全文获取类型
收费全文 | 185篇 |
免费 | 5篇 |
国内免费 | 2篇 |
专业分类
化学 | 150篇 |
晶体学 | 1篇 |
数学 | 27篇 |
物理学 | 14篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 27篇 |
2012年 | 9篇 |
2011年 | 14篇 |
2010年 | 9篇 |
2009年 | 6篇 |
2008年 | 10篇 |
2007年 | 10篇 |
2006年 | 8篇 |
2005年 | 6篇 |
2004年 | 7篇 |
2003年 | 3篇 |
2002年 | 7篇 |
2001年 | 2篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1969年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有192条查询结果,搜索用时 171 毫秒
101.
Emmanuel O. Jonah Margit Härting Eric Gullikson Andrew Aquila David T. Britton 《Journal of synchrotron radiation》2014,21(3):547-553
A new small‐angle scattering technique in reflection geometry is described which enables a topological study of rough surfaces. This is achieved by using long‐wavelength soft X‐rays which are scattered at wide angles but in the low‐Q range normally associated with small‐angle scattering. The use of nanometre‐wavelength radiation restricts the penetration to a thin surface layer which follows the topology of the surface, while moving the scattered beam to wider angles preventing shadowing by the surface features. The technique is, however, only applicable to rough surfaces for which there is no specular reflection, so that only the scattered beam was detected by the detector. As an example, a study of the surfaces of rough layers of silicon produced by the deposition of nanoparticles by blade‐coating is presented. The surfaces of the blade‐coated layers have rough features of the order of several micrometers. Using 2 nm and 13 nm X‐rays scattered at angular ranges of 5°≤θ≤ 51° and 5°≤θ≤ 45°, respectively, a combined range of scattering vector of 0.00842 Å?1≤Q≤ 0.4883 Å?1 was obtained. Comparison with previous transmission SAXS and USAXS studies of the same materials indicates that the new method does probe the surface topology rather than the internal microstructure. 相似文献
102.
Daniel W. Cranston Anja Pruchnewski Zsolt Tuza Margit Voigt 《Journal of Graph Theory》2012,71(1):18-30
The following question was raised by Bruce Richter. Let G be a planar, 3‐connected graph that is not a complete graph. Denoting by d(v) the degree of vertex v, is G L‐list colorable for every list assignment L with |L(v)| = min{d(v), 6} for all v∈V(G)? More generally, we ask for which pairs (r, k) the following question has an affirmative answer. Let r and k be the integers and let G be a K5‐minor‐free r‐connected graph that is not a Gallai tree (i.e. at least one block of G is neither a complete graph nor an odd cycle). Is G L‐list colorable for every list assignment L with |L(v)| = min{d(v), k} for all v∈V(G)? We investigate this question by considering the components of G[Sk], where Sk: = {v∈V(G)|d(v)8k} is the set of vertices with small degree in G. We are especially interested in the minimum distance d(Sk) in G between the components of G[Sk]. © 2011 Wiley Periodicals, Inc. J Graph Theory 71:18–30, 2012 相似文献
103.
Huong M. Bui Margit Lenninger Avinash P. Manian Mohammad Abu-Rous Christian B. Schimper K. Christian Schuster Thomas Bechtold 《Macromolecular Symposia》2008,262(1):50-64
The reorganization of cellulose fibers by swelling treatments in alkali solutions results in numerous changes to fiber structure, causing changes of chemical reactivity in the fiber-solution heterogeneous system. An important part of the change in chemical reactivity is the change of fiber accessibility because it results in exclusion of chemicals such as reagents or catalysts from the fiber. In the second of a two-part series of papers, we examine the influence of changes in fiber accessibility and/or reactivity due to treatment in swelling solutions on the performance or behavior of substrates during and after chemical finishing treatments. Changes in fiber accessibility due to alkali treatments are visualized with fluorescence microscopy. The effect of alkali treatments on enzymatic hydrolysis and pad-dry-cure crosslinking treatments of cellulose substrates are discussed as representative examples to demonstrate the effects of swelling processes on fiber reactivity and accessibility. Model calculations indicate that a considerable redistribution of chemicals in substrates occurs during dry-cure operations resulting from molecule-specific exclusion effects. Pilling tests on lyocell knit-fabrics show the impact of preceding alkali processes on the final physical performance of textile fabric highlighting the importance of correct selection of alkali processes to achieve desired behavior. 相似文献
104.
Nadira Ibrišimović Margit Barth Ulrich Bohrn Mirza Ibrišimović Fritz Pittner 《Monatshefte für Chemie / Chemical Monthly》2009,140(8):941-945
Abstract Conventional tests currently in use for the detection and identification of food-borne pathogens and also of microbial food
deterioration are time-consuming as they are based on conventional culturing techniques or monitoring environmental conditions
like the increase of temperature or change in pH. These parameters do not reflect the real quality of the meat to be tested.
The aim of our approach was to create a simple and cheap sensor providing reasonable sensitivity and selectivity to indicate
the bacterial infection in real-time monitoring combined with a memory effect that cannot easily be corrupted. Thus, an optical
thin film sensor chip was developed able to detect bacterial decay of food through a specific colour change. The design of
the sensor relates to the phenomenon of “anomalous absorption”, which can best be described as a thin film enhanced absorption.
A metal nanoparticle layer positioned at a well-defined distance to a smooth metal surface shows that the minimum of spectral
reflectivity strongly depends on the thickness of the distance layer. This setup represents a special kind of reflection interference
filter. In such a sensor setup a biomimetic polymer is integrated, which is degradable by lytic enzymes excreted by microorganisms
in food decay. Meat deterioration under controlled conditions is correlated to the amount of enzymes secreted by microorganisms
and the bacterial count. Thus, after incubation of the sensor setup with standard meat preparations, the enzymes released
from decaying cell material change the thickness of the polymer layer and generate an easily visible colour change. This setup
would be useful for integration into meat packaging.
