全文获取类型
收费全文 | 82篇 |
免费 | 0篇 |
国内免费 | 1篇 |
专业分类
化学 | 48篇 |
晶体学 | 1篇 |
力学 | 1篇 |
数学 | 18篇 |
物理学 | 15篇 |
出版年
2021年 | 2篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2016年 | 1篇 |
2013年 | 9篇 |
2012年 | 4篇 |
2011年 | 7篇 |
2010年 | 2篇 |
2009年 | 4篇 |
2008年 | 3篇 |
2007年 | 3篇 |
2006年 | 2篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2002年 | 5篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1994年 | 1篇 |
1986年 | 1篇 |
1984年 | 2篇 |
1982年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 3篇 |
1974年 | 2篇 |
排序方式: 共有83条查询结果,搜索用时 15 毫秒
21.
22.
Dana Ferraris Brandon Young Christopher Cox Travis Dudding William J Drury Lev Ryzhkov Andrew E Taggi Thomas Lectka 《Journal of the American Chemical Society》2002,124(1):67-77
Methodology for the practical synthesis of nonnatural amino acids has been developed through the catalytic, asymmetric alkylation of alpha-imino esters and N,O-acetals by enol silanes, ketene acetals, alkenes, and allylsilanes using chiral transition metal-phosphine complexes as catalysts (1-5 mol %). The alkylation products, which are prepared with high enantioselectivity (up to 99% ee) and diastereoselectivity (up to 25:1/anti:syn), are protected nonnatural amino acids that represent potential precursors to natural products and pharmaceuticals. A kinetic analysis of the catalyzed reaction of alkenes with alpha-imino esters is presented to shed light on the mechanism of this reaction. 相似文献
23.
The allylic lactone 1 was prepared from the reaction of lithium 3-lithiopropanoate (5) with isophorone (3) followed by mild acid treatment of the hydroxy acid adduct. 相似文献
24.
M Pattabiraman G Rangarajan Kwang-Yong Choi P Lemmens G Guentherodt G Balakrishnan DMcK Paul MR Lees 《Pramana》2002,58(5-6):1013-1017
We report polarized Raman scattering in single crystals of Nd0.7Sr0.3MnO3. The temperature dependence of the MnO6 octahedral bending and stretching modes observed in the XX spectra points to the existence of local lattice distortions,
possibly polarons. The XY spectra have been analyzed using a collision-dominated model, which allows the extraction of the
carrier scattering rate. 相似文献
25.
Hyemee Kim Maria Joselyn Castellon-Chicas Shirley Arbizu Stephen T. Talcott Nicholas L. Drury Shayna Smith Susanne U. Mertens-Talcott 《Molecules (Basel, Switzerland)》2021,26(9)
Mango is rich in polyphenols including gallotannins and gallic acid, among others. The bioavailability of mango polyphenols, especially polymeric gallotannins, is largely dependent on the intestinal microbiota, where the generation of absorbable metabolites depends on microbial enzymes. Mango polyphenols can favorably modulate bacteria associated with the production of bioactive gallotannin metabolites including Lactobacillus plantarum, resulting in intestinal health benefits. In several studies, the prebiotic effects of mango polyphenols and dietary fiber, their potential contribution to lower intestinal inflammation and promotion of intestinal integrity have been demonstrated. Additionally, polyphenols occurring in mango have some potential to interact with intestinal and less likely with hepatic enzymes or transporter systems. This review provides an overview of interactions of mango polyphenols with the intestinal microbiome, associated health benefits and underlying mechanisms. 相似文献
26.
27.
Owen B. Drury Miguel Velazquez Jonathan G. Dreyer Stephan Friedrich 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(3):913-917
We are developing superconducting ultrahigh resolution gamma-detectors for non-destructive analysis (NDA) of nuclear materials,
and specifically for spent fuel characterization in nuclear safeguards. The detectors offer an energy resolution below 100 eV
FWHM at 100 keV, and can therefore significantly increase the precision of NDA at low energies where line overlap affects
the errors of the measurement when using germanium detectors. They also increase the peak-to-background ratio and thus improve
the detection limits for weak gamma emissions from the fissile Pu and U isotopes at low energy in the presence of an intense
Compton background from the fission products in spent fuel. Here we demonstrate high energy resolution and high peak-to-background
ratio of our superconducting Gamma detectors, and discuss their relevance for measuring actinides in spent nuclear fuel. 相似文献
28.
The spectra of H2CS and D2CS were surveyed over the wavelength region from 230 to 180 nm and four distinct absorptions were identified. These are assigned to transitions from the ground state to the , , , and electronic states. A vibrational and rotational analysis of the second system was undertaken. The results indicate that the molecule is planar in the state and that while the CH and CS bond lengths remain near their ground-state values, the HCH angle increases substantially. 相似文献
29.
2,2-Disubstituted 3(2H)-furanones can be prepared readily by 1,2-addition of organometallic compounds to γ,γ-disubstituted β-bromo-α,β-butenolides followed by treatment of the adducts with acid. 相似文献
30.
Beulen MW Bugler J de Jong MR Lammerink B Huskens J Schonherr H Vancso GJ Boukamp BA Wieder H Offenhauser A Knoll W van Veggel FC Reinhoudt DN 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(7):1176-1183
We have developed synthesis routes for the introduction of short and long dialkylsulfides onto the primary side of alpha-, beta-, and gamma-cyclodextrins. Monolayers of these cyclodextrin adsorbates were characterized by electrochemistry, wettability studies, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and atomic force microscopy (AFM). The differences in thickness and polarity of the outerface of the monolayers were measured by electro-chemistry and wettability studies. On average about 70% of the sulfide moieties were used for binding to the gold, as measured by XPS. Tof-SIMS measurements showed that the cyclodextrin adsorbates adsorb without any bond breakage. AFM measurements revealed for beta-cyclodextrin monolayers a quasi-hexagonal lattice with a lattice constant of 20.6 A, which matches the geometrical size of the adsorbate. The alpha-cyclodextrin and gamma-cyclodextrin monolayers are less ordered. Interactions of the anionic guests 1-anilinonaphthalene-8-sulfonic acid (1,8-ANS) and 2-(p-toluidinyl)naphthalene-6-sulfonic acid (2,6-TNS) and the highly ordered monolayers of heptapodant beta-cyclodextrin adsorbates were studied by surface plasmon resonance (SPR) and electrochemical impedance spectroscopy. The SPR measurements clearly showed interactions between a beta-cyclodextrin monolayer and 1,8-ANS. Electrochemical impedance spectroscopy measurements gave high responses even at low guest concentrations (< or = 5 microM). The association constant for the binding of 1,8-ANS (K = 289,000 +/- 13,000M-1) is considerably higher than the corresponding value in solution. (Partial) methylation of the secondary side of the beta-cyclodextrin strongly decreases the binding. 相似文献