全文获取类型
收费全文 | 2110篇 |
免费 | 110篇 |
国内免费 | 118篇 |
专业分类
化学 | 888篇 |
晶体学 | 33篇 |
力学 | 15篇 |
综合类 | 5篇 |
数学 | 179篇 |
物理学 | 1218篇 |
出版年
2024年 | 5篇 |
2023年 | 21篇 |
2022年 | 25篇 |
2021年 | 22篇 |
2020年 | 29篇 |
2019年 | 18篇 |
2018年 | 29篇 |
2017年 | 31篇 |
2016年 | 20篇 |
2015年 | 19篇 |
2014年 | 45篇 |
2013年 | 141篇 |
2012年 | 50篇 |
2011年 | 73篇 |
2010年 | 54篇 |
2009年 | 130篇 |
2008年 | 155篇 |
2007年 | 160篇 |
2006年 | 151篇 |
2005年 | 125篇 |
2004年 | 121篇 |
2003年 | 114篇 |
2002年 | 89篇 |
2001年 | 109篇 |
2000年 | 84篇 |
1999年 | 68篇 |
1998年 | 52篇 |
1997年 | 38篇 |
1996年 | 38篇 |
1995年 | 39篇 |
1994年 | 42篇 |
1993年 | 36篇 |
1992年 | 35篇 |
1991年 | 17篇 |
1990年 | 14篇 |
1989年 | 10篇 |
1988年 | 14篇 |
1987年 | 18篇 |
1986年 | 11篇 |
1985年 | 10篇 |
1984年 | 7篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 11篇 |
1979年 | 12篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1974年 | 2篇 |
排序方式: 共有2338条查询结果,搜索用时 0 毫秒
1.
Q. Sun Q. Wang X.G. Gong V. Kumar Y. Kawazoe 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(1):77-81
We report results of the atomic and electronic structures of Al7C cluster using ab initio molecular dynamics with ultrasoft pseudopotentials and generalized gradient approximation. The lowest energy structure is
found to be the one in which carbon atom occupies an interstitial position in Al7 cluster. The electronic structure shows that the recent observation [Chem. Phys. Lett. 316, 31 (2000)] of magic behavior of Al7C- cluster is due to a large highest occupied and lowest unoccupied molecular orbital (HOMO-LUMO) gap which makes Al7C- chemically inert. These results have further led us to the finding of a new neutral magic cluster Al7N which has the same number of valence electrons as in Al7C- and a large HOMO-LUMO gap of 1.99 eV. Further, calculations have been carried out on (Al7N)2 to study interaction between magic clusters.
Received 28 July 2001 相似文献
2.
We present here a methodology for searching a robust pore size distribution (PSD) for adsorbent materials. The method is based on a combination of individual adsorption isotherms, obtained from Grand Canonical Monte Carlo simulations, a regularization procedure to invert the adsorption integral equation (Tikhonov regularization solved by singular value decomposition), and the needed experimental adsorption isotherm. The selection of several parameters from the available choices to start the procedure are discussed here: the size of the kernel (number of individual pores and number of experimental adsorption points to be included), the fulfillment of the Discrete Picard condition, and the L-curve criteria, all leading to find a reliable and robust PSD. The procedure is applied to plugged hexagonal templated silicas (PHTS), synthesized, and characterized in our laboratory. 相似文献
3.
The aim of this work is to study the dynamic formation and dissociation of trions and excitons in double barrier resonant tunneling diodes. We propose a system of rate equations that takes into account the formation, dissociation and annihilation of these complexes inside the quantum well. From the solutions of the coupled equations, we are able to study the modulation of excitons and trions formation in the device as a function of the applied bias. The results of our model agree qualitatively with the experiments showing the viability of these rate equations system to study the dynamics of complex systems. 相似文献
4.
An effective residual interaction between particles and holes for shell model calculations around 208Pb, derived from the interaction between free nucleons, is compared with the measured properties of proton-hole neutron states
in 208Tl and the interaction between proton holes is adjusted to newly measured level energies in 206Hg. These interaction elements are particularly relevant for neutron-rich nuclei. The adjustment of two mixing elements reproduces
the known γ-decay data in 208Tl.
