全文获取类型
收费全文 | 333篇 |
免费 | 6篇 |
学科分类
数理化 | 339篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 3篇 |
2017年 | 9篇 |
2016年 | 6篇 |
2015年 | 17篇 |
2014年 | 10篇 |
2013年 | 16篇 |
2012年 | 30篇 |
2011年 | 26篇 |
2010年 | 20篇 |
2009年 | 25篇 |
2008年 | 21篇 |
2007年 | 15篇 |
2006年 | 19篇 |
2005年 | 21篇 |
2004年 | 18篇 |
2003年 | 13篇 |
2002年 | 20篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1998年 | 7篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1994年 | 1篇 |
1992年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
排序方式: 共有339条查询结果,搜索用时 15 毫秒
1.
The chemical etching of silicon using HF-HNO3 mixtures is a widely used process in the processing of silicon wafers for microelectronic or photovoltaic applications. The control of the etch bath composition is the necessary condition for an effective bath utilization, for the replenishment of the consumed acids, and to maintain a certain etch rate. The present paper describes two methods for the total analysis of the individual etch bath constituents HF, HNO3, and H2SiF6. Both methods start with an aqueous acid-base titration determining the total acid concentration and the concentration of H2SiF6. The first method is an acid-base titration using a 0.1 mol L−1 methanolic solution of cyclohexylamine (CHA) as non-aqueous titrant to determine the content of nitric acid. Then, the amount of hydrofluoric acid is calculated from the difference between the total acid and nitric acid content. The second method is based on the determination of the total fluoride concentration using a fluoride ion-selective electrode (F-ISE). The content of hydrofluoric acid is obtained from the difference between the total fluoride content and the amount of fluoride bound as H2SiF6. The amount of nitric acid results finally calculated as difference to the total acid content. 相似文献
2.
3.
Meier MA de Gans BJ van den Berg AM Schubert US 《Rapid communications in mass spectrometry : RCM》2003,17(20):2349-2353
Recently, a new multiple-layer matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) sample spotting technique for poly(ethylene glycol), offering improved analysis possibilities, was described. In this contribution the application of ink-jet printing to automated, multiple-layer MALDI-TOFMS sample preparation of synthetic polymers is presented, allowing accurate deposition of matrix, additive and analyte solutions. The new sample preparation technique was evaluated for poly(ethylene glycol) as well as poly(methyl methacrylate) standards, and optimized settings for both synthetic polymers have been obtained. 相似文献
4.
Biosensors for environmental pollutants and food contaminants 总被引:4,自引:0,他引:4
Baeumner AJ 《Analytical and bioanalytical chemistry》2003,377(3):434-445
This review article provides an overview of the most recent literature on biosensors for environmental pollutants and food contaminants. Due to the large number of publications, only papers published between 2000 and January 2003 were considered. Also, while not all of the published literature could be reviewed here, over 200 references are cited to provide a good overview of research undertaken in the last two years. Older publications are covered by a number of earlier review articles. This article provides an introduction into the field including specific consideration of the application areas, describes the typical biosensor assay format used, and is subsequently structured according to the biorecognition elements used (i.e., nucleic acids, enzymes, whole cells, tissue and whole organisms, antibodies and receptors, and biomimetic materials). In addition, a section on microbiosensing systems is provided. Since only very few microbiosensors with applications in environmental and food systems have been published, enabling technology is also covered in this article.Abbreviations BOD biological oxygen demand - cfu colony forming units - DNP dinitrophenol - GFP green fluorescent protein - NASBA nucleic acid sequence-based amplification - PCR polymerase chain reaction - ppt parts per trillion - QCM quartz crystal microbalance - SPR surface plasmon resonance 相似文献
5.
G. Wytze Meindersma Lara M. Galán Sánchez Antje R. Hansmeier André B. de Haan 《Monatshefte für Chemie / Chemical Monthly》2007,138(11):1125-1136
Summary. Ionic liquids offer tremendous opportunities to intensify reactions and separations in process technologies by tuning their
physical and chemical properties. Several ionic liquids are suitable for the separation of aromatic and aliphatic hydrocarbons.
CO2 absorption behavior was influenced by the functionalized chains appended to the room temperature ionic liquid (RTIL) cation.
Ionic liquids seem able to combine the chemical features of amine solutions with the characteristic advantages of the physical
solvents used for CO2 absorption. 相似文献
6.
Antje Huefner Christa Hoeller Gottfried Reznicek 《Monatshefte für Chemie / Chemical Monthly》2004,9(2):447-459
The stereoselective syntheses of four unsaturated hydroxy fatty acids 13S,2E,4E,9E)- 13-hydroxy-2,4,9-tetradecatrienoic acid, (13S,9Z,11E)-13-hydroxy-9,11-tetradecadienoic acid, (13S,9E, 11E)-13-hydroxy-9,11-tetradecadienoic acid, and (13S,2E,4E,9E)-13-hydroxy-2,4,9,11-tetradecatrienoic acid, are described. Wittig reactions, regioselective oxidation of dialcohol 3, and diastereomerization were used. 相似文献
7.
