全文获取类型
收费全文 | 623篇 |
免费 | 37篇 |
专业分类
化学 | 531篇 |
晶体学 | 1篇 |
力学 | 4篇 |
数学 | 70篇 |
物理学 | 54篇 |
出版年
2023年 | 4篇 |
2022年 | 13篇 |
2021年 | 30篇 |
2020年 | 24篇 |
2019年 | 26篇 |
2018年 | 12篇 |
2017年 | 15篇 |
2016年 | 21篇 |
2015年 | 32篇 |
2014年 | 36篇 |
2013年 | 41篇 |
2012年 | 53篇 |
2011年 | 48篇 |
2010年 | 30篇 |
2009年 | 19篇 |
2008年 | 43篇 |
2007年 | 29篇 |
2006年 | 36篇 |
2005年 | 29篇 |
2004年 | 42篇 |
2003年 | 28篇 |
2002年 | 20篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 5篇 |
1997年 | 1篇 |
1996年 | 6篇 |
1995年 | 1篇 |
1994年 | 4篇 |
1993年 | 1篇 |
1987年 | 1篇 |
排序方式: 共有660条查询结果,搜索用时 31 毫秒
651.
Deyan Lesigyarski Žiga Šmit Boika Zlateva-Rangelova Kristina Koseva Ivelin Kuleff 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(3):1605-1619
Using PIXE (proton induced X-ray emission), PIGE (proton induced gamma emission) and ICP-AES (inductively coupled plasma-atomic emission spectroscopy) the concentrations of the 24 elements Al, As, Ba, Br, Ca, Cl, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Pb, Rb, S, Sb, Si, Sn, Sr, Ti, Zn and Zr in 53 archaeological glass samples from South-Eastern Bulgaria, were determined. The glasses are dated from the 1st to 6th century AD. The analytical data showed the samples to be typical soda-lime-silica glass, with natron as flux. A rather broad range of aluminium, titanium and iron impurities was found, with a tendency for more impure glass in the later periods. The decolouring agents were antimony and manganese oxides, with Sb prevailing in earlier, and Mn in later glass. 相似文献
652.
Denise Lowinsohn Patrick Gan Kristina Tschulik John S. Foord Richard G. Compton 《Electroanalysis》2013,25(11):2435-2444
The electrochemical behaviour of carbon paste electrodes prepared using nanocarbon and mineral oil was investigated and the results contrasted with different carbon and carbon pastes electrodes. The composition of carbon paste was studied by performing cyclic voltammetry performed in 0.1 M KCl solution in the presence of 4.0 mM Ru(NH3)6Cl3, a well‐characterized redox system commonly used to test the electrode behaviour. After optimisation of the paste composition, the sensors chosen were tested for the analysis and characterization of three different systems: Ru(NH3)63+/2+, FcCH2OH/FcCH2OH+ and acetaminophen. The ability to obtain high quality voltammetry from the nanocarbon electrode was demonstrated and simulation of the voltammetry allowed the extraction of electrode kinetic parameters with high precision. 相似文献
653.
Frank Kirschhöfer Annika Rieder Carolin Prechtl Boris Kühl Kristina Sabljo Christof Wöll Ursula Obst Gerald Brenner-Weiß 《Analytica chimica acta》2013
Proteinaceous conditioning films (pCFs) are thought to play a key role in microbial adhesion, leading to the fouling of technical and biomedical devices and biofilm formation, which in turn causes material damage or persistent infections, respectively. However, little is definitively known about the process of surface conditioning via proteins. Herein, we demonstrate the potential of quartz crystal microbalance with dissipation coupled to MALDI-ToF mass spectrometry (QCM-D-MALDI) to investigate protein adsorption on different surfaces, enabling both the monitoring of CF formation and the determination of the molecular composition of CFs. After running QCM-D experiments, a subsequent tryptic on chip digestion step allows the identification of the proteins deposited on the sensor chip surface via MALDI-ToF mass spectrometry. Prominent blood plasma proteins, i.e., human serum albumin (HSA), fibrinogen (FG) and fibronectin (FN), were used. Chemically well defined sensor surfaces were prepared, among others, via self-assembled monolayer (SAM) technology. In cases where protein adsorption was observed by QCM-D, the adsorbed proteins were clearly detected and identified using MALDI-ToF/MS for both single-protein solutions of HSA, FG and FN as well as for protein mixtures. However, for equimolar protein mixtures on TiO2 surfaces, only signals attributed to FG and FN were observed in the mass spectra. No signals indicating the presence of HSA could be detected. This finding leads to the assumption that only FG and FN attach to the TiO2 sensor surface under the given experimental conditions. 相似文献
654.
655.
Gedrich K Heitbaum M Notzon A Senkovska I Fröhlich R Getzschmann J Mueller U Glorius F Kaskel S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(7):2099-2106
Chiral metal–organic frameworks with a three‐dimensional network structure and wide‐open pores (>30 Å) were obtained by using chiral trifunctional linkers and multinuclear zinc clusters. The linkers, H3ChirBTB‐n, consist of a 4,4′,4′′‐benzene‐1,3,5‐triyltribenzoate (BTB) backbone decorated with chiral oxazolidinone substituents. The size and polarity of these substituents determines the network topology formed under solvothermal synthesis conditions. The resulting chiral MOFs adsorb even large molecules from solution. Moreover, they are highly active Lewis acid catalysts in the Mukaiyama aldol reaction. Due to their chiral functionalization, they show significant levels of enantioselectivity, thereby proving the validity of the modular design concept employed. 相似文献
656.
