全文获取类型
收费全文 | 16634篇 |
免费 | 2594篇 |
国内免费 | 1117篇 |
专业分类
化学 | 2900篇 |
晶体学 | 93篇 |
力学 | 1599篇 |
综合类 | 327篇 |
数学 | 9192篇 |
物理学 | 6234篇 |
出版年
2024年 | 28篇 |
2023年 | 142篇 |
2022年 | 289篇 |
2021年 | 421篇 |
2020年 | 480篇 |
2019年 | 501篇 |
2018年 | 469篇 |
2017年 | 609篇 |
2016年 | 647篇 |
2015年 | 501篇 |
2014年 | 758篇 |
2013年 | 1373篇 |
2012年 | 857篇 |
2011年 | 911篇 |
2010年 | 808篇 |
2009年 | 935篇 |
2008年 | 1073篇 |
2007年 | 997篇 |
2006年 | 904篇 |
2005年 | 809篇 |
2004年 | 680篇 |
2003年 | 733篇 |
2002年 | 676篇 |
2001年 | 614篇 |
2000年 | 595篇 |
1999年 | 502篇 |
1998年 | 419篇 |
1997年 | 390篇 |
1996年 | 303篇 |
1995年 | 235篇 |
1994年 | 212篇 |
1993年 | 148篇 |
1992年 | 143篇 |
1991年 | 145篇 |
1990年 | 113篇 |
1989年 | 102篇 |
1988年 | 101篇 |
1987年 | 85篇 |
1986年 | 65篇 |
1985年 | 98篇 |
1984年 | 97篇 |
1983年 | 48篇 |
1982年 | 60篇 |
1981年 | 60篇 |
1980年 | 30篇 |
1979年 | 38篇 |
1978年 | 32篇 |
1977年 | 30篇 |
1976年 | 24篇 |
1973年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 390 毫秒
71.
We develop a production policy that controls work-in-process (WIP) levels and satisfies demand in a multistage manufacturing system with significant uncertainty in yield, rework, and demand. The problem addressed in this paper is more general than those in the literature in three aspects: (i) multiple products are processed at multiple workstations, and the capacity of each workstation is limited and shared by multiple operations; (ii) the behavior of a production policy is investigated over an infinite-time horizon, and thus the system stability can be evaluated; (iii) the representation of yield and rework uncertainty is generalized. Generalizing both the system structure and the nature of uncertainty requires a new mathematical development in the theory of infinite-horizon stochastic dynamic programming. The theoretical contributions of this paper are the existence proofs of the optimal stationary control for a stochastic dynamic programming problem and the finite covariances of WIP and production levels under the general expression of uncertainty. We develop a simple and explicit sufficient condition that guarantees the existence of both the optimal stationary control and the system stability. We describe how a production policy can be constructed for the manufacturing system based on the propositions derived. 相似文献
72.
73.
A complete study of the spectrum of a finite-dimensional Bose operator is carried out in the paper. The cases in which the
spectrum is discrete or continuous are studied.
Translated fromMatematicheskie Zametki, Vol. 61, No. 6, pp. 835–854, June, 1997.
Translated by A. M. Chebotarev 相似文献
74.
A new scheme for controlling photodissociation through preparation of a variationally optimized linear superposition of field free vibrational eigenstates is applied for selective control of IBr and HI dissociation. The dependence of photodissociation on various field parameters and initial conditions is examined to investigate the mechanistic basis of selective control. The parametric equations of motion approach for determining vibrational dynamics as a function of field parameters without having to solve the time dependent Schrödinger equation explicitly for each field parameter separately is outlined and its use to identify field characteristics which will provide the requisite population mix represented by the optimal linear superposition of vibrational states is advocated. 相似文献
75.
76.
78.
研制出了用于计算氚投料量在FEB聚变堆各个子系统中的分布及其随时间变化的数值模拟程序包SWITRIM。通过近5年的使用,表明其运行良好、计算结果可靠。用SWITRIM数值模拟研究了聚变堆起动过程中的“氚坑深度和氚坑时间”新现象。简单介绍了SWITRIM程序包的组成和用户使用说明以及最新的运用等。 相似文献
79.
Europium (Eu+) ions were confined in a Paul trap and detected by non-destructive method. Storage time of Eu+ ions achieved in vacuum was improved by orders of magnitude employing buffer gas cooling. The experimentally detected signal
was fitted to the ion response signal and the total number of ions trapped was estimated. It is found that the peak signal
amplitude as well as the product of FWHM and the peak signal amplitude is proportional to the total number of trapped ions.
The trapped ion secular frequency was swept at different rates and its effect on the absorption line profile was studied both
experimentally and theoretically. 相似文献
80.
引入了随机环境中双移民生灭过程的概念,定义了过程的模态指示函数,在此基础上研究了其转移矩阵的平稳分布,给出了平稳分布众数的位置与模态指示函数之间的关系.研究了平稳分布的众数与边界关系. 相似文献