全文获取类型
收费全文 | 128篇 |
免费 | 5篇 |
国内免费 | 2篇 |
专业分类
化学 | 94篇 |
晶体学 | 1篇 |
力学 | 1篇 |
数学 | 11篇 |
物理学 | 28篇 |
出版年
2022年 | 2篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 5篇 |
2016年 | 6篇 |
2015年 | 4篇 |
2014年 | 9篇 |
2013年 | 6篇 |
2012年 | 2篇 |
2011年 | 3篇 |
2010年 | 5篇 |
2009年 | 4篇 |
2008年 | 9篇 |
2007年 | 8篇 |
2006年 | 13篇 |
2005年 | 2篇 |
2004年 | 3篇 |
2003年 | 2篇 |
2002年 | 10篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1995年 | 2篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 1篇 |
排序方式: 共有135条查询结果,搜索用时 15 毫秒
1.
M. T. Crespo J. M. Los Arcos C. E. Granados M. L. Aceña 《Journal of Radioanalytical and Nuclear Chemistry》1989,130(1):99-110
A new method of analysis of the efficiency of four filters of MnO2 in series which takes into account the reactions induced in plutonium by the sorbent is described. The system of differential equations describing the behaviour of plutonium in water as it passes through the filters is solved and the parameters of the filters are determined for a best fitting of the solutions corresponding to the experimental uncertainties. The method is checked by numerical simulation and then applied to water solutions with a known plutonium concentration and to some experimental results given by other authors. In all occassions the results are consistent with the possibility of determining the contents of plutonium in sea and continental waters with uncertainties of the order of 10%. 相似文献
2.
M. López Granados F. Cabello Galisteo M. Alifanti J.L.G. Fierro 《Applied Surface Science》2006,252(24):8442-8450
This work reports the research carried out by studying aliquots extracted at different axial coordinates from Three Way Catalyst (TWC) monoliths aged under real traffic conditions. Our study focused on the catalytic properties and on several chemical and physical effects caused in the Front and Rear monolith washcoat surfaces by vehicle aging after 60,000 km. Regarding the catalytic properties, all the used aliquots showed poorer activity than their corresponding fresh counterparts. The strongest deactivation was detected for NO and hydrocarbon conversion. CO conversion was less affected and the Rear monolith was as deactivated as the Front one. The characterisation techniques (TXRF, N2 adsorption-desorption isotherms, XRD and H2-TPR) detected - (i) the deposition of P, Zn and Pb; (ii) the formation of CePO4 on account of the Ce from the washcoat; (iii) thermal sintering; (iv) inhibition of the reducibility of Ce oxides - as the main effects brought about by vehicle aging conditions. The deactivation observed at the beginning of the Front monolith was the result of a combination of the former effects. When moving downstream to higher axial coordinates, Pb accumulation and the loss of specific area appeared to be the only probable sources of deactivation. 相似文献
3.
A method for heavy metal monitoring using spectrophotometric detection is presented. Traces of Cu(II), Pb(II) and Cd(II) at the low microg l(-1) level can be determined simultaneously after both selective removal of metal interferences and preconcentration using 'extraction chromatographic resins'. Lewatit TP807'84, which contains di(2,4,4-trimethylpentyl)phosphinic acid as active component, was used as solid adsorbent. Two minicolumns containing this resin were used: one at pH 3.2 for the removal of interferences, such as Zn(II) and Fe(III), and the other at pH 5.5 for the selective preconcentration of the target analytes. Spectrophotometric determination used FIA methodology with sulfarsazene as chromogenic reagent and partial least-squares multivariate calibration. The method was successfully applied to the analysis of surface waters from the Llobregat river and ground water samples from wells in the Guadiamar basin. Accuracy, expressed in terms of recoveries, was in the range 80-120% and relative standard deviations were below 10%. 相似文献
4.
Summary A method is reported for the determination of dibutyltin (DBT), diphenyltin (DPhT), tributyltin (TBT), and triphenyltin (TPhT)
species at the nanogram per litre concentration level in natural water samples. Analytes were isolated from samples by solid-phase
extraction and analysed both off-line and on-line by reversed-phase high-performance liquid chromatography with post-column
derivatization and fluorimetric detection. Several SPE cartridges and eluents were evaluated; C18 enrichment and elution with a mixture of methanol, acetic acid, and water was found most suitable. Preconcentration factors
up to 250 can be achieved when a 500-mL sample is processed. Detection limits, recovery rates, and the precision of the whole
process have been determined. The method has been applied to the determination of organotin species in spiked natural water
samples collected on the NW Mediterranean coast. Recovery rates range from 75 to 110% and detection limits are at the low
ng L−1 level (1–3 ng Sn L−1 for DPhT, DBT, and PhT and 40 ng Sn L−1 for TBT when 250 mL spiked sea water is processed.) 相似文献
5.
