首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   164篇
  免费   3篇
  国内免费   2篇
化学   57篇
晶体学   2篇
力学   3篇
数学   14篇
物理学   93篇
  2022年   2篇
  2019年   2篇
  2018年   1篇
  2017年   2篇
  2016年   3篇
  2015年   2篇
  2014年   7篇
  2013年   24篇
  2012年   8篇
  2011年   12篇
  2010年   8篇
  2009年   2篇
  2008年   6篇
  2007年   4篇
  2006年   4篇
  2005年   5篇
  2004年   3篇
  2003年   9篇
  2002年   5篇
  2001年   7篇
  2000年   1篇
  1999年   8篇
  1998年   4篇
  1997年   5篇
  1996年   4篇
  1995年   5篇
  1994年   5篇
  1993年   4篇
  1992年   2篇
  1990年   1篇
  1987年   1篇
  1985年   1篇
  1981年   2篇
  1979年   1篇
  1968年   2篇
  1957年   1篇
  1939年   1篇
  1934年   2篇
  1933年   2篇
  1867年   1篇
排序方式: 共有169条查询结果,搜索用时 281 毫秒
41.
We characterize statistical independence of sequences by the L p-discrepancy and the Wiener L p-discrepancy. Furthermore, we find asymptotic information on the distribution of the L 2-discrepancy of sequences  相似文献   
42.
Structural Interactions of Planar and Non‐planar Bis(1,2‐dithiosquarato)metalate Host Lattices with CuII Complexes – Structure and EPR Investigations 1,2‐Dithiosquaratometalates (M = Cu, Ni, Zn) are available by direct synthesis from metal salts with dipotassium‐1,2‐dithiosquarate. The structural influence of the planar and nonplanar host lattice systems (BzlEt3N)2[Cu/Ni(dtsq)2] and (BzlEt3N)2[Cu/Zn(dtsq)2] on the geometrical and electronic structure of the CuII guest complex [Cu(dtsq)2]2– is studied by EPR spectroscopy. The used host lattices (BzlEt3N)2[Ni(dtsq)2] (planar) and (BzlEt3N)2[Zn(dtsq)2] (tetrahedral) are characterized by X‐ray structure analysis. (BzlEt3N)2[Ni(dtsq)2] crystallizes in the triclinic unit cell P1 with a = 9.1021(8) Å, b = 9.4190(8) Å, c = 11.0119(10) Å, α = 92.8560(10)°, β = 95.375(2)°, γ = 104.5180(10)° and Z = 1. (BzlEt3N)2[Zn(dtsq)2] crystallizes in the monoclinic unit cell C2/c with a = 21.1299(14) Å, b = 16.6641(11) Å, c = 13.8324(9) Å, β = 123.9100(10)° and Z = 4. The g and A Cu tensors in the Cu/Ni system are nearly axial symmetric (g|| = 2.122, g = 2.028; A = –159.5 · 10–4 cm–1, A = –36.9 · 10–4 cm–1). The coordination geometry of the CuII guest complex in the tetrahedral Cu/Zn system is rather distorted, which is shown by the changed g and A Cu tensor parameters (g|| = 2.143, g = 2.042; A = –103.0 · 10–4 cm–1, A ≈ –5.0 · 10–4 cm–1). The spin density distribution is discussed using EHT molecular orbital calculations.  相似文献   
43.
The role of geometrical confinement on the dynamics of argon is studied. We have investigated 36Argon adsorbed in nanoporous Gelsil glass by inelastic neutron scattering. By fractional filling the `dimensionality' of the system is tuned from a two-dimensional towards the bulk state. Ab-initio calculations of plane sheets of Ar atoms and of bulk Ar are compared to the experimental results. A shift of various phonon modes to lower energies with decreasing dimensionality is observed in the results of both methods.  相似文献   
44.
45.
The 48Ca(e,e(')n) reaction has been investigated for excitation energies 11-25 MeV and momentum transfers 0.22-0.43 fm(-1) at the superconducting Darmstadt electron linear accelerator S-DALINAC. Electric dipole and quadrupole plus monopole strength distributions are extracted from a multipole decomposition of the spectra. Their fragmented structure is described by microscopic calculations allowing for coupling of the basic particle-hole excitations to more complex configurations. Comparison of the excitation spectrum of the residual nucleus 47Ca with statistical model calculations reveals a 39(5)% contribution of direct decay to the damping of the giant dipole resonance.  相似文献   
46.
47.
The recent microscopic model of Michel and Naudts for the interaction of ionic vibrational displacements and molecular rotational displacements is combined with the lattice dynamical shell model to calculate phonon dispersion curves of KCN and NaCN. Very good agreement with the existing experimental data is obtained. In particular, the upward dispersion of the TA phonon branches, characteristic of the alkali cyanide crystals, is well reproduced.  相似文献   
48.

The set of all statistical limit points of a given sequence is characterized as an -set. It is also characterized in terms of discontinuity points of distribution functions of .

  相似文献   

49.
Quantum Zeno and anti-Zeno paradoxes   总被引:1,自引:0,他引:1  
SM Roy 《Pramana》2001,56(2-3):169-178
Continuous observation of a time independent projection operator is known to prevent change of state (the quantum Zeno paradox). We discuss the recent result that generic continuous measurement of time dependent projection operators will in fact ensure change of state: an anti-Zeno paradox.  相似文献   
50.
Abstract

In the hydrosphere sulfates of the following origin may exist: (1) evaporitic; they come from the leaching of sulfate rocks, (2) biological, formed by sulfur-oxidizing bacteria and (3) anthropogenic, which get into water with wastes, fertilizers or acid rains. Chemical analyses may reveal sulfates in water, but their origin cannot be assessed by means of chemical analysis. The sulfates of various origin may differ in their isotopic compositions. However, sometimes we can observe the similarity of δ34S of sulfates whose origin was entirely different. This similarity may be so suggestive that it could be misleading.

This paper presents patterns of completely different sulfates whose δ34S are similar, though they have nothing in common. Other tables present patterns of sulfates whose origin is similar or even the same but their δ34S are characterized by great variety. All of the isotopic data presented in the tables were specially chosen from some of the results of the studies of the sulfates in waters in Poland.

Isotopes techniques are becoming more popular and are useful for studies in many fields. These patterns may be a warning against drawing hasty conclusions from the results of δ-measuring.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号