全文获取类型
收费全文 | 34989篇 |
免费 | 343篇 |
国内免费 | 305篇 |
专业分类
化学 | 14831篇 |
晶体学 | 377篇 |
力学 | 1476篇 |
综合类 | 13篇 |
数学 | 9694篇 |
物理学 | 9246篇 |
出版年
2023年 | 57篇 |
2022年 | 60篇 |
2021年 | 109篇 |
2020年 | 176篇 |
2019年 | 163篇 |
2018年 | 1263篇 |
2017年 | 1522篇 |
2016年 | 882篇 |
2015年 | 733篇 |
2014年 | 647篇 |
2013年 | 889篇 |
2012年 | 3457篇 |
2011年 | 2698篇 |
2010年 | 2015篇 |
2009年 | 1763篇 |
2008年 | 907篇 |
2007年 | 970篇 |
2006年 | 949篇 |
2005年 | 4750篇 |
2004年 | 4177篇 |
2003年 | 2481篇 |
2002年 | 693篇 |
2001年 | 392篇 |
2000年 | 192篇 |
1999年 | 239篇 |
1998年 | 200篇 |
1997年 | 147篇 |
1996年 | 143篇 |
1995年 | 134篇 |
1994年 | 99篇 |
1993年 | 86篇 |
1992年 | 232篇 |
1991年 | 211篇 |
1990年 | 201篇 |
1989年 | 152篇 |
1988年 | 146篇 |
1987年 | 107篇 |
1986年 | 84篇 |
1985年 | 94篇 |
1984年 | 73篇 |
1983年 | 69篇 |
1981年 | 70篇 |
1980年 | 62篇 |
1978年 | 58篇 |
1977年 | 56篇 |
1976年 | 111篇 |
1975年 | 60篇 |
1974年 | 60篇 |
1973年 | 90篇 |
1972年 | 62篇 |
排序方式: 共有10000条查询结果,搜索用时 406 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.
Julia K Pruns Jens-Peter Vietzke Manfred Strassner Claudius Rapp Ulrich Hintze Wilfried A K?nig 《Rapid communications in mass spectrometry : RCM》2002,16(3):208-211
A new solvent-free sample preparation method using silver trifluoroacetate (AgTFA) was developed for the analysis of low molecular weight paraffins and microcrystalline waxes by laser desorption/ionization time-of-flight mass spectrometry (LDI-TOFMS). Experiments show that spectral quality can be enhanced by dispersing AgTFA directly in liquid paraffins without the use of additional solvents. This preparation mixture is applied directly to the MALDI probe. Solid waxes could be examined by melting prior to analysis. The method also provides sufficiently reproducible spectra that peak area ratios between mono- and bicyclic alkane peaks indicated variations in the cycloalkane content of paraffin samples. Dehydrogenation of hydrocarbons observed during the desorption/ionization process was studied by analysis of alkane standards. 相似文献
8.
The versatile behavior of a trihydrazidophosphoradamantane allowing the synthesis of a variety of neutral, mono- or di-cationic water-soluble molecules of potential interest for biphasic catalysis is reported. 相似文献
9.
In this paper we construct an example of a word metric on an infinite cyclic subgroup. This example shows that subexponential
distortion does not obstruct non-trivial growth of connected radii. This answers a question of Gromov [6]. The constructed
metric has other pathological properies. Specifically, its asymptotic cone depends on the choice of ultrafilter and scaling
sequence.
The work has been partially supported by the Swiss National Science Foundation. 相似文献
10.
We build a metric space which is homeomorphic to a Cantor set but cannot be realized as the attractor of an iterated function system. We give also an example of a Cantor set K in R3 such that every homeomorphism f of R3 which preserves K coincides with the identity on K. 相似文献