全文获取类型
收费全文 | 558526篇 |
免费 | 4232篇 |
国内免费 | 1553篇 |
专业分类
化学 | 278776篇 |
晶体学 | 7889篇 |
力学 | 27714篇 |
综合类 | 29篇 |
数学 | 77463篇 |
物理学 | 172440篇 |
出版年
2021年 | 5059篇 |
2020年 | 5495篇 |
2019年 | 6227篇 |
2018年 | 9833篇 |
2017年 | 10222篇 |
2016年 | 12382篇 |
2015年 | 6731篇 |
2014年 | 10899篇 |
2013年 | 24131篇 |
2012年 | 21360篇 |
2011年 | 23970篇 |
2010年 | 17805篇 |
2009年 | 17519篇 |
2008年 | 21172篇 |
2007年 | 21055篇 |
2006年 | 19146篇 |
2005年 | 21766篇 |
2004年 | 20398篇 |
2003年 | 16803篇 |
2002年 | 14298篇 |
2001年 | 14909篇 |
2000年 | 11424篇 |
1999年 | 8871篇 |
1998年 | 7689篇 |
1997年 | 7529篇 |
1996年 | 6972篇 |
1995年 | 6290篇 |
1994年 | 6299篇 |
1993年 | 6037篇 |
1992年 | 6497篇 |
1991年 | 6978篇 |
1990年 | 6669篇 |
1989年 | 6570篇 |
1988年 | 6388篇 |
1987年 | 6179篇 |
1986年 | 5904篇 |
1985年 | 7431篇 |
1984年 | 7786篇 |
1983年 | 6556篇 |
1982年 | 6837篇 |
1981年 | 6338篇 |
1980年 | 6015篇 |
1979年 | 6525篇 |
1978年 | 6756篇 |
1977年 | 6645篇 |
1976年 | 6646篇 |
1975年 | 6327篇 |
1974年 | 6161篇 |
1973年 | 6468篇 |
1972年 | 4742篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
911.
912.
Parameters of Gaussian multivariate models are often estimated using the maximum likelihood approach. In spite of its merits, this methodology is not practical when the sample size is very large, as, for example, in the case of massive georeferenced data sets. In this paper, we study the asymptotic properties of the estimators that minimize three alternatives to the likelihood function, designed to increase the computational efficiency. This is achieved by applying the information sandwich technique to expansions of the pseudo-likelihood functions as quadratic forms of independent normal random variables. Theoretical calculations are given for a first-order autoregressive time series and then extended to a two-dimensional autoregressive process on a lattice. We compare the efficiency of the three estimators to that of the maximum likelihood estimator as well as among themselves, using numerical calculations of the theoretical results and simulations. 相似文献
913.
In this paper, by using elementary analysis, we establish some new Lyapunov-type inequalities for nonlinear systems of differential equations, special cases of which contain the well-known equations such as Emden-Fowler-type and half-linear equations. The inequalities obtained here can be used as handy tools in the study of qualitative behaviour of solutions of the associated equations. 相似文献
914.
This is a write-up on the foundation of the Sobolev Institute of Mathematics in 1957. 相似文献
915.
916.
917.
A nonlinear pulse systems with a time-variant continuous linear part is considered. A method for synthesizing an output-feedback robust stabilizing control is suggested. 相似文献
918.
A. Puiu G. Giubileo G. Addolorato L. Revelli G. Gasbarrini R. Bellantone A. D’Amore C. P. Lombardi C. Carrozza 《Laser Physics》2007,17(4):448-452
Nowadays, there is high demand for sensitive gas sensors both for human and environmental monitoring. This paper deals with a high-resolution (0.2 ppb) laser-based photoacoustic spectroscopic system realized at ENEA Frascati, Italy, applied for monitoring stress in scuba divers during sustained immersion by analyzing breath samples. Blood tests and psychometric tests for scuba divers were performed at Catholic University in Rome. Results will be reported and discussed. 相似文献
919.
920.