全文获取类型
收费全文 | 506篇 |
免费 | 16篇 |
国内免费 | 43篇 |
专业分类
化学 | 49篇 |
力学 | 6篇 |
综合类 | 1篇 |
数学 | 466篇 |
物理学 | 43篇 |
出版年
2023年 | 5篇 |
2022年 | 8篇 |
2021年 | 6篇 |
2020年 | 12篇 |
2019年 | 13篇 |
2018年 | 14篇 |
2017年 | 9篇 |
2016年 | 16篇 |
2015年 | 10篇 |
2014年 | 36篇 |
2013年 | 49篇 |
2012年 | 21篇 |
2011年 | 35篇 |
2010年 | 34篇 |
2009年 | 39篇 |
2008年 | 44篇 |
2007年 | 37篇 |
2006年 | 26篇 |
2005年 | 22篇 |
2004年 | 10篇 |
2003年 | 12篇 |
2002年 | 11篇 |
2001年 | 16篇 |
2000年 | 12篇 |
1999年 | 9篇 |
1998年 | 11篇 |
1997年 | 8篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有565条查询结果,搜索用时 15 毫秒
1.
In this paper, we evaluate various analytic Feynman integrals of first variation, conditional first variation, Fourier-Feynman
transform and conditional Fourier-Feynman transform of cylinder type functions defined over Wiener paths in abstract Wiener
space. We also derive the analytic Feynman integral of the conditional Fourier-Feynman transform for the product of the cylinder
type functions which define the functions in a Banach algebra introduced by Yoo, with n linear factors. 相似文献
2.
3.
In [W.-C. Kuo, C.C.A. Labuschagne, B.A. Watson, Discrete-time stochastic processes on Riesz spaces, Indag. Math. (N.S.) 15 (3) (2004) 435-451], we introduced the concepts of conditional expectations, martingales and stopping times on Riesz spaces. Here we formulate and prove order theoretic analogues of the Birkhoff, Hopf and Wiener ergodic theorems and the Strong Law of Large Numbers on Riesz spaces (vector lattices). 相似文献
4.
We introduce the time-consistency concept that is inspired by the so-called “principle of optimality” of dynamic programming
and demonstrate – via an example – that the conditional value-at-risk (CVaR) need not be time-consistent in a multi-stage
case. Then, we give the formulation of the target-percentile risk measure which is time-consistent and hence more suitable
in the multi-stage investment context. Finally, we also generalize the value-at-risk and CVaR to multi-stage risk measures
based on the theory and structure of the target-percentile risk measure. 相似文献
5.
Karl Sigman 《Operations Research Letters》2007,35(5):581-583
In Mandelbaum and Yechiali [The conditional residual service time in the M/G/1 queue, http://www.math.tau.ac.il/∼uriy/publications (No. 30a), 1979] and in Fakinos [The expected remaining service time in a single-server queue, Oper. Res. 30 (1982) 1014-1018] a simple formula is derived for the (stationary) expected remaining service time in a M/G/1 queue, conditional on the number of customers in the system. We give a short new proof of the formula using Rate Conservation Law, and generalize to handle higher moments. 相似文献
6.
S. Juneja 《Queueing Systems》2007,57(2-3):115-127
Efficient estimation of tail probabilities involving heavy tailed random variables is amongst the most challenging problems
in Monte-Carlo simulation. In the last few years, applied probabilists have achieved considerable success in developing efficient
algorithms for some such simple but fundamental tail probabilities. Usually, unbiased importance sampling estimators of such
tail probabilities are developed and it is proved that these estimators are asymptotically efficient or even possess the desirable
bounded relative error property. In this paper, as an illustration, we consider a simple tail probability involving geometric
sums of heavy tailed random variables. This is useful in estimating the probability of large delays in M/G/1 queues. In this setting we develop an unbiased estimator whose relative error decreases to zero asymptotically. The key
idea is to decompose the probability of interest into a known dominant component and an unknown small component. Simulation
then focuses on estimating the latter ‘residual’ probability. Here we show that the existing conditioning methods or importance
sampling methods are not effective in estimating the residual probability while an appropriate combination of the two estimates
it with bounded relative error. As a further illustration of the proposed ideas, we apply them to develop an estimator for
the probability of large delays in stochastic activity networks that has an asymptotically zero relative error.
相似文献
7.
研究了条件泛函及其导数的非参数估计,对随机与固定设计的条件泛函,分别利用核估计和非参数加权估计,在核函数及权函数满足一定条件下,证明了估计一致强收敛于待估函数的速度可达到最优。从而进一步推广和发展了Hrdle,etal.(1988)、Severini,etal.(1992)的许多结果。 相似文献
8.
基于CVaR风险计量技术,分别给出了正态和t分布情形下资产组合的CVaR值,对一般情形下风险资产组合的CVaR风险关于头寸的敏感度进行了分析,研究了其经济意义。 相似文献
9.
Guido Consonni Piero Veronese Eduardo Gutirrez-Pea 《Journal of multivariate analysis》2004,88(2):335-364
Reference analysis is one of the most successful general methods to derive noninformative prior distributions. In practice, however, reference priors are often difficult to obtain. Recently developed theory for conditionally reducible natural exponential families identifies an attractive reparameterization which allows one, among other things, to construct an enriched conjugate prior. In this paper, under the assumption that the variance function is simple quadratic, the order-invariant group reference prior for the above parameter is found. Furthermore, group reference priors for the mean- and natural parameter of the families are obtained. A brief discussion of the frequentist coverage properties is also presented. The theory is illustrated for the multinomial and negative-multinomial family. Posterior computations are especially straightforward due to the fact that the resulting reference distributions belong to the corresponding enriched conjugate family. A substantive application of the theory relates to the construction of reference priors for the Bayesian analysis of two-way contingency tables with respect to two alternative parameterizations. 相似文献
10.
CuO/CeO2和CuO/Al2O3催化剂的催化性能 总被引:13,自引:0,他引:13
本文以CO氧化为模式反应考察了CeO2和Al2O3负载氧化铜催化剂的氧化活性,运用XRD和TPR技术研究了催化剂的还原性能和物相结构,结果表明:载体性质对负载CuO催化剂的CO氧化活性有很大影响,CuO/CeO2催化剂活性明显高于CuO/Al2O3催化剂.催化剂的还原特性随载体不同而不同.同时发现,热处理对催化剂铜物种的存在形式,晶粒大小、还原特性及其催化活性有明显影响,CuO/Al2O3催化剂活性下降的主要因素是生成了活性较低的CuAl2O4相,而CuO/CeO2催化剂活性下降是由于CuO和CeO2发生烧结,晶粒变大 相似文献