全文获取类型
收费全文 | 12241篇 |
免费 | 315篇 |
专业分类
化学 | 6478篇 |
晶体学 | 65篇 |
力学 | 230篇 |
数学 | 2727篇 |
物理学 | 3056篇 |
出版年
2021年 | 115篇 |
2020年 | 150篇 |
2019年 | 123篇 |
2018年 | 263篇 |
2017年 | 265篇 |
2016年 | 536篇 |
2015年 | 373篇 |
2014年 | 439篇 |
2013年 | 1035篇 |
2012年 | 578篇 |
2011年 | 758篇 |
2010年 | 433篇 |
2009年 | 373篇 |
2008年 | 518篇 |
2007年 | 462篇 |
2006年 | 403篇 |
2005年 | 287篇 |
2004年 | 272篇 |
2003年 | 225篇 |
2002年 | 228篇 |
2001年 | 182篇 |
2000年 | 155篇 |
1999年 | 142篇 |
1998年 | 129篇 |
1997年 | 130篇 |
1996年 | 123篇 |
1995年 | 118篇 |
1994年 | 98篇 |
1993年 | 107篇 |
1992年 | 115篇 |
1991年 | 98篇 |
1990年 | 94篇 |
1989年 | 101篇 |
1988年 | 107篇 |
1987年 | 107篇 |
1986年 | 103篇 |
1985年 | 141篇 |
1984年 | 143篇 |
1983年 | 128篇 |
1982年 | 123篇 |
1981年 | 107篇 |
1980年 | 125篇 |
1979年 | 109篇 |
1978年 | 142篇 |
1977年 | 119篇 |
1976年 | 109篇 |
1975年 | 90篇 |
1974年 | 111篇 |
1973年 | 111篇 |
1965年 | 83篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
N. S. Simonović 《Few-Body Systems》2006,38(2-4):139-145
In agreement with the Kohn theorem the relative motion (rel) of three electrons in a two-dimensional parabolic trap separates
from the centre-of-mass (CM) motion. By introducing new coordinates the Hamiltonian for relative motion in the approximation
of non-interacting electrons can be taken to the normal form. The eigenstates of the normalized Hamiltonian are products of
the Fock-Darwin states for normal modes. The energy levels for relative motion are obtained by diagonalizing the exact Hamiltonian
in the eigenbasis for the non-interacting case. In this basis the interaction matrix elements can be obtained in the analytical
form. Since the rank of the Hamiltonian matrix is significantly reduced, the calculations are faster and more accurate than
those for the full (CM + rel) motion. This advantage is especially important for the calculations of excited states and the
analysis of energy spectra. 相似文献
2.
3.
We study condensation of ethanol-hexanol vapour by numerical solution of kinetic equations. The number of droplets formed
in unit volume is computed within self-consistent classical model. It is shown that formation of ethanol-rich droplets prevails
at the initial stage of nucleation process, but in the stationary state formation of droplets near the saddle point (on cluster
formation energy surface) plays the dominant role.
Presented at the 6th Joint Seminar “Development of Materials Science in Research and Education”, Karlštejn, Czech Republic,
17–19 September 1996.
This work was supported by Grant No. A1010615 of the Grant Agency of the Academy of Sciences of the Czech Republic. 相似文献
4.
The purpose of this paper is to give the Reid ``Roundabout Theorem' for quadratic functionals with general boundary conditions.
In particular, we describe the so-called coupled point and regularity condition introduced in [16] in terms of Riccati equation
solutions.
Accepted 27 February 1996 相似文献
5.
On‐line coupling of LC and ICP‐MS has been used for fractionation and detection of species of Cu, Fe, I, Se and Zn in human serum. It has been shown that anion exchange chromatography provided better separation capability (both intra‐ and inter‐element) than size‐exclusion chromatography. The mobile phases for ion exchange chromatography consisted of Tris–HNO3 buffer and ammonium salt (nitrate, acetate or formate). Formate was found to be the best mobile phase counter ion, enabling good chromatographic separation, and is acceptable for mass spectrometry too. The quantitative evaluation of element concentrations adhering to individual fractions was performed by the peak area normalization method. The repeatability of results ranged from 3 to 15% (depending on the element concentration level) and represented the main part of the result uncertainty. The accuracy of Cu and Zn fraction determinations was confirmed by comparison with the isotope dilution technique. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
6.
The complete set of self-consistent parameters of nominally undoped LiNbO3 crystals of congruent composition that describe the electro-optic, piezoelectric, elasto-optic, elastic, and dielectric response
has been determined by numerically evaluating available measurements. The parameters were determined at room temperature and
consist of the low-frequency clamped dielectric constants εS
ij, elastic stiffness constants at constant electric field CE
ijkl, piezoelectric stress coefficients eijk, elasto-optic constants at constant electric field pE
ijkl, and clamped electro-optic coefficients rS
ijk. It is shown that the complete set is required for calculating the effective electro-optic coefficients and dielectric constants
in photorefractive applications of LiNbO3.
Received: 4 January 2002 / Revised version: 1 February 2002 / Published online: 14 March 2002 相似文献
7.
Summary The paper addresses the problem of the implementation of nonhomogeneous essential Dirichlet type boundary conditions in thep-version of the finite element method.Partially supported by the Office of Naval Research under Grant N-00014-85-K-0169Research partially supported by the Air Force Office of Scientific Research, Air Force Systems Command, USAF, under Grant Number AFOSR 85-0322 相似文献
8.
9.
In this paper a new definition of a lattice valued intuitionistic fuzzy set (LIFS) is introduced, in an attempt to overcome
the disadvantages of earlier definitions. Some properties of this kind of fuzzy sets and their basic operations are given.
The theorem of synthesis is proved: For every two families of subsets of a set satisfying certain conditions, there is an
lattice valued intuitionistic fuzzy set for which these are families of level sets.
The research supported by Serbian Ministry of Science and Technology, Grant No. 1227. 相似文献
10.