全文获取类型
收费全文 | 352191篇 |
免费 | 3996篇 |
国内免费 | 1055篇 |
专业分类
化学 | 180150篇 |
晶体学 | 5491篇 |
力学 | 16074篇 |
综合类 | 7篇 |
数学 | 42622篇 |
物理学 | 112898篇 |
出版年
2021年 | 3369篇 |
2020年 | 3607篇 |
2019年 | 4051篇 |
2018年 | 5407篇 |
2017年 | 5619篇 |
2016年 | 7810篇 |
2015年 | 4555篇 |
2014年 | 7474篇 |
2013年 | 17122篇 |
2012年 | 13415篇 |
2011年 | 16112篇 |
2010年 | 11680篇 |
2009年 | 11572篇 |
2008年 | 14395篇 |
2007年 | 14363篇 |
2006年 | 13278篇 |
2005年 | 11617篇 |
2004年 | 10794篇 |
2003年 | 9510篇 |
2002年 | 9398篇 |
2001年 | 10712篇 |
2000年 | 7919篇 |
1999年 | 6204篇 |
1998年 | 5238篇 |
1997年 | 5100篇 |
1996年 | 4813篇 |
1995年 | 4099篇 |
1994年 | 4079篇 |
1993年 | 3957篇 |
1992年 | 4321篇 |
1991年 | 4528篇 |
1990年 | 4279篇 |
1989年 | 4227篇 |
1988年 | 4005篇 |
1987年 | 4111篇 |
1986年 | 3869篇 |
1985年 | 4899篇 |
1984年 | 5008篇 |
1983年 | 4100篇 |
1982年 | 4321篇 |
1981年 | 4025篇 |
1980年 | 3944篇 |
1979年 | 4210篇 |
1978年 | 4203篇 |
1977年 | 4187篇 |
1976年 | 4135篇 |
1975年 | 3910篇 |
1974年 | 3854篇 |
1973年 | 3863篇 |
1972年 | 2726篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
The Effect of the Spacer of Bis(biurea) Ligands on the Structure of A2L3‐type (A=anion) Phosphate Complexes 下载免费PDF全文
Prof. Biao Wu Dr. Shaoguang Li Prof. Yibo Lei Prof. Huaiming Hu Dr. Nader de Sousa Amadeu Prof. Dr. Christoph Janiak Dr. Jennifer S. Mathieson Dr. De‐Liang Long Prof. Leroy Cronin Prof. Xiao‐Juan Yang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2588-2593
By tuning the length and rigidity of the spacer of bis(biurea) ligands L, three structural motifs of the A2L3 complexes (A represents anion, here orthophosphate PO43?), namely helicate, mesocate, and mono‐bridged motif, have been assembled by coordination of the ligand to phosphate anion. Crystal structure analysis indicated that in the three complexes, each of the phosphate ions is coordinated by twelve hydrogen bonds from six surrounding urea groups. The anion coordination properties in solution have also been studied. The results further demonstrate the coordination behavior of phosphate ion, which shows strong tendency for coordination saturation and geometrical preference, thus allowing for the assembly of novel anion coordination‐based structures as in transition‐metal complexes. 相似文献
22.
23.
24.
25.
26.
27.
28.
29.
S. Q. Hou W. Wang Z. Y. Wang Z. W. Hu K. Liu 《Journal of Applied Mechanics and Technical Physics》2018,59(1):153-162
In order to investigate the characteristics of force chains in a granular flow system, a parallel plate shear cell is constructed to simulate the shear movement of an infinite parallel plate and observe variations in relevant parameters. The shear dilatancy process is divided into three stages, namely, plastic strain, macroscopic failure, and granular recombination. The stickslip phenomenon is highly connected with the evolution of force chains during the shear dilatancy process. The load–distribution rate curves and patterns of the force chains are utilized to describe the load-carrying behaviors and morphologic changes of force chains separately. Force chains, namely, “diagonal gridding,” “tadpole-shaped,” and “pinnate” are defined according to the form of the force chains in the corresponding three stages. 相似文献
30.
Robert G. W. Anderson 《Ambix》2015,62(4):333-344
Following colonisation of South America by the Spanish, many new naturally occurring substances were sent to Europe. One of these was the silvery, unreactive metal, platinum, discovered in New Grenada in the mid-eighteenth century. It was often found in granular form, associated with gold, and the challenge to chemists was to refine it, produce it as wire or sheet, and determine its chemical properties. This interested the professor of chemistry at the University of Edinburgh, Joseph Black, who was able to obtain samples from London-based Spanish contacts, particularly Ignacio Luzuriaga. This paper examines how Black transmitted his knowledge of the metal to large numbers of students attending his annual course. 相似文献