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   127篇
  免费   1篇
化学   87篇
数学   1篇
物理学   40篇
  2022年   1篇
  2021年   1篇
  2018年   1篇
  2015年   1篇
  2014年   1篇
  2013年   3篇
  2012年   3篇
  2011年   4篇
  2010年   4篇
  2009年   1篇
  2008年   6篇
  2007年   5篇
  2006年   5篇
  2005年   7篇
  2004年   11篇
  2003年   4篇
  2002年   9篇
  2001年   4篇
  2000年   1篇
  1999年   1篇
  1998年   3篇
  1996年   5篇
  1994年   1篇
  1993年   2篇
  1992年   3篇
  1991年   2篇
  1990年   3篇
  1989年   4篇
  1988年   1篇
  1987年   1篇
  1986年   4篇
  1985年   3篇
  1984年   1篇
  1983年   1篇
  1982年   2篇
  1981年   1篇
  1979年   1篇
  1978年   1篇
  1976年   1篇
  1975年   1篇
  1974年   1篇
  1973年   2篇
  1971年   1篇
  1970年   2篇
  1969年   1篇
  1966年   2篇
  1956年   1篇
  1941年   1篇
  1932年   2篇
  1931年   1篇
排序方式: 共有128条查询结果,搜索用时 31 毫秒
121.
Level structure of102Cd has been studied via both102In decay and nuclear reactions. Using92Mo+14N at 86 MeV, the nucleus102In was identified and its decay (T 1/2=24 ±4s) studied with the aid of on-line mass separation techniques. Levels of102Cd were also populated with92Mo+12C at 50 MeV and102Pd+3He at 35 MeV reactions and investigated by means of standard in-beam techniques. A level scheme including states up to 4.5 MeV excitation energy is proposed and then discussed in the frame of available calculations.  相似文献   
122.
123.
124.
The topological analysis of chiral molecular models has provided the framework of a general system for the specification of their chirality. The application, made in and before 1956, of this system to organic-chemical configurations is generally retained, but is redefined with respect to certain types of structure, largely in the light of experience gained since 1956 in the Beilstein Institute and elsewhere. The system is now extended to deal, on the one hand, with organic-chemical conformations, and, on the other, with inorganic-chemical configurations to ligancy six. Matters arising in connexion with the transference of chiral specifications from model to name are considered, notably that of the symbiosis in nomenclature of expressions of the general system and of systems of confined scope. For corrigendum see DOI: 10.1002/anie.196605111  相似文献   
125.
Hole drift mobilities have been measured in β-9,10 dichloroanthracene by the transient photoconductivity method. Mobilities were found to be isotropic in the ac plane, 0.6 cm2/V sec, and 0.18 cm2/V sec normal to this plane, b1, at room temperature. At lower temperatures the mobilities were thermally activated, with an activation energy of ~0.25eV. The crystal structure of β-9,10 dichloroanthracene has been determined; it is triclinic. a = 8.582 A?, b = 16.825 A?, c = 3.869 A?, α = 97.90,? β = 97.90°, γ = 75.99°. The influence of the crystal structures of the α- and β- forms on the intermolecular electronic overlap and hence carrier mobilities are discussed.  相似文献   
126.
In methanol/water, dpph(?) bleaching (519 nm) by quercetin, QH(2), exhibits biphasic kinetics. The dpph(?) reacts completely with the quercetin anion within 100 ms. Subsequent slower bleaching involves solvent and QH(2) addition to quinoid products. The fast reaction is first-order in dpph(?) but only ca. 0.38 order in [QH(2)]. This extraordinary nonintegral order is attributed to reversible formation of π-stacked {QH(-)/dpph(?)} complexes in which electron transfer to products, {QH(?)/dpph(-)}, is slow (k(ET) ≈ 10(5) s(-1)).  相似文献   
127.
The m-methoxy group is normally electron-withdrawing (EW), sigma(m) = +0.12, sigma(m+) = +0.05. The strong EW activity of a phenoxyl radical's O* atom causes the m-methoxy group to become electron-donating (ED), sigma(m)(+) = -0.14. In valence bond terms, this can be ascribed to the nonclassical resonance structures 1c-e. Although it has long been known that m-methoxy is ED in photoexcited states, it has now been found to be ED for homolytic O-H bond breaking in ground-state 3-methoxyphenol.  相似文献   
128.
Grossi and Strazzari have reported (J. Org. Chem. 2000, 65, 2748-2754) that the ceric ammonium nitrate modulated photooxidation of triphenylmethanol and 1,1-diphenylethanol yielded ESR spectra of the putative spiro-cyclohexadienyl intermediates in the O-neophyl rearrangements of the corresponding alkoxyl radicals, Ph2(R)CO* (R = Ph, CH3), to the phenoxymethyl radicals, Ph(R)C*OPh. Both ESR spectra are reassigned to the phenoxyl radical, C6H5O*, and the probable mechanism by which phenoxyl is formed in these systems is presented.  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