全文获取类型
收费全文 | 16439篇 |
免费 | 1812篇 |
国内免费 | 1245篇 |
专业分类
化学 | 2208篇 |
晶体学 | 23篇 |
力学 | 1397篇 |
综合类 | 344篇 |
数学 | 12053篇 |
物理学 | 3471篇 |
出版年
2024年 | 34篇 |
2023年 | 117篇 |
2022年 | 235篇 |
2021年 | 315篇 |
2020年 | 336篇 |
2019年 | 377篇 |
2018年 | 388篇 |
2017年 | 515篇 |
2016年 | 604篇 |
2015年 | 380篇 |
2014年 | 713篇 |
2013年 | 1290篇 |
2012年 | 825篇 |
2011年 | 853篇 |
2010年 | 775篇 |
2009年 | 921篇 |
2008年 | 1024篇 |
2007年 | 1050篇 |
2006年 | 983篇 |
2005年 | 893篇 |
2004年 | 802篇 |
2003年 | 654篇 |
2002年 | 693篇 |
2001年 | 591篇 |
2000年 | 570篇 |
1999年 | 533篇 |
1998年 | 421篇 |
1997年 | 389篇 |
1996年 | 317篇 |
1995年 | 293篇 |
1994年 | 216篇 |
1993年 | 191篇 |
1992年 | 179篇 |
1991年 | 142篇 |
1990年 | 118篇 |
1989年 | 86篇 |
1988年 | 70篇 |
1987年 | 73篇 |
1986年 | 68篇 |
1985年 | 76篇 |
1984年 | 87篇 |
1983年 | 31篇 |
1982年 | 51篇 |
1981年 | 24篇 |
1980年 | 33篇 |
1979年 | 35篇 |
1978年 | 23篇 |
1977年 | 29篇 |
1976年 | 15篇 |
1973年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
11.
SPECTRUM-PRESERVING ELEMENTARY OPERATORS ON B(X) 总被引:4,自引:0,他引:4
Hou Jinchuan 《数学年刊B辑(英文版)》1998,19(4):511-516
1.IntroductionLetXbeaninfinitedimensionalcomplexBanachspaceandB(X)theBanachalgebraofallboundedlinearoperatorsonX.ForTEB(X),a(T),asusual,willdenotethespectrumofT.Let4bealinearmapfromB(X)intoitself.4isspectrum-preservingifa(di(T))=a(T)forallTEB(X);4isspectrum-compressingifa(4(T))ga(T)forallTEB(X).Itisclearthatif4isunital(i.e.,ac(I)=I),thenacisspectrum-preserving(spectrum-compressing)ifandonlyif4preservesinvertibilityinbothdirections(preservesinvertibility),i.e.,4(T)isinvertibleifando… 相似文献
12.
The theory of tree-growing (RECPAM approach) is developed for outcome variables which are distributed as the canonical exponential family. The general RECPAM approach (consisting of three steps: recursive partition, pruning and amalgamation), is reviewed. This is seen as constructing a partition with maximal information content about a parameter to be predicted, followed by simplification by the elimination of ‘negligible’ information. The measure of information is defined for an exponential family outcome as a deviance difference, and appropriate modifications of pruning and amalgamation rules are discussed. It is further shown how the proposed approach makes it possible to develop tree-growing for situations usually treated by generalized linear models (GLIM). In particular, Poisson and logistic regression can be tree-structured. Moreover, censored survival data can be treated, as in GLIM, by observing a formal equivalence of the likelihood under random censoring and an appropriate Poisson model. Three examples are given of application to Poisson, binary and censored survival data. 相似文献
13.
A likelihood-based method for haplotype association studies of case-control data with genotyping uncertainty 总被引:1,自引:0,他引:1
ZHU Wensheng & GUO Jianhua School of Mathematics Statistics Northeast Normal University Changchun China 《中国科学A辑(英文版)》2006,49(1):130-144
This paper discusses the associations between traits and haplotypes based on Fl (fluorescent intensity) data sets. We consider a clustering algorithm based on mixtures of t distributions to obtain all possible genotypes of each individual (i.e. "GenoSpec-trum"). We then propose a likelihood-based approach that incorporates the genotyping uncertainty to assessing the associations between traits and haplotypes through a haplotype-based logistic regression model. Simulation studies show that our likelihood-based method can reduce the impact induced by genotyping errors. 相似文献
14.
Zhong Yin Xiao 《International Journal of Infrared and Millimeter Waves》2006,27(6):847-855
A new compact bandpass filter composed of two coupled linear tapered line resonators (LTLRs) is designed. The two resonators
are arranged in different layers. The filter has two transmission zeros on both sides of the passband. It has small size and
steep response below its passband. It is also shown that this filter has 0.6 dB low insertion loss at the centre frequency
and 10.5% 3dB bandwidth.
This work was supported by the Development Foundation of Shanghai Educational Committee (217608) and Shanghai Leading Academic
Discipline Project (T0102). 相似文献
15.
WANG Libin 《数学年刊B辑(英文版)》2002,23(4):439-454
The author gets a blow-up result of C1 solution to the Cauchy problem for a first order quasilinear non-strictly hyperbolic system in one space dimension. 相似文献
16.
17.
18.
Eva Lesanska 《Applications of Mathematics》2002,47(5):411-426
The problem is to determine nonsensitiveness regions for threshold ellipsoids within a regular mixed linear model. 相似文献
19.
A method using third order moments for estimating the regression coefficients as well as the latent state scores of the reduced-rank regression model when the latent variable(s) are non-normally distributed is presented in this paper. It is shown that the factor analysis type indeterminacy of the regression coefficient matrices is eliminated. A real life example of the proposed method is presented. Differences of this solution with the reduced-rank regression eigen solution are discussed. 相似文献
20.
LIU Jixue ZHANG Sanguo & CHEN Xiru Department of Statistics Finance University of Science Technology of China Hefei China Department of Mathematics Graduate School of Chinese Academy of Sciences Beijing China 《中国科学A辑(英文版)》2006,49(6):752-769
This paper studies the linear EV model when replicate observations are made only on independent variables. We construct the estimates of regression coefficients and prove the consistency and asymptotic normality under some proper conditions. Results obtained reveal the difference between the case where the independent and dependent variables are observed repeatedly and simultaneously and the case studied in this article. 相似文献