全文获取类型
收费全文 | 708篇 |
免费 | 20篇 |
国内免费 | 5篇 |
专业分类
化学 | 453篇 |
力学 | 13篇 |
数学 | 120篇 |
物理学 | 147篇 |
出版年
2023年 | 11篇 |
2022年 | 35篇 |
2021年 | 32篇 |
2020年 | 11篇 |
2019年 | 16篇 |
2018年 | 27篇 |
2017年 | 9篇 |
2016年 | 39篇 |
2015年 | 22篇 |
2014年 | 29篇 |
2013年 | 47篇 |
2012年 | 50篇 |
2011年 | 46篇 |
2010年 | 33篇 |
2009年 | 29篇 |
2008年 | 47篇 |
2007年 | 40篇 |
2006年 | 32篇 |
2005年 | 22篇 |
2004年 | 28篇 |
2003年 | 30篇 |
2002年 | 17篇 |
2001年 | 7篇 |
2000年 | 8篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1968年 | 1篇 |
1960年 | 1篇 |
1948年 | 1篇 |
1943年 | 2篇 |
1935年 | 1篇 |
1873年 | 1篇 |
排序方式: 共有733条查询结果,搜索用时 0 毫秒
671.
Mihaela Badea Laura Micheli Maria Cristina Messia Tiziana Candigliota Emanuele Marconi Toby Mottram Maria Velasco-Garcia Danila Moscone Giuseppe Palleschi 《Analytica chimica acta》2004,520(1-2):141-148
A flow-injection immunoassay (FI-IA) method with amperometric detection for aflatoxin M1 (AFM1) determination in milk has been developed. The first step consists in an incubation of the sample containing AFM1 (Ag) with fixed amounts of anti-AFM1 antibody (Ab) and of the tracer (Ag*, AFM1 covalently coupled to HRP) until equilibrium is reached. In this mixture a competition occurs between Ag and Ag* for the Ab. The mixture is then injected into a flow system where the separation of the free tracer (Ag*) and the antibody-bound tracer (AbAg*) is performed in a column with immobilized Protein G. The antigen–antibody complexes are retained in the column due to the high affinity of the Protein G for the antibody. The activity of the eluted enzyme label is then amperometrically detected.
The immunoassay was optimised relative to conditions for antibody–antigen incubation (pH, incubation time, ionic strength, temperature) and enzymatic label detection. This method showed a dynamic concentration range between 20 and 500 ppt AFM1, a low detection limit (11 ppt), good reproducibility (RSD < 8%) and a high throughput (six samples per hour in triplicate). Different milk samples were analysed and the results were in good agreement with those obtained by HPLC using the AOAC 2000.08 method. 相似文献
672.
Emanuela Di Cola Thomas A. Waigh Ralph H. Colby 《Journal of Polymer Science.Polymer Physics》2007,45(7):774-785
Light scattering techniques, video particle‐tracking microrheology, and bulk rheology were employed to examine the structure and dynamics of a series of alternating sodium maleate copolymers with moderately hydrophobic comonomers (diisobutylene, styrene, and isobutylene) in aqueous solutions. The scaling dependence of the specific viscosity (ηsp) on the polyelectrolyte concentration (c) was studied with and without added salt; similar trends were found in both conventional rheology and particle‐tracking microrheology measurements, showing good performance of the technique with flexible polyelectrolytes. Furthermore, with dynamic light scattering performed in high added salt conditions, we examined the behavior of the amplitude of the fast mode, which is in agreement with scaling predictions. In contrast, the slow modes are not understood and display three separate behaviors for the wavevector q dependence of the decay rate (Γ), depending on the comonomer; superdiffusive (Γ ~ q2.7, isobutylene) possibly because of sticky aggregates, wavevector independent (Γ ~ q0, styrene) most likely because of coupled polyion‐ion diffusion and diffusive (Γ ~ q2.0, diisobutylene) presumably because these aggregates are not sticky. The hydrophobicity of the comonomer appears to switch the aggregation process between “open,” “closed,” and “non” association for isobutylene, diisobutylene, and styrene respectively. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 774–785, 2007 相似文献
673.
Emanuele Coccia Fabio Marinetti Enrico Bodo Dr. Francesco A. Gianturco Prof. 《Chemphyschem》2008,9(9):1323-1330
Variational and diffusion Monte Carlo (VMC and DMC) calculations are presented for anionic electrolytes solvated in 4He. The electrolytes have the general structure X?(He)N, with X=F, Cl, Br and I, and N varying up to 40 (41 for I?). The overall interaction potential is obtained from accurate ab initio data for the two‐body components and then using the sum‐of‐potentials approximation. Our computational scheme is a robust procedure, giving us accurate trial wavefunctions that can be used to perform high‐quality DMC calculations. The results indicate very marked delocalization and permanence of the liquid‐like quantum features of the solvent adatoms surrounding the anionic impurities. This finding stands in contrast to the more structured, solid‐like behavior of the quantum solutions with alkali metal cations embedded in He nanodroplets. While other negatively charged species such as H? have shown an overall repulsive interaction with He, the present calculations clearly indicate that the halogen anions remain solvated within liquid‐like solvent “bubbles” of species‐dependent size. 相似文献
674.