Hitzfeld KL Gehre M Richnow HH 《Rapid communications in mass spectrometry : RCM》2011,25(20):3114-3122
A novel approach for the measurement of (37)Cl, (81)Br and (34)S in organic compounds containing chlorine, bromine, and sulphur is presented to overcome some of the major drawbacks of existing methods. Contemporary methods either require reference materials with the exact molecular compositions of the substances to be tested, or necessitate several laborious offline procedures prior to isotope analysis. In our online setup, organic compounds are separated by gas chromatography (GC) coupled to a high-temperature reactor. Using hydrogen as a makeup gas, the reactor achieves quantitative conversion of chlorinated, brominated and sulphurated organic compounds into gaseous hydrogen chloride (HCl), hydrogen bromide (HBr), and hydrogen sulphide (H(2)S), respectively. In this study, the GC interface was coupled to a quadrupole mass spectrometer operated in single-ion mode. The ion traces of either H(35)Cl (m/z 36) and H(37)Cl (m/z 38), H(79)Br (m/z 80) and H(81)Br (m/z 82), or H(2)(32)S (m/z 34) and H(2)(34)S (m/z 36), were recorded to determine the isotopic ratios of chlorine, bromine, and sulphur isotopes. The conversion interface presented here provides a basis for a novel method for compound-specific isotope analysis of halogenated and sulphur-containing compounds. Rapid online measurements of organic chlorine-, bromine- and sulphur-containing mixtures will facilitate the isotopic analysis of compounds containing these elements, and broaden their usage in fields of environmental forensics employing isotopic concepts. 相似文献
657.
An approximate mean field model of an ensemble of delayed coupled stochastic Hindmarsh-Rose bursting neurons is constructed and analyzed. Bifurcation analysis of the approximate system is performed using numerical continuation. It is demonstrated that the stability domains in the parameter space of the large exact systems are correctly estimated using the much simpler approximate model. 相似文献
658.
New amidino‐benzimidazolyl‐substituted bis‐1,2‐(2‐thienyl)ethenes ( 4, 5 , and 6 ) and benzo[1,2‐ b:4,3‐ b′]dithiophenes ( 8, 9 , and 10 ) were prepared by the condensation of amidino‐substituted o‐phenylene diamines with corresponding dialdehydes ( 3 and 7 ). All prepared amidino‐benzimidazolyl‐substituted compounds are of particular interest, because they can serve as intercalators or groove binders on DNA in anticancer therapy. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:218–222, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10126 相似文献
659.
Frank Würthner Stefan Brse Norbert Sewald Rainer Herges Matthias O. Senge Thorsten Bach Thomas Gottwald Thomas Kopf Kristina pehar Jens Hartung Dietmar Plattner Andreas Gansuer Martin Oestreich Reinhard Brückner Jrg Pietruszka Roderick Süßmuth Michael Müller Elmar Weinhold Andres Jschke Markus Albrecht Henning Priepke Gerhard Roth Klaus Ditrich Alexander Ernst Lars Wortmann Schering Ag 《Nachrichten aus der Chemie》2003,51(3):286-315
Die enantioselektive Synthese bleibt zentrales Thema in metallorganischen, metallfreien and bioorganischen Transformationen sowie in der industriellen organischen Chemie. Glanzpunkte zielmolekülorientierter Synthesechemie waren ein Zugang zu C60, die Route zum Diazonamid A und die Totalsynthese von Vinblastin. Mit „Pyrrolysin”︁ wurde die 22. proteinogene Aminosäure entdeckt. Trotz der immer höheren Zahl an Testsubstanzen besteht in der medizinischen Chemie ein Engpass an klinisch erfolgreichen Wirkstoffen. 相似文献
660.
Chenglong Luan Johanna Angona Arjun Bala Krishnan Manuel Corva Pouya Hosseini Markus Heidelmann Ulrich Hagemann Emmanuel Batsa Tetteh Wolfgang Schuhmann Kristina Tschulik Tong Li 《Angewandte Chemie (International ed. in English)》2023,62(28):e202305982
The role of β-CoOOH crystallographic orientations in catalytic activity for the oxygen evolution reaction (OER) remains elusive. We combine correlative electron backscatter diffraction/scanning electrochemical cell microscopy with X-ray photoelectron spectroscopy, transmission electron microscopy, and atom probe tomography to establish the structure–activity relationships of various faceted β-CoOOH formed on a Co microelectrode under OER conditions. We reveal that ≈6 nm β-CoOOH(01 0), grown on [ 0]-oriented Co, exhibits higher OER activity than ≈3 nm β-CoOOH(10 3) or ≈6 nm β-CoOOH(0006) formed on [02 - and [0001]-oriented Co, respectively. This arises from higher amounts of incorporated hydroxyl ions and more easily reducible CoIII−O sites present in β-CoOOH(01 0) than those in the latter two oxyhydroxide facets. Our correlative multimodal approach shows great promise in linking local activity with atomic-scale details of structure, thickness and composition of active species, which opens opportunities to design pre-catalysts with preferred defects that promote the formation of the most active OER species. 相似文献