全文获取类型
收费全文 | 126篇 |
免费 | 2篇 |
专业分类
化学 | 64篇 |
力学 | 17篇 |
数学 | 5篇 |
物理学 | 42篇 |
出版年
2022年 | 3篇 |
2021年 | 2篇 |
2020年 | 1篇 |
2017年 | 2篇 |
2016年 | 1篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 9篇 |
2012年 | 3篇 |
2011年 | 2篇 |
2010年 | 4篇 |
2009年 | 2篇 |
2008年 | 2篇 |
2007年 | 6篇 |
2006年 | 3篇 |
2005年 | 1篇 |
2004年 | 7篇 |
2003年 | 2篇 |
2002年 | 7篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 8篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 5篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1972年 | 3篇 |
1971年 | 3篇 |
1968年 | 2篇 |
1965年 | 1篇 |
1940年 | 1篇 |
排序方式: 共有128条查询结果,搜索用时 31 毫秒
81.
We address the problem of removing correlation from sets of states while preserving as much local quantum information as possible. We prove that states obtained from universal cloning can only be decorrelated at the expense of complete erasure of local information (i.e., information about the copied state). We solve analytically the problem of decorrelation for two qubits and two qumodes (harmonic oscillators in Gaussian states), and provide sets of decorrelable states and the minimum amount of noise to be added for decorrelation. 相似文献
82.
Cavity ring-down spectroscopy of jet-cooled silane isotopologues in the Si-H stretch overtone region
Absorption spectra of silane in the region of the first overtone of the Si-H stretch vibration have been recorded in a seeded supersonic jet expansion by cavity ring-down spectroscopy as well as in a static gas cell at room temperature by photoacoustic spectroscopy. Spectral simplification due to strong rotational cooling in the jet expansion enables us to clearly resolve and assign the rovibrational transitions of the (2000) and (1100) bands of the three isotopologues, (28)SiH(4), (29)SiH(4), and (30)SiH(4), in their natural isotopic abundance. Interconversion between different nuclear spin species of SiH(4) is found to be absent during the jet expansion. Isotope shifts for (29)SiH(4) and (30)SiH(4) relative to (28)SiH(4) are measured and found to be suitable for selective vibrational excitation of any of three silane isotopologues by pulsed laser excitation in a jet expansion. 相似文献
83.
Giannantonio Sacchi 《Meccanica》1971,6(3):168-171
Summary The expected value of the minimum weight of material necessary for a structure in order to support assigned loads is considered, when the « resistance » of each element is a random quantity.By going back to a theorem which gives a lower bound for this expected value, a way to compute an upper bound is shown.A way of evaluating the variation of the interval of the existence of the average is then set out.Such bounds are functions of random variables but are evaluated on the basis of a deterministic limit design.
Study supported by the C.N.R. (Consiglio Nazionale delle Ricerche). 相似文献
Sommario Richiamato un teorema[4] che fornisce un minorante del valore medio del volume minimo di strutture soggette a carichi noti e dotate di elementi costituiti da materiale a resistenza aleatoria, si dimostra l'esistenza di un maggiorante.Si dimostra poi come sia possibile stabilire un maggiorante ed un minorante della varianza del minimo volume, e quindi come si possa apprezzare il rischio d'errore connesso alla aleatorietà delle resistenze, nella valutazione del volume minimo.I limiti indicati, benchè derivati da elaborazioni statistiche sulle resistenze, risultano da un progetto ottimale sviluppato con soli calcoli deterministici.
Study supported by the C.N.R. (Consiglio Nazionale delle Ricerche). 相似文献
84.
