全文获取类型
收费全文 | 43614篇 |
免费 | 1504篇 |
国内免费 | 365篇 |
专业分类
化学 | 29581篇 |
晶体学 | 228篇 |
力学 | 1078篇 |
综合类 | 1篇 |
数学 | 8109篇 |
物理学 | 6486篇 |
出版年
2022年 | 355篇 |
2021年 | 589篇 |
2020年 | 722篇 |
2019年 | 684篇 |
2018年 | 523篇 |
2017年 | 506篇 |
2016年 | 1182篇 |
2015年 | 1082篇 |
2014年 | 1200篇 |
2013年 | 2257篇 |
2012年 | 2501篇 |
2011年 | 2966篇 |
2010年 | 1613篇 |
2009年 | 1381篇 |
2008年 | 2410篇 |
2007年 | 2379篇 |
2006年 | 2448篇 |
2005年 | 2203篇 |
2004年 | 2023篇 |
2003年 | 1583篇 |
2002年 | 1544篇 |
2001年 | 623篇 |
2000年 | 549篇 |
1999年 | 539篇 |
1998年 | 500篇 |
1997年 | 558篇 |
1996年 | 560篇 |
1995年 | 461篇 |
1994年 | 502篇 |
1993年 | 463篇 |
1992年 | 403篇 |
1991年 | 406篇 |
1990年 | 349篇 |
1989年 | 350篇 |
1988年 | 342篇 |
1987年 | 290篇 |
1986年 | 310篇 |
1985年 | 458篇 |
1984年 | 471篇 |
1983年 | 376篇 |
1982年 | 460篇 |
1981年 | 438篇 |
1980年 | 432篇 |
1979年 | 353篇 |
1978年 | 413篇 |
1977年 | 370篇 |
1976年 | 296篇 |
1975年 | 260篇 |
1974年 | 258篇 |
1973年 | 232篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
Andrzej Dabrowski Erich Robens Peter Klobes Klaus Meyer Przemyslaw Podkocielny 《Particle & Particle Systems Characterization》2003,20(5):311-322
Since a comprehensive survey published in 1999 [1] much work was done in standardizing measuring methods to characterize the surface geometry of dispersed and/or porous solids and to certify reference materials. The present paper is an extension of a short communication [2]. It gives a survey on existing standards and reports on new drafts and proposals. 相似文献
132.
133.
Let G be a set of n points in general
position (i.e., no three points are on a line)
in the plane, and let C be a caterpillar on n vertices.
We show that one can always find a rectilinear embedding of C in the plane
such that the vertices of C are the points of G and no two edges of C
go to parallel segments. This proves a conjecture of
Robert E. Jamison. 相似文献
134.
135.
We exhibit timelike geodesic paths for a metric, introduced by Bonnor [11] and considered also by Steadman [13], and show that coordinate time runs backward along a portion of these geodesics. 相似文献
136.
137.
138.
A robust and efficient adaptive reweighted estimator of multivariate location and scatter 总被引:1,自引:0,他引:1
Daniel Gervini 《Journal of multivariate analysis》2003,84(1):116-144
This article proposes a reweighted estimator of multivariate location and scatter, with weights adaptively computed from the data. Its breakdown point and asymptotic behavior under elliptical distributions are established. This adaptive estimator is able to attain simultaneously the maximum possible breakdown point for affine equivariant estimators and full asymptotic efficiency at the multivariate normal distribution. For the special case of hard-rejection weights and the MCD as initial estimator, it is shown to be more efficient than its non-adaptive counterpart for a broad range of heavy-tailed elliptical distributions. A Monte Carlo study shows that the adaptive estimator is as robust as its non-adaptive relative for several types of bias-inducing contaminations, while it is remarkably more efficient under normality for sample sizes as small as 200. 相似文献
139.
Design theory crosses the boundary between mathematics and statistics, and includes a wide range of disparate types of design. In this paper we present a classification scheme which aims to include as many important types as possible, based on a balance among concept, representation and use. 相似文献
140.
Manfred Brun Peter Hubner Dieter Oelkrug 《Fresenius' Journal of Analytical Chemistry》1992,344(4-5):209-213
Summary A theoretical model is derived that describes the influence of lateral light diffusion in a scattering medium on the absorptivity of an absorber spot on top of the substrate. The model uses the lateral resolved reflectivity under point irradiation that has been analyzed experimentally with a scanning-micro-laser-reflectometer. The model allows quantification of the absorptivity by one single equation that contains only the mean radial diffusion length of light and the spot area. Experiment and theory are applied to typical substrates for thin layer chromatography (alumina, silica, cellulose). The diffusion lengths in these substrates are given and the absorptivities of the spots are calculated as a function of the spot area. 相似文献