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   710篇
  免费   147篇
  国内免费   125篇
化学   289篇
晶体学   15篇
力学   12篇
综合类   12篇
数学   359篇
物理学   295篇
  2024年   2篇
  2023年   23篇
  2022年   44篇
  2021年   40篇
  2020年   51篇
  2019年   36篇
  2018年   34篇
  2017年   44篇
  2016年   60篇
  2015年   45篇
  2014年   75篇
  2013年   78篇
  2012年   77篇
  2011年   81篇
  2010年   64篇
  2009年   36篇
  2008年   25篇
  2007年   30篇
  2006年   28篇
  2005年   11篇
  2004年   6篇
  2003年   7篇
  2002年   14篇
  2001年   15篇
  2000年   11篇
  1999年   13篇
  1998年   6篇
  1997年   2篇
  1996年   1篇
  1995年   2篇
  1994年   3篇
  1993年   3篇
  1992年   2篇
  1991年   3篇
  1990年   2篇
  1989年   2篇
  1988年   2篇
  1986年   1篇
  1980年   1篇
  1959年   1篇
  1936年   1篇
排序方式: 共有982条查询结果,搜索用时 167 毫秒
41.
By using the B3P86/aug-cc-pvtz method,the accurate equilibrium geometry of the AlSO(CS,X2A″) molecule has been calculated and compared with available theoretical values.The obtained results show that the AlSO molecule has a most stable structure with bond lengths of R OAl = 0.1864 nm,R OS = 0.1623 nm,R AlS = 0.2450 nm,together with a dissociation energy of 13.88 eV.The possible electronic states and their reasonable dissociation limits for the ground state of the AlSO molecule were determined based on the principle of atomic and molecular reaction statics.The analytic potential energy function of the AlSO molecule was derived by the many-body expansion theory and the contour lines were constructed for the first time,which show the internal information of the AlSO molecule,including the equilibrium structure and stable point.The analysis demonstrates that the obtained potential energy function of AlSO is reasonable and successful and the present investigations provide important insights for further study on molecular reaction dynamics.  相似文献   
42.
吕兵  周勋  令狐荣锋  王晓璐  杨向东 《中国物理 B》2011,20(3):36104-036104
This paper carries out first principles calculation of the structure,electronic and optical properties of Be x Zn 1 x O alloys based on the density-functional theory for the compositions x = 0.0,0.25,0.5,0.75,1.0.The lattice constants deviations of alloys obey Vegard’s law well.The Be x Zn 1 x O alloys have the direct band gap(Γ-Γ) character,and the bowing coefficients are less than the available theoretical values.Moreover,it investigates in detail the optical properties(dielectric functions,absorption spectrum and refractive index) of these ternary mixed crystals.The obtained results agree well with the available theoretical and experimental values.  相似文献   
43.
Under the assumptions that E λ n is an n-dimensional, simply connected Riemannian manifold of constant sectional curvature λ and L λ r is an r-dimensional, totally geodesic submanifold of E λ n , the paper investigates the q-th integral of the mean curvature M q n of a convex body K r in E λ n and gives the expression of M q n in the terms of M p r , where M p r is the p-th integral of the mean curvature of K r > in L λ r . A result of L. A. Santaló [2] holds in particular.  相似文献   
44.
本文研究欧氏空间R3中关于一个凸体的Bonnesen型不等式.利用包含测度的方法,获得了几个Bonnesen型不等式.  相似文献   
45.
基于Huxley势函数的拟合势,通过精确度较高的密耦近似方法计算了入射能量为50meV和150meV时,氦原子的四种同位素3He,4He,9He,10He与HCl分子碰撞体系的激发分波截面.通过分析不同能量下,各碰撞体系分波截面的差异,探讨了不同入射能量时He的同位素对He-HCl碰撞体系的分波截面的影响,总结出其分波截面随量子数和体系约化质量的变化规律.  相似文献   
46.
沈光先  汪荣凯  令狐荣锋  杨向东 《物理学报》2011,60(1):13101-013101
采用超分子单双迭代(包括非迭代三重激发)耦合簇理论CCSD(T)方法,选择由原子中心高斯函数和高斯键函数3s3p2d1f组成的大基组,计算了He-H2(D2,T2)碰撞体系的H2分子取不同键长时的相互作用势能面.运用Tang-Toennies势模型和非线性最小二乘法拟合构造了He与同位素分子H2(D2,T2)在质心坐标系下的振转相互作用势.通过密耦计算得 关键词: 高斯键函数 Tang-Toennies势函数 分波截面 碰撞参数  相似文献   
47.
支启军  宇燕  郑强 《中国物理 C》2011,35(11):1022-1025
The Gamow-Teller transitions for pf shell nuclei with proton number less than 40 and neutron number larger than 40 were believed to be blocked, due to the full filling of the neutron orbit. However, recent experimental research shows that the Gamow-Teller transitions for these kinds of nuclei are not blocked. In this paper, we systematically calculate the GT transition of pf shell nuclei 76Se in different truncations, and the results are compared with experimental results. It is shown that, due to correlations, the believed blocked GT transition occurs, and the shell model calculations reproduce the experimental GT strength. In addition, the electron capture rates in a stellar environment are calculated and discussed.  相似文献   
48.
According to classification of the matrix Lie algebras, a type of explicit Lie algebras are constructed which can be decomposed into a few Lie subalgebras. These subalgebras constitute several coupling commutator pairs from which some continuous multi-integrable couplings could be generated if the proper isospectral Lax pairs could be set up. Then the above Lie algebras are again decomposed into a kind of Lie algebras which are also closed under the matrix multiplication. From such the Lie algebras, some discrete multi-integrable couplings could be worked out. Finally, a few examples are given. However, the Hamiltonian structures of the (continuous and discrete) integrable couplings obtained by the above Lie algebras cannot be computed by using the trace identity or the quadratic-form identity, which is a strange and interesting problem. The phenomenon indicates that the importance of the Lie-algebra classification. The problem also needs us to try to find an efficient scheme to deal with.  相似文献   
49.
罗世霞  张笑一  朱淮武  胡继伟  卫钢 《化学学报》2009,67(15):1784-1790
基于自洽反应场(SCRF)中的极化连续介质模型(PCM), 采用密度泛函理论B3LYP/6-31G**计算了以二硫醚和芳环为桥基的两类双β-二酮配体的空间构型和电子结构, 结合其配合物晶体结构数据, 研究配体分子电子结构与配位性的关联性. 结果表明, 配体分子的几何构型、前线轨道、偶极矩和电荷布居, 与配合物构型、活性配位原子和配位形式(单核或多核、分子内或分子间)之间的关联性与一致性十分有意义. 配体的理论计算研究可以在一定层次上为配合物几何结构特征和配位特性提供合理的分析与预测.  相似文献   
50.
郭双建  张晓辉 《数学学报》2019,62(6):853-864
本文讨论了双单子分配律的表示及其R-矩阵结构.设F和G是给定的双单子,刻画了单子双模范畴,并给出了其为辫子范畴的充要条件,由此构造了量子YangBaxter方程的一组新解系.  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