全文获取类型
收费全文 | 1825篇 |
免费 | 236篇 |
国内免费 | 147篇 |
专业分类
化学 | 659篇 |
晶体学 | 17篇 |
力学 | 69篇 |
综合类 | 21篇 |
数学 | 180篇 |
物理学 | 632篇 |
综合类 | 630篇 |
出版年
2024年 | 6篇 |
2023年 | 35篇 |
2022年 | 58篇 |
2021年 | 56篇 |
2020年 | 48篇 |
2019年 | 27篇 |
2018年 | 41篇 |
2017年 | 39篇 |
2016年 | 57篇 |
2015年 | 48篇 |
2014年 | 84篇 |
2013年 | 72篇 |
2012年 | 94篇 |
2011年 | 113篇 |
2010年 | 100篇 |
2009年 | 100篇 |
2008年 | 96篇 |
2007年 | 76篇 |
2006年 | 77篇 |
2005年 | 65篇 |
2004年 | 76篇 |
2003年 | 62篇 |
2002年 | 55篇 |
2001年 | 51篇 |
2000年 | 37篇 |
1999年 | 77篇 |
1998年 | 74篇 |
1997年 | 79篇 |
1996年 | 71篇 |
1995年 | 50篇 |
1994年 | 54篇 |
1993年 | 38篇 |
1992年 | 44篇 |
1991年 | 32篇 |
1990年 | 18篇 |
1989年 | 28篇 |
1988年 | 20篇 |
1987年 | 14篇 |
1986年 | 19篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 7篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有2208条查询结果,搜索用时 15 毫秒
1.
本文给出了ρ~0→π~+π~-衰变的么正计算及其衰变率和ρ~2极化插入的关系.ρ~0极化插入的虚部是用维度积分的方法来计算.极化插入虚部的计算方法是普适的. 相似文献
2.
G. Z. Ruan S. Y. Wang Y. Yamamoto S. S. Zhu 《Journal of Optimization Theory and Applications》2004,123(2):409-429
In this paper, a model of a linear multilevel programming problem with dominated objective functions (LMPPD(l)) is proposed, where multiple reactions of the lower levels do not lead to any uncertainty in the upper-level decision making. Under the assumption that the constrained set is nonempty and bounded, a necessary optimality condition is obtained. Two types of geometric properties of the solution sets are studied. It is demonstrated that the feasible set of LMPPD(l) is neither necessarily composed of faces of the constrained set nor necessarily connected. These properties are different from the existing theoretical results for linear multilevel programming problems. 相似文献
3.
A New Cohomology Theory of Orbifold 总被引:7,自引:0,他引:7
Based on the orbifold string theory model in physics, we construct a new cohomology ring for any almost complex orbifold. The key theorem is the associativity of this new ring. Some examples are computed.Both authors partially supported by the National Science Foundation 相似文献
4.
Shigui Ruan 《Natural Resource Modeling》1998,11(2):131-141
In this paper, we consider the Gierer-Meinhardt model of morphogenesis. It is shown that the homogeneous equilibrium solution and the homogeneous periodic solution become diffusively unstable if the diffusion coefficients of the two substances are chosen suitably. 相似文献
5.
The theoretical proton-40Ca optical potential is constructed based on theα-particle model of the nucleus. With this potential, the differential cross section, analysing power and the spin rotation function for 200 MeV proton-40Ca elastic scattering are calculated. The results are in good agreement with the experimental data. 相似文献
6.
阮世勋 《广西大学学报(自然科学版)》1988,(3)
本文简述定义两个新系数对Camp公式进行变换,以编制磁致伸缩换能器谐振尺寸和频率设计计算用表的方法,分别举例说明利用该表进行考虑修正和不考虑修正的换能器计算的方法。 相似文献
7.
Hong-jun Liu Wei Zhao Guo-fu Chen Yi-shan Wang Lian-jun Yu Chi Ruan Xue-feng Li 《Optics & Laser Technology》2004,36(4):3482-314
Experimental investigations of a type-I noncollinear phase-matched optical parametric amplification based on lithium triborate, which was pumped by a 5-ns second-harmonic pulses from a Q-switched Nd:YAG, seeded by a cw Ti:sapphire laser at 800 nm, was presented. The experiments generated 2-ns signal output pulses at 800 nm, the maximum signal output pulse energy reached 19 μJ, the corresponding parametric gain was 44 dB. Furthermore, the experiments demonstrate that the 65 nm-FWHM parametric fluorescence gain spectrum could also be observed. A quantitative account of the ultrabroadband parametric fluorescence gain spectrum was given with our theory. The experimental measurements are in agreement with theoretical calculations. 相似文献
8.
9.
The Hamiltonian formulation of the usual complex quantum mechanics in the theory of generalized quantum dynamics is discussed.
After the total trace Lagrangian, total trace Hamiltonian and two kinds of Poisson brackets are introduced, both the equations
of motion of some total trace functionals which are expressed by total trace Poisson brackets and the equations of motion
of some operators which are expressed by the without-total-trace Poisson brackets are obtained. Then a set of basic equations
of motion of the usual complex quantum mechanics are obtained, which are also expressed by the Poisson brackets and total
trace Hamiltonian in the generalized quantum dynamics. The set of equations of motion are consistent with the corresponding
Heisenberg equations.
Project supported by Prof. T.D. Lee’s NNSC Grant, the National Natural Science Foundation of China, the Foundation of Ph.
D. Directing Programme of Chinese University, and the Chinese Academy of Sciences. 相似文献
10.
Ruan C Paulose M Varghese OK Mor GK Grimes CA 《The journal of physical chemistry. B》2005,109(33):15754-15759
Anodization of titanium in a fluorinated dimethyl sulfoxide (DMSO) and ethanol mixture electrolyte is investigated. The prepared anodic film has a highly ordered nanotube-array surface architecture. Using a 20 V anodization potential (vs Pt) nanotube arrays having an inner diameter of 60 nm and 40 nm wall thickness are formed. The overall length of the nanotube arrays is controlled by the duration of the anodization, with nanotubes appearing only after approximately 48 h; a 72 h anodization results in a nanotube array approximately 2.3 mum in length. The photoelectrochemical response of the nanotube-array photoelectrodes is studied using a 1 M KOH solution under both UV and visible (AM 1.5) illumination. Enhanced photocurrent density is observed for samples obtained in the organic electrolyte, with an UV photoconversion efficiency of 10.7%. 相似文献