全文获取类型
收费全文 | 290篇 |
免费 | 6篇 |
国内免费 | 1篇 |
专业分类
化学 | 133篇 |
晶体学 | 6篇 |
力学 | 12篇 |
数学 | 15篇 |
物理学 | 131篇 |
出版年
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 4篇 |
2014年 | 6篇 |
2013年 | 5篇 |
2012年 | 11篇 |
2011年 | 6篇 |
2010年 | 4篇 |
2009年 | 3篇 |
2008年 | 6篇 |
2007年 | 15篇 |
2006年 | 8篇 |
2005年 | 3篇 |
2004年 | 6篇 |
2003年 | 5篇 |
2002年 | 5篇 |
2001年 | 7篇 |
2000年 | 8篇 |
1999年 | 13篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 9篇 |
1993年 | 5篇 |
1992年 | 11篇 |
1991年 | 7篇 |
1990年 | 11篇 |
1989年 | 7篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 11篇 |
1980年 | 6篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 9篇 |
1976年 | 7篇 |
1975年 | 9篇 |
1974年 | 8篇 |
1970年 | 3篇 |
1935年 | 2篇 |
1909年 | 1篇 |
排序方式: 共有297条查询结果,搜索用时 15 毫秒
81.
Photophysics of Acetophenone Interacting with DNA: Why the Road to Photosensitization is Open
下载免费PDF全文
![点击此处可从《Photochemistry and photobiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Miquel Huix‐Rotllant Elise Dumont Nicolas Ferré Antonio Monari 《Photochemistry and photobiology》2015,91(2):323-330
Deoxyribonucleic acid photosensitization, i.e. the photoinduced electron‐ or energy‐transfer of chromophores interacting with DNA, is a crucial phenomenon that triggers important DNA lesions such as pyrimidine dimerization, even upon absorption of relatively low‐energy radiation. Oxidative lesions may also be produced via the photoinduced production of reactive oxygen species. Aromatic ketones, and acetophenone in particular, are well known for their sensitization effects. In this contribution we model the structural and dynamical properties of the acetophenone/DNA aggregates as well as their spectroscopic and photophysical properties using high‐level hybrid quantum mechanics/molecular mechanics methods. We show that the key steps of the photochemistry of acetophenone in gas phase are conserved in the macromolecular environment and thus an ultrafast singlet–triplet conversion of acetophenone is expected prior to the transfer to DNA. 相似文献
82.
Juan C. López-Realpozo Reinaldo Rodríguez-Ramos Raúl Guinovart-Díaz Julián Bravo-Castillero J.A. Otero Federico J. Sabina F. Lebon Serge Dumont Igor Sevostianov 《International Journal of Solids and Structures》2014
In this contribution, effective elastic moduli are obtained by means of the asymptotic homogenization method, for oblique two-phase fibrous periodic composites with non-uniform imperfect contact conditions at the interface. This work is an extension of previous reported results, where only the perfect contact for elastic or piezoelectric composites under imperfect spring model was considered. The constituents of the composites exhibit transversely isotropic properties. A doubly periodic parallelogram array of cylindrical inclusions under longitudinal shear is considered. The behavior of the shear elastic coefficient for different geometry arrays related to the angle of the cell is studied. As validation of the present method, some numerical examples and comparisons with theoretical results verified that the present model is efficient for the analysis of composites with presence of imperfect interface and parallelogram cell. The effect of the non uniform imperfection on the shear effective property is observed. The present method can provide benchmark results for other numerical and approximate methods. 相似文献
83.
Especially in the last decade, a vast number of papers on Se and its role in health issues have been published. This review
gives a brief, critical overview of the main analytical findings reported in these papers. Of particular interest is the Se
content in different food sources worldwide and the extent to which their consumption is reflected in the Se content of human
tissues and body fluids. Several food sources, both natural (Brazil nuts, garlic, Brassica juncea) and Se-enriched (yeast-based supplements), are discussed as to origin, characteristics, Se metabolism and impact of their
consumption on the human body. The continuous development of new and improvement of existing analytical techniques has provided
different powerful tools to unravel the Se species and their function. An up-to-date literature study on Se speciation analysis
is given, illustrating how analytical chemistry in its different facets aids in the identification of Se compounds and provides
insight into the complete metabolic pathway of Se throughout the human body. This review includes a detailed image of the
current state-of-the-art of Se speciation analysis in these food sources and in human tissues and body fluids. 相似文献
84.
