全文获取类型
收费全文 | 125篇 |
免费 | 4篇 |
专业分类
化学 | 90篇 |
晶体学 | 4篇 |
力学 | 1篇 |
数学 | 7篇 |
物理学 | 27篇 |
出版年
2023年 | 1篇 |
2021年 | 2篇 |
2020年 | 2篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 3篇 |
2014年 | 5篇 |
2013年 | 5篇 |
2012年 | 11篇 |
2011年 | 15篇 |
2010年 | 8篇 |
2009年 | 2篇 |
2008年 | 8篇 |
2007年 | 6篇 |
2006年 | 9篇 |
2005年 | 7篇 |
2004年 | 9篇 |
2002年 | 7篇 |
2001年 | 1篇 |
2000年 | 7篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1996年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1924年 | 2篇 |
排序方式: 共有129条查询结果,搜索用时 265 毫秒
71.
J.M. Palomares E. Iordanova E.M. van Veldhuizen L. Baede A. Gamero A. Sola J.J.A.M. van der Mullen 《Spectrochimica Acta Part B: Atomic Spectroscopy》2010
The axial profiles of the electron density ne and electron temperature Te of argon surfatron plasmas in the pressure range of 6–20 mbar and microwave power between 32 and 82 W have been determined using Thomson Scattering of laser irradiation at 532 nm. For the electron density and temperature we found values in the ranges 5 × 1018 < ne < 8 × 1019 m− 3 and 1.1 < Te < 2.0 eV. Due to several improvements of the setup we could reduce the errors of ne and Te down to 8% and 3%, respectively. It is found that ne decreases in the direction of the wave propagation with a slope that is nearly constant. The slope depends on the pressure but not on the power. Just as predicted by theories we see that increasing the power leads to longer plasma columns. However, the plasmas are shorter than what is predicted by theories based on the assumption that for the plasma-wave interaction electron–atom collisions are of minor importance (the so-called collisionless regime). The plasma vanishes long before the critical value of the electron density is reached. In contrast to what is predicted by the positive column model it is found that Te does not stay constant along the column, but monotonically increases with the distance from the microwave launcher. Increases of more than 50% over 30 cm were found. 相似文献
72.
Martín M Sola E Tejero S Andrés JL Oro LA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(15):4043-4056
Complexes [IrH2(eta6-C6H6)(PiPr3)]BF4 (1) and [IrH2(NCMe)3(PiPr3)]BF4 (2) are catalyst precursors for homogeneous hydrogenation of N-benzylideneaniline under mild conditions. Precursor 1 generates the resting state [IrH2{eta5-(C6H5)NHCH2Ph}(PiPr3)]BF4 (3), while 2 gives rise to a mixture of [IrH{PhN=CH(C6H4)-kappaN,C}(NCMe)2(PiPr3)]BF4 (4) and [IrH{PhN=CH(C6H4)-kappaN,C}(NCMe)(NH2Ph)(PiPr3)]BF4 (5), in which the aniline ligand is derived from hydrolysis of the imine. The less hindered benzophenone imine forms the catalytically inactive, doubly cyclometalated compound [Ir{HN=CPh(C6H4)-kappaN,C}2(NH2CHPh2)(PiPr3)]BF4 (6). Hydrogenations with precursor 1 are fast and their reaction profiles are strongly dependent on solvent, concentrations, and temperature. Significant induction periods, minimized by addition of the amine hydrogenation product, are commonly observed. The catalytic rate law (THF) is rate = k[1][PhN=CHPh]p(H2). The results of selected stoichiometric reactions of potential catalytic intermediates exclude participation of the cyclometalated compounds [IrH{PhN=CH(C6H4)-kappaN,C}(S)2(PiPr3)]BF4 [S = acetonitrile (4), [D6]acetone (7), [D4]methanol (8)] in catalysis. Reactions between resting state 3 and D2 reveal a selective sequence of deuterium incorporation into the complex which is accelerated by the amine product. Hydrogen bonding among the components of the catalytic reaction was examined by MP2 calculations on model compounds. The calculations allow formulation of an ionic, outer-sphere, bifunctional hydrogenation mechanism comprising 1) amine-assisted oxidative addition of H2 to 3, the result of which is equivalent to heterolytic splitting of dihydrogen, 2) replacement of a hydrogen-bonded amine by imine, and 3) simultaneous H delta+/H delta- transfer to the imine substrate from the NH moiety of an arene-coordinated amine ligand and the metal, respectively. 相似文献
73.
L. Roso J. San Román I. J. Sola C. Ruiz V. Collados J. A. Pérez C. Méndez J. R. Vázquez de Aldana I. Arias L. Plaja 《Applied Physics A: Materials Science & Processing》2008,92(4):865-871
One of the problems when increasing the intensity of a femtosecond laser pulse is the propagation of the beam. As the intensity
increases nonlinear effects begin to play a significant role. When arriving to the terawatt domain, nonlinear effects and
filamentation give rise to a new phenomenology in the propagation. The aim of this paper is to analyze new possibilities to
control the beam shape to Taylor the interaction of the beam with the target at large distances. 相似文献
74.
