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   165篇
  免费   6篇
  国内免费   1篇
化学   102篇
晶体学   4篇
力学   5篇
数学   30篇
物理学   31篇
  2020年   3篇
  2019年   3篇
  2016年   5篇
  2014年   3篇
  2013年   26篇
  2012年   5篇
  2011年   6篇
  2010年   2篇
  2009年   2篇
  2008年   10篇
  2007年   4篇
  2006年   7篇
  2005年   7篇
  2004年   2篇
  2003年   9篇
  2002年   3篇
  1996年   1篇
  1995年   2篇
  1994年   1篇
  1992年   2篇
  1991年   1篇
  1989年   2篇
  1986年   2篇
  1985年   2篇
  1984年   4篇
  1983年   1篇
  1982年   8篇
  1981年   5篇
  1980年   3篇
  1979年   1篇
  1978年   3篇
  1977年   1篇
  1976年   3篇
  1975年   1篇
  1974年   2篇
  1972年   2篇
  1971年   1篇
  1970年   2篇
  1969年   2篇
  1968年   1篇
  1964年   1篇
  1963年   1篇
  1960年   1篇
  1959年   2篇
  1939年   1篇
  1936年   1篇
  1934年   2篇
  1933年   5篇
  1932年   1篇
  1929年   1篇
排序方式: 共有172条查询结果,搜索用时 15 毫秒
131.
Berry and Klein [J. Mod. Opt. 43, 2139-2164 (1997)] showed that the Talbot effects in classical optics are naturally expressed by Gauss sums in number theory. Their result was obtained by a computation of Helmholtz equation. In this article, we calculate the effects using Fresnel integral and show that the result is also represented by Gauss sums. However function forms of these two computational results are apparently different. We show that the reciprocity law of Gauss sums connects these results and both completely agree with. The Helmholtz equation can be regarded as an equation based upon wavy nature in optics whereas the Fresnel integral is defined by a sum over the paths based upon a particle picture in optics. Thus the agreement of these two computational results could be interpreted in terms of the concept of the wave-particle complementarity, though the concept is for quantum mechanical phenomenon. This interpretation leads us to a relation between the reciprocity of Gauss sums in number theory and the wave-particle complementarity in wave physics. We discuss it in detail.  相似文献   
132.
One-dimensional coordination polymers (1D-CPs) tend either to dissociate into constitutive ligands and metals readily in solution, or to aggregate randomly and amorphously, which prevents them from widespread application. In the present research, 1D-CPs comprising bridging dipyrrin ligands and divalent metal ions (Zn2+, Ni2+, and Cu2+) are synthesized. A liquid/liquid interfacial reaction gives rise to single crystals suitable for X-ray diffraction analysis: A dichloromethane solution of the ligand is layered with aqueous metal(ii) acetate, such that the coordination reaction proceeds at the liquid/liquid interface. Isolated single fibers of the zinc coordination polymer may be exfoliated from the single crystal or bulk solid upon ultrasonication. Atomic force microscopy (AFM) detects the isolated fibers with lengths of more than several μm. The exfoliated 1D-CP wires feature good processability, realizing a conjugate with single-wall carbon nanotubes (SWCNTs), and a thin film on a transparent SnO2 electrode. The processed materials show electric conversion ability: For example, the modified SnO2 electrode serves as a photoanode for a photoelectric conversion system. The designability and tunability of the present 1D-CPs is demonstrated by a ligand modification, affording a luminescent property and an extension of the photoelectric conversion response to longer wavelengths.  相似文献   
133.
When protein was irradiated by γ-rays from a 60Co source, a post-irradiation effect of protein reaction was caused. An empirical equation for the optical rotation was obtained, and the phenomena were explained on the basis of the molecular mechanism. The general equation for the optical rotation is given by [α] f= a ? b log t, where [α] f is the final specific rotation of the solution, t is time after γ irradiation, and a and b are adjustable constants.  相似文献   
134.
When protein in various liquids containing aromatic hydrocarbons, such as benzene, naphthalene, and phenanthrene, is irradiated by γ-rays from a 60Co source, the breaking of secondary bonding in the protein molecule varies with the irradiation liquids containing aromatic hydrocarbons. Protein irradiated by γ-rays from a 60Co source in air showed the effect of pH on the breaking of secondary bonding in the protein molecule. In both cases an empirical equation for the viscosity change was obtained, and the phenomena were explained on the basis of the molecular mechanism.  相似文献   
135.
136.
137.
138.
Four new compounds, rearranged noreremophilan-8,6-olide, rearranged dinoreremophilanone, epoxy γ-lactone, and 2α-hydroxyermophil-11-en-9-one, along with eremophilenolides related to ligularol and other known terpenoids, were isolated from Ligularia virgaurea (ligularol type) collected from the northern Sichuan Province of China. Three of the new compounds had degraded and unique structures. The absolute configuration of 2α-hydroxyermophil-11-en-9-one was determined on the basis of density functional theory calculation. The back octant rule cannot be applied to this compound because of the contribution of the hydroxy group to the front octant.  相似文献   
139.
Anisotropy of the susceptibility, which depends on vanadium concentration, was observed for (Ti1?xVx)2O3(x=0.005, 0.015, 0.02) single crystals. The anisotropy is hard to interpret by localized magnetic states of vanadium ions.  相似文献   
140.
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