全文获取类型
收费全文 | 7321篇 |
免费 | 289篇 |
国内免费 | 368篇 |
专业分类
化学 | 1585篇 |
晶体学 | 4篇 |
力学 | 285篇 |
综合类 | 61篇 |
数学 | 4827篇 |
物理学 | 1216篇 |
出版年
2024年 | 7篇 |
2023年 | 74篇 |
2022年 | 125篇 |
2021年 | 168篇 |
2020年 | 122篇 |
2019年 | 157篇 |
2018年 | 125篇 |
2017年 | 201篇 |
2016年 | 209篇 |
2015年 | 148篇 |
2014年 | 304篇 |
2013年 | 622篇 |
2012年 | 365篇 |
2011年 | 385篇 |
2010年 | 364篇 |
2009年 | 504篇 |
2008年 | 497篇 |
2007年 | 503篇 |
2006年 | 365篇 |
2005年 | 278篇 |
2004年 | 286篇 |
2003年 | 215篇 |
2002年 | 206篇 |
2001年 | 147篇 |
2000年 | 134篇 |
1999年 | 138篇 |
1998年 | 151篇 |
1997年 | 117篇 |
1996年 | 140篇 |
1995年 | 105篇 |
1994年 | 124篇 |
1993年 | 84篇 |
1992年 | 86篇 |
1991年 | 59篇 |
1990年 | 46篇 |
1989年 | 36篇 |
1988年 | 31篇 |
1987年 | 27篇 |
1986年 | 38篇 |
1985年 | 47篇 |
1984年 | 45篇 |
1983年 | 18篇 |
1982年 | 45篇 |
1981年 | 21篇 |
1980年 | 27篇 |
1979年 | 30篇 |
1978年 | 19篇 |
1977年 | 13篇 |
1976年 | 9篇 |
1973年 | 5篇 |
排序方式: 共有7978条查询结果,搜索用时 828 毫秒
91.
利用集值映射不动点定理及最优化问题与变分不等式的关系给出线性G^↑ateaux可微的锥凸映射的广义有效点的一个存在性定理。 相似文献
92.
Efficiencies of the maximum pseudolikelihood estimator and a number of related estimators for the case-cohort sampling design in the proportional hazards regression model are studied. The asymptotic information and lower bound for estimating the parametric regression parameter are calculated based on the effective score, which is obtained by determining the component of the parametric score orthogonal to the space generated by the infinite-dimensional nuisance parameter. The asymptotic distributions of the maximum pseudolikelihood and related estimators in an i.i.d. setting show that these estimators do not achieve the computed asymptotic lower bound. Simple guidelines are provided to determine in which instances such estimators are close enough to efficient for practical purposes. 相似文献
93.
Sam Efromovich 《Annals of the Institute of Statistical Mathematics》2004,56(2):205-223
A blockwise shrinkage is a popular procedure of adaptation that has allowed the statisticians to establish an impressive bouquet
of asymptotic mathematical results and develop softwares for solving practical problems. Traditionally risks of the estimates
are studied via upper bounds that imply sufficient conditions for a blockwise shrinkage procedure to be minimax. This article
suggests to analyze the estimates via exact (non-asymptotic) lower bounds established for a no-signal setting. The approach
complements the familiar minimax, Bayesian and numerical analysis, it allows to find necessary conditions for a procedure
to attain desired rates, and it sheds a new light on popular choices of blocks and thresholds recommended in the literature.
Mathematical results are complemented by a numerical study.
Supported in part by NSF Grants DMS-9971051 and DMS-0243606. 相似文献
94.
This paper considers the estimation problem for a trigonometric regression model with the noise specified by the Ornstein–Uhlenbeck
process with unknown parameter. We propose a sequential procedure which ensures a prescribed mean square precision uniformly
in the nuisance parameter. The asymptotic behaviour of the procedure duration mean has been studied.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
95.
A linear inequality system with infinitely many constraints is polynomial (analytical) if its index set is a compact interval
of the real line and all its coefficients are polynomial (analytical, respectively) functions of the index on this interval.
This paper provides an example of analytical system whose solution set cannot be the solution set of any polynomial system.
Research supported by DGES of Spain and FEDER of UE, Grant BFM2002-04114-C02-01.
Research supported by CONACyT of Mexico, Grant 130036.
Research partially supported by CONACyT of Mexico, Grant 44003. 相似文献
96.
In the paper, the behaviour of interior point algorithms is analyzed by using a variable metric method approach. A class of
polynomial variable metric algorithms is given achieving O ((n/β)L) iterations for solving a canonical form linear optimization problem with respect to a wide class of Riemannian metrics,
wheren is the number of dimensions and β a fixed value. It is shown that the vector fields of several interior point algorithms
for linear optimization is the negative Riemannian gradient vector field of a linear a potential or a logarithmic barrier
function for suitable Riemannian metrics.
Research Partially supported by the Hungarian National Research Foundation, Grant Nos. OTKA-T016413 and OTKA-2116. 相似文献
97.
THE SCHWARZIAN DERIVATIVE IN SEVERAL COMPLEX VARIABLES(II) 总被引:1,自引:0,他引:1
THESCHWARZIANDERIVATIVEINSEVERALCOMPLEXVARIABLES(II)GONGSHENGYUQIHUANGZHENGXUEANManuscriptreceivedAugust30,1996.De... 相似文献
98.
具有离散参数齐次随机场的线性预测(V) 总被引:1,自引:1,他引:0
本文提出并研究下列四类线性预测问题:2(n0),6(n0),5(NO,n0)及3(N0,n0).不仅求出了它们的预测误差,而且也求出了它们的预测值.因而不仅推广了而且也改进了[2-5]中的结果.本文还给出了场{X(m,n)}的一个新形式的表示式. 相似文献
99.
100.
Ro Jin Pak Ayanendranath Basu 《Annals of the Institute of Statistical Mathematics》1998,50(3):503-521
This paper deals with the minimum disparity estimation in linear regression models. The estimators are defined as statistical quantities which minimize the blended weight Hellinger distance between a weighted kernel density estimator of errors and a smoothed model density of errors. It is shown that the estimators of the regression parameters are asymptotic normally distributed and efficient at the model if the weights of the density estimators are appropriately chosen. 相似文献