S. I. Cristini B. Sacchi E. Guerrini S. Trasatti St. P. Trasatti 《Russian Journal of Electrochemistry》2010,46(10):1094-1100
Duplex stainless steels (DSS) may undergo various structural transformations as a function of temperature, leading to formation
of secondary phases when exposed to temperatures in the range 600–1000°C for prolonged periods of time. Among these phases,
apart from carbides and nitrides, sigma is the most prominent intermetallic compound, since it is known to adversely affect
mechanical properties and corrosion resistance of DSS as a consequence of Cr and Mo depletion in the boundary zones of ferrite
grains. As a result of sigma precipitation, DSS become susceptible to localized corrosion via a mechanism resembling sensitization
in austenitic stainless steels. Electrochemical methods, known to successfully detect sensitization in austenitic SS, have
been used to identify reliable test conditions with appropriate sensitivity also for DSS. A modified electrochemical potentiokinetic
reactivation method was developed to investigate 22% Cr DSS sensitivity under different thermal cycles. Modifications were
designed by closely analysing DSS anodic behaviour changes with respect to the operating testing conditions. All findings
were confirmed by SEM, optical microscopy and XRD. 相似文献
85.
86.
Martina Costa Reis Yongqi Wang Adalberto Bono Maurizio Sacchi Bassi 《Journal of mathematical chemistry》2014,52(2):441-463
This work focuses on formulating constitutive models for the bulk and double layer regions of an electrochemical system based on the fundamentals of modern continuum thermodynamics. Particularly, the constitutive models proposed accounting for transport phenomena in electrochemical systems by emphasizing the possibility of cross-coupling between two or more phenomena. Upon deriving a set of thermodynamic restrictions from the Müller-Liu approach of the second law of thermodynamics and axioms of constitutive theory, non-equilibrium quantities are examined in detail, and constitutive answers of the bulk and double layer regions are discussed. Moreover, the conditions for the thermodynamic equilibrium are evaluated for each region as well as the occurrence of dissipative mechanisms. Besides offering a proper formulation for non-equilibrium electrochemical systems, the approach described in this work can be easily extended to more complex chemical systems. 相似文献
87.
A simple nitrogen pumped dye laser is described which, sequentially in time, generates two pulses, one due to superradiance
and the other to laser action. The duration of both the pulses can be changed continuously on a nanosecond time scale, down
to a few tenths of a nanosecond for the superradiant pulse. Pulses as short as 0.4 nsec have been obtained for the superradiant
beam.
Work supported by Consiglio Nazionale delle Ricerche. 相似文献
88.
Kim-Cuong T. Nguyen Lawrence H. Le Tho N.H.T. Tran Mauricio D. Sacchi Edmond H.M. Lou 《Ultrasonics》2014
Long bones are good waveguides to support the propagation of ultrasonic guided waves. The low-order guided waves have been consistently observed in quantitative ultrasound bone studies. Selective excitation of these low-order guided modes requires oblique incidence of the ultrasound beam using a transducer-wedge system. It is generally assumed that an angle of incidence, θi, generates a specific phase velocity of interest, co, via Snell’s law, θi = sin−1(vw/co) where vw is the velocity of the coupling medium. In this study, we investigated the excitation of guided waves within a 6.3-mm thick brass plate and a 6.5-mm thick bovine bone plate using an ultrasound phased array system with two 0.75-mm-pitch array probes. Arranging five elements as a group, the first group of a 16-element probe was used as a transmitter and a 64-element probe was a receiver array. The beam was steered for six angles (0°, 20°, 30°, 40°, 50°, and 60°) with a 1.6-MHz source signal. An adjoint Radon transform algorithm mapped the time-offset matrix into the frequency-phase velocity dispersion panels. The imaged Lamb plate modes were identified by the theoretical dispersion curves. The results show that the 0° excitation generated many modes with no modal discrimination and the oblique beam excited a spectrum of phase velocities spread asymmetrically about co. The width of the excitation region decreased as the steering angle increased, rendering modal selectivity at large angles. The phenomena were well predicted by the excitation function of the source influence theory. The low-order modes were better imaged at steering angle ?30° for both plates. The study has also demonstrated the feasibility of using the two-probe phased array system for future in vivo study. 相似文献
89.
90.
Summary We propose a multidomain spectral collocation scheme for the approximation of the two-dimensional Stokes problem. We show that the discrete velocity vector field is exactly divergence-free and we prove error estimates both for the velocity and the pressure.Deceased 相似文献