全文获取类型
收费全文 | 531篇 |
免费 | 20篇 |
专业分类
化学 | 294篇 |
晶体学 | 1篇 |
力学 | 16篇 |
数学 | 123篇 |
物理学 | 117篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 21篇 |
2021年 | 23篇 |
2020年 | 25篇 |
2019年 | 19篇 |
2018年 | 17篇 |
2017年 | 11篇 |
2016年 | 28篇 |
2015年 | 24篇 |
2014年 | 29篇 |
2013年 | 33篇 |
2012年 | 49篇 |
2011年 | 43篇 |
2010年 | 26篇 |
2009年 | 24篇 |
2008年 | 31篇 |
2007年 | 29篇 |
2006年 | 23篇 |
2005年 | 15篇 |
2004年 | 9篇 |
2003年 | 10篇 |
2002年 | 12篇 |
2001年 | 2篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1989年 | 3篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1973年 | 2篇 |
1967年 | 1篇 |
排序方式: 共有551条查询结果,搜索用时 62 毫秒
501.
S. Alessio H. Bilokon B. D'Ettorre Piazzoli G. Mannocchi P. Picchi K. Sitte 《Il Nuovo Cimento C》1980,3(6):573-588
Summary The customary assumption of a unique structure function of the formf(r)∞r
−αexp[−r/R
0] with parameters independent of the shower size and the nature of the primary is tested against evidence on the multiplicity
distribution of shower muons. The experimental data were obtained with an array of three spark chamber telescopes installed
at the Mt. Cappuccini underground station, Torino, at depths of about 40 to 60 hg/cm2. They pertain to events with mean shower sizes between about 105 and a few 107 electrons. It is shown that the results are incompatible with this assumption, whatever values are assigned to the exponent
α and to the characteristic radiusR
0 of the structure function. A modified representation allowing for a variation ofR
0 with the shower size and with the massA of the primary is suggested. The resulting distribution is in reasonable agreement both with thorough Monte Carlo evaluations
for proton and iron primaries and with direct experimental observations of other authors.
Riassunto L'ipotesi usuale di una funzione di struttura unica della formaf(r)∞r −αexp[−r/R 0] con parametri indipendenti dalle dimensioni dello sciame e dalla natura dei primari è provata rispetto alle prove sperimentali sulla distribuzione di molteplicità dei muoni dello sciame. I dati sperimentali sono stati ottenuti con un sistema di tre telescopi con camere a scintille istallati nella stazione sotterranea del Monte dei Capuccini, Torino, a profondità da 40 a 60 hg/cm2. Essi riguardano eventi con grandezze medie di sciami tra circa 105 e pochi 107 elettroni. Si mostra che i risultati non sono compatibili con questa ipotesi, qualsiasi valore sia assegnato all'esponente α e al raggio caratteristicoR 0 della funzione di struttura. Si suggerisce una rappresentazione modificata che consente una variazione diR 0 con la grandezza dello sciame e con la massaA dei primari. La distribuzione risultante è in ragionevole accordo sia con tutte le valutazioni di Montecarlo per primari di protoni e di ferro e con osservazioni sperimentali dirette di altri autori.
Резюме Исследуется обычное предположение о единственной структурной функции видаf(r)∼r −αexp[−r/R 0], с параметрами, не зависяцими от размеров ливня и природы первичной частицы, на основе данных о распределении множественности мюонов в ливне. Зкспериментальные данные получены с помошью системы трех телескпов искровых камеп, установленных на подземной стандии Капучини в Турине, на глубинах от 40 до 60 гг/см2. Полученные данные относятся к событиям со средними размерами ливня от 105 до 107 злектронов. Показывается, что полученные результаты являются несовместимыми с зтим предположением, какие бы значения зкспоненте α и характерному радиусуR 0 структурной функции не были бы приписаны. Предлагается модифицированное представление, учитывающее изменение велиьиныR 0 с размером ливия и с массойA первичной частицы. Полученное распределение хорошо согласуется и с оценками по Монте-Карло для первичных протонов и ядер железа и с непосредственными экспериментальными результатами других авторов.相似文献
502.