Julia Post Vanessa Kogel Anja Schaffrath Philipp Lohmann N. Jon Shah Karl-Josef Langen Dieter Willbold Antje Willuweit Janine Kutzsche 《Molecules (Basel, Switzerland)》2021,26(6)
Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterised by selective neuronal death in the brain stem and spinal cord. The cause is unknown, but an increasing amount of evidence has firmly certified that neuroinflammation plays a key role in ALS pathogenesis. Neuroinflammation is a pathological hallmark of several neurodegenerative disorders and has been implicated as driver of disease progression. Here, we describe a treatment study demonstrating the therapeutic potential of a tandem version of the well-known all-d-peptide RD2 (RD2RD2) in a transgenic mouse model of ALS (SOD1*G93A). Mice were treated intraperitoneally for four weeks with RD2RD2 vs. placebo. SOD1*G93A mice were tested longitudinally during treatment in various behavioural and motor coordination tests. Brain and spinal cord samples were investigated immunohistochemically for gliosis and neurodegeneration. RD2RD2 treatment in SOD1*G93A mice resulted not only in a reduction of activated astrocytes and microglia in both the brain stem and lumbar spinal cord, but also in a rescue of neurons in the motor cortex. RD2RD2 treatment was able to slow progression of the disease phenotype, especially the motor deficits, to an extent that during the four weeks treatment duration, no significant progression was observed in any of the motor experiments. Based on the presented results, we conclude that RD2RD2 is a potential therapeutic candidate against ALS. 相似文献
8.
Investigation of sulfur release in ETV-ICP-AES and its application for the determination of sulfates 总被引:3,自引:0,他引:3
Antje Mroczek Gerhard Werner R. Wennrich Werner Schr?n 《Fresenius' Journal of Analytical Chemistry》1998,361(1):34-42
Electrothermal vaporization inductively coupled plasma atomic emission spectrometry was applied to the determination of sulfur
species in aqueous solutions. The sensitivity for sulfur as sulfate was found to be depending on the cations in the sample.
For understanding this phenomenon the thermal behavior of sulfuric acid, ammonium sulfate and the sulfates of sodium, zinc,
magnesium and silver was studied. There were significant differences in the thermal release of sulfur from these sulfates.
To explain these phenomena different reaction mechanisms were calculated using thermodynamic data. Pd(NO3)2 and Ge in KOH were successfully applied as modifiers for the stabilization of the sulfates during the thermal pre-treatment
step and to establish a uniform thermal behavior of different sulfates. The stabilization of sulfur using Ge and Pd as modifiers
is based on the reduction of the sulfates in presence of carbon, resulting in the formation of GeS and PdS, respectively.
This explanation has been supported by comparing the experimental results with thermodynamic calculations considering different
reactions for the thermal decomposition of the sulfates. Applying Ge (in KOH) as modifier the absolute detection limit was
300 pg sulfur (e.g. LOD 30 ng mL–1). The significant influence of phosphates on the determination of sulfur could be essentially reduced by Pd as modifier.
Received: 11 November 1997 / Revised: 14 January 1998 / Accepted: 18 January 1998 相似文献
9.
Budischowsky David Zwirchmayr Nele Sophie Hosoya Takashi Bacher Markus Hettegger Hubert Potthast Antje Rosenau Thomas 《Cellulose (London, England)》2021,28(10):6051-6071
Cellulose - Chromophores, colored substances of rather high stability that reduce brightness, are present in all kinds of cellulosic products, such as pulp, fibers, aged cellulosic material, and... 相似文献
10.
Electrochemiluminescence Bioassays with a Water‐Soluble Luminol Derivative Can Outperform Fluorescence Assays 下载免费PDF全文
Michael Mayer Prof. Dr. Shigehiko Takegami Michael Neumeier Simone Rink Prof. Dr. Axel Jacobi von Wangelin Silja Schulte Moritz Vollmer Prof. Dr. Axel G. Griesbeck PD Dr. Axel Duerkop Prof. Dr. Antje J. Baeumner 《Angewandte Chemie (International ed. in English)》2018,57(2):408-411
The most efficient and commonly used electrochemiluminescence (ECL) emitters are luminol, [Ru(bpy)3]2+, and derivatives thereof. Luminol stands out due to its low excitation potential, but applications are limited by its insolubility under physiological conditions. The water‐soluble m‐carboxy luminol was synthesized in 15 % yield and exhibited high solubility under physiological conditions and afforded a four‐fold ECL signal increase (vs. luminol). Entrapment in DNA‐tagged liposomes enabled a DNA assay with a detection limit of 3.2 pmol L?1, which is 150 times lower than the corresponding fluorescence approach. This remarkable sensitivity gain and the low excitation potential establish m‐carboxy luminol as a superior ECL probe with direct relevance to chemiluminescence and enzymatic bioanalytical approaches. 相似文献