全文获取类型
收费全文 | 77篇 |
免费 | 3篇 |
专业分类
化学 | 23篇 |
数学 | 5篇 |
物理学 | 52篇 |
出版年
2020年 | 1篇 |
2019年 | 2篇 |
2016年 | 3篇 |
2015年 | 2篇 |
2013年 | 5篇 |
2012年 | 5篇 |
2011年 | 1篇 |
2010年 | 4篇 |
2009年 | 2篇 |
2007年 | 4篇 |
2006年 | 5篇 |
2005年 | 2篇 |
2003年 | 1篇 |
2002年 | 2篇 |
2001年 | 3篇 |
1998年 | 2篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1910年 | 1篇 |
排序方式: 共有80条查询结果,搜索用时 15 毫秒
31.
E. Costa L. Piro P. Soffitta E. Massaro G. Matt G. C. Perola S. Giarrusso G. La Rosa G. Manzo A. Santangelo T. Hamilton P. Kaaret C. Martin R. Novick P. Shaw E. Silver R. Elsner M. Weisskopf G. Chanan G. Fraser I. Lapshov R. Sunyaev 《Il Nuovo Cimento C》1992,15(5):791-799
Summary TheStellar X-ray Polarimeter (SXRP) is a focal plane instrument which will be flown on the SPECTRUM-X-Gamma mission in 1993. The polarimeter is composed
of two separate instruments: the first exploits the dependence on the polarization of the Bragg reflection from a graphite
crystal, and of the Thomson scattering from a metallic lithium target. The second instrument makes use of the recently discovered
polarization dependence of X-ray photoemission from CsI. The SXRP will permit sensitive measurements of several hundreds of
known X-ray sources. X-ray polarization measurements will allow us to constrain the physical mechanisms and the geometries
of several classes of galactic X-ray sources, such as X-ray pulsars, black-hole candidates and supernova remnants. Moreover,
and for the first time, SXRP will be able to perform highly sensitive measurements of the brightest extragalactic sources.
Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990. 相似文献
32.
C. G. Beneventano I. V. Fialkovsky E. M. Santangelo 《Theoretical and Mathematical Physics》2016,187(1):497-510
We establish some properties of the zeros of sums and differences of contiguous Bessel functions of the first kind. As a by-product, we also prove that the zeros of the derivatives of Bessel functions of the first kind of different orders are interlaced the same way as the zeros of the Bessel functions themselves. As a physical motivation, we consider gated graphene nanodots subject to Berry–Mondragon boundary conditions. We determine the allowed energy levels and calculate the mean charge at zero temperature. We discuss its dependence on the gate (chemical) potential in detail and also comment on the effect of temperature. 相似文献
33.
Controlled surface functionalization of carbon nanotubes by nitric acid vapors generated from sub‐azeotropic solution 下载免费PDF全文
Saveria Santangelo 《Surface and interface analysis : SIA》2016,48(1):17-25
Controlled surface modification of nanocarbons is crucial for their use in applications. The paper deals with the functionalization of carbon nanotubes (CNTs) with HNO3 vapors. Sub‐azeotropic HNO3 + H2O + Mg(NO3)2 solution is used for the generation of nitric acid vapors. Because this approach allows tuning the HNO3 concentration in the vapor phase, the effect of its variation on the surface chemistry and structural properties of the CNTs is investigated. A combination of analytical techniques is applied to evaluate oxidation extent of the CNT surface, selectivity towards the formation of carboxyl groups compared with other oxygenated functionalities, and CNT integrity. The comparison with liquid‐phase functionalization in H2SO4 + HNO3 mixture (1 : 3–3 : 1 v/v), conventionally utilized for oxidizing CNTs, shows that vapor‐phase functionalization affords greater surface oxygen uptakes and higher selectivity towards the formation of carboxyl groups, with smaller tube damage; more importantly, it evidences that, regardless of the method and conditions chosen, the selectivity towards carboxyl groups increases linearly with the surface oxygen concentration. The presented results prove that the product of HNO3 concentration in the vapor‐phase (25–93 wt%) and vapor‐phase functionalization duration (0.5–5 h) controls the surface oxygen concentration. A simple rate model is proposed to account for its increase. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
34.
Santangelo G Matteo AD Müller-Plathe F Milano G 《The journal of physical chemistry. B》2007,111(11):2765-2773
This paper introduces a systematic procedure to obtain well-relaxed atomistic melt structures from mesocale models of vinyl polymers based on sequences of diads. Following the methodology introduced by Milano and Müller-Plathe [J. Phys. Chem. B. 2005, 109, 18609], coarse-grain models consisting of sequences of superatoms of two different types meso and racemo have been used to relax mesocale melts of atactic and syndiotactic polystyrene. The proposed method, based on a fully geometrical approach, does not involve expensive potential energy and force evaluations and allows a very fast and efficient reconstruction of the atomistic detail. The method, successfully tested against experimental data, allows us to obtain all atom models of both stereoregular and stereoirregular polymers and opens the possibility of relaxing large molecular weight melts of vinyl chains. 相似文献
35.
