全文获取类型
收费全文 | 228篇 |
免费 | 3篇 |
专业分类
化学 | 158篇 |
晶体学 | 12篇 |
数学 | 32篇 |
物理学 | 29篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 5篇 |
2019年 | 5篇 |
2018年 | 1篇 |
2017年 | 4篇 |
2016年 | 5篇 |
2015年 | 1篇 |
2014年 | 11篇 |
2013年 | 8篇 |
2012年 | 15篇 |
2011年 | 10篇 |
2010年 | 15篇 |
2009年 | 9篇 |
2008年 | 15篇 |
2007年 | 6篇 |
2006年 | 10篇 |
2005年 | 16篇 |
2004年 | 7篇 |
2003年 | 5篇 |
2002年 | 8篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 4篇 |
1997年 | 7篇 |
1996年 | 6篇 |
1995年 | 8篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1977年 | 2篇 |
排序方式: 共有231条查询结果,搜索用时 31 毫秒
1.
Agustín Tashdjian María Guadalupe Sánchez Loredo Graciela Alicia González 《Electroanalysis》2013,25(9):2124-2129
Waste of electrical and electronic equipment is an interesting secondary resource of base and precious metals. Particularly the use of thiourea‐leaching in acidic medium was proposed for noble metals recovery. In this work, a novel and easy‐to‐use electrochemical sensor was developed, aimed to test thiourea from leaching solutions containing significant thiourea and copper amounts. The sensor was constructed using silver nanoparticles (AgNPs) deposited on screen‐printed electrodes. Its performance was studied in a synthetic leaching solution; changes in the overall surface charge of AgNPs resulting in changes in the charge‐transfer resistance for the copper ions were evaluated by electrochemical impedance spectroscopy. 相似文献
2.
Determination of mazindol in human oral fluid by high performance liquid chromatography–electrospray ionization mass spectrometry 下载免费PDF全文
Marcella Herbstrith de Oliveira Graciela Carlos Ana Maria Bergold Flavio Pechansky Renata Pereira Limberger Pedro Eduardo Fröehlich 《Biomedical chromatography : BMC》2014,28(8):1064-1069
Brazil is one of the countries most affected by abuse of stimulant medications by professional drivers, especially fenproporex, amfepramone and mazindol. Even though their sale is banned, they can be found in illegal markets, such as those located on the country's borders. The use of oral fluid to monitor drug levels has many advantages over plasma and urine because it is noninvasive, easier to collect and more difficult to adulterate. The aim of this study was to develop and validate a sensitive and specific method to quantify mazindol in human oral fluid by liquid chromatography–mass spectrometry (LC‐MS). The LC system consisted of an LC‐MS system operated in selected ion monitoring mode. The mobile phase was composed of water at pH 4.0, acetonitrile and methanol (60:15:25 v/v/v) at a flow rate of 1.0 mL/min and propranolol was used as internal standard. Total running time was 10 min. The lower limit of quantification was 0.2 ng/mL and the method exhibited good linearity within the 0.2–20 ng/mL range (r = 0.9987). A rapid, specific, sensitive, linear, precise and accurate method was developed for determination of mazindol in human oral fluid according to European Medicines Agency guidelines, and is suitable for monitoring mazindol levels in oral fluid of professional drivers. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
3.
4.
Human Y‐chromosome SNP characterization by multiplex amplified product‐length polymorphism analysis 下载免费PDF全文
Laura Smeldy Jurado Medina Marina Muzzio Marisol Schwab María Leticia Bravi Costantino Guillermo Barreto Graciela Bailliet 《Electrophoresis》2014,35(17):2524-2527
We designed an allele‐specific amplification protocol to optimize Y‐chromosome SNP typing, which is an unavoidable step for defining the phylogenetic status of paternal lineages. It allows the simultaneous highly specific definition of up to six mutations in a single reaction by amplification fragment length polymorphism (AFLP) without the need of specialized equipment, at a considerably lower cost than that based on single‐base primer extension (SNaPshot?) technology or PCR‐RFLP systems, requiring as little as 0.5 ng DNA and compatible with the small fragments characteristic of low‐quality DNA. By designation of two primers recognizing the derived and ancestral state for each SNP, which can be differentiated by size by the addition of a noncomplementary nucleotide tail, we could define major Y clades E, F, K, R, Q, and subhaplogroups R1, R1a, R1b, R1b1b, R1b1c, J1, J2, G1, G2, I1, Q1a3, and Q1a3a1 through amplification fragments that ranged between 60 and 158bp. 相似文献
5.
Graciela Silvia Birman 《Journal of Geometry》2001,72(1-2):11-17
In the Lorentzian plane, the support function of a closed convex curve is not a periodic one. We redefine this concept and
the envelope of a families of lines. Using these, we prove integral formulas in the Crofton's style for convex sets in the
Lorentzian plane.
