全文获取类型
收费全文 | 140036篇 |
免费 | 2180篇 |
国内免费 | 395篇 |
专业分类
化学 | 62773篇 |
晶体学 | 1142篇 |
力学 | 7758篇 |
综合类 | 1篇 |
数学 | 42287篇 |
物理学 | 28650篇 |
出版年
2023年 | 471篇 |
2022年 | 391篇 |
2021年 | 691篇 |
2020年 | 954篇 |
2019年 | 918篇 |
2018年 | 11282篇 |
2017年 | 11066篇 |
2016年 | 8185篇 |
2015年 | 2701篇 |
2014年 | 2207篇 |
2013年 | 4582篇 |
2012年 | 7758篇 |
2011年 | 14010篇 |
2010年 | 7940篇 |
2009年 | 7897篇 |
2008年 | 9919篇 |
2007年 | 11782篇 |
2006年 | 3279篇 |
2005年 | 4140篇 |
2004年 | 3918篇 |
2003年 | 3890篇 |
2002年 | 2719篇 |
2001年 | 1592篇 |
2000年 | 1602篇 |
1999年 | 1089篇 |
1998年 | 887篇 |
1997年 | 741篇 |
1996年 | 989篇 |
1995年 | 664篇 |
1994年 | 707篇 |
1993年 | 716篇 |
1992年 | 676篇 |
1991年 | 541篇 |
1990年 | 583篇 |
1989年 | 496篇 |
1988年 | 492篇 |
1987年 | 458篇 |
1986年 | 447篇 |
1985年 | 600篇 |
1984年 | 556篇 |
1983年 | 445篇 |
1982年 | 434篇 |
1981年 | 442篇 |
1980年 | 388篇 |
1979年 | 385篇 |
1978年 | 373篇 |
1977年 | 338篇 |
1976年 | 346篇 |
1975年 | 309篇 |
1973年 | 345篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Deutsch and Hayden have proposed an alternative formulation of quantum mechanics which is completely local. We argue that
their proposal must be understood as having a form of ‘gauge freedom’ according to which mathematically distinct states are
physically equivalent. Once this gauge freedom is taken into account, their formulation is no longer local.
相似文献
992.
The liquid to solid transformation of ternary Ag42.4Cu21.6Sb36 eutectic alloy was accomplished in an ultrasonic field with a frequency of 35 kHz, and the growth mechanism of this ternary eutectic was examined. Theoretical calculations predict that the sound intensity in the liquid phase at the solidification interface increases gradually as the interface moves up from the sample bottom to its top. The growth mode of (ε θ Sb) ternary eutectic exhibits a transition of "divorced eutectic- mixture of anomalous and regular structures-regular eutectic" along the sample axis due to the inhomogeneity of sound field distribution. In the top zone with the highest sound intensity, the cavitation effect promotes the three eutectic phases to nucleate independently, while the acoustic streaming efficiently suppresses the coupled growth of eutectic phases. In the meantime, the ultrasonic field accelerates the solute transportation at the solid-liquid interface, which reduces the solute solubility of eutectic phases. 相似文献
993.
R. Boutami M. J.G. Borge H. Mach L. M. Fraile K. Gulda A. J. Aas L. M. García-Raffi E. Hagebø W. Kurcewicz G. Løvhøiden T. Martínez B. Rubio J. L. Taín O. Tengblad 《The European physical journal. Special topics》2007,150(1):87-88
There is lack of knowledge of the structure of the 231Ac
nucleus located in the upper border of the
island of octupole deformation centered around A = 225.
We have populated the excited states in 231Ac by beta-decay from the parent 231Ra
produced at ISOLDE, CERN.
The low-energy structure of 231Ac has been investigated by
means of γ, conversion electrons, γ-γ and γ-e-
spectroscopy. We report here in the precise
determination in 231Ac of the half-life of the most intensively populated states
by the Advanced Time Delayed ββγ(t) technique. 相似文献
994.
The interactive two-state model of cell membrane ion channels in an electric field is formulated on the Bethe lattice by means
of the exact recursion relations. The probability of channel opening or maximum fractions of open potassium and sodium channels
are obtained by solving a non-linear algebraic equation. Using known parameters for the conventional mean-field theory the
model gives a good agreement with the experiment both at low and high trans-membrane potential values. For intermediate voltages,
the numerical results imply that collective effects are introduced by trans-membrane voltage. 相似文献
995.
