全文获取类型
收费全文 | 7149篇 |
免费 | 289篇 |
国内免费 | 45篇 |
专业分类
化学 | 5032篇 |
晶体学 | 124篇 |
力学 | 133篇 |
综合类 | 8篇 |
数学 | 857篇 |
物理学 | 1329篇 |
出版年
2023年 | 53篇 |
2022年 | 51篇 |
2021年 | 96篇 |
2020年 | 163篇 |
2019年 | 158篇 |
2018年 | 95篇 |
2017年 | 92篇 |
2016年 | 200篇 |
2015年 | 207篇 |
2014年 | 216篇 |
2013年 | 297篇 |
2012年 | 402篇 |
2011年 | 467篇 |
2010年 | 261篇 |
2009年 | 268篇 |
2008年 | 416篇 |
2007年 | 423篇 |
2006年 | 398篇 |
2005年 | 368篇 |
2004年 | 315篇 |
2003年 | 231篇 |
2002年 | 247篇 |
2001年 | 124篇 |
2000年 | 115篇 |
1999年 | 85篇 |
1998年 | 97篇 |
1997年 | 86篇 |
1996年 | 110篇 |
1995年 | 100篇 |
1994年 | 63篇 |
1993年 | 75篇 |
1992年 | 77篇 |
1991年 | 60篇 |
1990年 | 71篇 |
1989年 | 48篇 |
1988年 | 53篇 |
1987年 | 55篇 |
1986年 | 48篇 |
1985年 | 61篇 |
1984年 | 47篇 |
1983年 | 42篇 |
1982年 | 37篇 |
1981年 | 53篇 |
1980年 | 53篇 |
1979年 | 32篇 |
1978年 | 44篇 |
1977年 | 44篇 |
1976年 | 40篇 |
1973年 | 45篇 |
1971年 | 29篇 |
排序方式: 共有7483条查询结果,搜索用时 15 毫秒
1.
Laurens Kooijman Dr. Matthias Schuster Christian Baumann Simon Jurt Dr. Frank Löhr Dr. Boris Fürtig Prof. Dr. Peter Güntert Prof. Dr. Oliver Zerbe 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(47):21151-21158
To achieve efficient proton pumping in the light-driven proton pump bacteriorhodopsin (bR), the protein must be tightly coupled to the retinal to rapidly convert retinal isomerization into protein structural rearrangements. Methyl group dynamics of bR embedded in lipid nanodiscs were determined in the dark-adapted state, and were found to be mostly well ordered at the cytosolic side. Methyl groups in the M145A mutant of bR, which displays only 10 % residual proton pumping activity, are less well ordered, suggesting a link between side-chain dynamics on the cytosolic side of the bR cavity and proton pumping activity. In addition, slow conformational exchange, attributed to low frequency motions of aromatic rings, was indirectly observed for residues on the extracellular side of the bR cavity. This may be related to reorganization of the water network. These observations provide a detailed picture of previously undescribed equilibrium dynamics on different time scales for ground-state bR. 相似文献
2.
3.
4.
5.
6.
7.
Steven D. Bull Simon W. Epstein Nadeam Mujtaba Edward D. Savory Juan A. Tamayo 《Tetrahedron》2006,62(33):7911-7925
Enolates of (S)-N,N′-bis-(p-methoxybenzyl)-3-iso-propylpiperazine-2,5-dione exhibit high levels of enantiodiscrimination in alkylations with (RS)-1-aryl-1-bromoethanes and (RS)-2-bromoesters, affording substituted diketopiperazines containing two new stereogenic centres in high de. Deprotection and hydrolysis of the resultant substituted diketopiperazines provides a route to the asymmetric synthesis of homochiral methyl 2-amino-3-aryl-butanoates and 3-methyl-aspartates in high de and ee. 相似文献
8.
9.
Mao‐Chuan Yuan Ping‐I Shih Chen‐Han Chien Ching‐Fong Shu 《Journal of polymer science. Part A, Polymer chemistry》2007,45(14):2925-2937
We have synthesized a blue‐light‐emitting polyfluorene (PF) derivative ( PF‐CBZ‐OXD ) that presents bulky hole‐transporting carbazole and electron‐transporting oxadiazole pendent groups functionalized at the C‐9 positions of alternating fluorene units. The results from photoluminescence and electrochemical measurements indicate that both the side chains and the PF main chain retain their own electronic characteristics in the copolymer. An electroluminescent device incorporating this polymer as the emitting layer was turned on at 4.5 V; it exhibited a stable blue emission with a maximum external quantum efficiency of 1.1%. Moreover, we doped PF‐CBZ‐OXD and its analogue PF‐TPA‐OXD with a red‐light‐emitting iridium phosphor for use as components of phosphorescent red‐light emitters to investigate the effect of the host's HOMO energy level on the degree of charge trapping and on the electrophosphorescent efficiency. We found that spectral overlap and individual energy level matching between the host and guest were both crucial features affecting the performance of the electroluminescence devices. Atomic force microscopy measurements indicated that the dipolar nature of PF‐CBZ‐OXD , in contrast to the general nonpolarity of polydialkylfluorenes, provided a stabilizing environment that allowed homogeneous dispersion of the polar iridium triplet dopant. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2925–2937, 2007 相似文献
10.