全文获取类型
收费全文 | 374篇 |
免费 | 11篇 |
国内免费 | 1篇 |
专业分类
化学 | 266篇 |
晶体学 | 1篇 |
力学 | 3篇 |
数学 | 39篇 |
物理学 | 77篇 |
出版年
2023年 | 3篇 |
2022年 | 5篇 |
2021年 | 3篇 |
2020年 | 6篇 |
2019年 | 9篇 |
2018年 | 4篇 |
2017年 | 6篇 |
2016年 | 13篇 |
2015年 | 11篇 |
2014年 | 15篇 |
2013年 | 22篇 |
2012年 | 33篇 |
2011年 | 21篇 |
2010年 | 6篇 |
2009年 | 14篇 |
2008年 | 20篇 |
2007年 | 27篇 |
2006年 | 14篇 |
2005年 | 20篇 |
2004年 | 14篇 |
2003年 | 13篇 |
2002年 | 13篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 8篇 |
1998年 | 2篇 |
1997年 | 9篇 |
1996年 | 3篇 |
1995年 | 8篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1977年 | 6篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1933年 | 1篇 |
1910年 | 1篇 |
排序方式: 共有386条查询结果,搜索用时 15 毫秒
101.
102.
(146)Sm (T(1/2) = 10(8) y) is a long-lived radionuclide which has been produced in significant amounts during burning in a supernova (SN). Detection of this SN produced long-lived radionuclide on Earth may be helpful for getting information on nuclear synthesis at the time of our solar system's formation. Only accelerator mass spectrometry (AMS) can determine such minute traces of (146)Sm still expected in the Earth's crust. However, the villain of (146)Sm measurement through AMS is its naturally occurring stable isobar (146)Nd which is a million times more abundant than the trace amount of (146)Sm. Therefore an efficient method for the separation of samarium and neodymium is required to measure (146)Sm through AMS. A simple liquid-liquid extraction (LLX) based method for separation of samarium and neodymium has been developed using radiometric simulation. Di-(2-ethylhexyl)phosphoric acid (HDEHP) has been used as the organic reagent. A very high separation factor ( approximately 10(6)) can be achieved when a solution containing samarium and neodymium is reduced by hydroxylamine hydrochloride followed by extraction with 0.1% HDEHP diluted in cyclohexane from 0.025 M HCl solution. 相似文献
103.
Positivity - A commutative ring with unity is of a c-type if it is (ring) isomorphic with C(X) for some space X. In this paper, we have described a structural representation of c-type subrings of... 相似文献
104.
D. Nayak S. Lahiri A. Mukhopadhyay R. Pal 《Journal of Radioanalytical and Nuclear Chemistry》2003,256(3):535-539
The bio-sorption of heavy and toxic radionuclides by three genera of algae from different taxonomic groups was studied employing the recently developed 'Tracer Packet' technique. The tracer packet of heavy and toxic metals' contained 197Hg, 198,199,200,201Tl, 199,200,201Pb, 204Bi and 204,205Po radionuclides in carrier-free state and was produced by irradiating a gold metal foil with medium energy 7Li and 12C beams successively in a 12 MV Pelletron. Three genera, Spirulina from Cyanophyceae, Oedogonium from Chlorophyceae and Catenella from Rhodophyceae were cultured in laboratory condition and were used in the experiment. The radionuclide accumulation varied according to different genera at different pH levels. At basic pH Spirulina showed a maximum radionuclide accumulation in comparison to other genera. 相似文献
105.
Oscillatory mode coupling between two coherent laser beams is produced when an interference pattern moves against a quasi-static electrically strobed grating in a photorefractive AlGaAs/GaAs multiple-quantum-well diode operated in the quantum-confined Stark geometry. The oscillation frequency is equal to the frequency difference between the two laser beams and provides a method to measure high-frequency Doppler shifts or large surface displacements for laser-based ultrasound. Combined photorefractive gains (normally forbidden by symmetry in the Stark geometry) and absorptive gains approach 1200cm(-1)during two-wave mixing using moving gratings. 相似文献
106.