Received 10 February 2000. 相似文献
6.
Gabriela R. Argiroffo Silvia M. Bianchi Graciela L. Nasini 《Mathematical Methods of Operations Research》2008,67(2):245-256
Lehman (Polyhedral combinatorics 1 of DIMACS series in discrete math. and theoretical computer science, pp 101–105, 1990) described some conditions regular
minimally nonideal (mni) matrices must satisfy. Although, there are few results on sufficient conditions for mni matrices.
In most of these results, the covering polyhedron must have a unique fractional extreme point. This condition corresponds
to ask the matrix to be the blocker of a near-ideal matrix, defined by the authors in a previous work (2006). In this paper
we prove that, having the blocker of a near-ideal matrix, only a few very easy conditions have to be checked in order to decide
if the matrix is regular mni. In doing so, we define the class of quasi mni matrices, containing regular mni matrices, and
we find a generalization on the number of integer extreme points adjacent to the fractional extreme point in the covering
polyhedron. We also give a relationship between the covering and stability number of regular mni matrices which allows to
prove when a regular mni matrix can be a proper minor of a quasi mni.
Partially supported by CONICET Grant PIP 2807/2000 (Argentina) and by CNPq/PROSUL Grant 490333/2004-4 (Brasil). 相似文献
7.
Graciela Martínez‐Paredes María Begoña González‐García Agustín Costa‐García 《Electroanalysis》2009,21(8):925-930
Gold nanostructured screen‐printed carbon electrodes are demonstrated to be suitable transducers for the determination of lead using square‐wave voltammetry. Reproducible gold nanostructures have been obtained by direct electrochemical deposition. A calibration plot from 2.5 to 250 μg/L was obtained in acidic solutions of Pb(II) with a reproducibility of 4% (n=10). The detection limit was 0.09 μg/L of lead. The method is then applied to perform a blood lead analysis by adjusting square‐wave parameters in capillary or venous blood with a minimum sample pretreatment and excellent accuracy and reproducibility. 相似文献
8.
M. Mercedes Blanco Graciela Buldain Celia B. Schapira Isabel Perillo 《Journal of heterocyclic chemistry》2002,39(2):341-346
The 13C‐NMR spectra of some 1,6‐naphthyridines 2 and 1,7‐naphthyridines 3 , as well as those of N‐methyl derivatives 4 and 5 , were recorded and analyzed. Results in dimethyl‐d6 sulfoxide and deuteriochlo‐roform provide useful data on intra and intermolecular hydrogen bonds. 相似文献
9.
Stewart S. J. Mercader R. C. Punte G. Desimoni J. Cernicchiaro G. Scorzelli R. B. 《Hyperfine Interactions》2004,158(1-4):89-93
In this paper we analyze trend of EFG values measured at Cd impurity in a group of semiconducting delafossites with chemical
formula CuBO2 (B = Al, Fe, Cr, Nd). We conclude that this trend reveals one of the most subtle details in electronic spectrum of the compounds:
if impurity states are formed within or out of the band gap. In CuAlO2 and CuFeO2 the Cd EFG exhibits larger value than in CuCrO2 and CuNdO2, when Cd substitutes the Cu atom. This occurs because in the first two compounds the Cd forms shallow band within the gap,
and in the second two compounds does not. When Cd occupies the B position it exhibits almost the same EFG in all delafossites.
In this case, Cd does not form its states within the gap in none of the compounds. To arrive to these conclusions we analyzed
and calculated various systems (Cd-doped CuAlO2 and CuCrO2 compounds, fictitious molecules), using the FP-LAPW method. 相似文献
10.
Cristina Vázquez Graciela Custo Laura Dawidowski Darío Gómez Marina Villegas Martha Ortiz Mayumi Miyagusuku 《Analytical sciences》2005,21(7):763-767
Multielemental composition and morphology of particulate matter samples were examined to detect the presence of two potential responsible pollutant emitters at four sites impacted during a pollution episode in the City of Campana, Argentina. Coke and smoke black are the main constituents associated to the industrial plants that were considered, a priori, as responsible pollutant emitters. Wavelength dispersive X-ray fluorescence (WDXRF) was employed for the analysis of metals in samples coming from both, suspected sources and four sites. On the basis of multielemental composition profiles, a screening analysis was undertaken for exploring similarities among sources and sample sites adopting the average concentration profile of the crustal rock as soil surrogate. Particle morphology was studied by scanning electron microscopy (SEM) in source samples and in those environmental samples selected through the screening analysis. Two types of collected samples were analyzed: 1) those with composition profiles closer to the potential sources and 2) those closer to the cluster rock. This strategy was adequate to identify the responsible source of the contamination episode. 相似文献