Graphical Abstract
M. Barth, U. Bohrn and M. Ibrišimović contributed equally to this work. 相似文献
105.
2H NMR spectra of perdeuterated tris(diimine)ruthenium(II) complexes have been recorded in lyotropic liquid crystalline phase formed by the chiral polypeptide, poly-gamma-benzyl-L-glutamate (PBLG) and co-solvents. It is demonstrated that the left- and right-rotation isomers of these octahedral metal complexes with D3 symmetry can be distinguished. The effects of temperature and ligand size on spectral resolution were also studied. Although in the case of free bipyridine ligands excellent optical resolution could be obtained at room temperature in the complexes studied, the increase in ligand size has a detrimental effect on the resolution. This can be compensated to some extent by elevating the sample temperature and decreasing the deuterium relaxation rates, but the available temperature range and therefore the applicability of the technique are limited. 相似文献
106.
Gy. Szabó Edit Csató Katalin Offenmüller Margit Dévai Anna Borbély-Kuszmann Gy. Liptai 《Chromatographia》1988,26(1):255-258
Summary Three different phenyl phases were prepared. The amount of organic moiety bound on silica support was determined from thermogravimetric curves of the modified silica gel. The specific surface areas of gels were obtained from nitrogen sorption measurement at –196°C. The effect on separation and selectivity of the different bonded-phenyl functional groups was studied. The selectivity of the phenyl-bonded silica gels was examined and compared with octadecyl (ODS) silica in liquid chromatography. Corresponding to the high surface concentration of functional groups, the capacity factors of solutes, normalized to unit surface area of the adsorbent, k/SBET were found to decrease in the sequence phenylmethyl>diphenyl>triphenyl. Polar solutes are retained in greater extent on the phenyl phases than on the ODS phase. 相似文献
107.
An uncertainty principle for Hankel transforms 总被引:1,自引:0,他引:1
Margit Rö sler Michael Voit 《Proceedings of the American Mathematical Society》1999,127(1):183-194
There exists a generalized Hankel transform of order on , which is based on the eigenfunctions of the Dunkl operator
For this transform coincides with the usual Fourier transform on . In this paper the operator replaces the usual first derivative in order to obtain a sharp uncertainty principle for generalized Hankel transforms on . It generalizes the classical Weyl-Heisenberg uncertainty principle for the position and momentum operators on ; moreover, it implies a Weyl-Heisenberg inequality for the classical Hankel transform of arbitrary order on
108.
Bauer I Gruner M Goutal S Habicher WD 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(16):4011-4016
Reaction of in,in-phosphite 1 with thiophosphoryl azide 2 affords in,in-dithiophosphate 3, in,in-thiophosphate-imidophosphate 4, and in,in-phosphite-imidophosphate 5. Compounds 4 and 5 are the first examples of the modification of in-bridgehead positions in macrobicyclic compounds with groups larger than methyl. The benzaldehyde arms of the in-substituent in 4 and 5 jut out of the cage bars. In 4 they are trapped between the macrocyclic arms to give the NMR spectra of a Cs-symmetric solution-state structure. In contrast, in 5 the benzaldehyde arms can move between the gaps of the cage. This results in 1H and 13C NMR spectra which are consistent for a compound with C3v symmetry. In,out-diimidophosphate 7 is obtained in moderate yield by reaction of in,out-phosphite 6 with thiophosphoryl azide 2. Its in-benzaldehyde moieties are not fixed between the cage arms, but can freely move from one gap to the next as is indicated by NMR measurements. 相似文献
109.
Herndl A Marzban G Kolarich D Hahn R Boscia D Hemmer W Maghuly F Stoyanova E Katinger H Laimer M 《Electrophoresis》2007,28(3):437-448
The importance of apple allergens has been repeatedly emphasized, and their presence has been confirmed both in pollen and in fruits. In the present study, a combination of proteomic tools have been used to build a complete allergen map of apple. The water-soluble fraction of an apple extract was precipitated using a phenol-based procedure and separated by 2-DE. Initially four previously classified allergens, Mal d 1, Mal d 2, Mal d 3 and Mal d 4, could be identified in Western blots with polyclonal rabbit antibodies directed to the four respective allergens, and subsequently matched to the bands recognized by several patient sera. Further, all four known apple allergens were localized on a 2-DE map and they were matched with spots recognized by sera of patients with different allergic patterns. Moreover, a new, putative allergen could be identified using MS. We evaluated the influence of post-translational modifications and the immunoreactivity under different analytical conditions. The comparison of different visualization methods for 2-DE gels and blots revealed that even very low concentrations of the intact epitopes are detectable by IgEs of patients, and therefore might be sufficient to trigger allergic symptoms in sensitized individuals. 相似文献
110.
Uwe B. Sleytr Paul Messner Dietmar Pum Margit Sra 《Angewandte Chemie (International ed. in English)》1999,38(8):1034-1054
An astonishingly broad application potential in biotechnology, biomimetics, and nanotechnology is revealed by studies on the structure, chemistry, biosynthesis, genetics, self-assembly, and function of supramolecular surface layers (S layers). These are monomolecular, crystalline assemblies of protein or glycoprotein subunits and represent one of the most commonly observed surface structures of prokaryotic cell envelopes (see schematic representation of an archaebacterial cell envelope). 相似文献