全文获取类型
收费全文 | 3657篇 |
免费 | 183篇 |
国内免费 | 207篇 |
专业分类
化学 | 968篇 |
晶体学 | 6篇 |
力学 | 279篇 |
综合类 | 58篇 |
数学 | 1996篇 |
物理学 | 740篇 |
出版年
2024年 | 7篇 |
2023年 | 25篇 |
2022年 | 78篇 |
2021年 | 110篇 |
2020年 | 72篇 |
2019年 | 75篇 |
2018年 | 67篇 |
2017年 | 133篇 |
2016年 | 153篇 |
2015年 | 83篇 |
2014年 | 169篇 |
2013年 | 348篇 |
2012年 | 178篇 |
2011年 | 170篇 |
2010年 | 155篇 |
2009年 | 212篇 |
2008年 | 176篇 |
2007年 | 213篇 |
2006年 | 203篇 |
2005年 | 171篇 |
2004年 | 150篇 |
2003年 | 120篇 |
2002年 | 107篇 |
2001年 | 83篇 |
2000年 | 80篇 |
1999年 | 96篇 |
1998年 | 91篇 |
1997年 | 81篇 |
1996年 | 64篇 |
1995年 | 61篇 |
1994年 | 53篇 |
1993年 | 30篇 |
1992年 | 43篇 |
1991年 | 38篇 |
1990年 | 16篇 |
1989年 | 12篇 |
1988年 | 17篇 |
1987年 | 12篇 |
1986年 | 13篇 |
1985年 | 18篇 |
1984年 | 19篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 3篇 |
1980年 | 8篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1973年 | 3篇 |
1957年 | 1篇 |
排序方式: 共有4047条查询结果,搜索用时 171 毫秒
31.
The asymptotic null distribution of the likelihood ratio test for two cases of ordered hypotheses in a particular genetic model is considered. A simple iterative process is proposed in order to get the restricted estimates. It is shown that both tests have asymptotically a chi-bar squared distribution and the same size. A simulation study is also conducted in order to compare the usual unrestricted test with the corresponding one of ordered hypotheses. Finally, the results are extended to some special cases. 相似文献
32.
Dmitry Yu. Murzin 《Reaction Kinetics and Catalysis Letters》2007,90(2):225-232
Reaction route analysis is applied to visualize reaction networks in several heterogeneous catalytic reactions. Combination
of the theory of complex reactions with the notion of catalytic cycles results in a topological representation of complex
mechanisms with the nodes comprising all possible surface species including free sites and branches indicating interconnections
between reactions. 相似文献
33.
信息化对区域经济影响的数理分析 总被引:7,自引:0,他引:7
本文以信息化与经济指标资料为基础,运用加权回归、因子分析和聚类分析等方法,讨论了全国31个省(市、区)信息化水平及其与经济发展关系,给出地区综合发展水平的排行榜。并提出若干促进信息化建设的建议。 相似文献
34.
我国居民收入、人口、教育、财政政策和货币政策与居民消费模型的实证分析 总被引:5,自引:0,他引:5
本文从影响消费的各个因素:居民收入、人口、教育、国家宏观政策等着手,对各因素进行了相关分析,运用多元统计中的岭回归估计法建立消费模型。从定量和定性分析的角度,分析了我国居民消费水平、居民收入、人口增长率、各层次教育、国家财政支出和银行利率等相关因素之间相互影响的数量变动关系和内在规律,就如何提高居民消费水平促进经济协调发展提出若干对策。 相似文献
35.
In this paper, we present a new algorithm to estimate a regression function in a fixed design regression model, by piecewise
(standard and trigonometric) polynomials computed with an automatic choice of the knots of the subdivision and of the degrees
of the polynomials on each sub-interval. First we give the theoretical background underlying the method: the theoretical performances
of our penalized least-squares estimator are based on non-asymptotic evaluations of a mean-square type risk. Then we explain
how the algorithm is built and possibly accelerated (to face the case when the number of observations is great), how the penalty
term is chosen and why it contains some constants requiring an empirical calibration. Lastly, a comparison with some well-known
or recent wavelet methods is made: this brings out that our algorithm behaves in a very competitive way in term of denoising
and of compression. 相似文献
36.
在误差序列为Lqmixingale情形下,给出了半参数回归模型中β和g(t)估计,研究了估计量的q阶平均相合性在较一般的条件下,得到了理想的结果 相似文献
37.
半参数回归模型中小波估计的随机加权逼近速度 总被引:10,自引:1,他引:9
把小波光滑方法和随机加权方法结合在一起,获得了半参数回归模型中参数分量的小波估计的随机加权逼近速度为σ(n^-1/2)。因此,从大样本意义上说,小波光滑方法和随机加权方法对半参数回归模型是可用的。 相似文献
38.
Joanna Tarasińska 《Applications of Mathematics》2003,48(1):67-72
Two estimates of the regression coefficient in bivariate normal distribution are considered: the usual one based on a sample and a new one making use of additional observations of one of the variables. They are compared with respect to variance. The same is done for two regression lines. The conclusion is that the additional observations are worth using only when the sample is very small. 相似文献
39.
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
40.
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