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   255篇
  免费   13篇
  国内免费   3篇
化学   201篇
力学   5篇
数学   27篇
物理学   38篇
  2023年   1篇
  2022年   12篇
  2021年   14篇
  2020年   15篇
  2019年   14篇
  2018年   9篇
  2017年   10篇
  2016年   12篇
  2015年   7篇
  2014年   15篇
  2013年   20篇
  2012年   12篇
  2011年   14篇
  2010年   6篇
  2009年   14篇
  2008年   12篇
  2007年   11篇
  2006年   6篇
  2005年   14篇
  2004年   11篇
  2003年   9篇
  2002年   7篇
  2001年   2篇
  2000年   2篇
  1999年   1篇
  1998年   5篇
  1997年   2篇
  1996年   2篇
  1995年   1篇
  1991年   1篇
  1982年   2篇
  1981年   1篇
  1978年   1篇
  1974年   1篇
  1973年   1篇
  1968年   1篇
  1966年   1篇
  1916年   2篇
排序方式: 共有271条查询结果,搜索用时 0 毫秒
101.
The well known Kochen-Specker’s theorem (Kochen and Specker J. Math. Mech. 17:59–87, 1967) is devoted to the problem of hidden variables in quantum mechanics. In the paper we present a geometric proof for an indefinite analogy of Kochen-Specker’s theorem. On the real three-dimensional Krein space there exists unique two-valued probability measure.  相似文献   
102.
Matvejchuk  Marjan 《Positivity》2019,23(1):101-109
Positivity - In the paper we study probability measure on real-orthogonal projections acting on complex Euclidean space. We proof an analog of Gleason’s theorem. We study Hermitian measure...  相似文献   
103.
Journal of Thermal Analysis and Calorimetry - A thermodynamic model was developed to assess the energetic performance of a dual receiver concentrated photovoltaic/thermal plant for the...  相似文献   
104.
105.
The generation of 3-indolylacyl radicals from the corresponding phenyl selenoesters and the scope of their participation in intermolecular addition reactions to carbon-carbon double bonds under both reductive and nonreductive conditions have been studied.  相似文献   
106.
A new asymmetric diamine containing diarylimodazole pendant was synthesized from the nucleophilic substitution reaction of 1-fluoro-4-nitrobenzene and 2,4-dihydroxy benzaldehyde in the presence of K2CO3, followed by reaction with benzil and ammonium acetate for the preparation of imidazole ring. This novel diamine was used to prepare poly(amide-ether) (PAE) in reaction with different commercially available dicarboxylic acids via direct polycondensation using triphenyl phosphite and pyridine (Py) as catalyst. The PAEs were fully characterized and their properties such as inherent viscosity, solubility, optical, thermal and kinetics of thermal decomposition, and electrochemical oxidation were investigated. The polymers had inherent viscosity in the range of 0.47–0.65 dL/g and were noncrystalline with excellent solubility in various polar aprotic organic solvents. Their Tg values ranged from 200 to 355°C and 10% weight loss temperature above 450°C in nitrogen and left more than 70% residue at 650°C. The kinetic parameters of thermal degradation such as activation energy, entropy, enthalpy and Gibbs free energy of thermal decomposition have been evaluated using different equations. We also report electrochemical oxidation of the resulting polymers in aqueous solution by using cyclic voltammetry technique on the multi-walled carbon nanotube-modified glassy carbon electrode.  相似文献   
107.
Derivatives of indan-1-one and 3,4-dihydronaphthalen-1(2H)-one bearing hydroxy or methoxy substituent on the aromatic ring were efficiently iodinated regioselectively at the α carbonyl position using elemental iodine activated by 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (Selectfluor™ F-TEDA-BF4) in methanol.  相似文献   
108.
Correct and rapid identification of microorganisms is the key to the success of many important applications in health and safety, including, but not limited to, infection treatment, food safety, and biodefense. With the advance of mass spectrometry (MS) technology, the speed of identification can be greatly improved. However, the increasing number of microbes sequenced is challenging correct microbial identification because of the large number of choices present. To properly disentangle candidate microbes, one needs to go beyond apparent morphology or simple ‘fingerprinting’; to correctly prioritize the candidate microbes, one needs to have accurate statistical significance in microbial identification. We meet these challenges by using peptidome profiles of microbes to better separate them and by designing an analysis method that yields accurate statistical significance. Here, we present an analysis pipeline that uses tandem MS (MS/MS) spectra for microbial identification or classification. We have demonstrated, using MS/MS data of 81 samples, each composed of a single known microorganism, that the proposed pipeline can correctly identify microorganisms at least at the genus and species levels. We have also shown that the proposed pipeline computes accurate statistical significances, i.e., E-values for identified peptides and unified E-values for identified microorganisms. The proposed analysis pipeline has been implemented in MiCId, a freely available software for Microorganism Classification and Identification. MiCId is available for download at http://www.ncbi.nlm.nih.gov/CBBresearch/Yu/downloads.html.
Graphical Abstract ?
  相似文献   
109.
The electrophilic enantioselective sulfenylation of 1,3-dicarbonyl compounds with phenylsulfenyl chloride is effectively catalyzed by [Ti(TADDOLato)] complexes. The corresponding products are obtained in moderate to high yields. The highest ee values (up to 97 %) are obtained in toluene at room temperature and with a typical catalyst loading of 5 mol %. Bulky ester groups and sterically undemanding substituents at the alpha-position were found to be crucial structural features of the starting materials in order to assure high enantioselectivity. The absolute configuration of one of the chiral products has been determined. The stereochemical course of the reaction is similar to that of analogous [Ti(TADDOLato)]-catalyzed atom-transfer reactions. A common side-reaction the sulfenylated products undergo is a deacylation leading to racemic alpha-sulfenylated esters.  相似文献   
110.
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