全文获取类型
收费全文 | 407篇 |
免费 | 5篇 |
国内免费 | 3篇 |
专业分类
化学 | 257篇 |
晶体学 | 3篇 |
力学 | 9篇 |
数学 | 58篇 |
物理学 | 88篇 |
出版年
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2018年 | 4篇 |
2017年 | 5篇 |
2016年 | 5篇 |
2015年 | 7篇 |
2014年 | 6篇 |
2013年 | 20篇 |
2012年 | 21篇 |
2011年 | 20篇 |
2010年 | 19篇 |
2009年 | 7篇 |
2008年 | 15篇 |
2007年 | 11篇 |
2006年 | 8篇 |
2005年 | 12篇 |
2004年 | 16篇 |
2003年 | 12篇 |
2002年 | 23篇 |
2001年 | 9篇 |
2000年 | 3篇 |
1999年 | 6篇 |
1998年 | 7篇 |
1997年 | 8篇 |
1996年 | 8篇 |
1995年 | 10篇 |
1994年 | 3篇 |
1990年 | 10篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1985年 | 13篇 |
1984年 | 10篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 6篇 |
1973年 | 5篇 |
1971年 | 2篇 |
1969年 | 3篇 |
1967年 | 3篇 |
1966年 | 2篇 |
1964年 | 2篇 |
1930年 | 2篇 |
排序方式: 共有415条查询结果,搜索用时 0 毫秒
71.
A Lagrangian study of two-dimensional turbulence for two different geometries, a periodic and a confined circular geometry, is presented to investigate the influence of solid boundaries on the Lagrangian dynamics. It is found that the Lagrangian acceleration is even more intermittent in the confined domain than in the periodic domain. The flatness of the Lagrangian acceleration as a function of the radius shows that the influence of the wall on the Lagrangian dynamics becomes negligible in the center of the domain, and it also reveals that the wall is responsible for the increased intermittency. The transition in the Lagrangian statistics between this region, not directly influenced by the walls, and a critical radius which defines a Lagrangian boundary layer is shown to be very sharp with a sudden increase of the acceleration flatness from about 5 to about 20. 相似文献
72.
Dr. Esmail Doustkhah Prof. Dr. Jianjian Lin Prof. Dr. Sadegh Rostamnia Prof. Dr. Christophe Len Prof. Dr. Rafael Luque Prof. Dr. Xiliang Luo Prof. Dr. Yoshio Bando Prof. Dr. Kevin C.-W. Wu Dr. Jeonghun Kim Prof. Dr. Yusuke Yamauchi Dr. Yusuke Ide 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(7):1614-1635
Sulfonic acid based mesostructures (SAMs) have been developed in recent years and have important catalytic applications. The primary applications of these materials are in various organic synthesis reactions, such as multicomponent reactions, carbon–carbon bond couplings, protection reactions, and Fries and Beckman rearrangements. This review aims to provide an overview of the recent developments in the field of SAMs with a particular emphasis on the reaction scope and advantages of heterogeneous solid acid catalysts. 相似文献
73.
74.
A small number of bifunctional monomers are mixed with a nematic liquid crystal (LC) and cured with a distributed electric field, which is produced by a circular-hole-patterned electrode structure. A gradient type of lens, that is, a LC microlens, is investigated for various polymer concentrations. Addition of 3% polymer is enough to freeze the gradient-index properties of the structure in the form of a convex lens, and a polymer-stabilized LC microlens is demonstrated. Although a lower concentration of polymer cannot hold the distribution properties in a curing process, it can maintain the variable focus as a nematic material can. The polymer networks can also eliminate the disclination line that usually appears and causes the lens in this type of LC device to deteriorate. 相似文献
75.
76.
77.
We discuss three natural pseudodistances and pseudometrics on a bounded domain in based on polynomial inequalities. 相似文献
78.
High pressure synthesis of late rare earth RFeAs(O,F) superconductors; R = Tb and Dy 总被引:1,自引:0,他引:1
Bos JW Penny GB Rodgers JA Sokolov DA Huxley AD Attfield JP 《Chemical communications (Cambridge, England)》2008,(31):3634-3635
New TbFeAs(O,F) and DyFeAs(O,F) superconductors with critical temperatures T(c) = 46 and 45 K and very high critical fields, >/=100 T, have been prepared at 1100-1150 degrees C and 10-12 GPa, demonstrating that high pressure may be used to synthesise late rare earth derivatives of the recently reported RFeAs(O,F) (R = La-Nd, Sm, Gd) high temperature superconductors. 相似文献
79.
80.
Nejmanová J Coufal P Bosáková Z Suchánková J Tesarová E 《Journal of separation science》2007,30(13):2123-2129
Various thioacridine derivatives are potential chemotherapeutics against various diseases which are intensively synthesized, characterized, and investigated by many research groups. Efficient, fast, and reliable separation and quantification methods for their analysis are still to be developed. MEKC and capillary LC (CLC) were applied for the separation and quantification of five highly hydrophobic, weakly basic, and structurally similar 9-(alkylthio)acridines. Since the common anionic and cationic surfactants failed to separate the strongly hydrophobic thioacridines by MEKC, sodium cholate was used in an alkaline BGE and successfully employed for their fast separation. In CLC, the weakly basic nature of the thioacridines necessitated use of LiChrosorb RP-select B sorbent as the stationary phase, which combined with a very simple mobile phase methanol/water yielded an efficient chromatographic separation system. Both, the MEKC and CLC optimized separation methods were then applied to quantify the thioacridines within a concentration range of 1.0 x 10(-5)-1.0 x 10(-3) mol/L and the obtained experimental results were critically compared. In practical terms, the MEKC analytical method can quantify the analytes much faster but with a lower reliability while the CLC method performs slower analysis with a higher repeatability of the experimental results. 相似文献