全文获取类型
收费全文 | 14569篇 |
免费 | 1132篇 |
国内免费 | 1443篇 |
专业分类
化学 | 4238篇 |
晶体学 | 119篇 |
力学 | 702篇 |
综合类 | 258篇 |
数学 | 8362篇 |
物理学 | 3465篇 |
出版年
2024年 | 15篇 |
2023年 | 147篇 |
2022年 | 350篇 |
2021年 | 393篇 |
2020年 | 425篇 |
2019年 | 427篇 |
2018年 | 441篇 |
2017年 | 443篇 |
2016年 | 524篇 |
2015年 | 373篇 |
2014年 | 737篇 |
2013年 | 1245篇 |
2012年 | 619篇 |
2011年 | 775篇 |
2010年 | 691篇 |
2009年 | 852篇 |
2008年 | 899篇 |
2007年 | 951篇 |
2006年 | 777篇 |
2005年 | 721篇 |
2004年 | 657篇 |
2003年 | 616篇 |
2002年 | 529篇 |
2001年 | 430篇 |
2000年 | 396篇 |
1999年 | 354篇 |
1998年 | 336篇 |
1997年 | 259篇 |
1996年 | 267篇 |
1995年 | 190篇 |
1994年 | 171篇 |
1993年 | 122篇 |
1992年 | 101篇 |
1991年 | 81篇 |
1990年 | 79篇 |
1989年 | 79篇 |
1988年 | 74篇 |
1987年 | 52篇 |
1986年 | 34篇 |
1985年 | 77篇 |
1984年 | 52篇 |
1983年 | 30篇 |
1982年 | 56篇 |
1981年 | 52篇 |
1980年 | 42篇 |
1979年 | 47篇 |
1978年 | 32篇 |
1977年 | 37篇 |
1976年 | 39篇 |
1973年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
A.Y. El-Etre 《Applied Surface Science》2006,252(24):8521-8525
The inhibitive effect of the extract of khillah (Ammi visnaga) seeds, on the corrosion of SX 316 steel in HCl solution was determined using weight loss measurements as well as potentiostatic technique. It was found that the presence of the extract reduces markedly the corrosion rate of steel in the acid solution. The inhibition efficiency increases as the extract concentration is increased. The inhibitive effect of khillah extract was discussed on the basis of adsorption of its components on the metal surface. Negative values were calculated for the energy of adsorption indicating the spontaneity of the adsorption process. The formation of insoluble complexes as a result of interaction between iron cations and khellin, which present in the extract, was also discussed. 相似文献
2.
Kasper K. Berthelsen Jesper Møller 《Bulletin of the Brazilian Mathematical Society》2002,33(3):351-367
This primer provides a self-contained exposition of the case where spatial birth-and-death processes are used for perfect
simulation of locally stable point processes. Particularly, a simple dominating coupling from the past (CFTP) algorithm and
the CFTP algorithms introduced in [13], [14], and [5] are studied. Some empirical results for the algorithms are discussed.
Received: 30 June 2002 相似文献
3.
4.
Piotr Garbaczewski 《Journal of statistical physics》2006,123(2):315-355
We analyze the functioning of Gibbs-type entropy functionals in the time domain, with emphasis on Shannon and Kullback-Leibler entropies of time-dependent continuous probability distributions. The Shannon entropy validity is extended to probability distributions inferred from L
2(R
n
) quantum wave packets. In contrast to the von Neumann entropy which simply vanishes on pure states, the differential entropy quantifies the degree of probability (de)localization and its time development. The associated dynamics of the Fisher information functional quantifies nontrivial power transfer processes in the mean, both in dissipative and quantum mechanical cases.
PACS NUMBERS: 05.45.+b, 02.50.-r, 03.65.Ta, 03.67.-a 相似文献
5.
We consider Markov processes built from pasting together pieces of strong Markov processes which are killed at a position
dependent rate and connected via a transition kernel. We give necessary and sufficient conditions for local absolute continuity
of probability laws for such processes on a suitable path space and derive an explicit formula for the corresponding likelihood
ratio process. The main tool is the consideration of the process between successive jumps – what we call ‘elementary experiments’
– and criteria for absolute continuity of laws of the process there. We apply our results to systems of branching diffusions
with interactions and immigrations.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
6.
Relying on reliability growth testing to improve system designis neither usually effective nor efficient. Instead it is importantto design in reliability. This requires models to estimate reliabilitygrowth in the design that can be used to assess whether goalreliability will be achieved within the target timescale forthe design process. Many models have been developed for analysisof reliability growth on test, but there has been much lessattention given to reliability growth in design. This paperdescribes and compares two models: one motivated by the practicalengineering process; the other by extending the reasoning ofstatistical reliability growth modelling. Both models are referencedin the recently revised edition of international standard IEC61164. However, there has been no reported evaluation of theirproperties. Therefore, this paper explores the commonalitiesand differences between these models through an assessment oftheir logic and their application to an industrial example.Recommendations are given for the use of reliability growthmodels to aid management of the design process and to informproduct development. 相似文献
7.
We extend the matrix version of Cochran's statistical theorem to outer inverses of a matrix. As applications, we investigate the Wishartness and independence of matrix quadratic forms for Kronecker product covariance structures. 相似文献
8.
Jeannette H. C. Woerner 《商业与工业应用随机模型》2005,21(1):27-44
In the framework of stochastic volatility models we examine estimators for the integrated volatility based on the pth power variation (i.e. the sum of pth absolute powers of the log‐returns). We derive consistency and distributional results for the estimators given high‐frequency data, especially taking into account what kind of process we may add to our model without affecting the estimate of the integrated volatility. This may on the one hand be interpreted as a possible flexibility in modelling, for example adding jumps or even leaving the framework of semimartingales by adding a fractional Brownian motion, or on the other hand as robustness against model misspecification. We will discuss possible choices of p under different model assumptions and irregularly spaced data. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
9.
L. Brian Lawrence 《Transactions of the American Mathematical Society》2005,357(7):2535-2556
Working in ZFC, we give an example as indicated in the title.
10.
In the ever fusion experiments in SWIP, pellet forming process was carried out through adjusting relative devices by staff member in site, which will make every pellet-forming process slight distinction and will result in pellet difference in shape, size and intensity. In the intervals of HL-2A discharges, staff member have to go site to accomplish the pellet-forming process, this wastes human power and increase the potential danger. So it is necessary to develop a remote control system to perform the pellet-forming process. The control system needs have the features of real-time, reliability and be easy to operate and maintain. 相似文献