Received: 2 April 2002 / Accepted: 2 May 2002 相似文献
5.
Jin Hu Gang Liu Jixiu Zhang Lingchao Kong Weidong Fei 《Applied Surface Science》2006,253(5):2792-2795
The microstructure of a laser treated Al18B4O33w/2024Al composite has been investigated using transmission electron microscope (TEM), low-angle (glancing angle) X-ray diffraction (XRD) techniques. Various surface microstructures were observed in the laser treated composite. The Al18B4O33 whisker on the surface of the composite was decomposed during laser surface melting, various decomposition products were studied in the laser treated composite. Eutectic phases and the precipitation in the matrix of the composite with laser-treated were observed. The main phases detected in the molten zone were aluminum and decomposition products Al2O3. The effect of laser treatment on the hardness of the composite was also examined. A surface hardness of 400 Hv was noted. 相似文献
6.
We perform three tests on our proposal to implement diffeomorphism invariance in the non-abelian D0-brane DBI action as a base-point independence constraint between matrix Riemann normal coordinate systems. First, we show that T-duality along an isometry correctly interchanges the potential and kinetic terms in the action. Second, we show that the method to impose base-point independence using an auxiliary dN2-dimensional nonlinear sigma model also works for metrics which are curved along the brane, provided a physical gauge choice is made at the end. Third, we show that without alteration this method is applicable to higher order in velocities. Testing specifically to order 4, we elucidate the range of validity of the symmetrized trace approximation to the non-abelian DBI action. 相似文献
7.
Deformation quantization is a powerful tool for quantizing theories with bosonic and fermionic degrees of freedom. The star products involved generate the mathematical structures which have recently been used in attempts to analyze the algebraic properties of quantum field theory. In the context of quantum mechanics they provide a quantization procedure for systems with either bosonic or fermionic degrees of freedom. We illustrate this procedure for a number of physical examples, including bosonic, fermionic, and supersymmetric oscillators. We show how non-relativistic and relativistic particles with spin can be naturally described in this framework. 相似文献
8.
Manju Lata Rao 《Solid State Communications》2004,129(12):781-784
Bulk amorphous Co(100−x)Ptx (0≤x≤50) nano-alloys have been synthesized using high frequency ultrasound, displaying single domain (4-5 nm) behavior wherein weakly exchange-coupled particles lead to a field-dependent resistivity behavior. Magneto-resistivity is correlated to the order-disorder parameter in these powder compacts. The plot of Δρ/ρ0 as a function of reduced magnetization indicates that all the systems are weakly exchange coupled. 相似文献
9.
A. O. Barut 《Applied physics. B, Lasers and optics》1995,60(2-3):123-128
The theory of many-body systems constitutes one of the most complex part of quantum mechanics. Closed results are not readily available and approximations become extremely involved. It is, therefore, of considerable interest that the quantization of certain simple collective motions of particles can describe the energies of atoms, nuclei and particle models rather well. We describe here the most elementary examples of such structures.Dedicated to H. Walther, a great scientist and who demonstrated among many other things the regular shapes of atomic particles, the subject of this essay 相似文献
10.
C. Bréchignac Ph. Cahuzac F. Carlier C. Colliex M. de Frutos N. Kébaïli J. Le Roux A. Masson B. Yoon 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):265-268
We studied shape relaxation of nano-fractal islands,
during annealing, after their growth from antimony cluster
deposition on graphite surface. Annealing at
180°C shows evidence of an increase
of the fractal branch width with time followed by branch
fragmentation, without changing the fractal dimension. The time
evolution of the width of the arm suggests the surface
self-diffusion mechanism as the main relaxation process. With
Monte Carlo simulations, we confirmed the observed behavior.
Comparison is done with our previous results on fragmentation of
nano-fractal silver islands when impurity added to the incident
cluster promotes rapid fragmentation by surface self-diffusion
enhancement [1]. 相似文献