全文获取类型
收费全文 | 192篇 |
免费 | 4篇 |
专业分类
化学 | 111篇 |
晶体学 | 3篇 |
力学 | 3篇 |
数学 | 8篇 |
物理学 | 71篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2021年 | 2篇 |
2020年 | 6篇 |
2019年 | 1篇 |
2018年 | 4篇 |
2017年 | 1篇 |
2016年 | 8篇 |
2015年 | 4篇 |
2014年 | 6篇 |
2013年 | 6篇 |
2012年 | 9篇 |
2011年 | 20篇 |
2010年 | 7篇 |
2009年 | 7篇 |
2008年 | 11篇 |
2007年 | 14篇 |
2006年 | 10篇 |
2005年 | 5篇 |
2004年 | 10篇 |
2003年 | 11篇 |
2002年 | 5篇 |
2001年 | 2篇 |
2000年 | 5篇 |
1999年 | 7篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1988年 | 3篇 |
1986年 | 2篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 2篇 |
排序方式: 共有196条查询结果,搜索用时 32 毫秒
1.
Pu Duan Bo Zhi Luke Coburn Christy L. Haynes Klaus Schmidt-Rohr 《Magnetic resonance in chemistry : MRC》2020,58(11):1130-1138
The composition of fluorescent polymer nanoparticles, commonly referred to as carbon dots, synthesized by microwave-assisted reaction of citric acid and ethylenediamine was investigated by 13C, 13C{1H}, 1H─13C, 13C{14N}, and 15N solid-state nuclear magnetic resonance (NMR) experiments. 13C NMR with spectral editing provided no evidence for significant condensed aromatic or diamondoid carbon phases. 15N NMR showed that the nanoparticle matrix has been polymerized by amide and some imide formation. Five small, resolved 13C NMR peaks, including an unusual ═CH signal at 84 ppm (1H chemical shift of 5.8 ppm) and ═CN2 at 155 ppm, and two distinctive 15N NMR resonances near 80 and 160 ppm proved the presence of 5-oxo-1,2,3,5-tetrahydroimidazo[1,2-a]pyridine-7-carboxylic acid (IPCA) or its derivatives. This molecular fluorophore with conjugated double bonds, formed by a double cyclization reaction of citric acid and ethylenediamine as first shown by Y. Song, B. Yang, and coworkers in 2015, accounts for the fluorescence of the carbon dots. Cross-peaks in a 1H─13C HETCOR spectrum with brief 1H spin diffusion proved that IPCA is finely dispersed in the polyamide matrix. From quantitative 13C and 15N NMR spectra, a high concentration (18 ± 2 wt%) of IPCA in the carbon dots was determined. A pronounced gradient in 13C chemical-shift perturbations and peak widths, with the broadest lines near the COO group of IPCA, indicated at least partial transformation of the carboxylic acid of IPCA by amide or ester formation. 相似文献
2.
3.
4.
5.
Ulrike Troitzsch Andrew G. Christy David J. Ellis 《Journal of solid state chemistry》2007,180(10):2885-2895
We report a new zirconium titanate compound (Zr,Ti)O2 with 27.5-35 mol% titania (TiO2) formed from the oxides at 35-38 kbar, 1400-1500 °C. Crystal structure investigations at atmospheric conditions with powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed a monoclinic structure related to that of M-fergusonite (beta). Unit-cell dimensions (from 27.5 to 35 mol% TiO2): a=7.267(20)-7.340(2) Å, b=10.435(3)-10.429(1) Å, c=5.023(11)-5.040(1) Å, β=136.45(12)-137.55(1)°, V=262.44(92)-260.40(12) Å3, Z=4. Rietveld refinement (RF=1.55) of a sample with 32.8 mol% TiO2 indicates that site A is 8-fold coordinated, mostly occupied by Zr, while site B has 6-fold average coordination, occupied by Ti and Zr. Site B is at least partly ordered, as indicated by superstructure reflections 0 0 1 and −2 0 1 detected with TEM, reducing the space group from C2/c to C2. Pronounced streaking of selected diffraction spots is linked to the boundaries of lamellar domains in twin orientation, with twin planes either (200) or (20−2). Adjacent lamellae differ slightly in composition, causing subtle asymmetry of the twin diffraction patterns. 相似文献
6.
7.
8.
9.
Tvaskis V Christy ME Arrington J Asaturyan R Baker OK Blok HP Bosted P Boswell M Bruell A Cochran A Cole L Crowder J Dunne J Ent R Fenker HC Filippone BW Garrow K Gasparian A Gomez J Jackson HE Keppel CE Kinney E Lapikás L Liang Y Lorenzon W Lung A Mack DJ Martin JW McIlhany K Meekins D Milner RG Mitchell JH Mkrtchyan H Moreland B Nazaryan V Niculescu I Opper A Piercey RB Potterveld DH Rose B Sato Y Seo W Smith G Spurlock K van der Steenhoven G Stepanyan S Tadevosian V Uzzle A Vulcan WF Wood SA 《Physical review letters》2007,98(14):142301
We report on a study of the longitudinal to transverse cross section ratio, R=sigmaL/sigmaT, at low values of x and Q2, as determined from inclusive inelastic electron-hydrogen and electron-deuterium scattering data from Jefferson Laboratory Hall C spanning the four-momentum transfer range 0.06相似文献
10.
Tripathi S Armstrong DS Christy ME Clark JH Gorringe TP Hasinoff MD Kovash MA Wright DH Zołnierczuk PA 《Physical review letters》2002,89(25):252501
We report the first observation of double radiative capture on pionic hydrogen. The experiment was conducted at the TRIUMF cyclotron using the RMC spectrometer and detected gamma-ray coincidences following pi(-) stops in liquid hydrogen. We found the branching ratio for double radiative capture to be [3.05+/-0.27(stat)+/-0.31(syst)]x10(-5). The measured branching ratio and angle-energy distributions support the theoretical prediction of a dominant contribution from the pipi-->gammagamma annihilation mechanism. 相似文献