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11.
Anil Kumar Nain 《Journal of solution chemistry》2006,35(10):1417-1439
The densities, ρ, of binary mixtures of tetrahydrofuran (THF) with benzene, toluene, o-xylene, m-xylene, p-xylene and mesitylene, including those of the pure liquids, were measured over the entire composition range at the temperatures (278.15, 283.15, 288.15, 293.15, 298.15, 303.15, 308.15, 313.15 and 318.15) K and atmospheric pressure. From the experimental data, the excess molar volume, V
m
E, partial molar volumes,
m,1
∘ and
m,2
∘, and excess partial molar volumes,
m,1
∘E and
m,2
∘E, at infinite dilution were calculated. The V
m
E values were found to be negative over the whole composition range for all of the mixtures and at each temperature studied, except for THF + mesitylene, which exhibits a sigmoid trend wherein V
m
E changes sign from negative to positive as the concentration of THF in the mixture is increased, indicating the presence of specific interactions between THF and aromatic hydrocarbon molecules. The extent of negative deviations in the V
m
E values follows the order: benzene > toluene > p-xylene > m-xylene > o-xylene > mesitylene. It is observed that the V
m
E values depend upon the number and position of the methyl groups in these aromatic hydrocarbons. 相似文献
12.
Densities and ultrasonic speeds have been measured in binary mixtures of benzene with 1‐pentanol, 1‐heptanol and 1‐octanol, and in the pure components, as a function of composition at 35 °C. The isentropic compressibility, intermolecular free length, relative association, acoustic impedance, isothermal compressibility, thermal expansion coefficient, deviations in isentropic compressibility, excess free length, excess volume, deviations in ultrasonic speed, excess acoustic impedance, apparent molar compressibility, apparent molar volume, partial molar volume of 1‐alkanol in benzene have been calculated from the experimental data of densities and ultrasonic speeds. The variation of these parameters with composition indicates weak interaction between the component molecules and this interaction decreases in the order: 1‐pentanol > l‐heptanol> 1‐octanol. Further, theoretical values of ultrasonic speeds were evaluated using free length theory, collision factor theory, Nomoto's relation and Van Dæl‐Vangeel ideal mixing relation. The relative merits of these theories and relations were discussed for these systems. 相似文献
13.
In this note we develop a framework for computing upper and lower bounds of an exponential form for a class of stochastic recursive equations with uniformly recurrent Markov modulated inputs. These bounds generalize Kingman's bounds for queues with renewal inputs. 相似文献
14.
R. S. Saini Mahabir Nain R. P. Chauhan Nawal Kishore S. K. Chakarvarti 《Indian Journal of Physics》2009,83(8):1197-1200
Radon pollution is an important global problem of radiation hygiene. Radon and its progeny are the major contributors in the
radiation dose received by general population of the world. Keeping this in mind the environmental monitoring of radon, thoron
and their progeny in some dwellings of northern part of Haryana state of India has been carried out. The radon-thoron twin
dosimeter cups were used for the study. The aim of the study is the possible health risk assessment in the dwellings under
consideration. 相似文献
15.
We have redetermined the values of the effective scaling parameters ?/k and σ for the Ne-Xe and Ar-Xe systems in the Kestin-Mason correlation. In our method of determination we have employed the more accurate Hogervorst diffusion data available over a wider temperature range than those originally used by Kestin and Mason. 相似文献
16.
Two independent Poisson streams of jobs flow into a single-server service system having a limited common buffer that can hold at most one job. If a type- $i$ job ( $i=1,2$ ) finds the server busy, it is blocked and routed to a separate type- $i$ retrial (orbit) queue that attempts to re-dispatch its jobs at its specific Poisson rate. This creates a system with three dependent queues. Such a queueing system serves as a model for two competing job streams in a carrier sensing multiple access system. We study the queueing system using multi-dimensional probability generating functions, and derive its necessary and sufficient stability conditions while solving a Riemann–Hilbert boundary value problem. Various performance measures are calculated and numerical results are presented. In particular, numerical results demonstrate that the proposed multiple access system with two types of jobs and constant retrial rates provides incentives for the users to respect their contracts. 相似文献
17.
18.
19.
Satinder V. Kessar Paramjit Singh Kamal Nain Singh P. Venugopalan Amarjit Kaur Manu Mahendru Rajiv Kapoor 《Tetrahedron letters》2005,46(39):6753-6755
Lithiation of a series of cyclic aralkyl tertiary amines with sec-BuLi in various solvents has been studied. There is a subtle sensitivity to steric factors and lithium coordinating solvents/additives have an adverse effect. ortho-Lithiation is observed only in the case of an eight-membered cyclic amine and the ease of benzylic lithiation with respect to nitrogen is in the surprising order γ > β ? α, δ. These observations are discussed in the context of nitrogen coordination promoted lithiation. 相似文献
20.
Philippe Nain 《Statistical Inference for Stochastic Processes》2002,5(3):307-320
The impact of bursty traffic on queues is investigated in this paper. We consider a discrete-time single server queue with
an infinite storage room, that releases customers at the constant rate of c customers/slot. The queue is fed by an M/G/∞ process. The M/G/∞ process can be seen as a process resulting from the superposition
of infinitely many ‘sessions’: sessions become active according to a Poisson process; a station stays active for a random
time, with probability distribution G, after which it becomes inactive. The number of customers entering the queue in the time-interval [t, t + 1) is then defined as the number of active sessions at time t (t = 0,1, ...) or, equivalently, as the number of busy servers at time t in an M/G/∞ queue, thereby explaining the terminology. The M/G/∞ process enjoys several attractive features: First, it can
display various forms of dependencies, the extent of which being governed by the service time distribution G. The heavier the tail of G, the more bursty the M/G/∞ process. Second, this process arises naturally in teletraffic as the limiting case for the aggregation
of on/off sources [27]. Third, it has been shown to be a good model for various types of network traffic, including telnet/ftp
connections [37] and variable-bit-rate (VBR) video traffic [24]. Last but not least, it is amenable to queueing analysis due
to its very strong structural properties. In this paper, we compute an asymptotic lower bound for the tail distribution of
the queue length. This bound suggests that the queueing delays will dramatically increase as the burstiness of the M/G/∞ input
process increases. More specifically, if the tail of G is heavy, implying a bursty input process, then the tail of the queue length will also be heavy. This result is in sharp
contrast with the exponential decay rate of the tail distribution of the queue length in presence of ‘non-bursty’ traffic
(e.g. Poisson-like traffic).
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献