全文获取类型
收费全文 | 146篇 |
免费 | 3篇 |
专业分类
化学 | 85篇 |
力学 | 1篇 |
数学 | 33篇 |
物理学 | 30篇 |
出版年
2022年 | 2篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2016年 | 1篇 |
2015年 | 3篇 |
2013年 | 3篇 |
2012年 | 6篇 |
2011年 | 9篇 |
2010年 | 5篇 |
2009年 | 4篇 |
2008年 | 10篇 |
2007年 | 9篇 |
2006年 | 10篇 |
2005年 | 8篇 |
2004年 | 12篇 |
2003年 | 7篇 |
2002年 | 6篇 |
1999年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1989年 | 1篇 |
1986年 | 4篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1977年 | 8篇 |
1976年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1968年 | 3篇 |
1967年 | 1篇 |
1966年 | 2篇 |
1965年 | 1篇 |
1964年 | 3篇 |
1961年 | 1篇 |
排序方式: 共有149条查询结果,搜索用时 15 毫秒
51.
The ALIc-Model is a thermodynamically consistent pore filling model which allows microporous and mesoporous adsorptive gas/adsorbent systems to be described and compared directly. Examples of this will be shown on 20 systems. To this end, the standard-molar-free-enthalpy of adsorption is divided into a material-specific concentrate term and a geometric mixing term. At standard pressure and boiling temperature, all the curves of the standard-molar-free-enthalpy of adsorption as a function of the degree of pore filling end at the point of free-enthalpy of adsorption = 0 and at the degree of pore filling = 1. From these characteristic curves, finite molar values for free-enthalpy, enthalpy and entropy of adsorption can be calculated for the adsorbate-concentrate at a negligible degree of pore filling. Alkanes on activated carbons and CO2 on Zeolite 5A are used as demonstrating examples. These values and curves obtained from measurement of adsorption-isotherm-fields enable the interaction of the adsorbate with the adsorbent to be characterized, thus providing additional information for adsorption processes and for the development of adsorbents. 相似文献
52.
Egbert Harzheim 《Results in Mathematics》2002,41(1-2):114-117
V. Novák proved: If H is an ordered set and G ? H a subset such that every element of H is = supS = in f T for sets S, T ? G, then H has the same dimension as G. In particular this implies that the Dedekind-MacNeille closure of an ordered set S has the same dimension as S. In this paper we give a short proof of the latter statement. 相似文献
53.
Gabriele Kremser Oliver T. Hofmann Stefan Sax Stefan Kappaun Emil J. W. List Egbert Zojer Christian Slugovc 《Monatshefte für Chemie / Chemical Monthly》2008,139(3):223-231
Summary. 3,6-Diphenyl-9-hexyl-9H-carbazole derivatives bearing electron withdrawing groups, such as the formyl or the nitro-group in 4-positions of the phenyl
substituents, were prepared and characterized. Their photophysical properties were evaluated and compared with those of the
unsubstituted counterpart 3,6-diphenyl-9-hexyl-9H-carbazole. The electron withdrawing groups bearing compounds exhibited considerable red shifts of the absorption and the
emission maxima. While 3,6-di(4-nitrophenyl)-9-hexyl-9H-carbazole emitted in the orange region of the visible spectrum with its emission maximum peaking at 585 nm, 3,6-di(4-formylphenyl)-9-hexyl-9H-carbazole gave a pure blue emission with a luminescence quantum yield of 95% peaking at 450 nm. Observed features were explained
using quantum mechanical calculations and organic light emitting diodes using the formylphenyl substituted compound as emissive
layer were built demonstrating the practical applicability of this class of compounds. 相似文献
54.