E. A. De Wolf J. J. Dumont M. Van Immerseel F. Verbeure F. Grard D. Denegri C. Lewin I. V. Ajinenko P. V. Chliapnikov L. N. Gerdyukov V. V. Kniazev V. N. Riadovikov V. A. Uvarov CERN-Soviet Union Collaboration French-Soviet Union Collaboration 《Zeitschrift fur Physik C Particles and Fields》1981,8(3):189-197
Results are presented on two-particle inclusive production inK + p interactions at 32 GeV/c. We study thex 1,2=x 1+x 2 dependence of invariant structure functions of (ππ)-pairs and compare them to single particle inclusive distributions in the fragmentation regions. Distributions of particles observed at Feynmanx 2 in association with various “trigger” particles or systems atx 1 in the same hemisphere are dicussed in terms of the reduced variable \(\tilde x_2 = x_2 /(1 - |x_1 |)\) . We further present absolute production rates and production ratios of π+'s and π?'s associated with π±,K s 0 , Λ, \(\bar \Lambda \) ,K *+ (890), (K s 0 π+), and (π+ π?)-triggers, and compare them with qualitative predictions of the quark recombination model. Forwardbackward correlations between (K s 0 π±), (K s 0 ,p), (Λ, π?), \((\bar \Lambda \pi ^ \pm )\) , and (p, π?) pairs are also discussed. 相似文献
85.
Alain Krief Thierry Van Wemmel Martine Redon Willy Dumont Cathy Delmotte 《Angewandte Chemie (International ed. in English)》1999,38(15):2245-2248
The addition of elemental selenium to organolithium compounds 1 or organic selenates 2 gives organic diselenolates 3 . The reactions proceed by the insertion of two selenium atoms into the carbon–metal bonds or of one selenium atom into a selenolate. Evidence for the existence of n-butyldisilenol has also been obtained. 相似文献
86.
87.
D.M. De Castro Rizzo E. Bozek S. Cavallaro B. Delaunay J. Delaunay H. Dumont M.G. Saint-Laurent F. Terrasi 《Nuclear Physics A》1984,427(1):151-172
Fusion excitation functions for the systems 12C + 46, 48, 50Ti, 28, 30Si + 30Si and 18O + 44Ca have been determined at energies near and below the Coulomb barrier. Inelastic excitation functions for the targets 48, 50Ti and 44Ca have been also measured in the same energy range. The absolute cross sections were obtained by in-beam γ-ray spectroscopy technique using a rotating target. Fusion cross sections ranging in magnitude from ~ 0.3 mb to ~ 1300 mb were determined with an accuracy of 10–20%. The fusion excitation functions are analysed in the frame of a semiclassical barrier-penetration model. From the analysis, the height, the radius and the curvature of the fusion barrier for the different systems are extracted. The fusion cross sections are compared with the calculations performed using different heavy-ion potentials. The enhancement of the cross sections at sub-Coulomb energies can be reproduced with a one-dimensional barrier-penetration model taking into account the zero-point motion of the surface of the reaction partners. The fusion cross section of the system 18O + 44Ca is well reproduced by quantum-mechanical calculations, introducing a new degree of freedom taking into account the formation of a neck during the fusion process. 相似文献
88.
89.
E. Chikoidze Y. Dumont H.J. von Bardeleben J. Gleize O. Gorochov 《Journal of magnetism and magnetic materials》2007
We studied the influence of thermal annealing in oxygen on the physical properties of MOCVD grown Zn1−xMnxO thin layers. Annealing in the 300–1000 °C temperature range modifies both lattice parameters and magnetic properties of the layers. Correlation of the results from X-ray diffraction, EPR studies and Raman spectroscopy indicate a modification of the Mn+2-related features in the ZnO matrix. 相似文献
90.
Donagh O’Mahony Thomas Dumont Thomas Lippert Alexander Wokaun 《Applied Surface Science》2007,254(4):811-815
Laser ablation is widely used to assist in the fabrication of prototype lithium manganate (LiMn2O4) thin film structures for Li-ion battery electrodes via the pulsed laser deposition technique. However, films can be considerably Li and/or O deficient, depending the deposition conditions used. Here we present data on the ionic component of laser-produced plasma in laser ablation of lithium manganate with ns excimer laser. Plasma was monitored using an electrical Langmuir ion probe, in time-of-flight mode in conjunction with mass spectrometry to identify the dominant ionic species. Ablation in vacuum at ∼2.5 J cm−2 revealed the plasma's ionic component was composed primarily of singly charged Li and Mn ions. The time-of-flight data indicates significant deceleration of the plasma when ablation is carried out in an oxygen background gas pressure of the order of 10 Pa. The implications for thin film growth are considered in terms of the possible gas phase interactions and/or thin film re-sputtering yield. 相似文献