Determination of macrolide antibiotics by liquid chromatography 总被引:7,自引:0,他引:7
The liquid chromatographic separation of seven macrolides used in food producing animals in the European Union has been studied. Separation was performed by using an end-capped high-purity silica-based C18 column and mobile phases consisting of phosphate buffer (pH 2.5)–acetonitrile mixtures. The effect of pH and acetonitrile percentage on the separation was examined. Two UV-based detection systems, wavelength programming and diode array, were assayed. Detection limits were in the range 6–33 μg l−1 for spiramycin, tilmicosin, tylosin, kitasamicin and josamicin and about 400 μg l−1 for erythromycin and oleandomycin. The suitability of the method for multiresidue determination of the five macrolides is demonstrated by the analysis of spiked samples of chicken muscle. 相似文献
6.
The potassium hydroxide-induced (Stevens) rearrangement of 1,3,4-trimethyl-1-(3,4,5-trimethoxybenzyl)-1,2,5,6-tetrahydropyridinium chloride (I) gives the desired 1,3,4-trimethyl-2-(3,4,5-trimethoxybenzyl)-1,2,5,6-tetrahydropyridine (III) and the Hofmann elimination product, N-methyl-N-(3,4,5-trimethoxybenzyl)-2,3-dimethyl-2,4-pentadienamine (II). In the presence of ethereal phenyllithium, the salt I undergoes rearrangement giving the expected tetrahydropyridine III in about 17% yield and four other products, N-(3,4,5-trimethoxybenzyl)methylamine (VI), 1,3,4-trimethyl-2-(6-methyl-2,3,4-trimethoxyphenyl)-1,2,5,6-tetrahydropyridine (IV), 1,3,3-trirnethyl-2-(3,4,5-trimethoxyphenyl)-4-rnethylenepiperidine (V) and 1,3,4-trimethyl-4-(3,4,5-trimethoxybenzyl)-1,4,5,6-tetrahydropyridine (VII), the latter being the 1,4-Stevens rearrangement product which cyclizes easily to β-2′,3′,4′-trimethoxy-2,5,9-trimethyl-7,8-benzomorphan (VIII). Their structures have been proved both by analytical and spectral data. A possible route for VIII and its stereochemical aspects are discussed. 相似文献
7.
8.
Kleemans NA Bominaar-Silkens IM Fomin VM Gladilin VN Granados D Taboada AG García JM Offermans P Zeitler U Christianen PC Maan JC Devreese JT Koenraad PM 《Physical review letters》2007,99(14):146808
We report the direct measurement of the persistent current carried by a single electron by means of magnetization experiments on self-assembled InAs/GaAs quantum rings. We measured the first Aharonov-Bohm oscillation at a field of 14 T, in perfect agreement with our model based on the structural properties determined by cross-sectional scanning tunneling microscopy measurements. The observed oscillation magnitude of the magnetic moment per electron is remarkably large for the topology of our nanostructures, which are singly connected and exhibit a pronounced shape asymmetry. 相似文献
9.
E. Miralles R. Compañó M. Granados M. D. Prat 《Analytical and bioanalytical chemistry》1999,365(6):516-520
Total cyanide species are determined in a flow injection system which includes UV-photodissociation, gas-diffusion separation and spectrofluorimetric detection. Without the irradiation step, only cyanide easily released in acid medium, i.e. labile cyanide, is determined. Cyanide diffuses through a microporous PTFE membrane from an acid donor stream to a sodium hydroxide acceptor stream. Then, the transferred cyanide reacts with ¶o-phthalaldehyde and glycine to form a highly fluorescent isoindole derivative. Complete cyanide recoveries were obtained for the most important metal cyanide complexes found in environmental samples, excepting cobaltocyanide. The sampling frequency for total cyanide was 4 samples h–1 and the detection limit was 0.4 μg L–1. Recoveries of total cyanide from river water obtained with this method are about 90% of those obtained with APHA Method 4500-CN C for total cyanide. 相似文献
10.
Magnetobiosensors Based on Viral Protein p19 for MicroRNA Determination in Cancer Cells and Tissues 下载免费PDF全文
Dr. Susana Campuzano Dr. Eva López‐Hernández Felipe Conzuelo Dr. Rosario Granados Dr. José M. Sánchez‐Puelles Prof. José M. Pingarrón 《Angewandte Chemie (International ed. in English)》2014,53(24):6168-6171
MicroRNAs (miRs) have emerged as important clinical biomarkers with both diagnostic and prognostic value for relevant diseases, such as cancer. MiRs pose unique challenges for detection and are currently detected by northern blotting, real‐time PCR, and microarray techniques. These expensive, complicated, and time‐consuming techniques are not feasible for on‐site miR determination. In this study, amperometric magnetobiosensors involving RNA‐binding viral protein p19 as a selective biorecognition element were developed for miR quantification. The p19‐based magnetosensors were able to detect 0.4 fmol of a synthetic target and endogenous miR‐21 (selected as a model for its role in a wide variety of cancers) in only 2 h in total RNA extracted from cancer cells and human breast‐tumor specimens without PCR amplification and sample preprocessing. These results open up formidable perspectives for the diagnosis and prognosis of human cancers and for drug‐discovery programs. 相似文献