Yun Chen Qing-sheng Wu Rong-hui Yin Ya-ping Ding 《Journal of nanoparticle research》2007,9(2):283-287
Uniform Pb(OH)Cl nanotubes were synthesized for the first time through a reverse micelles system. The system was consisting
of C12E9 as a surfactant, n-pentanol as a cosurfactant, hexamethylene as the continuous oil phase and lead acetate or sodium chloride
solution as the dispersed aqueous phase. The obtained Pb(OH)Cl nanotubes have an average outer diameter of 60 nm, inner diameter
of about 40 nm, and an length up to 3 μm as TEM picture showed. And the range of the nanotube diameter is from 50 nm to 70 nm.
XRD result indicated that Pb(OH)Cl crystallized in an orthorhombic phase. Photoluminescent (PL) spectrum showed that the product
emit in near ultraviolet region and visible region at 335 nm and 439 nm respectively. The experimental results show that reaction
temperature have effect on the shape of Pb(OH)Cl nanotubes. A possible formation mechanism was also discussed. 相似文献
996.
We explain the (non-)validity of close-to-equilibrium entropy production principles in the context of linear electrical circuits.
Both the minimum and the maximum entropy production principles are understood within dynamical fluctuation theory. The starting
point are Langevin equations obtained by combining Kirchoff’s laws with a Johnson-Nyquist noise at each dissipative element
in the circuit. The main observation is that the fluctuation functional for time averages, that can be read off from the path-space
action, is in first order around equilibrium given by an entropy production rate.
That allows to understand beyond the schemes of irreversible thermodynamics (1) the validity of the least dissipation, the
minimum entropy production, and the maximum entropy production principles close to equilibrium; (2) the role of the observables’
parity under time-reversal and, in particular, the origin of Landauer’s counterexample (1975) from the fact that the fluctuating
observable there is odd under time-reversal; (3) the critical remark of Jaynes (1980) concerning the apparent inappropriateness
of entropy production principles in temperature-inhomogeneous circuits. 相似文献
997.
Oleg I. Bogoyavlenskij 《Communications in Mathematical Physics》2007,269(2):545-556
The necessary and sufficient conditions for the decoupling of a quasi-linear system of partial differential equations into k non-interacting subsystems are derived. Several necessary conditions for the decoupling are found and applied to the Benney system. 相似文献
998.
Using conformal coordinates associated with conformal relativity—associated with de Sitter spacetime homeomorphic projection into Minkowski spacetime—we obtain a conformal Klein-Gordon partial differential equation, which is intimately related to the production of quasi-normal modes (QNMs) oscillations, in the context of electromagnetic and/or gravitational perturbations around, e.g., black holes. While QNMs arise as the solution of a wave-like equation with a Pöschl-Teller potential, here we deduce and analytically solve a conformal ‘radial’ d’Alembert-like equation, from which we derive QNMs formal solutions, in a proposed alternative to more completely describe QNMs. As a by-product we show that this ‘radial’ equation can be identified with a Schrödinger-like equation in which the potential is exactly the second Pöschl-Teller potential, and it can shed some new light on the investigations concerning QNMs. 相似文献
999.
The Schlesinger equations S
(n,m) describe monodromy preserving deformations of order m Fuchsian systems with n + 1 poles. They can be considered as a family of commuting time-dependent Hamiltonian systems on the direct product of n copies of m × m matrix algebras equipped with the standard linear Poisson bracket. In this paper we present a new canonical Hamiltonian formulation
of the general Schlesinger equations S
(n,m) for all n, m and we compute the action of the symmetries of the Schlesinger equations in these coordinates. 相似文献
1000.
Pei-Hong Gu Xiao-Jun Bi Xinmin Zhang 《The European Physical Journal C - Particles and Fields》2007,50(3):655-659
In this paper we study dynamical CPT-violation in the neutrino sector as induced by the dark energy of the universe. Specifically
we consider a dark energy model where the dark energy scalar derivatively interacts with the right-handed neutrinos. This
type of derivative coupling leads to cosmological CPT-violation during the evolution of the background field of the dark energy.
We calculate the induced CPT-violation of left-handed neutrinos and find that the CPT-violation produced in this way is consistent
with the present experimental limit and sensitive to future neutrino oscillation experiments such as the neutrino factory.
PACS 95.36.+x; 14.60.St 相似文献