全文获取类型
收费全文 | 29134篇 |
免费 | 857篇 |
国内免费 | 236篇 |
专业分类
化学 | 19764篇 |
晶体学 | 133篇 |
力学 | 677篇 |
综合类 | 1篇 |
数学 | 5623篇 |
物理学 | 4029篇 |
出版年
2022年 | 202篇 |
2021年 | 306篇 |
2020年 | 372篇 |
2019年 | 333篇 |
2018年 | 291篇 |
2017年 | 305篇 |
2016年 | 653篇 |
2015年 | 658篇 |
2014年 | 703篇 |
2013年 | 1479篇 |
2012年 | 1474篇 |
2011年 | 1758篇 |
2010年 | 979篇 |
2009年 | 843篇 |
2008年 | 1510篇 |
2007年 | 1504篇 |
2006年 | 1591篇 |
2005年 | 1414篇 |
2004年 | 1359篇 |
2003年 | 1131篇 |
2002年 | 1065篇 |
2001年 | 463篇 |
2000年 | 417篇 |
1999年 | 407篇 |
1998年 | 394篇 |
1997年 | 439篇 |
1996年 | 402篇 |
1995年 | 365篇 |
1994年 | 395篇 |
1993年 | 347篇 |
1992年 | 326篇 |
1991年 | 326篇 |
1990年 | 278篇 |
1989年 | 285篇 |
1988年 | 263篇 |
1987年 | 222篇 |
1986年 | 248篇 |
1985年 | 369篇 |
1984年 | 380篇 |
1983年 | 317篇 |
1982年 | 354篇 |
1981年 | 321篇 |
1980年 | 340篇 |
1979年 | 272篇 |
1978年 | 302篇 |
1977年 | 282篇 |
1976年 | 226篇 |
1975年 | 190篇 |
1974年 | 196篇 |
1973年 | 166篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
91.
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
92.
93.
94.
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
95.
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
96.
Peter Amrhein 《Annals of the Institute of Statistical Mathematics》1995,47(1):167-170
Although the theory of rank tests is rather complete in the one-sided case, it was not even known in 1959, whether the Wilcoxon two-sample test and other similar tests are unbiased against the two-sided alternatives (Lehmann (1959,Testing Statistical Hypotheses, p. 240, Wiley, New York)). A partial answer to this question was given by Sugiura in 1965, who found, that the test named above may be biased (Sugiura (1965,Ann. Inst. Statist. Math.,17, 261–263)). According to Lehmann (1986,Testing Statistical Hypotheses, 2nd ed., pp. 322–324, Wiley, New York) it seems to be still open, whether the same is true for the WILCOXON one-sample test, which is also known as WILCOXON signed rank test. This will be shown in the present paper. 相似文献
97.
We carry out a careful study of operator algebras associated with Delone dynamical systems. A von Neumann algebra is defined using noncommutative integration theory. Features of these algebras and the operators they contain are discussed. We restrict our attention to a certain C
*-subalgebra to discuss a Shubin trace formula. 相似文献
98.
99.
Capillary gas chromatography coupled to microwave-inducedplasma detection furnishes sensitivity adequate for trace analysis when the signal is monitored at a carbon emission line. Work performed with one of these systems at high electronic gain for the carbon signal has revealed solvent band widths in excess of four minutes; these impeded quantification of peaks eluting after the solvent. This report discusses two phenomena which could be related to the unexpected intensity of this solvent response: photomultiplier tube saturation and carbon deposits in the quartz plasma discharge tube. 相似文献
100.