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   19618篇
  免费   3408篇
  国内免费   2794篇
化学   4409篇
晶体学   116篇
力学   3122篇
综合类   701篇
数学   9258篇
物理学   8214篇
  2024年   96篇
  2023年   416篇
  2022年   434篇
  2021年   444篇
  2020年   355篇
  2019年   445篇
  2018年   305篇
  2017年   508篇
  2016年   535篇
  2015年   648篇
  2014年   1353篇
  2013年   1049篇
  2012年   1540篇
  2011年   1566篇
  2010年   1309篇
  2009年   1501篇
  2008年   2181篇
  2007年   1231篇
  2006年   1093篇
  2005年   1361篇
  2004年   988篇
  2003年   1139篇
  2002年   907篇
  2001年   829篇
  2000年   543篇
  1999年   442篇
  1998年   449篇
  1997年   340篇
  1996年   293篇
  1995年   317篇
  1994年   278篇
  1993年   175篇
  1992年   183篇
  1991年   157篇
  1990年   154篇
  1989年   120篇
  1988年   42篇
  1987年   30篇
  1986年   18篇
  1985年   15篇
  1984年   9篇
  1983年   5篇
  1982年   6篇
  1981年   1篇
  1979年   3篇
  1959年   2篇
  1951年   5篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
以《固体物理》为改革对象,按照物理专业学生的培养规律和教学特点,充分利用慕课等优质教学资源,融合线上线下教学模式,依托科研项目培养学生科学素养,构成“建立教学资源储备库、线上线下融合教学、课后线上答疑、依托科研项目促进知识吸收升华、全学习过程考核评价、线上收集学生反馈并完善修改课程内容”的高效闭环式教学模式,探索科学教学方法与手段,将有助于整体提升物理专业学生的培养水平.  相似文献   
992.
以苯并噻二唑分子为母体,设计了5个系列的衍生物,采用AM1半经验量子化学方法,研究了共轭π桥的不同增长方式和不同推拉电子基团对分子的电子结构及非线性光学性质的影响.结果表明:共轭链较短时,分子的二阶极化率和三阶极化率与共轭链长的线性相关性较好;而当共轭链较长时,分子的二价极化率和三阶极化率随着共轭链的增长而呈起伏性变化;与三氰基呋喃相比,三硝基呋喃对非线性极化率的影响更大;部分目标分子的一阶极化率α与Δμ·ΔE-1、二阶极化率β与α·ΔE-1、三阶极化率γ与α·ΔE-2和β·ΔE-1都有较好的相关性.  相似文献   
993.
<正>We demonstrate a photonic band gap(PBG) from one-dimensional(1D) periodic structures created by a double-layer unit cell with an air layer and an anisotropic nonmagnetic left-handed metamaterial(LHM) layer whose permittivity elements are partially negative.The requirements imposed on the materials and structures to realize a PBG are derived when the frequency is above or below the cutoff frequency,and the transmission properties of the PBG are discussed by utilizing 4×4 transfer-matrix method with dispersive semiconductor metamaterial.  相似文献   
994.
于发军  张鸿庆 《中国物理 B》2008,17(5):1574-1580
This paper presents a set of multicomponent matrix Lie algebra, which is used to construct a new loop algebra A^-M. By using the Tu scheme, a Liouville integrable multicomponent equation hierarchy is generated, which possesses the Hamiltonian structure. As its reduction cases, the multicomponent (2+1)-dimensional Glachette-Johnson (G J) hierarchy is given. Finally, the super-integrable coupling system of multicomponent (2+1)-dimensional GJ hierarchy is established through enlarging the spectral problem.  相似文献   
995.
李桂霞  高涛  张云光 《中国物理 B》2008,17(6):2040-2047
This paper reports that the splitting of potential energy curves for the low-lying or low excited states for hydride molecules (cations) (MgH, AlH^+, SiH, PH^+, SH,ClH^+) of the third period under Spin-Orbit Coupling has been calculated by using the Spin-Orbit Multi-Configuration Quasi-Degenerate Perturbation Theory (SO-MCQDPT) method. Then, spectroscopic constants of the split states have been derived from the Murrell-Sorbie function. The calculated dissociation energies for the spectrum branch terms have been given, respectively. The spectroscopic constants and dissociation energies for the spectrum branch terms are given for the first time in this paper.  相似文献   
996.
The B-spline basis set plus complex scaling method is applied to the numerical calculation of the exact resonance parameters Er and Г/2 of a hydrogen atom in parallel electric and magnetic fields. The method can calculate the ground and higher excited resonances accurately and efficiently. The resonance parameters with accuracies of 10^-9 - 10^-12 for hydrogen atom in parallel fields with different field strengths and symmetries are presented and compared with previous ones. Extension to the calculation of Rydberg atom in crossed electric and magnetic fields and of atomic double excited states in external electric fields is discussed.  相似文献   
997.
It is a very complex and time-consuming process to simulate the nuclear reactor neutron spectrum from the reactor core to the export channel by applying a Monte Carlo program. This paper presents a new method to calculate the neutron spectrum by using the convolution technique which considers the channel transportation as a linear system and the transportation scattering as the response function. It also applies Monte Carlo Neutron and Photon Transport Code (MCNP) to simulate the response function numerically. With the application of convolution technique to calculate the spectrum distribution from the core to the channel, the process is then much more convenient only with the simple numerical integral numeration. This saves computer time and reduces some trouble in re-writing of the MCNP program.  相似文献   
998.
A potential integration method for Birkhoffian system   总被引:1,自引:0,他引:1       下载免费PDF全文
胡楚勒  解加芳 《中国物理 B》2008,17(4):1153-1155
This paper is intended to apply the potential integration method to the differential equations of the Birkhoffian system. The method is that, for a given Birkhoffian system, its differential equations are first rewritten as 2n first-order differential equations. Secondly, the corresponding partial differential equations are obtained by potential integration method and the solution is expressed as a complete integral. Finally, the integral of the system is obtained.  相似文献   
999.
用Tang-Toennies势模型和密耦近似方法计算了不同能量下惰性气体原子He与H2及其同位素D2,T2替代碰撞体系的振转激发碰撞截面. 通过分析He-H2(D2,T2)各碰撞体系分波截面的差异,总结出在H2分子的对称同位素替代情形下He-H2(D2,T2)碰撞体系分波截面随量子数和体系  相似文献   
1000.
刘小贤  童培庆 《中国物理 B》2008,17(11):3930-3935
A second-order dynamic phase transition in a non-equilibrium Eggers urn model for the separation of sand is studied. The order parameter, the susceptibility and the stationary probability distribution have been calculated. By applying the Lee-Yang zeros method of equilibrium phase transitions, we study the distributions of the effective partition function zeros and obtain the same result for the model. Thus, the Lee-Yang theory can be applied to a more general non-equilibrium system.  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