Christian Mayer Emmanuel Stiakakis Emanuela Zaccarelli Christos N. Likos Francesco Sciortino Piero Tartaglia Hartmut Löwen Dimitris Vlassopoulos 《Rheologica Acta》2007,46(5):611-619
We examine the rheological transition from an arrested to a fluid state for different mixtures of star polymers with varying
functionality and size ratios. As a general trend, we find that addition of smaller star polymers in an arrested, concentrated
solution of larger ones brings about melting of the large star glass. At the same time, the dependence of the amount of additives
needed to melt the glass has a nontrivial dependence on the size ratio. Theoretical analysis, based on effective interactions
and Mode Coupling Theory, reproduces the experimental results and helps identify two distinct types of glasses in the composite
system.
This paper was presented at Annual European Rheology Conference (AERC) held in Hersonisos, Crete, Greece, April 27–29, 2006. 相似文献
675.
676.
Simone Alidori Filippo Cocchioni Giancarlo Falcioni Donatella Fedeli Gaia Emanuela Gioia Lobbia Marilena Mancini Maura Pellei Carlo Santini 《应用有机金属化学》2008,22(1):43-48
Triorganotin(IV) derivatives containing the anionic ligand bis(1‐methyl‐1H‐imidazol‐2‐ylthio)acetate [(S‐tim)2CHCO2]− were synthesized from the reaction between R3SnCl acceptors (R = Me and Ph) and the sodium salt of the ligand. Mono‐nuclear complexes of the type [(S‐tim)2CHCO2]SnR3 were obtained, which were fully characterized by elemental analyses and FT‐IR in the solid state, and by NMR (1H, 13C and 119Sn) spectroscopy and electrospray ionization mass in solution. The toxic effects shown by these compounds on trout erythrocyte components showed that the toxicity of the organotin(IV) complexes depends on the nature and on the lipophilicity of the substituents on the metal centre. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
677.
Emanuela Tamburri Francesco Toschi Valeria Guglielmotti Elisa Scatena Silvia Orlanducci Maria Letizia Terranova 《Journal of nanoparticle research》2009,11(6):1311-1319
Ordered arrays of carbon nanotubes (CNT) have been coated by Ni nanoparticles and Ni thin films by using the chronoamperometry
technique for nickel reduction. Two different kinds of nanotube arrays have been used: aligned bundles of CNT grown on Si
substrates by chemical vapour deposition (CVD) and networks of CNT bundles positioned via a dielectrophoretic post-synthesis
process between the electrodes of a multifinger device. The morphology and structure of the Ni-coated CNT bundles have been
characterized by field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). By changing the parameters
of the electrochemical process, it is possible to modulate the morphological characteristics of the Ni deposits, which can
be obtained in form of nanoparticles uniformly distributed along the whole length of the CNT bundles or of Ni thin films.
A qualitative study of the nucleation and growth mechanism of Ni onto CNT has been performed using the theoretical model for
diffusion-controlled electrocrystallization, and a correlation between growth mechanism and samples morphology is presented
and discussed. The possibility to maintain the architecture of the pristine nanotube deposits after the Ni coating process
opens new perspectives for integration of CNT/Ni systems in magnetic and spintronics devices. 相似文献
678.
Francesca Caramia Ada Francia Caterina Mainero Emanuele Tinelli Maria Giuseppina Palmieri Claudio Colonnese Luigi Bozzao Maria Donatella Caramia 《Magnetic resonance imaging》2009
Functional magnetic resonance imaging (fMRI) research has shown that brain arteriovenous malformations (AVMs) lead to reorganization of cortical motor areas. Since it is known that blood oxygenation level-dependent signal in fMRI may be influenced by the hemodynamic perturbation associated with the presence of the AVM, in the present study, a combined exploration with fMRI and transcranial magnetic stimulation was performed in a patient with a right rolandic AVM in order to explore the relationship between neuronal and hemodynamic activity. The combined protocol of investigation adopted in this study was able to provide significant information regarding neuronal activity of the different cortical areas that partake to post-lesional reorganization. 相似文献
679.
Giovanni Batignani Emanuele Pontecorvo Davide Bossini Carino Ferrante Giuseppe Fumero Giulio Cerullo Shaul Mukamel Tullio Scopigno 《Annalen der Physik》2019,531(12)
Illuminating a magnetic material with femtosecond laser pulses induces complex ultrafast dynamical processes. The resulting optically detectable response usually contains contributions from both the optical properties and the magnetic degrees of freedom. Disentangling all the different components concurring to the generation of the total signal is a major challenge of contemporary experimental solid‐state physics. Here, this problem is tackled, addressing the purely optical, nonmagnetic artifacts on the time resolved two‐magnon stimulated Raman spectrum of an antiferromagnet, rationalizing the recent observation on the exchange energy modification upon photo‐excitation. It is demonstrated how the genuine dynamics of the magnetic eigenmode can be disentangled from the nonlinear optical effects, generated by cross phase modulation, on the femtosecond timescale. The introduced approach can be extended for the investigation of <100 fs dynamic processes by means of coherent Raman scattering. 相似文献
680.
Numerical calculation of FSS/RSS transition in highly overexpanded rocket nozzle flows 总被引:1,自引:0,他引:1
Turbulent flow separation in over-expanded rocket nozzles is investigated numerically in a sub-scale parabolic nozzle fed
with cold nitrogen. Depending upon the feeding to ambient pressure ratio either a free shock separation or a restricted shock
separation is computed, with a significant hysteresis between these two flow regimes. This hysteresis was also found in experimental
tests with the same nozzle geometry. The present study is mainly focused on the transition between the two shock separation
patterns. The analysis of the numerical solutions aims to provide clues for the explanation of the hysteresis cycle. 相似文献