physical conditions on the relative energies and occupation of thel andb states. We argue that this microscopic coexistence of the two types of electronic states, and their relative occupation and spatial correlation is the key to manganite physics. Dedicated to Professor C N R Rao on his 70th birthday  相似文献   
77.
胡明亮  田东平 《中国物理 C》2006,30(11):1132-1136
研究了存在次近邻相互作用(耦合)时Heisenberg XX链的纠缠特性. 结果表明对近邻格点, 随着耦合常数J的变化, 次近邻相互作用的存在可能使其纠缠度增大或者减小; 而对次近邻格点, 引进次近邻相互作用却可以产生纠缠, 并且使其随着|J|的增大而增大. 近邻格点间纠缠存在的临界温度Tc随着J的增大而降低, 次近邻格点间纠缠存在的临界温度Tc随着|J|的增大而升高. 此外对纠缠W态的制备, 次近邻相互作用的存在还使得三量子位情形时W态产生的时刻改变, 而对于四量子位情形却没有影响.  相似文献   
78.
It is useful to know the maximum number of clear two-factor interactions in a_Ⅲ~(m-(m-k))design.This paper provides a method to construct a 2_Ⅲ~(m-(m-k))design with the maximum number of clear two-factorinteractions.And it is proved that the resulting designs have more clear two-factor interactions than thoseconstructed by Tang et al.Moreover,the designs constructed are shown to have concise grid representations.  相似文献   
79.
采用蒙特卡罗模型AMPT 究了(S_(NN))~(1/2)=130GeV Au Au碰撞中部分子相互作用对两粒子横向动量关联的影响,结果表明部分子相互作用对两粒子的横向动量关联有重要的贡献.还计算了AMPT模型中(S_(NN))~(1/2)=130GeV Au Au碰撞的两粒子横向动量关联与碰撞对心性的依赖关系并与来自STAR的实验数据进行了比较,发现AMPT的理论预言很好地符合实验数据.  相似文献   
80.
The solubilities of o-, m- and p-xylene in water were measured at 25.0°C up to 250, 385, and 50 MPa, respectively. The solubility increased with increasing pressure up to 120 MPa (50 MPa for p-xylene) and then decreased. The reaction volumes, Vo accompanying the dissolution at 0.1 MPa were estimated as –3.6±0.5, –3.4±0.5, and –4.1±0.5 cm3-mol–1 for o-, m-, and p-xylene, respectively, from the pressure dependences of the solubilities. The limiting partial molar volumes, of p- and o-xylene in water under high pressure were estimated from Vo and the molar volume of the xylene. The partial molar volumes decreased with increasing pressure. The reaction volume for the formation of intra-molecular pairwise hydrophobic interaction between the methyl groups, as proposed by Ben-Naim, is discussed for the Vo of p- and o-xylene at 0.1 MPa.  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