Odd-even effects in self-assembled monolayers of omega-(biphenyl-4-yl)alkanethiols: a first-principles study 总被引:1,自引:0,他引:1
Heimel G Romaner L Brédas JL Zojer E 《Langmuir : the ACS journal of surfaces and colloids》2008,24(2):474-482
Conjugated molecules with a saturated alkyl linker between a thiol docking group and the pi-conjugated core have been shown to form self-assembled monolayers (SAMs) with a high degree of long-range order and uniformity. Additionally, pronounced odd-even effects have been observed in a number of properties characterizing these SAMs. We focus on omega-(biphenyl-4-yl)alkanethiols with n = 0-6 -(CH2)n- units deposited on Au(111) and investigate the microscopic origin of these odd-even effects in terms of the local sulfur-gold bonding geometry by employing first-principles calculations. An additional structural parameter, the torsion angle between the two phenyl rings in the biphenyl moiety, is identified and its relation to the experimentally observed odd-even effects is discussed. More importantly, we address relevant quantities for the application of these SAMs in molecular electronic devices, in particular, the modification of the work function of the underlying metal substrate and the energetic alignment of the molecular orbitals in the SAM with the Fermi level. While no clear trend emerges for the former, we find pronounced odd-even effects for the latter. Furthermore, the insertion of a single methylene unit between the biphenyl core and the thiol appears to largely decouple the valence electronic systems of the pi-conjugated segment and the gold substrate. Our results thus provide a solid theoretical basis for the interface energetics in this important class of systems. 相似文献
55.
Egbert Mujuni 《Mathematics in Computer Science》2008,1(4):701-708
Smooth 4-regular hamiltonian graphs are generalizations of cycle plus triangles graphs. It has been shown that both the independent
set and 3-colorability problems are NP-Complete in this class of graphs. In this paper we show that these problems are fixed
parameter tractable if we choose the number of inner cycles as parameter.
The reseach has been supported by International Science Programme (ISP) of Sweden, under the project titled “The Eastern African
Universities Mathematics Programme (EAUMP)”. 相似文献
56.
Pietka-Ottlik M Wójtowicz-Młochowska H Kołodziejczyk K Piasecki E Młochowski J 《Chemical & pharmaceutical bulletin》2008,56(10):1423-1427
Different N-substituted benzisoselenazol-3(2H)-ones, analogues of ebselen were designed as new antiviral and antimicrobial agents. We report their synthesis, chemical properties as well as study on biological activity against broad spectrum of pathogenic microorganisms (Staphylococcus aureus, Staphylococcus simulans, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Candida albicans, Aspergillus niger) and viruses (herpes simplex virus type 1 (HSV-1), encephalomyocarditis virus (EMCV), vesicular stomatitis virus (VSV)), in vitro. Most of them exhibited high activity against viruses (HSV-1, EMCV) and gram-positive bacteria strains (S. aureus, S. simulans), while their activity against gram-negative bacteria strains (E. coli, P. aeruginosa, K. pneumoniae) was substantially lower. Some of tested compounds were active against yeast C. albicans and filamentous fungus A. niger. 相似文献
57.
58.
59.
Oesterschulze E Kehrbusch P Radzio B Ilin EA Thyssen A Deitmer JW Kehrbusch J 《Lab on a chip》2012,12(7):1316-1319
The application of microresonators in fluids is predominantly constrained by the strong damping caused by the viscid drag and the additional inertia of the liquid in the interfacial layer. In this paper we propose the new concept of partial wetting that exploits another property of liquids, its surface energy, to adapt physically the interface of the microresonator to the liquid by the formation of a meniscus. First experiments performed with technically simple batch-fabricated prototypes validate the potential of partial wetting as a vital route to improve the quality factor of microresonators in viscid fluids to values up to 600 exceeding those of conventional microresonators by almost two orders of magnitude. 相似文献
60.
Mitochondrial oxygen tension can be measured in vivo by means of oxygen-dependent quenching of delayed fluorescence of protoporphyrin IX (PpIX). Here we demonstrate that mitochondrial PO(2) (mitoPO(2)) can be measured in the skin of a rat after topical application of the PpIX precursor 5-aminolevulinic acid (ALA). Calibration of mitoPO(2) measurements was done by comparison with simultaneous measurements of the cutaneous microvascular PO(2) This was done under three different conditions: in normal skin tissue, in nonrespiration skin tissue due to the application of cyanide, and in anoxic skin tissue after the ventilation with 100% nitrogen. The results of this study show that it is feasible to measure the mitoPO(2) after the topical application of ALA cream by means of the PpIX-triplet state lifetime technique. 相似文献