S. Santangelo G. Messina G. Faggio M. Lanza C. Milone 《Journal of Raman spectroscopy : JRS》2011,42(4):593-602
Commercially available and laboratory‐prepared multi‐walled carbon nanotubes (MWCNTs) are systematically investigated by the use of micro‐Raman spectroscopy (MRS), thermogravimetric analysis (TGA) and complementary techniques (scanning electron microscopy (SEM) and transmission electron microscopy (TEM)) with the aim of establishing a standardised post‐growth diagnostic protocol for the assessment of their overall crystalline quality. By studying a set of ‘reference’ samples, clear correlations are evidenced between the Raman graphitisation indexes (D/G, G′/G and G′/D intensity ratios) commonly adopted to describe the crystalline arrangement of nanotubes, and their reactivity towards oxygen, as measured by the apparent activation energy needed for their oxidation, inferred from the kinetic analysis in quasi‐isothermal conditions. The higher the crystalline perfection degree, the higher the energy needed for oxidising them. The efficacy of the found correlations in indirectly assessing the reactivity of nanotubes prepared under different conditions is successfully demonstrated by the use of a second set of samples. The physical meaning and range of validity of the shown correlations are further discussed. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
36.
We study, numerically and theoretically, defects in an anisotropic liquid that couple to the extrinsic geometry of a surface. Though the intrinsic geometry tends to confine topological defects to regions of large Gaussian curvature, extrinsic couplings tend to orient the order along the local direction of maximum or minimum bending. This additional frustration is generically unavoidable, and leads to complex ground-state thermodynamics. Using the catenoid as a prototype, we show, in contradistinction to the well-known effects of intrinsic geometry, that extrinsic curvature expels disclinations from the region of maximum curvature above a critical coupling threshold. On catenoids lacking an "inside-outside" symmetry, defects are expelled altogether above a critical neck size. 相似文献
37.
We study the cylinder to sphere morphological transition of diblock copolymers in aqueous solution with a hydrophobic block
and a charged block. We find a metastable undulated cylinder configuration for a range of charge and salt concentrations which,
nevertheless, occurs above the threshold where spheres are thermodynamically favorable. By modeling the shape of the cylinder
ends, we find that the free-energy barrier for the transition from cylinders to spheres is quite large and that this barrier
falls significantly in the limit of high polymer charge and low solution salinity. This suggests that observed undulated cylinder
phases are kinetically trapped structures. 相似文献
38.
Bryan JD Santangelo SA Keveren SC Gamelin DR 《Journal of the American Chemical Society》2005,127(44):15568-15574
Colloidal Co(2+)- and Cr(3+)-doped TiO(2) nanorods and nanocrystals were synthesized and studied by X-ray powder diffraction, electronic absorption spectroscopy, magnetic circular dichroism spectroscopy, magnetic susceptibility, and transmission electron microscopy. The nanorods were paramagnetic as colloids but showed room-temperature ferromagnetism when spin-coated aerobically into films. Crystalline domain size, thermal annealing, and dopant or defect migration are not the dominating factors converting the doped TiO(2) nanocrystals from the paramagnetic state to the ferromagnetic state. The most important factor for activating ferromagnetism is found to be the creation of grain boundary defects, proposed to be oxygen vacancies at nanocrystal fusion interfaces. These defects are passivated and the ferromagnetism destroyed by further aerobic annealing. These results not only help elucidate the origins of the TM(n+):TiO(2) DMS ferromagnetism but also represent an advance toward the controlled manipulation of high-T(C) DMS ferromagnetism using external chemical perturbations. 相似文献
39.
M.G. Donato G. Faggio M. Marinelli G. Messina E. Milani A. Paoletti S. Santangelo A. Tucciarone G. Verona Rinati 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,20(1):133-139
High quality synthetic diamonds were grown on single-crystal silicon by microwave plasma enhanced chemical vapour deposition
(CVD). A careful optimisation of both the experimental setup and the growth parameters was necessary before that the achievement
of the best results was made possible. The films were deposited using a CH4-H2 gas mixture at methane concentrations variable in the range 0.6-2.2%, while the substrate temperature was fixed at 750 °C. Raman spectroscopy and photoluminescence (PL) were utilised to monitor the quality of the deposited films and to study
the spatial distribution of defects, respectively. Micro-Raman analysis shows that linewidths of the diamond peak lower than
2.4 cm-1 can be easily measured at the growth surface, indicating that the crystalline quality of individual grains is comparable
to that of the best natural diamonds. The excellent phase purity of the diamond microcrystals at the growth surface is witnessed
by the complete absence of any non-diamond carbon feature and by a very weak luminescence background in the 1.6-2.4 eV spectral
range. A worsening of the quality of the diamond particles is found moving from the growth surface towards the film-substrate
interface. A photoluminescence feature at about 1.68 eV, commonly associated to Si impurities, is distinctly observed as the
exciting laser beam is focused close to the interface. A progressive degradation of the global quality of the films is found
with increasing methane concentration in the gas mixture, as witnessed by an increased PL background in the films grown at
higher methane concentrations.
Received 24 November 2000 相似文献
40.
In this paper we present the science potential of the enhanced X-ray Timing and Polarimetry(eXTP) mission for studies of strongly magnetized objects. We will focus on the physics and astrophysics of strongly magnetized objects, namely magnetars, accreting X-ray pulsars, and rotation powered pulsars. We also discuss the science potential of eXTP for QED studies. Developed by an international Consortium led by the Institute of High Energy Physics of the Chinese Academy of Sciences, the eXTP mission is expected to be launched in the mid 2020s. 相似文献