全文获取类型
收费全文 | 85篇 |
免费 | 2篇 |
专业分类
化学 | 67篇 |
力学 | 1篇 |
数学 | 1篇 |
物理学 | 18篇 |
出版年
2022年 | 3篇 |
2021年 | 1篇 |
2019年 | 1篇 |
2016年 | 1篇 |
2015年 | 4篇 |
2014年 | 1篇 |
2013年 | 4篇 |
2012年 | 1篇 |
2011年 | 2篇 |
2009年 | 2篇 |
2008年 | 9篇 |
2007年 | 5篇 |
2006年 | 1篇 |
2005年 | 11篇 |
2004年 | 5篇 |
2003年 | 7篇 |
2002年 | 4篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1979年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有87条查询结果,搜索用时 990 毫秒
51.
Ahmed SN Anthony AE Beier EW Bellerive A Biller SD Boger J Boulay MG Bowler MG Bowles TJ Brice SJ Bullard TV Chan YD Chen M Chen X Cleveland BT Cox GA Dai X Dalnoki-Veress F Doe PJ Dosanjh RS Doucas G Dragowsky MR Duba CA Duncan FA Dunford M Dunmore JA Earle ED Elliott SR Evans HC Ewan GT Farine J Fergani H Fleurot F Formaggio JA Fowler MM Frame K Frati W Fulsom BG Gagnon N Graham K Grant DR Hahn RL Hall JC Hallin AL Hallman ED Hamer AS Handler WB Hargrove CK Harvey PJ Hazama R Heeger KM 《Physical review letters》2004,92(10):102004
Data from the Sudbury Neutrino Observatory have been used to constrain the lifetime for nucleon decay to "invisible" modes, such as n-->3nu. The analysis was based on a search for gamma rays from the deexcitation of the residual nucleus that would result from the disappearance of either a proton or neutron from 16O. A limit of tau(inv)>2 x 10(29) yr is obtained at 90% confidence for either neutron- or proton-decay modes. This is about an order of magnitude more stringent than previous constraints on invisible proton-decay modes and 400 times more stringent than similar neutron modes. 相似文献
52.
Dr. Kunihiro Matsumura Dr. Keisuke Nishikawa Hiroaki Yoshida Toshiki Niwa Yuichiro Fushii Dr. Matsumi Doe Prof. Dr. Yoshiki Morimoto 《化学:亚洲杂志》2021,16(14):1882-1886
Histrionicotoxin (HTX) alkaloids isolated from the poison arrow frogs possess a unique structure characterized by a 1-azaspiro[5.5]undecane skeleton common to the HTX family. The unique molecular architecture of HTXs and the interest as potential target drugs have prompted synthetic chemists to promote the total synthesis so far. However, all of the synthetic strategies to access the 1-azaspiro[5.5]undecane framework of HTXs take a multistep approach from linear starting materials due to stepwise construction of either six-membered carbo- or azacycle. Herein, we report the direct one-step construction of the 1-azaspiro[5.5]undecane skeleton from linear amino ynone substrates bearing an N-methoxycarbonyl group utilizing our mercuric triflate (Hg(OTf)2)-catalyzed cycloisomerization reaction. The utility of this novel methodology was demonstrated by the total and formal syntheses of HTX-235A and HTX-283A, respectively, from the azaspirocycle. 相似文献
53.
Takahashi K Iwasaki E Matsumi Y Wallington TJ 《The journal of physical chemistry. A》2007,111(7):1271-1276
The gas-phase reactions of Cl atoms with acetone, butanone, 2-pentanone, 3-pentanone, 2-hexanone, 3-hexanone, and cyclopentanone at 295 +/- 2 K were studied using pulsed laser photolysis vacuum UV laser-induced fluorescence (PLP-LIF) techniques. Cl(2P(3/2)) atoms were produced by photolysis of Cl2 at 351 nm and monitored by LIF spectroscopy at 134.72 nm (3p(5) 2P(3/2)-3p(4)4s 2P(3/2) transition). Rate coefficients for reactions of Cl atoms with acetone, butanone, 2-pentanone, 3-pentanone, 2-hexanone, 3-hexanone, and cyclopentanone are (2.30 +/- 0.12) x 10(-12), (4.08 +/- 0.21) x 10(-11), (1.23 +/- 0.13) x 10(-10), (8.87 +/- 0.92) x 10(-11), (2.08 +/- 0.32) x 10(-10), (1.43 +/- 0.19) x 10(-10) and (1.16 +/- 0.12) x 10(-10) cm3 molecule(-1) s(-1), respectively. The results for acetone and butanone are consistent with previous studies. The results for 2-pentanone, 3-pentanone, 2-hexanone, and 3-hexanone are approximately a factor of 2-3 higher than those from previous absolute rate studies. Likely explanations for these discrepancies are discussed. Tropospheric lifetimes of ketones with respect to reaction with Cl atoms are estimated and discussed. 相似文献
54.