Intermolecular potential parameters corresponding to atom—atom interactions of the Buckingham form are refined on the basis of static and dynamic properties of some chlorinated benzene crystals. The model reproduces well the observed properties, including k ≠ 0 vibrations. 相似文献
503.
In this paper, we continue the study of the Killing symmetries of a N-dimensional generalized Minkowski space, i.e., a space endowed with a (in general non-diagonal) metric tensor, whose coefficients do depend on a set of non-metrical coordinates. We discuss here the translations in such spaces, by confining ourselves (without loss of generality) to the four-dimensional case. In particular, the results obtained are specialized to the case of a deformed Minkowski space
(i.e. a pseudoeuclidean space with metric coefficients depending on energy). 相似文献
504.
S. Alessio L. Briatore E. Ferrero C. Ferrero C. Giraud A. Longhetto O. Morra 《Il Nuovo Cimento C》1992,15(4):461-472
Summary The experimental research described here deals with a problem of diffusion and transport on local scale (30 km) of pollutants
of urban and industrial origin, emitted into the atmosphere of a complex terrain site, with noticeable orographical features.
The diffusion process was visualized and analysed in detail. The results of this research allowed acquiring the capability
of forecasting environmental impact on the area, due to the sources considered. On account of its spatial scale, the phenomenon
was investigated in a rotating hydraulic channel, by the method of simulation on physical model at reduced scale. Typical
local atmospheric conditions, taking into account diurnal evolution of stability inside a turbulent, rotating planetary boundary
layer, were modeled. Seasonal variations of sources emission rates were considered. Measurements of dilution factors at several
spatial points of the model and at five levels (from ground up to a height equivalent to about 1000m) allowed mapping out
concentration isolines over the site in various conditions and producing evolving contour plots which visualized the diffusion
processes in a very useful way for planning purposes. 相似文献
505.
Alessio Pomponio 《Journal of Differential Equations》2006,227(1):258-281
Coupled nonlinear Schrödinger systems describe some physical phenomena such as the propagation in birefringent optical fibers, Kerr-like photorefractive media in optics and Bose-Einstein condensates. In this paper, we study the existence of concentrating solutions of a singularly perturbed coupled nonlinear Schrödinger system, in presence of potentials. We show how the location of the concentration points depends strictly on the potentials. 相似文献
506.
Summary Theoretical power spectra for the fluctuations of high-rigidity cosmic rays (R≳100 GV) as detected in underground muon stations are obtained. The high-rigidity limit of diffusion theory is used and nonlinear
interactions between particles and interplanetary magnetic fields are considered according to nonlinear-closure approximation
theory.
Riassunto Si presentano i risultati sullo spettro di potenza atteso per fluttuazioni di raggi cosmici primari (rigidità >100 GV) rivelati in stazioni sottoterra. Si fa uso della teoria di diffusione nel limite di alta rigidità, e si considerano le interazioni non lineari fra particelle e campi magnetici interplanetari tramite la teoria di ?nonlinear-closure approximation?.
Резюме Получены теоретические степенные спектры для флуктуаций косми-ческих лучей с высокой жесткостью (R≳100 GV), которые регистрируются на подземных мюонных станциях. Используется предел высокой жесткости для диф-фузионной теории. В рамках приближения ?незамкнутости? рассматриваются нелинейные взаимодействия между частицами и межпланетными магнитными полями.相似文献
507.
Summary Plume trajectories and patterns of ground-level concentration of dense well opening emissions in complex terrain sites were
derived from model simulations in water channel facilities. A satisfactory agreement was found among model results, field
observations and theoretical models concerning plume rise and effluent dilution. This confirms the reliability of this technique
when applied to previsional studies of natural gas venting or industrial losses from chemical factories and its capability
to show details of the phenomenology under investigation.
