全文获取类型
收费全文 | 329篇 |
免费 | 3篇 |
国内免费 | 1篇 |
专业分类
化学 | 178篇 |
晶体学 | 7篇 |
力学 | 11篇 |
数学 | 54篇 |
物理学 | 83篇 |
出版年
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 8篇 |
2020年 | 6篇 |
2019年 | 7篇 |
2018年 | 3篇 |
2017年 | 7篇 |
2016年 | 9篇 |
2015年 | 9篇 |
2014年 | 7篇 |
2013年 | 19篇 |
2012年 | 40篇 |
2011年 | 25篇 |
2010年 | 23篇 |
2009年 | 27篇 |
2008年 | 18篇 |
2007年 | 12篇 |
2006年 | 17篇 |
2005年 | 6篇 |
2004年 | 13篇 |
2003年 | 6篇 |
2002年 | 10篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1962年 | 1篇 |
1960年 | 1篇 |
1933年 | 1篇 |
排序方式: 共有333条查询结果,搜索用时 15 毫秒
1.
The asymptotic null distribution of the likelihood ratio test for two cases of ordered hypotheses in a particular genetic model is considered. A simple iterative process is proposed in order to get the restricted estimates. It is shown that both tests have asymptotically a chi-bar squared distribution and the same size. A simulation study is also conducted in order to compare the usual unrestricted test with the corresponding one of ordered hypotheses. Finally, the results are extended to some special cases. 相似文献
2.
Gilberto Dini Angela Selvaggi Primicerio 《Rendiconti del Circolo Matematico di Palermo》1989,38(1):60-64
LetR be a Reinhardt domain andD a bounded simply connected strictly pseudoconvex domain withC ∞ boundary. We prove that any proper holomorphic mapF:R →D is, up to biholomorphism ofD, of the form \((z_1^{d_1 } , z_2^{d_2 } , \ldots , z_n^{d_n } )\) withd 1,d 2,…,d n ∈ IN. 相似文献
3.
Cesarino Balsamini Gilberto Spadoni Annalida Bedini Giorgio Tarzia Maurizio Lanfranchi Maria Angela Pellinghelli 《Journal of heterocyclic chemistry》1992,29(6):1593-1598
The alkyl N-(diphenylmethylene)-α,β-dehydroamino acids 1 have been submitted to 1,3-dipolar cycloadditions with nitrile oxides. The reactivity of these compounds depends on the type and on the stereochemistry of the β-substituents. With the unsubstituted terms 1a,b the reaction occurs on the C,C double bond, providing a good method for the synthesis of the 4,5-dihydroisoxazole derivatives 3a,b,c and for the gem-functionalized 4,5-dihydroisoxazoles amino carboxylic ester 5. The β-substituted compounds 1c,d,e , inert to 1,1-dimethylethylnitrile oxide, undergo the reaction to the N,C double bond, thus giving with 2a,b the 4,5-dihydro-1,2,4-oxadiazole derivatives 4. All the reactions occur with high site- and regioselectivity. 相似文献
4.
5.
Gilberto Schiavon Gianni Zotti Gino Bontempelli 《Journal of Electroanalytical Chemistry》1984,161(2):323-335
The electrochemical reduction of [Ni(PPh3)2(p-C6H4Br)Br] in acetonitrile results in a polymeric coating of a nickel-containing poly-p-phenylene, formulated as [-Ni(p-C6H4)n-] (n=6?7) on the basis of elemental analysis, IR, UV, MS and ESCA measurements. This coating is found to undergo a two-electron reversible reduction and a one-electron reversible oxidation with a large potential window (3.6 V), without the polymeric film being destroyed. Moreover, the polymer obtained is shown to be electroactive towards dissolved reactants via permeation or mediated electron transfer, depending on the molecular size of the electroactive species employed. 相似文献
6.
Gino Bontempelli Franco Magno Benedetto Corain Gilberto Schiavon 《Transition Metal Chemistry》1985,10(1):8-11
Summary The reduction of nickel perchlorate in the presence of carbon monoxide and substituted phosphines or diphosphines has been studied in acetonitrile by cyclic voltammetry. The results show that only mono- and bis-carbonylphosphinenickel(O) complexes are formed, while no evidence for the formation of carbonyl-nickel(I) and -nickel(II) species was obtained. Although the oxidation processes are not reversible, a good correlation between the anodic peak potentials relative to nickel(O) complexes and the -donor--acceptor abilities of the phosphines employed was observed. 相似文献
7.
