全文获取类型
收费全文 | 254篇 |
免费 | 13篇 |
国内免费 | 1篇 |
专业分类
化学 | 179篇 |
晶体学 | 3篇 |
力学 | 20篇 |
数学 | 39篇 |
物理学 | 27篇 |
出版年
2023年 | 1篇 |
2022年 | 7篇 |
2021年 | 18篇 |
2020年 | 10篇 |
2019年 | 7篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 10篇 |
2015年 | 13篇 |
2014年 | 11篇 |
2013年 | 16篇 |
2012年 | 17篇 |
2011年 | 26篇 |
2010年 | 17篇 |
2009年 | 15篇 |
2008年 | 21篇 |
2007年 | 8篇 |
2006年 | 8篇 |
2005年 | 9篇 |
2004年 | 9篇 |
2003年 | 4篇 |
2002年 | 10篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1986年 | 1篇 |
排序方式: 共有268条查询结果,搜索用时 31 毫秒
91.
Amperometric Sniffer for Volatile Amines Based on Paper‐Supported Room Temperature Ionic Liquids Enabling Rapid Assessment of Fish Spoilage
下载免费PDF全文
![点击此处可从《Electroanalysis》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Rosanna Toniolo Nicolò Dossi Rossella Svigely Sabina Susmel Innocenzo G. Casella Gino Bontempelli 《Electroanalysis》2014,26(9):1966-1974
A gas sensors based on a room temperature ionic liquid (RTIL) supported on paper is proposed as amperometric sniffer for monitoring volatile amines (VAs) released from fish samples, in order to gain indication of their state of turning spoiled. It was used as a paper electrochemical detector (PED) for a flow injection system in which controlled headspace volumes in equilibrium with ice‐stored fish samples were directly injected. The performance of this RTIL‐PED sensor was preliminarily tested on synthetic samples of trimethylamine (TMA), dimethylamine (DMA), methylamine (MA) and ammonia (i.e. the main species responsible for the typical flavor of spoiled fish), thus verifying that only TMA, DMA and MA can be detected because NH3 oxidation occurred beyond the solvent discharge. This notwithstanding, detection of the sole TMA, DMA and MA as a whole turned out to be well suited for the rapid assessment of fish spoilage, since during storage the release enhancement for these amines is largely predominant over that of NH3. Repeatable (8 % RSD) sharp peaks were detected for all amines above over a wide range (5–1000 nmol) and a detection limit of a little more than 3 nmol was inferred for a signal‐to‐noise ratio of 3. This approach was applied to the detection of VAs released from real fish samples (sardines), in parallel to the determination of their total volatile basic nitrogen (TVBN), which is a conventional indicator frequently adopted for the chemical quality assessment of fish. A substantially satisfactory agreement was found by comparing the data achieved by these two approaches. 相似文献
92.
Kamali Saeed Häggström Lennart Ronneteg Sabina Berger Rolf 《Hyperfine Interactions》2004,156(1-4):315-319
Hyperfine Interactions - The quasi two-dimensional antiferromagnetic compound TlCo2Se2 has been studied by 57Fe Mössbauer spectroscopy. Small single crystals have been made with 2% Fe doping.... 相似文献
93.
Continuing some investigations started in previous papers, we introduce and study a sequence of multidimensional positive integral operators which generalize the Gauss-Weierstrass operators. We show that this sequence is an approximation process in some classes of weighted L p spaces on ? N , N ≥ 1. Estimates of the rate of convergence are also obtained. Our mean tool is a Korovkin-type theorem which we establish in the context of L p (X, µ) spaces, X being a locally compact Hausdorff space and µ a regular positive Borel measure on X. Several examples are explicitly indicated as well. 相似文献
94.
We study the structure of classifying spaces of Kač-Moody groups from a homotopy theoretic point of view. They behave in
many respects as in the compact Lie group case. The mod p cohomology algebra is noetherian and Lannes'T functor computes the mod p cohomology of classifying spaces of centralizers of elementary abelian p-subgroups. Also, spaces of maps from classifying spaces of finite p-groups to classifying spaces of Kač-Moody groups are described in terms of classifying spaces of centralizers while the classifying
space of a Kač-Moody group itself can be described as a homotopy colimit of classifying spaces of centralizers of elementary
abelian p-subgroups, up to p-completion. We show that these properties are common to a larger class of groups, also including parabolic subgroups of Kač-Moody
groups, and centralizers of finite p-subgroups.
Received: 15 June 2000 / in final form: 20 September 2001 / Published online: 29 April 2002 相似文献
95.
JPC – Journal of Planar Chromatography – Modern TLC - Tea is one of the most popular beverages in the world. The exact composition of tea depends on the manufacturing process. Our goal... 相似文献
96.
Izzo I Licen S Maulucci N Autore G Marzocco S Tecilla P De Riccardis F 《Chemical communications (Cambridge, England)》2008,(26):2986-2988
1,3-Alternate cationic calix[4]arene proved highly selective for proton/halogens symport transport and showed antiproliferative activity against murine monocyte/macrophage J774.A1 cancer cells. 相似文献
97.
Romanus K Van Neer W Marinova E Verbeke K Luypaerts A Accardo S Hermans I Jacobs P De Vos D Waelkens M 《Analytical and bioanalytical chemistry》2008,390(2):783-793
Burned greasy deposits were found inside shells of the large Nile bivalve Chambardia rubens, excavated in an eight- to tenth- century AD church of the Coptic monastery of Bawit, Egypt, and supposedly used as oil lamps.
