全文获取类型
收费全文 | 8064篇 |
免费 | 804篇 |
国内免费 | 675篇 |
专业分类
化学 | 3480篇 |
晶体学 | 40篇 |
力学 | 185篇 |
综合类 | 94篇 |
数学 | 4610篇 |
物理学 | 1134篇 |
出版年
2024年 | 10篇 |
2023年 | 43篇 |
2022年 | 170篇 |
2021年 | 202篇 |
2020年 | 207篇 |
2019年 | 231篇 |
2018年 | 190篇 |
2017年 | 272篇 |
2016年 | 321篇 |
2015年 | 254篇 |
2014年 | 438篇 |
2013年 | 754篇 |
2012年 | 480篇 |
2011年 | 481篇 |
2010年 | 431篇 |
2009年 | 499篇 |
2008年 | 539篇 |
2007年 | 577篇 |
2006年 | 396篇 |
2005年 | 362篇 |
2004年 | 266篇 |
2003年 | 286篇 |
2002年 | 258篇 |
2001年 | 259篇 |
2000年 | 206篇 |
1999年 | 190篇 |
1998年 | 142篇 |
1997年 | 133篇 |
1996年 | 128篇 |
1995年 | 120篇 |
1994年 | 103篇 |
1993年 | 85篇 |
1992年 | 80篇 |
1991年 | 72篇 |
1990年 | 30篇 |
1989年 | 40篇 |
1988年 | 36篇 |
1987年 | 29篇 |
1986年 | 26篇 |
1985年 | 40篇 |
1984年 | 24篇 |
1983年 | 18篇 |
1982年 | 25篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 22篇 |
1978年 | 10篇 |
1977年 | 12篇 |
1975年 | 8篇 |
1973年 | 7篇 |
排序方式: 共有9543条查询结果,搜索用时 0 毫秒
41.
42.
Supply Chain Management (SCM) is an important activity in all producing facilities and in many organizations to enable vendors,
manufacturers and suppliers to interact gainfully and plan optimally their flow of goods and services. To realize this, a
dynamic modelling approach for characterizing supply chain activities is opportune, so as to plan efficiently the set of activities
over a distributed network in a formal and scientific way. The dynamical system will result so complex that it is not generally
possible to specify the functional forms and the parameters of interest, relating outputs to inputs, states and stochastic
terms by experiential specification methods. Thus the algorithm that will presented is Data Driven, determining simultaneously
the functional forms, the parameters and the optimal control policy from the data available for the supply chain. The aim
of this paper is to present this methodology, by considering dynamical aspects of the system, the presence of nonlinear relationships
and unbiased estimation procedures to quantify these relations, leading to a nonlinear and stochastic dynamical system representation
of the SCM problem. Moreover, the convergence of the algorithm will be proved and the satisfaction of the required statistical
conditions demonstrated. Thus SCM problems may be formulated as formal scientific procedures, with well defined algorithms
and a precise calculation sequence to determine the best alternative to enact. A “Certainty equivalent principle” will be
indicated to ensure that the effects of the inevitable uncertainties will not lead to indeterminate results, allowing the
formulation of demonstrably asymptotically optimal management plans. 相似文献
43.
Optimal production and rationing decisions in supply chains with information sharing 总被引:1,自引:0,他引:1
Boray Huang 《Operations Research Letters》2007,35(5):669-676
This paper considers a two-echelon capacitated supply chain with two non-identical retailers and information sharing. We characterize the optimal inventory policies. We also study the benefits of the optimal stock rationing policy over the first come first served (FCFS) and the modified echelon-stock rationing (MESR) policies. 相似文献
44.
We construct random locally compact real trees called Lévy trees that are the genealogical trees associated with continuous-state
branching processes. More precisely, we define a growing family of discrete Galton–Watson trees with i.i.d. exponential branch
lengths that is consistent under Bernoulli percolation on leaves; we define the Lévy tree as the limit of this growing family
with respect to the Gromov–Hausdorff topology on metric spaces. This elementary approach notably includes supercritical trees
and does not make use of the height process introduced by Le Gall and Le Jan to code the genealogy of (sub)critical continuous-state
branching processes. We construct the mass measure of Lévy trees and we give a decomposition along the ancestral subtree of
a Poisson sampling directed by the mass measure.
T. Duquesne is supported by NSF Grants DMS-0203066 and DMS-0405779. M. Winkel is supported by Aon and the Institute of Actuaries,
EPSRC Grant GR/T26368/01, le département de mathématique de l’Université d’Orsay and NSF Grant DMS-0405779. 相似文献
45.
Robert S. Maier 《Random Structures and Algorithms》1991,2(4):379-420
We analyze the performance of a prototypical scheme for shared storage allocation: two initially empty stacks evolving in a contiguous block of memory of size m. We treat the case in which the stacks are more likely to shrink than grow, but with the probabilities of insertion and deletion allowed to depend arbitrarily on stack height as a fraction of m. New results are obtained on the m → ∞ asymptotics of the stack collision time, and of the final stack heights. The results of Wentzell and Freidlin on the large deviations of Markov chains are used, and the relation of their formalism to the Hamiltonian formulation of classical mechanics is emphasized. Certain results on higher-order asymptotics follow from WKB expansions. 相似文献
46.
47.
一种供应链中的知识管理绩效评价方法研究 总被引:7,自引:0,他引:7
作为知识管理的重要组成部分,知识管理绩效评价旨在帮助企业找出影响绩效提高的关键因素并及时采取有效措施,提高知识管理水平。本文从创造顾客价值、知识的获取能力、知识的共享与传播能力、知识的运用水平、知识的存量水平和知识管理平台等六个方面,分析了评价供应链的知识管理绩效应考虑的主要因素,建立了供应链的知识管理绩效评价指标体系,在此基础上,提出了运用D-S证据推理方法,对供应链知识管理绩效进行评价,并给出了证据推理的算法步骤,最后通过算例分析,说明该方法的有效性、实用性。 相似文献
48.
We analyze the statistical behavior of signals in nonlinear circuits with delayed feedback in the presence of external Markovian noise. For the special class of circuits with intense phase mixing we develop an approach for the computation of the probability distributions and multitime correlation functions based on the random phase approximation. Both Gaussian and Kubo-Andersen models of external noise statistics are analyzed and the existence of the stationary (asymptotic) random process in the long-time limit is shown. We demonstrate that a nonlinear system with chaotic behavior becomes a noise amplifier with specific statistical transformation properties. 相似文献
49.
Howel Tong 《应用数学学报(英文版)》2002,18(2):177-184
Abstract I reflect upon the development of nonlinear time series analysis since 1990 by focusing on five majorareas of development. These areas include the interface between nonlinear time series analysis and chaos,thenonparametric/semiparametric approach,nonlinear state space modelling,financial time series and nonlinearmodelling of panels of time series. 相似文献
50.
标的股价服从混合过程的期权定价公式及有限元算法 总被引:2,自引:0,他引:2
本文将马尔科夫跳跃过程叠加于 Ito过程 ,形成混合过程 ,并用该过程来刻画股价走势情况。而后在标的股价服从混合过程的基础上 ,推导出了欧式看涨期权的定价公式 ,并对美式看跌期权定价给出了有限元算法。 相似文献