107.
108.
Ghumaan S Sarkar B Patra S van Slageren J Fiedler J Kaim W Lahiri GK 《Inorganic chemistry》2005,44(9):3210-3214
109.
Kar S Sarkar B Ghumaan S Roy D Urbanos FA Fiedler J Sunoj RB Jimenez-Aparicio R Kaim W Lahiri GK 《Inorganic chemistry》2005,44(24):8715-8722
The bis-bidentate bridging function of gbha2- with N,O-/N,O- coordination was observed for the first time in the complex (mu-gbha)[Ru(III)(acac)2]2 (1). Density functional theory calculations of 1 yield a triplet ground state with a large (deltaE > 6000 cm(-1)) singlet-triplet gap. Intermolecular antiferromagnetic coupling was observed (J approximately -5.3 cm(-1)) for the solid. Complex 1 undergoes two one-electron reduction and two one-electron oxidation steps; the five redox forms [(mu-gbha)[Ru(acac)2]2]n (n = -2, -1, 0, +1, +2) were characterized by UV-vis-NIR spectroelectrochemistry (NIR = near infrared). The paramagnetic intermediates were also investigated by electron paramagnetic resonance (EPR) spectroscopy. The monoanion with a comproportionation constant K(c) of 2.7 x 10(8) does not exhibit an NIR band for a Ru(III)/Ru(II) mixed-valent situation; it is best described as a 1,4-diazabutadiene radical anion containing ligand gbha*3-, which binds two ruthenium(III) centers. A Ru(III)-type EPR spectrum with g1 = 2.27, g2 = 2.21, and g3 = 1.73 is observed as a result of antiferromagnetic coupling between one Ru(III) and the ligand radical. The EPR-active monocation (K(c) = 1.7 x 10(6)) exhibits a broad (deltanu(1/2) = 2600 cm(-1)) intervalence charge-transfer band at 1800 nm, indicating a valence-averaged (Ru3.5)2 formulation (class III) with a tendency toward class II (borderline situation). 相似文献
110.
Summary A rapid volumetric method has been worked out for the indirect determination of 0.25–2.5 mg of gold in presence of many common ions. It is based on the reduction of gold(III) to metal with excess of cobalt(II) in the presence of 1,10-phenanthroline at pH 3 and 50°, and estimation of the unreacted cobalt(II) in the filtrate by visual, potentiometric or biamperometric titration with standardized cerium(IV) sulphate solution. It has been found that there is no interference from Ni(II), Pb(II), Zn(II), Cd(II), Mn(II), Mg(II), Ca(II), Al(III), Cr(III), Ti(IV), V(V) and W(VI). Interference due to Pd(II) and Ag(I) can be eliminated. Fe(III), Cu(II), Mo(VI), Hg(II) and Pt(IV) interfere, even present in small amounts.
Zusammenfassung Ein schnelles maßanalytisches Verfahren zur indirekten Bestimmung von 0,25–2,5 mg Gold in Gegenwart vieler Ionen wurde ausgearbeitet. Es beruht auf der Reduktion zu metallischem Gold mit überschüssigem Kobalt(II) in Anwesenheit von 1,10-Phenanthrolin bei pH 3 und 50°. Die Rückbestimmung des unverbrauchten Kobalts im Filtrat erfolgt durch potentiometrische oder biamperometrische Titration mit Cer(IV)sulfat. Ni(II), Pb(II), Zn(II), Cd(II), Mn(II), Mg(II), Ca(II), Al(II), Cr(III), Ti(IV), V(V) und W(VI) stören nicht. Eine Störung durch Pd(II) oder Ag(I) kann man ausschalten. Fe(III), Cu(II), Mo(VI), Hg(II) und Pt(IV) stören auch in geringen Mengen.相似文献