全文获取类型
收费全文 | 342841篇 |
免费 | 5214篇 |
国内免费 | 1101篇 |
专业分类
化学 | 187205篇 |
晶体学 | 4590篇 |
力学 | 13656篇 |
综合类 | 7篇 |
数学 | 41577篇 |
物理学 | 102121篇 |
出版年
2020年 | 2385篇 |
2019年 | 2223篇 |
2018年 | 2335篇 |
2017年 | 2223篇 |
2016年 | 4636篇 |
2015年 | 3872篇 |
2014年 | 5126篇 |
2013年 | 15580篇 |
2012年 | 11874篇 |
2011年 | 14814篇 |
2010年 | 9084篇 |
2009年 | 8890篇 |
2008年 | 13709篇 |
2007年 | 13887篇 |
2006年 | 13402篇 |
2005年 | 12232篇 |
2004年 | 10874篇 |
2003年 | 9570篇 |
2002年 | 9368篇 |
2001年 | 10603篇 |
2000年 | 8180篇 |
1999年 | 6456篇 |
1998年 | 5196篇 |
1997年 | 5019篇 |
1996年 | 5187篇 |
1995年 | 4717篇 |
1994年 | 4505篇 |
1993年 | 4401篇 |
1992年 | 4814篇 |
1991年 | 4558篇 |
1990年 | 4316篇 |
1989年 | 4059篇 |
1988年 | 4363篇 |
1987年 | 4038篇 |
1986年 | 3894篇 |
1985年 | 5671篇 |
1984年 | 5733篇 |
1983年 | 4703篇 |
1982年 | 5065篇 |
1981年 | 5119篇 |
1980年 | 4857篇 |
1979年 | 4942篇 |
1978年 | 4978篇 |
1977年 | 4930篇 |
1976年 | 4862篇 |
1975年 | 4745篇 |
1974年 | 4590篇 |
1973年 | 4775篇 |
1972年 | 2672篇 |
1971年 | 1991篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Experimental Mechanics - Temperature gradients significantly affect the material fatigue process. A reliable and robust test procedure is needed for quantifying the effects of temperature gradients... 相似文献
2.
Machado J. A. Tenreiro Rocha-Neves J. M. Azevedo Filipe Andrade J. P. 《Nonlinear dynamics》2021,106(2):1525-1555
Nonlinear Dynamics - Given a data-set of Ribonucleic acid (RNA) sequences we can infer the phylogenetics of the samples and tackle the information for scientific purposes. Based on current data and... 相似文献
3.
Kobayashi M. Zhang Y. Ishikawa H. Sun J. Oddershede J. Juul Jensen D. Miura H. 《Experimental Mechanics》2021,61(5):817-828
Experimental Mechanics - The internal strain distribution developing during plastic deformation is important for understanding the mechanical properties of polycrystalline materials. Such... 相似文献
4.
Laguel Yassine Pillutla Krishna Malick Jérôme Harchaoui Zaid 《Set-Valued and Variational Analysis》2021,29(4):967-996
Set-Valued and Variational Analysis - R. Tyrell Rockafellar and his collaborators introduced, in a series of works, new regression modeling methods based on the notion of superquantile (or... 相似文献
5.
6.
In a 2:2 reaction with silver(I) chloride or bromide, 1,5-bis(1-phospholano)pentane ( 1a ) afforded frame-like macrocyclic structures, with intra- ( 2 , Cl) or intermolecular ( 3 , Br) halido bridges. In contrast, 1,7-bis(1-phospholano)heptane ( 1b ) formed coordination polymers 4a (Cl) and 4b (Br) with bridging bis-phospholane and halido ligands. A unique paddle wheel-type metallacryptand structure 5 was obtained from 1a and silver(I) bromide in a 2:3 reaction (M:L). All complexes were fully characterized by NMR, IR spectroscopy, mass spectrometry, and X-ray crystallography. 相似文献
7.
Haixing Guan Qianwen Zhang Prof. Dr. Patrick J. Walsh Prof. Dr. Jianyou Mao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(13):5210-5215
A unique nickel/organic photoredox co-catalyzed asymmetric reductive cross-coupling between α-chloro esters and aryl iodides is developed. This cross-electrophile coupling reaction employs an organic reductant (Hantzsch ester), whereas most reductive cross-coupling reactions use stoichiometric metals. A diverse array of valuable α-aryl esters is formed under these conditions with high enantioselectivities (up to 94 %) and good yields (up to 88 %). α-Aryl esters represent an important family of nonsteroidal anti-inflammatory drugs. This novel synergistic strategy expands the scope of Ni-catalyzed reductive asymmetric cross-coupling reactions. 相似文献
8.
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
9.
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
![点击此处可从《Rapid communications in mass spectrometry : RCM》网站下载免费的PDF全文](/ch/ext_images/free.gif)
10.