全文获取类型
收费全文 | 20230篇 |
免费 | 3667篇 |
国内免费 | 2539篇 |
专业分类
化学 | 14282篇 |
晶体学 | 265篇 |
力学 | 1370篇 |
综合类 | 129篇 |
数学 | 2344篇 |
物理学 | 8046篇 |
出版年
2024年 | 73篇 |
2023年 | 426篇 |
2022年 | 730篇 |
2021年 | 725篇 |
2020年 | 838篇 |
2019年 | 777篇 |
2018年 | 736篇 |
2017年 | 678篇 |
2016年 | 1072篇 |
2015年 | 962篇 |
2014年 | 1170篇 |
2013年 | 1473篇 |
2012年 | 1899篇 |
2011年 | 1840篇 |
2010年 | 1298篇 |
2009年 | 1233篇 |
2008年 | 1399篇 |
2007年 | 1217篇 |
2006年 | 1100篇 |
2005年 | 966篇 |
2004年 | 667篇 |
2003年 | 578篇 |
2002年 | 606篇 |
2001年 | 497篇 |
2000年 | 407篇 |
1999年 | 406篇 |
1998年 | 317篇 |
1997年 | 276篇 |
1996年 | 313篇 |
1995年 | 300篇 |
1994年 | 224篇 |
1993年 | 176篇 |
1992年 | 177篇 |
1991年 | 172篇 |
1990年 | 151篇 |
1989年 | 110篇 |
1988年 | 97篇 |
1987年 | 75篇 |
1986年 | 63篇 |
1985年 | 49篇 |
1984年 | 40篇 |
1983年 | 34篇 |
1982年 | 23篇 |
1981年 | 17篇 |
1980年 | 11篇 |
1977年 | 5篇 |
1973年 | 5篇 |
1972年 | 5篇 |
1971年 | 4篇 |
1957年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 622 毫秒
61.
62.
63.
B. Pignataro L. Chi S. Gao B. Anczykowski C. Niemeyer M. Adler H. Fuchs 《Applied Physics A: Materials Science & Processing》2002,74(3):447-452
Self-assembled oligomeric nanostructures consisting of bisbiotinylated DNA fragments connected by the protein streptavidin
(STV) are studied by dynamic scanning force microscopy (SFM) operating in air. A comparison of the images taken in repulsive
and attractive regimes is systematically made on DNA and STV structures. Stable and reproducible SFM images are obtained in
the attractive regime by using a special feedback circuit, called Q-control. On the other hand, when SFM is operating in the
repulsive regime, deformation of the structures that reduce the resolution and the image quality are clearly observable. The
heights of both DNA and STV have been measured as a function of the tip/molecule interaction forces. This study offers the
possibility to suggest a different mechanical behavior of DNA with respect to STV.
Received: 24 July 2001 / Accepted: 3 December 2001 / Published online: 4 March 2002 相似文献
64.
65.
本文通过对大量的黄酮类化合物13C NMR图谱的分析和研究,总结了不同类型的黄酮类化合物的13C NMR图谱特征及化学位移规律.对影响黄酮类化合物结构骨架上不同位置碳原子化学位移的因素进行了分析,建立了用于黄酮类天然产物13C NMR图谱智能解析的知识库. 相似文献
66.
高智民 《纯粹数学与应用数学》1994,10(2):1-5
本文证明了:若X是K-半分层空间,f是闭映射,则f(X)是K-半分层空间,这一结果推广改进了Lutzer与高国士的有关结果。 相似文献
67.
Observation of spontaneous pattern with six-fold symmetry in disk-shaped ZnO complex microstructures
L.W. Yang Y.J. Gao X.L. Wu Y.M. Yang G.S. Huang Z.Y. Zhang P.K. Chu 《Applied Physics A: Materials Science & Processing》2007,89(1):173-176
Using a simple vapor phase transport technique, we have fabricated unique complex disk-shaped ZnO microstructures comprising
a small disk coaxially grown on a large one and observed spatially perfect six-fold symmetric patterns. The observed results
can be explained based on the spontaneous nanoindentation (NI) effect under the geometric constraints and the explanation
can be extended to fathom the growth mechanism of other highly symmetrical ZnO nanostructures. Our results indicate that NI
not only can elucidate the mechanical properties of surfaces and thin films but also is an effective approach to fabricate
ordered nanostructures with high precision on the location of the building blocks.
PACS 81.16.Rf; 81.07.-b; 81.05.Dz 相似文献
68.
Several functionalized β-diketones and their europium complexes have been synthesized and characterized. The UV-Vis absorption, photoluminescent spectra, thermal and electrochemical properties of these complexes were investigated. The thermal analysis shows that the complexes have good thermal stability. By introducing the number of extended phenyl rings we succeeded in obtaining europium complexes with extremely high photoluminescent quantum yield (PLQY) in solution due to strong site isolation effect. 相似文献
69.
70.
WU Ke ZHAO Weizhong & GUO Hanying Department of Mathematics Capital Normal University Beijing China Institute of Theoretical Physics Chinese Academy of Sciences Beijing China 《中国科学A辑(英文版)》2006,(11)
In a way similar to the continuous case formally, we define in different but equivalent manners the difference discrete connection and curvature on discrete vector bundle over the regular lattice as base space. We deal with the difference operators as the discrete counterparts of the derivatives based upon the differential calculus on the lattice. One of the definitions can be extended to the case over the random lattice. We also discuss the relation between our approach and the lattice gauge theory and apply to the discrete integrable systems. 相似文献