全文获取类型
收费全文 | 25297篇 |
免费 | 4439篇 |
国内免费 | 4051篇 |
专业分类
化学 | 15398篇 |
晶体学 | 263篇 |
力学 | 2980篇 |
综合类 | 211篇 |
数学 | 1897篇 |
物理学 | 13038篇 |
出版年
2024年 | 77篇 |
2023年 | 305篇 |
2022年 | 679篇 |
2021年 | 840篇 |
2020年 | 1112篇 |
2019年 | 880篇 |
2018年 | 870篇 |
2017年 | 986篇 |
2016年 | 1136篇 |
2015年 | 1017篇 |
2014年 | 1392篇 |
2013年 | 2215篇 |
2012年 | 1560篇 |
2011年 | 1701篇 |
2010年 | 1403篇 |
2009年 | 1683篇 |
2008年 | 1641篇 |
2007年 | 1712篇 |
2006年 | 1590篇 |
2005年 | 1363篇 |
2004年 | 1228篇 |
2003年 | 1105篇 |
2002年 | 924篇 |
2001年 | 852篇 |
2000年 | 757篇 |
1999年 | 689篇 |
1998年 | 608篇 |
1997年 | 507篇 |
1996年 | 423篇 |
1995年 | 391篇 |
1994年 | 336篇 |
1993年 | 243篇 |
1992年 | 219篇 |
1991年 | 204篇 |
1990年 | 153篇 |
1989年 | 126篇 |
1988年 | 124篇 |
1987年 | 99篇 |
1986年 | 98篇 |
1985年 | 88篇 |
1984年 | 73篇 |
1983年 | 33篇 |
1982年 | 57篇 |
1981年 | 47篇 |
1980年 | 45篇 |
1979年 | 45篇 |
1978年 | 21篇 |
1977年 | 38篇 |
1976年 | 24篇 |
1973年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
101.
In this work two non-local problems for the parabolic-hyperbolic type equation with non-characteristic line of changing type
are considered. Unique solvability of these problems is proven. The uniqueness of the solution is proven by the method of
energy integrals and the existence is proven by the method of integral equations. 相似文献
102.
LUO You-Hua GE Zi-Ming 《理论物理通讯》2006,46(12)
In noncommutative space, we examine the problem of a noninteracting and harmonically trapped BoseEinstein condensate, and derive a simple analytic expression for the effect of spatial noncommutativity on energy spectrum of the condensate. It indicates that the ground-state energy incorporating the spatial noncommutativity is reduced to a lower level, which depends upon the noncommutativity parameter θ. The gap between the noncommutative space and commutative one for the ground-state level of the condensate should be a signal of spatial noncommutativity. 相似文献
103.
在e-A深度非弹性散射过程中, 喷注穿过冷核介质时, 多重散射诱导胶子辐射会导致对碎裂函数的修正及喷注的能量损失.前期研究中关于计算e-A深度非弹性散射中胶子辐射振幅的两种方法: 螺旋振幅近似和微扰QCD严格计算都异常繁杂.
本文发展了一种新的方法, 可以方便计算出多重散射导致胶子辐射的振幅, 得到的碎裂函数的修正以及能量损失与严格计算的结果一致. 相似文献
104.
Jae-Yeon Lee Eugene Lubarsky Ben T. Zinn 《Proceedings of the Combustion Institute》2005,30(2):1757-1764
This paper describes an experimental investigation of the feasibility of using “slow” active control approaches, which “instantaneously” change liquid fuel spray properties, to suppress combustion instabilities. The objective of this control approach was to break up the feedback between the combustion process heat release and combustor pressure oscillations that drive the instability by changing the characteristics of the combustion process (e.g., the characteristic combustion time). To demonstrate the feasibility of such control, this study used a proprietary fuel injector (NanomiserTM), which can vary its fuel spray properties, to investigate the dependence of acoustics–combustion process coupling, i.e., the driving of combustion instabilities, upon the fuel spray properties. This study showed that by changing the spray characteristics it is possible to significantly damp combustion instabilities. Furthermore, using combustion zone chemiluminescence distributions, which were obtained by Abel’s deconvolution synchronized with measured acoustic data, it has been shown that the instabilities were mostly driven midway between the combustor centerline and wall, a short distance downstream from the flame holder, where the mean axial flow velocity is approximately zero in the vortex near the flame holder. The results of this study strongly suggest that a “slow” active control system that employs controllable fuel injectors could be effectively used to prevent the onset of detrimental combustion instabilities. 相似文献
105.
Kwang-Hua W. Chu 《International Journal of Theoretical Physics》2007,46(12):3230-3233
The modified Gross–Pitaevskii equation was derived and solved to obtain the 1D solution in the zero-energy limit. This stationary
solution could account for the dominated contributions due to the kinetic effect as well as the chemical potential in inhomogeneous
Bose gases. 相似文献
106.
Quantitative H–Al distances in acid sites of two zeolites with MFI and IFR framework topology were obtained by numerical simulation of 1H{27Al} rotational echo adiabatic passage double resonance (REAPDOR) experiments. A 27Al offset-dependent data set yields for each resolved 1H NMR line a corresponding nuclear electric quadrupole coupling constant of the neighboring 27Al site. This information is used for analyzing a second data set for on-resonance irradiation, where the dipolar evolution time (number of rotor cycles) was varied, to yield the 1H–27Al dipolar coupling constant. Numerical simulations indicate that the REAPDOR method does not depend significantly on the polar angles, defining the orientation of the electric field gradient tensor of 27Al with respect to the Al–H dipolar vector. In contrast, the transfer of populations in double resonance sequence is sensitive to these angles, and it can be thus used to measure them. 相似文献
107.
F.Oner R.A.Mamedoy 《理论物理通讯》2002,37(3):327-330
Behavior of the Coulomb energy difference for light nuclei is explained in terms of the different values of the average Coulomb interaction between two particles.Coulomb energy difference according to shell model of light mirror nuclei in the Coulomb and exchange integrals in the formula can be explained with exponential-type wavefunctions.In this study,using the one-center expansion of exponential-type wavefunctions in terms of Slater-type orbitals with the same center,we derived formula for Coulomb energy difference of light mirror nuclei. 相似文献
108.
用密耦近似方法计算了He和N2体系的微分截面和总截面及转动激发分波截面,得出微分截面及总截面随入射能量变化的规律. 相似文献
109.
A proposal is presented for teleporting Schrding-cat states. The process of the teleportation is achieved through the dispersive atom-cavity-field interaction. In this proposal, only measurement on the cavity field and on the singlet atomic states are used. 相似文献
110.
In this paper we discuss thermodynamics parameters of black hole horizon and cosmological horizon in general high-dimensional space-time. We obtain that the entropy of a cosmological horizon can be described by the Cardy-Verlinde formula. However, the entropy of black hole horizon will be expressed in a form of the Cardy-Verlinde formula, if one adopts the methods given by Abbott and Deser to compute the mass of a black hole in general high-dimensional space-time. Through discussion, relation among various thermodynamics parameters of the black hole in general high-dimensional space-time is given. That is, differential formula of the first law of thermodynamics is obtained. Because we discuss the general high-dimensional space-time, our result has universality.
PACS: 04.20.Dw, 97.60.Lf 相似文献