全文获取类型
收费全文 | 360644篇 |
免费 | 4311篇 |
国内免费 | 1171篇 |
专业分类
化学 | 185462篇 |
晶体学 | 5578篇 |
力学 | 16275篇 |
综合类 | 7篇 |
数学 | 43940篇 |
物理学 | 114864篇 |
出版年
2021年 | 3511篇 |
2020年 | 3777篇 |
2019年 | 4200篇 |
2018年 | 5558篇 |
2017年 | 5811篇 |
2016年 | 8141篇 |
2015年 | 4817篇 |
2014年 | 7772篇 |
2013年 | 17557篇 |
2012年 | 14079篇 |
2011年 | 16998篇 |
2010年 | 12074篇 |
2009年 | 11839篇 |
2008年 | 15091篇 |
2007年 | 15049篇 |
2006年 | 13983篇 |
2005年 | 12221篇 |
2004年 | 11285篇 |
2003年 | 9951篇 |
2002年 | 9838篇 |
2001年 | 10795篇 |
2000年 | 8039篇 |
1999年 | 6319篇 |
1998年 | 5297篇 |
1997年 | 5144篇 |
1996年 | 4928篇 |
1995年 | 4206篇 |
1994年 | 4111篇 |
1993年 | 3971篇 |
1992年 | 4369篇 |
1991年 | 4530篇 |
1990年 | 4298篇 |
1989年 | 4216篇 |
1988年 | 4012篇 |
1987年 | 4115篇 |
1986年 | 3880篇 |
1985年 | 4977篇 |
1984年 | 5022篇 |
1983年 | 4130篇 |
1982年 | 4274篇 |
1981年 | 4009篇 |
1980年 | 3937篇 |
1979年 | 4185篇 |
1978年 | 4171篇 |
1977年 | 4140篇 |
1976年 | 4096篇 |
1975年 | 3887篇 |
1974年 | 3830篇 |
1973年 | 3861篇 |
1972年 | 2708篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
A. E. Angervaks S. A. Dimakov S. I. Kliment’ev A. I. Ryskin A. S. Shcheulin 《Optics and Spectroscopy》2002,93(2):307-314
The diffraction efficiency and the recording and relaxation times of dynamic reflection holograms, recorded in CdF2 crystals with bistable centers are studied experimentally in the temperature range 20–100°C. In the model experiments which measured the quality of the wave reflected from the hologram, the dynamic wavefront distortions are demonstrated to be efficiently compensated using a holographic corrector based on these crystals. CdF2 crystals with bistable centers are likely to be useful in solving problems of correction of laser light wavefront and image correction in observation telescopes with nonideal primary mirrors. 相似文献
172.
F. Iachello S. Oss 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(3):307-314
We present a brief review of algebraic techniques developed and applied in molecular spectroscopy in the last five years.
We also outline perspectives for new applications of the Lie algebraic method in the first decade of the new century.
Received 21 November 2001 相似文献
173.
C. J. S. Clarke 《Israel Journal of Mathematics》1983,45(1):9-16
It is shown that any finite dimensionalC 0 manifold (connected and Hausdorff but otherwise unrestricted) has an atlas of cardinality not greater than that of the continuum; while if it has a Hölder continuous pseudo-Riemannian metric then there is a countable atlas. 相似文献
174.
B. R. Harvey M. B. Lovett S. J. Boggis 《Journal of Radioanalytical and Nuclear Chemistry》1987,115(2):357-368
Selected experiences in the control of contamination and the threat it poses to the quality of analytical date are discussed in the context of the whole analytical process from collection of marine environmental samples, through handling and radiochemical separation, to the final interpretation of results. Examples include a demonstration of the contamination introduced during sediment core sectioning, contamination of sea water by a ship's pumping system, and the effect of filtration on the apparent partitioning of radionuclides between solid and liquid phases of sea water. 相似文献
175.
176.
177.
178.
Capillary Electrophoresis Chiral Separation for Enantiomeric Purity Determination of a Basic Drug in Pharmaceutical Formulations 总被引:1,自引:0,他引:1
Capillary electrophoresis using a running buffer composed of β-cyclodextrin as the chiral selector and ethanolamine mesylate at pH 9.6 is being used to monitor the stereochemical stability of a hydrophobic drug, containing two chiral centers, in two different formulated self-emulsifying drug delivery system (SEDDS) products. The separation takes place in less than 25 min. Strategies for enhancing the method reproducibility and detection sensitivity in the lower potency formulation are presented. The results demonstrating the specificity, assay precision, recovery, linearity and range achieved during the method validation experiments are presented in this paper.Presented at: CE in the Biotechnology and Pharmaceutical Industries: 7th Symposium on the Practical Applications for the Analysis of Proteins, Nucleotides and Small Molecules, Montreal, Canada, August 12–16, 2005. 相似文献
179.
An efficient synthesis of isothiazolidines in good yields is described. 相似文献
180.