全文获取类型
收费全文 | 2865篇 |
免费 | 209篇 |
国内免费 | 14篇 |
专业分类
化学 | 2012篇 |
晶体学 | 7篇 |
力学 | 71篇 |
数学 | 505篇 |
物理学 | 493篇 |
出版年
2023年 | 50篇 |
2022年 | 38篇 |
2021年 | 67篇 |
2020年 | 131篇 |
2019年 | 144篇 |
2018年 | 64篇 |
2017年 | 43篇 |
2016年 | 153篇 |
2015年 | 131篇 |
2014年 | 126篇 |
2013年 | 178篇 |
2012年 | 239篇 |
2011年 | 262篇 |
2010年 | 131篇 |
2009年 | 95篇 |
2008年 | 164篇 |
2007年 | 133篇 |
2006年 | 113篇 |
2005年 | 131篇 |
2004年 | 89篇 |
2003年 | 75篇 |
2002年 | 42篇 |
2001年 | 32篇 |
2000年 | 29篇 |
1999年 | 29篇 |
1998年 | 17篇 |
1997年 | 16篇 |
1996年 | 26篇 |
1995年 | 20篇 |
1994年 | 19篇 |
1993年 | 12篇 |
1992年 | 8篇 |
1989年 | 8篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1986年 | 7篇 |
1984年 | 7篇 |
1982年 | 9篇 |
1981年 | 9篇 |
1980年 | 11篇 |
1979年 | 12篇 |
1977年 | 8篇 |
1976年 | 10篇 |
1975年 | 19篇 |
1974年 | 16篇 |
1973年 | 8篇 |
1972年 | 7篇 |
1971年 | 9篇 |
1969年 | 7篇 |
1966年 | 7篇 |
排序方式: 共有3088条查询结果,搜索用时 31 毫秒
1.
Interactions of Pt‐ttpy with G‐Quadruplexes Originating from Promoter Region of the c‐myc Gene Deciphered by NMR and Gel Electrophoresis Analysis
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
2.
If the Riemann–Christoffel tensor associated with a field of class of positive definite symmetric matrices of order three vanishes in a connected and simply connected open subset , then this field is the metric tensor field associated with a deformation of class of the set , uniquely determined up to isometries of . We establish here that the mapping defined in this fashion is continuous, for ad hoc metrizable topologies. To cite this article: P.G. Ciarlet, F. Laurent, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 489–493. 相似文献
3.
Karl Gruber Christoph Kratky 《Journal of polymer science. Part A, Polymer chemistry》2004,42(3):479-486
Hydroxynitrile lyases catalyze the reversible cleavage of α-cyanohydrins to yield hydrocyanic acid and the corresponding aldehyde or ketone. Besides its biological interest, this class of enzymes is also of relevance in industrial biocatalysis for the enantioselective condensation of HCN with a variety of aldehydes and ketones. Several distinctly different types of hydroxynitrile lyases (HNLs) are known, which must have originated through convergent evolution from different ancestral proteins. Three-dimensional structural data are known for three classes of hydroxynitrile lyases. Insights into the reaction mechanisms emerged from a combination of structural, enzyme kinetic, spectroscopic, and molecular modeling data. For all three types of HNLs, mechanisms involving acid–base catalysis were proposed. In members belonging to the α,β-hydrolase type, the amino acid residues of the catalytic triad presumably act as general acid/base, whereas for flavine adenine dinucleotide (FAD)-dependent HNLs a single histidine residue fulfills this function. In the third type of HNL—which is related to carboxypeptidase—acid–base catalysis involves the carboxylate of the C-terminal residue. The catalytic relevance of a positive electrostatic potential in the active site was suggested in some of the mechanistic proposals. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 479–486, 2004 相似文献
4.
The piston problem is investigated in the case where the length of the cylinder is infinite (on both sides) and the ratio m/M is a very small parameter, where m is the mass of one particle of the gaz and M is the mass of the piston. Introducing initial conditions such that the stochastic motion of the piston remains in the average at the origin (no drift), it is shown that the time evolution of the fluids, analytically derived from Liouville equation in a previous work, agrees with the Second Law of thermodynamics. We thus have a non equilibrium microscopical model whose evolution can be explicitly shown to obey the two laws of thermodynamics. 相似文献
5.
We obtain asymptotic formulas for all the moments of certain arithmetic functions with linear recurrence sequences. We also apply our results to obtain asymptotic formulas for some mean values related to average orders of elements in finite fields. 相似文献
6.
Manil B. Anagnostopoulos D. F. Biri S. Borchert G. L. Breunlich W. Egger J. P. Gotta D. Gruber A. Hennebach M. Indelicato P. Jensen T. Liu Y. W. Markushin V. Nelms N. Simons L. M. Zmeskal H. 《Hyperfine Interactions》2003,146(1-4):343-347
Hyperfine Interactions - An experiment to measure the strong interaction width (Γ1s ) and shift (ε1s ) of the ground state of pionic hydrogen (π?p), in order to determine the... 相似文献
7.
8.
Optimale Quantisierung 总被引:1,自引:0,他引:1
Peter M. Gruber 《Mathematische Semesterberichte》2002,49(2):227-251
Zusammenfassung. Optimale Quantisierungen oder – damit ?quivalent – minimale Summen von Momenten spielen in mehreren Zweigen der Mathematik
und ihrer Anwendungen eine Rolle. Ausgehend von der Fejes Tóth'schen Ungleichung für Summen von Momenten in der euklidischen
Ebene und einem zugeh?rigen Stabilit?tssatz, werden gewisse Erweiterungen auf normierte R?ume und riemannsche Mannigfaltigkeiten
h?herer Dimension besprochen. Die Ergebnisse werden dann auf Probleme aus folgenden Bereichen angewendet: (i) Datenübertragung,
(ii) Wahrscheinlichkeitstheorie, (iii) numerische Integration, (iv) Approximation konvexer K?rper und (v) isoperimetrische
Probleme.
Eingegangen am 29. Mai 2002 / Angenommen am 8. Juli 2002 相似文献
9.
10.
Gruber JW Kittipongpatana N Bloxton JD Der Marderosian A Schaefer FT Gibbs R 《Journal of chromatographic science》2004,42(4):196-199
Devil's root, Oplopanax horridus, is a widely used folk medicine in Alaska and British Columbia. The inner bark of the root and stem has been used to treat colds, cough, fever, and diabetes. The present study involves the development of high-pressure liquid chromatography (HPLC) and thin-layer chromatography (TLC) methods to detect the presence of trans-nerolidol and sterols in the root bark. The HPLC and TLC analytical methods presented are suitable for the characterization and identification of Oplopanax horridus. 相似文献