Cynthia Amaning Danquah Prince Amankwah Baffour Minkah Theresa A. Agana Phanankosi Moyo Michael Ofori Peace Doe Sibusiso Rali Isaiah Osei Duah Junior Kofi Bonsu Amankwah Samuel Owusu Somuah Isaac Newton Nugbemado Vinesh J. Maharaj Sanjib Bhakta Simon Gibbons 《Molecules (Basel, Switzerland)》2022,27(14)
Amaryllidaceae is a significant source of bioactive phytochemicals with a strong propensity to develop new drugs. The genera Allium, Tulbaghia, Cyrtanthus and Crinum biosynthesize novel alkaloids and other phytochemicals with traditional and pharmacological uses. Amaryllidaceae biomolecules exhibit multiple pharmacological activities such as antioxidant, antimicrobial, and immunomodulatory effects. Traditionally, natural products from Amaryllidaceae are utilized to treat non-communicable and infectious human diseases. Galanthamine, a drug from this family, is clinically relevant in treating the neurocognitive disorder, Alzheimer’s disease, which underscores the importance of the Amaryllidaceae alkaloids. Although Amaryllidaceae provide a plethora of biologically active compounds, there is tardiness in their development into clinically pliable medicines. Other genera, including Cyrtanthus and Tulbaghia, have received little attention as potential sources of promising drug candidates. Given the reciprocal relationship of the increasing burden of human diseases and limited availability of medicinal therapies, more rapid drug discovery and development are desirable. To expedite clinically relevant drug development, we present here evidence on bioactive compounds from the genera Allium, Tulgbaghia, Cyrtanthus and Crinum and describe their traditional and pharmacological applications. 相似文献
55.
Ogoshi T Ueshima N Yamagishi TA Toyota Y Matsumi N 《Chemical communications (Cambridge, England)》2012,48(29):3536-3538
A room-temperature ionic liquid containing macrocyclic compound pillar[5]arene in its core was synthesized. The ionic liquid showed high thermal stability, moderate ionic conductivity and solvent-free complexation ability with the guest tetracyanoethylene. 相似文献
56.
Back Cover: Discovery of a Single Monooxygenase that Catalyzes Carbamate Formation and Ring Contraction in the Biosynthesis of the Legonmycins (Angew. Chem. Int. Ed. 43/2015) 下载免费PDF全文
57.
58.
Pankaj Sehgal Reinhard Wimmer Jesper E. Mogensen Hidekazu Doe 《Journal of Dispersion Science and Technology》2013,34(8):1262-1271
Interfacial tension (γ), conductivity (κ), nuclear magnetic resonance (NMR), and fluorescence measurements have been carried out to study the mixed interfacial and micellar behavior of cationic surfactants cetyltributylphosphonium bromide (CTBB) and the cetyltrimethylammonium bromide (CTAB). From the γ versus log C s plots, the values of critical micellar concentration (cmc) and various interfacial parameters were computed. From κ measurements, the equivalent conductivities of the monomers (Λ mon), the micelles (Λ mic) states and the degree of counterion dissociation (δ) have been evaluated. The cmc values have been analyzed in the context of the pseudophase separation model and regular solution theory. The interaction parameters, βm and βσ, in the mixed micelle as well as in the mixed monolayer, respectively, also have been computed. The self‐diffusion coefficients for the micelles have been evaluated by using NMR spectroscopy. From the fluorescence quenching method, the mean micellar aggregation number (N agg) of the pure and mixed micelles has been obtained from the slope of the ratio of fluorescence intensities in the absence and in the presence of quencher (ln (I 1,0/I 1) versus [Q] plots. It was found that the incorporation of CTBB into the mixed micelle decreases the N agg. The microviscosity of the fluorescence probe Rhodamine (RB) was monitored by using fluorescence polarization measurements. The values of fluorescence anisotropies (r) indicate that the penetration of CTBB monomer into CTAB micelles produced less rigid mixed micelles. 相似文献
59.
Daisuke Takano Yuki Fukunaga Matsumi Doe Kazuo Yoshihara Takamasa Kinoshita 《Journal of heterocyclic chemistry》1997,34(4):1111-1114
The title compound was efficiently synthesized from 3-furoic acid and 3-bromoanisole via the Birch reduction. 相似文献
60.
Wataru Shibayama Asako Narita Noriyoshi Matsumi Hiroyuki Ohno 《Journal of organometallic chemistry》2009,694(11):1642-1870
A series of triple ionic compounds consisting of double armed anions and one cation were prepared as lithium cation conductive matrices. As anions, lithium borates derived from lithium-9-borabicyclo[3,3,1]nonane hydride were introduced. The sterically hindered borate anion structures prevented the crystallization of triple ionic compounds. Introduction of ethylene oxide chains attached to the borate anions led to lower glass transition temperature, and also improved ionic conductivity. A lithium transference number of 0.73 was observed in spite of the presence of ethylene oxide chains. 相似文献