全文获取类型
收费全文 | 3041篇 |
免费 | 235篇 |
国内免费 | 205篇 |
专业分类
化学 | 319篇 |
晶体学 | 7篇 |
力学 | 349篇 |
综合类 | 15篇 |
数学 | 1372篇 |
物理学 | 1419篇 |
出版年
2024年 | 2篇 |
2023年 | 30篇 |
2022年 | 41篇 |
2021年 | 41篇 |
2020年 | 76篇 |
2019年 | 75篇 |
2018年 | 74篇 |
2017年 | 73篇 |
2016年 | 82篇 |
2015年 | 84篇 |
2014年 | 159篇 |
2013年 | 228篇 |
2012年 | 144篇 |
2011年 | 212篇 |
2010年 | 140篇 |
2009年 | 224篇 |
2008年 | 245篇 |
2007年 | 200篇 |
2006年 | 152篇 |
2005年 | 138篇 |
2004年 | 155篇 |
2003年 | 133篇 |
2002年 | 119篇 |
2001年 | 91篇 |
2000年 | 73篇 |
1999年 | 74篇 |
1998年 | 56篇 |
1997年 | 62篇 |
1996年 | 54篇 |
1995年 | 32篇 |
1994年 | 34篇 |
1993年 | 33篇 |
1992年 | 29篇 |
1991年 | 9篇 |
1990年 | 12篇 |
1989年 | 11篇 |
1988年 | 11篇 |
1987年 | 8篇 |
1986年 | 10篇 |
1985年 | 14篇 |
1984年 | 9篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有3481条查询结果,搜索用时 15 毫秒
131.
Ring-shaped lead zirconate titanate (PZT) piezoelectric vibrators were subjected to non-uniform mechanical stress applied by bolt clamping. The effect of mechanical stress on the effective electromechanical coupling factor (keff) and mechanical quality factor (Qm) of the thickness and wall thickness modes was studied by an equivalent electric circuit analysis. The initiation and propagation of cracks under mechanical stress were also discussed based on the resonance method and the indentation technique. keff for both the thickness and wall thickness modes decreased with increase in mechanical stress due to de-poling of the PZT. Qm of the thickness mode dropped sharply with increase in mechanical stress while Qm of the wall thickness mode remained almost unchange. Existence of microcracks in a PZT vibrator can be detected by the occurrence of spurious vibrations at the wall thickness mode in the electrical impedance vs. frequency spectra. 相似文献
132.
V.S. Gerdjikov 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):237-241
We compare the Hamiltonian properties of the N-soliton solutions of the NLSE in the adiabatic approximation and show how it matches the Hamiltonian formulation for the
complex Toda chain which describes the adiabatic N-soliton interactions.
Received 21 October 2001 Published online 2 October 2002
RID="a"
ID="a"e-mail: gerjikov@inrne.bas.bg 相似文献
133.
Fundamental theory presented in Part (I)[8] is used to analyze anisotropic plane stress problems. First we construct the generalized variational principle to enter Hamiltonian
system and get Hamiltonian differential operator matrix; then we solve eigen problem; finally, we present the process of obtaining
analytical solutions and semi-analytical solutions for anisotropic plane stress problems on rectangular area. 相似文献
134.
135.
136.
蔡清 《原子与分子物理学报》1996,(2)
采用连续分数法得到了具有分子晶体中的分子之间的相互作用势为V(r)=A1r-10-A2r-6(A1,A2>0)的分子晶体的Hamiltonian算子的精确的能量本征值(即分子晶体的束缚能的精确值)。 相似文献
137.
A.?N.?IvanovEmail author M.?Cargnelli M.?Faber H.?Fuhrmann V.?A.?Ivanova J.?Marton N.?I.?Troitskaya J.?Zmeskal 《The European Physical Journal A - Hadrons and Nuclei》2005,25(3):329-338
We argue that due to isospin and U-spin invariance of strong low-energy interactions the S-wave scattering lengths a
0
0 and a
1
0 of ˉN scattering with isospin I = 0 and I = 1 satisfy the low-energy theorem a
0
0 +3a
1
0 = 0 valid to leading order in chiral expansion. In the model of strong low-energy ˉN interactions at threshold (Eur. Phys. J. A 21, 11 (2004)) we revisit the contribution of the Σ(1750) resonance, which does not saturate the low-energy theorem a
0
0 +3a
1
0 = 0, and replace it by the baryon background with properties of an SU(3) octet. We calculate the S-wave scattering amplitudes of K-N and K-d scattering at threshold. We calculate the energy level displacements of the ground states of kaonic hydrogen and deuterium.
The result obtained for kaonic hydrogen agrees well with recent experimental data by the DEAR Collaboration. We analyse the
cross-sections for elastic and inelastic K-p scattering for laboratory momenta 70MeV/c < p
K < 150MeV/c of the incident K--meson. The theoretical results agree with the available experimental data within two standard deviations. 相似文献
138.
Quantum systems with quadratic Hamiltonians are considered. Some results about the time evolution of homogeneous polynomials and of quantum correlation functions are given. The image of arbitrary orbit of Weyl–Heisenberg group under this time evolution is shown to be again an orbit of this group. For quantum free particle it is shown that its time evolution intersects arbitrary such orbit at most once. A result about existence of more orbits having the same dispersion of some quantum position is presented.PACS: 02.20.Qs, 02.30.Sa 相似文献
139.
In a recent paper, a “distance” function,
, was defined which measures the distance between pure classical and quantum systems. In this work, we present a new definition of a “distance”, D, which measures the distance between either pure or impure classical and quantum states. We also compare the new distance formula with the previous formula, when the latter is applicable. To illustrate these distances, we have used 2 × 2 matrix examples and two-dimensional vectors for simplicity and clarity. Several specific examples are calculated. 相似文献
140.
Sami?I.?MuslihEmail author Hosam?A.?El-Zalan Eqab?M.?Rabei 《International Journal of Theoretical Physics》2005,44(8):1271-1279
In this paper, constrained Hamiltonian systems with linear velocities are investigated by using the Hamilton–Jacobi method.
The integrablity conditions are considered on the equations of motion and the action function as well in order to obtain the
path integral quantization of singular Lagrangians with linear velocities. 相似文献