全文获取类型
收费全文 | 565篇 |
免费 | 103篇 |
国内免费 | 17篇 |
专业分类
化学 | 29篇 |
力学 | 17篇 |
综合类 | 68篇 |
数学 | 527篇 |
物理学 | 44篇 |
出版年
2023年 | 5篇 |
2022年 | 31篇 |
2021年 | 26篇 |
2020年 | 17篇 |
2019年 | 22篇 |
2018年 | 17篇 |
2017年 | 23篇 |
2016年 | 23篇 |
2015年 | 15篇 |
2014年 | 41篇 |
2013年 | 49篇 |
2012年 | 20篇 |
2011年 | 28篇 |
2010年 | 24篇 |
2009年 | 39篇 |
2008年 | 43篇 |
2007年 | 25篇 |
2006年 | 27篇 |
2005年 | 21篇 |
2004年 | 11篇 |
2003年 | 23篇 |
2002年 | 21篇 |
2001年 | 10篇 |
2000年 | 17篇 |
1999年 | 12篇 |
1998年 | 9篇 |
1997年 | 9篇 |
1996年 | 12篇 |
1995年 | 4篇 |
1994年 | 10篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 2篇 |
1990年 | 7篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1987年 | 8篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有685条查询结果,搜索用时 31 毫秒
71.
A symmetric queue is known to have a nice property, the so-called insensitivity. In this paper, we generalize this for a single node queue with Poisson arrivals and background state, which changes at completion instants of lifetimes as well as at the arrival and departure instants. We study this problem by using the decomposability property of the joint stationary distribution of the queue length and supplementary variables, which implies the insensitivity. We formulate a Markov process representing the state of the queue as an RGSMP (reallocatable generalized semi-Markov process), and give necessary and sufficient conditions for the decomposability. We then establish general criteria to be sufficient for the queue to possess the property. Various symmetric-like queues with background states, including continuous time versions of moving server queues, are shown to have the decomposability.This author is partially supported by NEC C&C Laboratories. 相似文献
72.
Masakiyo Miyazawa 《Queueing Systems》1997,25(1-4):45-75
We consider characterizations of departure functions in Markovian queueing networks with batch movements and state-dependent
routing in discrete-time and in continuous-time. For this purpose, the notion of structure-reversibility is introduced, which
means that the time-reversed dynamics of a queueing network corresponds with the same type of queueing network. The notion
is useful to derive a traffic equation. We also introduce a multi-source model, which means that there are different types
of outside sources, to capture a wider range of applications. Characterizations of the departure functions are obtained for
any routing mechanism of customers satisfying a recurrent condition. These results give a unified view to queueing network
models with linear traffic equations. Furthermore, they enable us to consider new examples as well as show limited usages
of this kind of queueing networks.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
73.
We consider a polling model in which a number of queues are served, in cyclic order, by a single server. Each queue has its own distinct Poisson arrival stream, service time, and switchover time (the server's travel time from that queue to the next) distribution. A setup time is incurred if the polled queue has one or more customers present. This is the polling model with State-Dependent service (the SD model). The SD model is inherently complex; hence, it has often been approximated by the much simpler model with State-Independent service (the SI model) in which the server always sets up for a service at the polled queue, regardless of whether it has customers or not. We provide an exact analysis of the SD model and obtain the probability generating function of the joint queue length distribution at a polling epoch, from which the moments of the waiting times at the various queues are obtained. A number of numerical examples are presented, to reveal conditions under which the SD model could perform worse than the corresponding SI model or, alternately, conditions under which the SD model performs better than a corresponding model in which all setup times are zero. We also present expressions for a variant of the SD model, namely, the SD model with a patient server. 相似文献
74.
This article examines how performance-contingent pricing schemes with long-term statistical performance guarantees can be applied to many IT services. We study two forms of performance-contingent pricing, with rebate proportional to failure rate and fixed rebate for below-threshold performance. We show that threshold-performance contingency pricing can increase both profits and fairness (customers who receive higher benefits pay higher effective price) relative to standard pricing. But an even better solution is to offer a menu of performance guarantees: this can increase the firm’s profit and segment the market. Only service providers whose performance level is sufficiently better than the industry standard can benefit from this pricing mechanism. 相似文献
75.
J. Sztrik 《European Journal of Operational Research》1985,20(2):261-268
The aim of the present paper is to give the main characteristics of the finite-source queue in equilibrium. Here unit i stays in the source for a random time having general distribution function Fi(x) with density fi(x). The service times of all units are assumed to be identically and exponentially distributed random variables with means 1/μ. It is shown that the solution to this model is similar in most important respects to that for the M/M/r model. 相似文献
76.
We consider a loss system model of interest in telecommunications. There is a single service facility with N servers and no waiting room. There are K types of customers, with type ί customers requiring A
ί servers simultaneously. Arrival processes are Poisson and service times are exponential. An arriving type ί customer is accepted
only if there are Rί(⩾Aί ) idle servers. We examine the asymptotic behavior of the above system in the regime known as critical loading where both
N and the offered load are large and almost equal. We also assume that R
1,..., R
K-1 remain bounded, while R
K
N
←∞ and R
K
N
/√N ← 0 as N ← ∞. Our main result is that the K dimensional “queue length” process converges, under the appropriate normalization, to a particular K dimensional diffusion. We show that a related system with preemption has the same limit process. For the associated optimization
problem where accepted customers pay, we show that our trunk reservation policy is asymptotically optimal when the parameters
satisfy a certain relation.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
77.
We consider a multiphase service system with a Poisson input flow. Its intensity depends on the number of customers under
service. The stationary distribution for this system can be found in an explicit form. We study the rate of convergence to
this stationary distribution as well as the bounds for some mixing coefficients. Coupling arguments and Liapunov's function
approach form the basis of considerations.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
78.
针对多阶段区间信息集结与决策问题,提出一种考虑最小化集结矩阵与阶段区间矩阵之间距离的新方法,寻求更趋近帕累托最优的集结结果,使最终评价值更符合多阶段评价的目标。 首先,根据多阶段专家评价值将区间信息转化为二维坐标点,并将其映射到二维坐标系中。然后,构建区间信息离差最小化集结模型,并基于植物模拟生长算法(PGSA)进行群体判断信息的集结,再通过合成各方案的属性评价值,给出各决策方案的综合评价值并进行排序,进而给出最优决策方案。最后,以物流服务商的多阶段绩效评价为例,验证了该方法的合理性和有效性。 相似文献
79.
We study asymmetric polling systems where: (i) the incoming workflow processes follow general Lévy-subordinator statistics; and, (ii) the server attends the channels according to the gated service regime, and incurs random inter-dependentswitchover times when moving from one channel to the other. The analysis follows a dynamical-systems approach: a stochastic Poincaré map, governing the one-cycle dynamics of the polling system is introduced, and its statistical characteristics are studied. Explicit formulae regarding the evolution of the mean, covariance, and Laplace transform of the Poincaré map are derived. The forward orbit of the maps transform – a nonlinear deterministic dynamical system in Laplace space – fully characterizes the stochastic dynamics of the polling system. This enables us to explore the long-term behavior of the system: we prove convergence to a (unique) steady-state equilibrium, prove the equilibrium is stationary, and compute its statistical characteristics. 相似文献
80.