Sola Conde Luis Eduardo; Wisniewski Jaroslaw A. 《Proceedings London Mathematical Society》2004,89(2):273-290
A line bundle over a complex projective variety is called bigand 1-ample if a large multiple of it is generated by globalsections and a morphism induced by the evaluation of the spanningsections is generically finite and has at most 1-dimensionalfibers. A vector bundle is called big and 1-ample if the relativehyperplane line bundle over its projectivisation is big and1-ample. The main theorem of the present paper asserts that any complexprojective manifold of dimension 4 or more, whose tangent bundleis big and 1-ample, is equal either to a projective space orto a smooth quadric. Since big and 1-ample bundles are almostample, the present result is yet another extension of the celebratedMori paper Projective manifolds with ample tangent bundles(Ann. of Math. 110 (1979) 593606). The proof of the theorem applies results about contractionsof complex symplectic manifolds and of manifolds whose tangentbundles are numerically effective. In the appendix we re-provethese results. 2000 Mathematics Subject Classification 14E30,14J40, 14J45, 14J50. 相似文献
75.
The calculated rate of events in some of the existing solar neutrino detectors is directly proportional to the rate of the
7Be(p, γ)8B reaction measured in the laboratory at low energies. However, the low-energy cross sections of this reaction are quite uncertain
as various measurements differ from each other by 30–40%. The Coulomb dissociation process which reverses the radiative capture
by the dissociation of 8B in the Coulomb field of a target, provides an alternate way of accessing this reaction. While this method has several advantages
(like large breakup cross sections and flexibility in the kinematics), the difficulties arise from the possible interference
by the nuclear interactions, uncertainties in the contributions of the various multipoles and the higher order effects, which
should be considered carefully. We review the progress made so far in the experimental measurements and theoretical analysis
of the breakup of 8B and discuss the current status of the low-energy cross sections (or the astrophysical S-factor) of the 7Be(p, γ)8B reaction extracted therefrom. The future directions of the experimental and theoretical investigations are also suggested.
Work supported by EPSRC, UK, grant nos J/95867 and L/94574. 相似文献
76.
Marina Cretich Daniela Breda Francesco Damin Marta Borghi Laura Sola Selim M. Unlu Samuele E. Burastero Marcella Chiari 《Analytical and bioanalytical chemistry》2010,398(4):1723-1733
We have recently introduced a silicon substrate for high-sensitivity microarrays, coated with a functional polymer named copoly(DMA-NAS-MAPS).
The silicon dioxide thickness has been optimized to produce a fluorescence intensification due to the optical constructive
interference between the incident and reflected lights of the fluorescent radiation. The polymeric coating efficiently suppresses
aspecific interaction, making the low background a distinctive feature of these slides. Here, we used the new silicon microarray
substrate for allergy diagnosis, in the detection of specific IgE in serum samples of subjects with sensitizations to inhalant
allergens. We compared the performance of silicon versus glass substrates. Reproducibility data were measured. Moreover, receiver-operating
characteristic (ROC) curves were plotted to discriminate between the allergy and no allergy status in 30 well-characterized
serum samples. We found that reproducibility of the microarray on glass supports was not different from available data on
allergen arrays, whereas the reproducibility on the silicon substrate was consistently better than on glass. Moreover, silicon
significantly enhanced the performance of the allergen microarray as compared to glass in accurately identifying allergic
patients spanning a wide range of specific IgE titers to the considered allergens. 相似文献
77.
Recently, control over the bond length of a diatomic molecule with the use of parabolic chirped pulses was predicted on the basis of numerical calculations [Chang; et al. Phys. Rev. A 2010, 82, 063414]. To achieve the required bond elongation, a laser scheme was proposed that implies population inversion and vibrational trapping in a dissociative state. In this work we identify two regimes where the scheme works, called the strong and the weak adiabatic regimes. We define appropriate parameters to identify the thresholds where the different regimes operate. The strong adiabatic regime is characterized by a quasi-static process that requires longer pulses. The molecule is stabilized at a bond distance and at a time directly controlled by the pulse in a time-symmetrical way. In this work we analyze the degree of control over the period and elongation of the bond as a function of the pulse bandwidth. The weak adiabatic regime implies dynamic deformation of the bond, which allows for larger bond stretch and the use of shorter pulses. The dynamics is anharmonic and not time-symmetrical and the final state is a wave packet in the ground potential. We show how the vibrational energy of the wave packet can be controlled by changing the pulse duration. 相似文献
78.
Self-compressed (SC) pulses have been achieved through the filamentation process in air without any additional dispersion compensation, using the input pulse chirp as the control parameter. For any studied input pulse energy (3-5 mJ), we have found two opposite sign input group-delay dispersion values for which SC pulses can be achieved systematically. In addition, we have observed that the energy coupled into the inner core of the filament is always of the order of 20% of the total input pulse energy, which opens the way to a scalable technique to obtain intense short pulses directly from the filamentation process. 相似文献
79.
A laser scheme using a periodically changing frequency is used to induce oscillations of the internuclear motion, which are quantum analogs of classical vibrations in diatomic molecules. This is what we call the periodic laser adiabatic manipulation of the bond, or p-LAMB scheme. In p-LAMB, the carrier frequency of the laser must vary periodically from the blue to the red of a photodissociation band and backwards, following for instance a cosine-dependent frequency of period τ(c). In the adiabatic regime the dynamics is fully time-reversible. The amplitude of the internuclear oscillation is controlled by the pulse frequency ω(t), while τ(c) determines the duration (or period) of the bond oscillation. In the presence of efficient dipole coupling, the bandwidth of the pulse is the main constraint to the maximum bond stretch that can be obtained. Before the onset of the adiabatic regime the dynamics are more complex, showing dispersion of the vibrational wave packet and anharmonic deformation of the bond. However, the nonadiabatic effects are mostly canceled and full revivals are observed at certain multiples of τ(c). 相似文献
80.
A. Gregoire E. Carpiaux E. Larose und Th. Sola 《Fresenius' Journal of Analytical Chemistry》1924,64(8-9):342
Ohne Zusammenfassung 相似文献