全文获取类型
收费全文 | 569篇 |
免费 | 7篇 |
国内免费 | 1篇 |
专业分类
化学 | 362篇 |
晶体学 | 13篇 |
力学 | 22篇 |
数学 | 51篇 |
物理学 | 129篇 |
出版年
2022年 | 4篇 |
2021年 | 7篇 |
2019年 | 3篇 |
2018年 | 12篇 |
2017年 | 6篇 |
2016年 | 19篇 |
2015年 | 4篇 |
2014年 | 10篇 |
2013年 | 21篇 |
2012年 | 11篇 |
2011年 | 23篇 |
2010年 | 7篇 |
2009年 | 10篇 |
2008年 | 26篇 |
2007年 | 22篇 |
2006年 | 19篇 |
2005年 | 24篇 |
2004年 | 21篇 |
2003年 | 22篇 |
2002年 | 27篇 |
2001年 | 17篇 |
2000年 | 12篇 |
1999年 | 16篇 |
1998年 | 6篇 |
1997年 | 11篇 |
1996年 | 9篇 |
1995年 | 10篇 |
1994年 | 4篇 |
1993年 | 7篇 |
1992年 | 8篇 |
1991年 | 13篇 |
1990年 | 7篇 |
1988年 | 6篇 |
1987年 | 11篇 |
1986年 | 4篇 |
1985年 | 24篇 |
1984年 | 12篇 |
1983年 | 5篇 |
1982年 | 11篇 |
1980年 | 5篇 |
1979年 | 12篇 |
1978年 | 11篇 |
1977年 | 11篇 |
1976年 | 4篇 |
1975年 | 9篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1970年 | 3篇 |
1968年 | 2篇 |
1933年 | 4篇 |
排序方式: 共有577条查询结果,搜索用时 15 毫秒
571.
With rising atmospheric CO2 levels, there has been increasing interest in artificial photosynthetic schemes for converting this greenhouse gas into valuable fuels and small organics. Photoelectrochemical schemes for activating the inert CO2 molecule, however, operate at excessive overpotentials and thus do not convert actual light energy to chemical energy. Here we describe the selective conversion of CO2 to methanol at a p-GaP semiconductor electrode with a homogeneous pyridinium ion catalyst, driving the reaction with light energy to yield faradaic efficiencies near 100% at potentials well below the standard potential. 相似文献
572.
573.
High‐temperature tensile cell for in situ real‐time investigation of carbon fibre carbonization and graphitization processes
下载免费PDF全文
![点击此处可从《Journal of synchrotron radiation》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Michael Behr James Rix Brian Landes Bryan Barton Gerry Billovits Eric Hukkanen Jasson Patton Weijun Wang Denis Keane Steven Weigand 《Journal of synchrotron radiation》2016,23(6):1379-1389
A new high‐temperature fibre tensile cell is described, developed for use at the Advanced Photon Source at Argonne National Laboratory to enable the investigation of the carbonization and graphitization processes during carbon fibre production. This cell is used to heat precursor fibre bundles to temperatures up to ~2300°C in a controlled inert atmosphere, while applying tensile stress to facilitate formation of highly oriented graphitic microstructure; evolution of the microstructure as a function of temperature and time during the carbonization and higher‐temperature graphitization processes can then be monitored by collecting real‐time wide‐angle X‐ray diffraction (WAXD) patterns. As an example, the carbonization and graphitization behaviour of an oxidized polyacrylonitrile fibre was studied up to a temperature of ~1750°C. Real‐time WAXD revealed the gradual increase in microstructure alignment with the fibre axis with increasing temperature over the temperature range 600–1100°C. Above 1100°C, no further changes in orientation were observed. The overall magnitude of change increased with increasing applied tensile stress during carbonization. As a second example, the high‐temperature graphitizability of PAN‐ and pitch‐derived commercial carbon fibres was studied. Here, the magnitude of graphitic microstructure evolution of the pitch‐derived fibre far exceeded that of the PAN‐derived fibres at temperatures up to ~2300°C, indicating its facile graphitizability. 相似文献
574.
