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   110篇
  免费   5篇
  国内免费   1篇
化学   66篇
晶体学   1篇
力学   7篇
数学   20篇
物理学   22篇
  2023年   1篇
  2022年   1篇
  2021年   4篇
  2020年   3篇
  2019年   4篇
  2018年   5篇
  2017年   2篇
  2016年   6篇
  2015年   2篇
  2014年   4篇
  2013年   15篇
  2012年   5篇
  2011年   10篇
  2010年   9篇
  2009年   6篇
  2008年   8篇
  2007年   2篇
  2006年   5篇
  2005年   5篇
  2004年   3篇
  2003年   1篇
  2002年   1篇
  2000年   2篇
  1999年   3篇
  1998年   1篇
  1997年   2篇
  1993年   1篇
  1985年   2篇
  1984年   1篇
  1982年   1篇
  1981年   1篇
排序方式: 共有116条查询结果,搜索用时 31 毫秒
21.
The problem of determining a normal linear model with possible perturbations, viz. change-points and outliers, is formulated as a problem of testing multiple hypotheses, and a Bayes invariant optimal multi-decision procedure is provided for detecting at most k (k > 1) such perturbations. The asymptotic form of the procedure is a penalized log-likelihood procedure which does not depend on the loss function nor on the prior distribution of the shifts under fairly mild assumptions. The term which penalizes too large a number of changes (or outliers) arises mainly from realistic assumptions about their occurrence. It is different from the term which appears in Akaikes or Schwarz criteria, although it is of the same order as the latter. Some concrete numerical examples are analyzed.  相似文献   
22.
The platinacyclopentane derivative [Cl(CH2)3R2P](Cl)PtPR2CH2CH2CH2 is formed by action of Cl(CH2)3PR2 on Pt(COD)2 in n-hexane via the not isolable Pt[PR2(CH2)3Cl]2 (R  C6H11) by oxidative addition of a CCl bond to platinum. [μ-CIRh(CO)2]2 reacts in benzene with Cl(CH2)3PR2 under partially CO substitution to give the stable intermediate Cl(OC)Rh[PR2(CH2)3Cl]2. In boiling toluene oxidative addition of a CCl bond to rhodium occurs under formation of the phospharhodacyclopentane [CI(CH2)3R2P] Cl2(OC)-RhPR2CH2CH2CH2 (R  C6H5). The 31P{1H}-NMR spectra of the rhodium compound is characterized by an ABX system, that of the platinum by superposition of an ABX pattern with an AB spectrum.  相似文献   
23.
24.
The use of the mixture of aluminum chloride-N,N-dimethylformamide 1,2 (AlCl 3 -DMF, 11:1) reagent in the Friedl-Crafts C acylation reaction of 2(3H)-benzothiazolones was previously reported. 3 These acylations reactions were found to proceed with high regioselectivity. The precise position of acylation was uniquivocally assigned by x-ray single-crystal defraction in the case of 6-benzoyl-2(3H)-benzothiazolone. 4 The assignment of the position of acylation was extended to other compounds by the use of high-field 1 H-NMR . 3  相似文献   
25.
In this paper, we propose a perturbation method to determine an approximation and conditions of existence of quasi-periodic (QP) solutions and bursting dynamics in a quasi-periodically driven system. The QP forcing consists of two periodic excitations, one with a very slow frequency and the other with a frequency of the same order of the proper frequency of the oscillator. A first averaging is done over the fast dynamics, then the quasi-static solutions of the modulation equations of amplitude and phase are determined and their stability analyzed. We show that a necessary condition for the occurrence of periodic bursters is that the slow excitation is parametric.  相似文献   
26.
A simple self-referenced nondestructive method is proposed for measuring the cutoff wavelength of microstructured optical fibers (MOFs). It is based on the analysis of the time-dependent optical power transmitted through a bow-tie slit rotating in the far-field pattern of the fiber under test. As a first demonstration, the cutoff wavelength of a 2 m MOF sample is found to be close to that provided by numerical predictions (approximately 25 nm higher). Because of the high dynamics of the measurement, the uncertainty is limited to Dlambda= +/-10 nm.  相似文献   
27.
A new series of "bi-substrate" analogues have been synthesized as potential inhibitors of the glyceraldehyde-3-phosphate dehydrogenase and one lead compound has been identified that inhibits the enzyme from Trypanosoma cruzi with good affinity and very high (50-fold) specificity.  相似文献   
28.
A new helically chiral hexacyclic system, containing one pyridine unit, was prepared through a four-step synthesis involving palladium promoted Mizoroki-Heck couplings and classical oxidative photodehydrocyclisation.  相似文献   
29.
The use of polyphosphoric acid and the complex AlCl 3 -DMF in 6-acylation of 2(3H)-benzothiazolones previously have been reported. Instead of the frequently used AlCl 3 as a catalyst in the Friedl-Crafts reactions, we conducted the acylation of 2(3H)-benzothiazones using zinc chloride as a catalyst in DMF as solvent and acid chlorides or anhydrides as acylating agents.  相似文献   
30.
New thiacalix[4]arenes appended with three amide functions have been prepared. Their conformations have been solved thanks to 1H NMR 2D correlation spectroscopy (COSY) and nuclear overhauser and exchange spectroscopy (NOESY). The complexation ability of these ligands towards various metal ions (Cd2 + , Pb2 + , Pd2 + , Ni2 + , Hg2 + , Hg+, Ag+, Zn2 +  and Cu2 + ) has been investigated by the UV–vis absorption and the stoichiometry of the metal–ligand complexes was determined.  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