全文获取类型
收费全文 | 8873篇 |
免费 | 356篇 |
国内免费 | 57篇 |
专业分类
化学 | 6157篇 |
晶体学 | 135篇 |
力学 | 190篇 |
综合类 | 1篇 |
数学 | 1220篇 |
物理学 | 1583篇 |
出版年
2023年 | 73篇 |
2022年 | 114篇 |
2021年 | 137篇 |
2020年 | 213篇 |
2019年 | 209篇 |
2018年 | 145篇 |
2017年 | 126篇 |
2016年 | 265篇 |
2015年 | 272篇 |
2014年 | 290篇 |
2013年 | 418篇 |
2012年 | 543篇 |
2011年 | 673篇 |
2010年 | 358篇 |
2009年 | 354篇 |
2008年 | 541篇 |
2007年 | 528篇 |
2006年 | 516篇 |
2005年 | 459篇 |
2004年 | 390篇 |
2003年 | 287篇 |
2002年 | 283篇 |
2001年 | 142篇 |
2000年 | 124篇 |
1999年 | 82篇 |
1998年 | 107篇 |
1997年 | 96篇 |
1996年 | 118篇 |
1995年 | 102篇 |
1994年 | 62篇 |
1993年 | 73篇 |
1992年 | 70篇 |
1991年 | 60篇 |
1990年 | 69篇 |
1989年 | 47篇 |
1988年 | 49篇 |
1987年 | 51篇 |
1986年 | 44篇 |
1985年 | 66篇 |
1984年 | 47篇 |
1983年 | 44篇 |
1982年 | 38篇 |
1981年 | 54篇 |
1980年 | 51篇 |
1979年 | 27篇 |
1978年 | 40篇 |
1977年 | 40篇 |
1976年 | 36篇 |
1973年 | 45篇 |
1971年 | 28篇 |
排序方式: 共有9286条查询结果,搜索用时 15 毫秒
1.
2.
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
3.
The influence of different referencing methods on the accuracy of δ13C value measurement of ethanol fuel by gas chromatography/combustion/isotope ratio mass spectrometry 下载免费PDF全文
4.
5.
6.
7.
8.
9.
Ozonolysis of a Series of Methylated Alkenes: Reaction Rate Coefficients and Gas‐Phase Products 下载免费PDF全文
Tristan Braure Véronique Riffault Alexandre Tomas Romeo Iulian Olariu Cecilia Arsene Yuri Bedjanian Patrice Coddeville 《国际化学动力学杂志》2015,47(9):596-605
The gas‐phase ozonolysis of three methylated alkenes, i.e., trans‐2,2‐dimethyl‐3‐hexene (22dM3H), trans‐2,5‐dimethyl‐3‐hexene (25dM3H), and 4‐methyl‐1‐pentene (4M1P), has been investigated in the presence of sufficient hydroxyl radical scavenger in a laminar flow reactor at ambient temperature (296 ± 2 K) and P = 1 atm of dry air (RH ≤ 5%). Ozone levels in the reactor were monitored by an automatic analyzer. Alkene and gas‐phase product concentrations were determined via online sampling either on three‐bed adsorbent cartridges followed by thermodesorption and GC/FID‐MS analysis or on 2,4‐dinitrophenylhydrazine (DNPH) cartridges for subsequent HPLC/UV analysis. Reaction rate coefficients of (3.38 ± 0.12) × 10?17 for 22dM3H and (2.71 ± 0.26) × 10?17 for 25dM3H, both in cm3 molecule?1 s?1 units, have been obtained under pseudo–first‐order conditions. Primary carbonyl products have been identified for the three investigated alkenes, and branching ratios are reported. In the case of 4M1P ozonolysis, the yield of a Criegee intermediate was indirectly determined. Kinetics and product study results are compared to those of literature when available. This work represents the first investigation of reaction products in the ozonolysis of 22dM3H, 25dM3H, and 4M1P in a flow reactor. 相似文献