Saines PJ Tan JC Yeung HH Barton PT Cheetham AK 《Dalton transactions (Cambridge, England : 2003)》2012,41(28):8585-8593
The structures of four new 2,2-dimethylsuccinate frameworks suitable for exfoliation into nanosheets using ultrasonication are reported. These hybrid compounds contain either monovalent (Li(+)) or divalent (Co(2+) and Zn(2+)) cations, and they all feature hydrophobically capped covalently bonded layers that only interact with each other via weak van der Waals forces. Critically this shows that the use of this dicarboxylate ligand generally yields two dimensional compounds suitable for simple and affordable nanosheet exfoliation. This extends the range of frameworks that can be exfoliated and highlights the 2,2-dimethylsuccinate ligand as an excellent versatile platform for the production of nanosheets. The topologies of the layers in each framework were found to vary significantly and this appears to have a significant effect on the relative size of the nanosheets produced; increased space between methyl groups and more extensive inorganic connectivity appears to favour the formation of thin nanosheets with larger lateral dimensions. Additionally the magnetic properties of two of these frameworks were examined, and it was found that both exhibit strong low dimensional antiferromagnetic coupling despite their well-separated layers preventing three dimensional magnetic order. 相似文献
575.
Zhao C Degallaix J Ju L Fan Y Blair DG Slagmolen BJ Gray MB Lowry CM McClelland DE Hosken DJ Mudge D Brooks A Munch J Veitch PJ Barton MA Billingsley G 《Physical review letters》2006,96(23):231101
In an experiment to simulate the conditions in high optical power advanced gravitational wave detectors, we show for the first time that the time evolution of strong thermal lenses follows the predicted infinite sum of exponentials (approximated by a double exponential), and that such lenses can be compensated using an intracavity compensation plate heated on its cylindrical surface. We show that high finesse approximately 1400 can be achieved in cavities with internal compensation plates, and that mode matching can be maintained. The experiment achieves a wave front distortion similar to that expected for the input test mass substrate in the Advanced Laser Interferometer Gravitational Wave Observatory, and shows that thermal compensation schemes are viable. It is also shown that the measurements allow a direct measurement of substrate optical absorption in the test mass and the compensation plate. 相似文献
576.
Back BB Baker MD Ballintijn M Barton DS Betts RR Bickley AA Bindel R Budzanowski A Busza W Carroll A Chai Z Decowski MP García E Gburek T George N Gulbrandsen K Gushue S Halliwell C Hamblen J Hauer M Heintzelman GA Henderson C Hofman DJ Hollis RS Hołyński R Holzman B Iordanova A Johnson E Kane JL Katzy J Khan N Kucewicz W Kulinich P Kuo CM Lin WT Manly S McLeod D Mignerey AC Nouicer R Olszewski A Pak R Park IC Pernegger H Reed C Remsberg LP Reuter M Roland C Roland G Rosenberg L Sagerer J 《Physical review letters》2006,97(1):012301
We report on measurements of directed flow as a function of pseudorapidity in Au + Au collisions at energies of square root of SNN = 19.6, 62.4, 130 and 200 GeV as measured by the PHOBOS detector at the BNL Relativistic Heavy Ion Collider. These results are particularly valuable because of the extensive, continuous pseudorapidity coverage of the PHOBOS detector. There is no significant indication of structure near midrapidity and the data surprisingly exhibit extended longitudinal scaling similar to that seen for elliptic flow and charged particle pseudorapidity density. 相似文献
577.
Rainovski G Pietralla N Ahn T Lister CJ Janssens RV Carpenter MP Zhu S Barton CJ 《Physical review letters》2006,96(12):122501
Excited states in 138Ce have been studied via the 12C(138Ce, 138Ce*) Coulomb excitation reaction at 480 MeV. Relative cross sections have been determined from the gamma-ray yields observed with Gammasphere. The E2 and M1 strength distributions between the lowest six 2+ states up to 2.7 MeV enables us to identify the 2(4)+ state in 138Ce as the dominant fragment of the one-phonon 2(1,ms)+ mixed-symmetry state. Mixing between this level and a nearby isoscalar state is observed and is more than 4 times larger than in the neighboring isotone 136Ba. This is direct evidence that the stability of mixed-symmetry states strongly depends on the underlying subshell structure. 相似文献