Rosanna Toniolo Alan Valentino G. Bontempelli Gilberto Schiavon 《Fresenius' Journal of Analytical Chemistry》1998,360(2):260-262
A simple method for the analysis of nanoliter droplets is proposed, which is profitable when larger samples cannot be collected
as, for instance, in the case of several biological fluids and particularly in clinical chemistry. A glass capillary associated
to a micromanipulator is used to collect submicroliter volumes which are partially transferred into transparent polymeric
tubings with known internal diameters (120–178 μm), where the volumes sampled are measured by meniscus collimations with a
collimator microscope at suitable magnification. Both ends of these tubings are preliminarily equipped with ferrules and fittings,
so as to make them suitable for connection as the loop to a conventional high-pressure injection valve. The reliability of
this procedure has been tested for the analysis of Na+, K+ and Ca2+ present in minute synthetic standard samples (10–200 nL) by a conventional ion-chromatographic instrumentation. Relative
standard deviations in peak area measurements (5–6%) are discussed in terms of the whole approximation affecting volume measurements,
which depends on both the inconstancy of the inner diameter of the polymeric tubings employed and the uncertainty characterizing
meniscus collimations. The proposed procedure can be easily extended to the determination of any organic or inorganic species
present in very small samples, provided that their detection can be achieved by any chromatographic approach or, more generally,
by flow injection analysis.
Received: 16 June 1997 / Revised: 12 August 1997 / Accepted: 14 August 1997 相似文献
8.
Gino Bontempelli Nicola Comisso Rosanna Toniolo Gilberto Schiavon 《Electroanalysis》1997,9(6):433-443
Electroanalytical sensors, suitable for the analysis and monitoring of electroactive analytes present in gaseous phase or low-conductive liquid media, and based on electrodes in close contact with perfluorinated ion-exchange polymers are reviewed. The basic operative mechanism of these sensors, in which ion-exchange polymers act as solid polymer electrolytes (SPE's), is thoroughly discussed, while stressing the fundamental reasons why their behavior differs from that of conventional membrane electrodes. The procedures for preparing composite working electrodes by coating one side of ion-exchange membranes with stable porous films of conductive materials are described, along with the most common strategies followed to assemble this type of sensors. Useful examples of measurements in electrolyte-free media of inorganic and organic electroactive species of interest mainly for environmental analysis are given. Future prospects for the development of these sensors are also discussed. 相似文献
9.
Assessment of pharmacokinetic interaction between piracetam and l‐carnitine in healthy subjects 下载免费PDF全文
Gustavo D. Mendes Gabriela Traldi Zaffalon Antonio Sérgio Silveira Juliana Cama Ramacciato Rogério Heládio Lopes Motta Thiago Gagliano‐Jucá Anibal Gil Lopes José Cássio de Almeida Magalhães Gilberto De Nucci 《Biomedical chromatography : BMC》2016,30(4):536-542
A rapid, sensitive and specific method for quantifying piracetam in human plasma using Piracetam d‐8 as the internal standard (IS) is described. The analyte and the IS were extracted from plasma by one‐step precipitation of protein using an acetonitrile (100%). The extracts were analyzed by high‐performance liquid chromatography coupled with electrospray tandem mass spectrometry (HPLC‐MS/MS). The method had a chromatographic run time of 3.8 min and a linear calibration curve over the range 0.5–50 µg/mL (r > 0.99). This LC‐MS‐MS procedure was used to assess the bioavailability of two piracetam formulations: piracetam + l‐carnitine (Piracar®; 270/330 mg tablet) and piracetam (Nootropil®; 800 mg tablet) in healthy volunteers of both sexes. The geometric means with corresponding 90% confidence interval (CI) for test/reference percentage ratios were 88.49% (90% CI = 81.19 – 96.46) for peak concentration/dose and 102.55% (90% CI = 100.62 – 104.51) for AUCinf/dose. The limit of quantitation of 0.5 µg/mL is well suited for pharmacokinetic studies in healthy volunteers. It was concluded that piracetam (Piracar®; 270/330 mg tablet) has a bioavailability equivalent to the piracetam (Nootropil®; 800 mg tablet) formulation with regard to both the rate and the extent of absorption. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
10.
Maíra Fasciotti Gustavo B. Sanvido Vanessa G. Santos Priscila M. Lalli Michael McCullagh Gilberto F. de Sá Romeu J. Daroda Martin G. Peter Marcos N. Eberlin 《Journal of mass spectrometry : JMS》2012,47(12):1643-1647
The use of CO2 as a massive and polarizable drift gas is shown to greatly improve peak‐to‐peak resolution (Rp‐p), as compared with N2, for the separation of disaccharides in a Synapt G2 traveling wave ion mobility cell. Near or baseline Rp‐p was achieved for three pairs of sodiated molecules of disaccharide isomers, that is, cellobiose and sucrose (Rp‐p = 0.76), maltose and sucrose (Rp‐p = 1.04), and maltose and lactose (Rp‐p = 0.74). Ion mobility mass spectrometry using CO2 as the drift gas offers therefore an attractive alternative for fast and efficient separation of isomeric disaccharides. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献