Riassunto Sono state simulate su modelli in seala in vasca idraulica le emissioni dal suolo in atmosfera di gas inerti pesanti al fine di visualizzarne il comportamento del pennacchio e le concentrazioni di ricaduta al suolo in un sito complesso con deboli venti. I risultati sono in buon accordo con le misure reali e con i dati previsti dai modelli teorici relativamente all'innalzamento dei getti e all'allargamento, sul terreno della nube ricaduta. Ciò conferma l'affidabilità e la versatilità del metodo, in particolare relativamente a valutazioni previsionali di emissioni naturali o artificiali, e la possibilità da esso offerta di visualizzare i dettagli dei fenomeni oggetto di studio.
Резюме Из моделЫной имитации при помощи оборудования водянйх каналов, бйли определены плюмаж-траектории и диаграммы концентрации на поверхности земли при змиссии тяжелых инертных газов из почвы. Модельные результаты хорошо согласуются с результатами полевых измерений и данными теоретических моделей, описывающих подъем струек газа и увеличение облачности Полученные результаты подтверждают надежность предложенной техники для предсказаний естественной эмиссии или индустриальных потерь на химических заводаш, а также возможность исследовать подробности рассматриваемого явления.相似文献
508.
Valeria Corti Yovan Sanchez-Ruiz Giovanni Piccoli Andrea Bergamaschi Carlo V Cannistraci Linda Pattini Sergio Cerutti Angela Bachi Massimo Alessio Antonio Malgaroli 《BMC neuroscience》2008,9(1):36
Background
All studies aimed at understanding complex molecular changes occurring at synapses face the problem of how a complete view of the synaptic proteome and of its changes can be efficiently met. This is highly desirable when synaptic plasticity processes are analyzed since the structure and the biochemistry of neurons and synapses get completely reshaped. Because most molecular studies of synapses are nowadays mainly or at least in part based on protein extracts from neuronal cultures, this is not a feasible option: these simplified versions of the brain tissue on one hand provide an homogeneous pure population of neurons but on the other yield only tiny amounts of proteins, many orders of magnitude smaller than conventional brain tissue. As a way to overcome this limitation and to find a simple way to screen for protein changes at cultured synapses, we have produced and characterized two dimensional electrophoresis (2DE) maps of the synaptic proteome of CA3-CA1 hippocampal neurons in culture. 相似文献509.
Alessio Becheri Maximilian Dürr Pierandrea Lo Nostro Piero Baglioni 《Journal of nanoparticle research》2008,10(4):679-689
We report the synthesis and characterization of nanosized zinc oxide particles and their application on cotton and wool fabrics
for UV shielding. The nanoparticles were produced in different conditions of temperature (90 or 150 °C) and reacting medium
(water or 1,2-ethanediol). A high temperature was necessary to obtain small monodispersed particles. Fourier transformed infrared
spectroscopy (FTIR), transmission electron microscopy (TEM), and X-ray powder diffractometry (XRD) were used to characterize
the nanoparticles composition, their shape, size and crystallinity. The specific surface area of the dry powders was also
determined. ZnO nanoparticles were then applied to cotton and wool samples to impart sunscreen activity to the treated textiles.
The effectiveness of the treatment was assessed through UV–Vis spectrophotometry and the calculation of the ultraviolet protection
factor (UPF). Physical tests (tensile strength and elongation) were performed on the fabrics before and after the treatment
with ZnO nanoparticles. 相似文献
510.
In this paper we prove that a strictly convex Alexandrov solution u of the Monge–Ampère equation, with right-hand side bounded away from zero and infinity, is $W^{2,1}_{\mathrm{loc}}$ . This is obtained by showing higher integrability a priori estimates for D 2 u, namely D 2 u∈Llog k L for any k∈?. 相似文献