The residues were subjected to a combination of chromatographic residue analysis techniques. The rather high concentrations
of unsaturated fatty acids, as analysed by gas chromatography (GC) in the methylated extract, suggest the presence of a vegetal
oil. Analysis of the stable carbon isotopes (δ
13C values) of the methyl esters also favoured plants over animals as the lipid source. In the search for biomarkers by GC coupled
to mass spectrometry on a silylated extract, a range of diacids together with high concentrations of 13,14-dihydroxydocosanoate
and 11,12-dihydroxyeicosanoate were found. These compounds are oxidation products of erucic acid and gondoic acid, which are
abundantly present in seeds of Brassicaceae plants. Liquid chromatography coupled to mass spectrometry analysis showed low
concentrations of unaltered triglycerides, but revealed sizeable amounts of triglycerides with at least one dihydroxylated
acyl chain. The unusual preservation of dihydroxylated triglycerides and α,ω-dicarboxylic acids can be related to the dry preservation conditions. Analysis of the stereoisomers of the dihydroxylated
fatty acids allows one to determine whether oxidation took place during burning of the fuel or afterwards. The results prove
that the oil of rapeseed (Brassica napus L.) or radish (Raphanus sativus L.) was used as illuminant in early Islamic Egypt, and that not only ceramic lamps but also mollusk shells were used as fuel
containers. 相似文献
98.
Cindrić M Cepo T Marinc S Paskvan I Mijić I Bindila L Peter-Katalinić J 《Journal of separation science》2008,31(20):3489-3496
Dithiothreitol (DTT) and other reducing agents are typically used in refolding processes of recombinant human proteins during their purification from inclusion bodies. Due to its toxicity, it is essential to monitor the clearance of DTT throughout the analytical flow from the refolding phase to the final formulated product. Here we report a direct, simple, and fast liquid chromatography method using UV and tandem mass spectrometry (MS/MS) detection for DTT evaluation in complex protein mixtures. In aqueous solution DTT exists as an equilibrium mixture of the oxidized and the reduced form (H(2)DTT --> DTT(ox)) and the quantitation tools should therefore be applicable to both forms in a single step or in multiple steps. Oxidation of DTT with aqueous copper(II) nitrate trihydrate solution was introduced to determine a single oxidized compound, i. e. DTT(ox). Proteins and other components of high molecular masses were separated from DTT(ox) by ultrafiltration. Consequently, efficient separation of the DTT(ox )from other flow-through mixture components (sugars, polymers, salts, protein stabilizers) was achieved on an Atlantis dC(18) column. After chromatographic separation, DTT(ox) was selectively identified by UV absorbance at 285 nm or by selected reaction monitoring, measuring signal transition between m/z 151 --> 105. The method was validated in terms of specificity, accuracy, precision, linearity, and limit of quantification and detection. A reversed-phase HPLC separation method with atmospheric pressure chemical ionization and MS/MS detection in negative ion mode is highlighted as a viable alternative to currently existing quantitation methods involving DTT derivatization and HPLC fluorescence detection. The described approach offers simple, straightforward, selective, and high-throughput DTT quantitation in protein mixtures. 相似文献
99.
Formation and Structural Characterization of Metal Complexes derived from Thiosalicylic Acid
下载免费PDF全文
![点击此处可从《无机化学与普通化学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Minu G. Bhowon Sabina Jhaumeer‐Laulloo Salma Moosun Lisa Humphreys Simon Coles Roshni Fowdram Evena Mungra 《无机化学与普通化学杂志》2017,643(18):1167-1172
The formation and structural aspects of some metal complexes of thiosalicylic acid (TSA) were studied. The μ‐bridging tetra‐coordinated Ru complex, [Ru(C6H4(CO2)(μ‐S)(H2O)]2 ( 1 ) was formed by hydrothermal reaction of TSA with RuCl3. The complexes [M(dtdb)(phen)(H2O)]n ( 2 – 4 ) (M = ZnII, CoII, NiII, dtdb = 2,2′‐dithiodibenzoate anion, phen = 1,10‐phenanthroline) were obtained by the slow diffusion technique and the in situ S–S bond formation was confirmed by elemental, spectral and X‐ray analysis. Reaction of TSA with CuCl2 and 2,2′‐bipyridine (bipy) under the slow diffusion technique yielded the dimer [Cu(tdb)(bipy)] ( 5 ) (tdb = thiodibenzoic acid), where the in situ generation of 2,2′‐thiodibenzoic acid was observed. 相似文献
100.
A bifurcation problem governed by the boundary condition II 总被引:1,自引:0,他引:1
Garcia-Melian Jorge; Rossi Julio D.; Sabina De Lis Jose C. 《Proceedings London Mathematical Society》2007,94(1):1-25
In this work we consider the problem u = a(x)up in on , where is a smooth bounded domain, isthe outward unit normal to , is regarded as a parameter and0 < p < 1. We consider both cases where a(x) > 0 in or a(x) is allowed to vanish in a whole subdomain 0 of . Ourmain results include existence of non-negative non-trivial solutionsin the range 0 < < 1, where 1 is characterized by meansof an eigenvalue problem, uniqueness and bifurcation from infinityof such solutions for small , and the appearance of dead coresfor large enough . 相似文献