全文获取类型
收费全文 | 174篇 |
免费 | 18篇 |
国内免费 | 16篇 |
专业分类
化学 | 55篇 |
力学 | 19篇 |
综合类 | 1篇 |
数学 | 74篇 |
物理学 | 59篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 2篇 |
2020年 | 6篇 |
2019年 | 1篇 |
2017年 | 3篇 |
2016年 | 8篇 |
2015年 | 2篇 |
2014年 | 2篇 |
2013年 | 7篇 |
2012年 | 2篇 |
2011年 | 9篇 |
2010年 | 11篇 |
2009年 | 16篇 |
2008年 | 15篇 |
2007年 | 13篇 |
2006年 | 8篇 |
2005年 | 4篇 |
2004年 | 11篇 |
2003年 | 2篇 |
2002年 | 5篇 |
2001年 | 6篇 |
2000年 | 16篇 |
1999年 | 8篇 |
1998年 | 12篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
排序方式: 共有208条查询结果,搜索用时 0 毫秒
81.
After introducing morphisms between projective geometries, some categorical questions are examined. It is shown that there are three kinds of embeddings and two kinds of quotients. Furthermore the morphisms decompose in a canonical way into four factors. 相似文献
82.
W. S. Weiglhofer 《International Journal of Infrared and Millimeter Waves》1998,19(7):993-1005
Novel expressions for the depolarization dyadics in an axially uniaxial bianisotropic medium (AUBM) are presented. Explicit formulae for the depolarization dyadics are derived for cubical, cylindrical and spherical geometries and their dependence on the magnetoelectric coupling parameter is studied graphically. 相似文献
83.
Methods for the computation of flow problems based on finite‐volume discretizations and pressure‐correction methods frequently require the interpolation of control volume face values from nodal values. The simple, often employed central differencing scheme (CDS) leads to a significant loss in accuracy when the numerical grid is non‐regular as it is usual when modelling complex geometries. An alternative technique based on a multi‐dimensional Taylor series expansion (TSE) is proposed, which preserves the CDS‐like sparsity pattern of the discrete system. While the TSE scheme computationally is only slightly more expensive than the CDS approach, it results in a significantly higher accuracy, where the difference increases with the grid irregularity. The method is investigated and compared to the CDS approach for some representative test cases. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
84.
Theoretical Chemistry Accounts - An INDO method extended to include a contribution from the solvent by means of an effective solvent field (ESF) is applied to the three isomeric benzosemiquinones... 相似文献
85.
Summary The use of finite differences and finite second differences in order to approximate gradients and second derivatives of the energy for geometry optimization and determination of normal modes of vibration on the CI level of computation is discussed in connection with the semiempirical MNDOC-CI valence electron method. Results are given for ground and excited states of ethylene, acetylene, formaldehyde, acetaldehyde, acetone, formamide and acetamide and are compared with experimental andab initio data. Mean absolute errors for bond lengths, bond angles, excitation energies and vibrational frequencies indicate that the MNDOC-CI method is well suited to describe ground and excited states of organic molecules on the same level of approximation and with comparable accuracy. 相似文献
86.
Karsten Malsch Rupert Rebentisch Petra Swiderek Georg Hohlneicher 《Theoretical chemistry accounts》1998,100(1-4):171-182
Valence and low-lying Rydberg states of acetylene (C2H2) are reexamined in the singlet as well as in the triplet manifold. The major goal of this work is a better understanding
of the valence states that contribute to the low-energy electron-energy-loss spectrum recorded under conditions where transitions
to triplet states are enhanced. An appropriate theoretical treatment of these states has to include the low-lying Rydberg
states because of their energetic proximity to some of the valence states. The CASSCF/CASPT2 method provides a suitable framework
for such a task. For some important states the geometry was optimized at the CASPT2 level to allow a comparison with the results
of other highly accurate methods that have been applied to acetylene in the past.
Received: 11 June 1998 /Accepted: 30 July 1998 / Published online: 19 October 1998 相似文献
87.
88.
Wiberg KB 《Journal of computational chemistry》2004,25(11):1342-1346
The effect of basis sets on MP2 and CCSD calculated geometries has been investigated for a series of small organic molecules with two to four nonhydrogen atoms. Whereas 6-311++G** usually leads to satisfactory structures, this was not true with aug-cc-pVDZ, although it uses more basis functions than the former set. In addition, the smaller 6-311++G** invariably leads to lower calculated energies than aug-cc-pVDZ. With a given basis set, CCSD gives more satisfactory calculated geometries than MP2, but with a much greater computation time. For the compounds in this report, B3LYP/6-311++G** is quite effective in giving satisfactory calculated geometries at a relatively small computational cost. 相似文献
89.
Based on a special form of the molecular virial theorem, the recently proposed method of momentum density for interatomic interactions is here applied to the problem of molecular geometry. Two molecules BH
2
–
and BH
2
+
, which have the same nuclear framework but favor respectively bent and linear conformations, are comparatively studied. Using an approximate Hartree-Fock momentum density, the total molecular energy (including the nuclear repulsion) is partitioned into orbital components, and a geometry correlation diagram is derived. An atom-bond partitioning of the total energy is also examined based on the one- and two-center decomposition of the momentum density. 相似文献
90.
Andrea Gambioli 《Annals of Global Analysis and Geometry》2008,34(1):77-100
In this article, we classify 7- and 8-dimensional manifolds M admitting an SU(3) action of cohomogeneity one such that (i) M is simply connected and the orbit space M/G is isomorphic to [0, 1], and (ii) \({M/G\cong S^{1}}\) and the principal orbits are simply connected. We discuss applications to the study of the group manifold SU(3) and to 8-dimensional quaternion-Kähler spaces, and links between dimension 7 and 8 given by circle actions. 相似文献