全文获取类型
收费全文 | 390篇 |
免费 | 5篇 |
专业分类
化学 | 218篇 |
晶体学 | 4篇 |
力学 | 11篇 |
数学 | 44篇 |
物理学 | 118篇 |
出版年
2020年 | 8篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 5篇 |
2016年 | 5篇 |
2015年 | 8篇 |
2013年 | 14篇 |
2012年 | 15篇 |
2011年 | 12篇 |
2010年 | 9篇 |
2009年 | 6篇 |
2008年 | 12篇 |
2007年 | 15篇 |
2006年 | 18篇 |
2005年 | 13篇 |
2004年 | 8篇 |
2003年 | 9篇 |
2002年 | 10篇 |
2001年 | 11篇 |
2000年 | 15篇 |
1999年 | 3篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 8篇 |
1992年 | 20篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1979年 | 4篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1974年 | 4篇 |
1973年 | 9篇 |
1971年 | 3篇 |
1970年 | 5篇 |
1967年 | 3篇 |
1934年 | 4篇 |
1932年 | 2篇 |
1930年 | 2篇 |
1927年 | 2篇 |
排序方式: 共有395条查询结果,搜索用时 15 毫秒
91.
Michael FitzPatrick Pascale Champagne Michael F. Cunningham 《Cellulose (London, England)》2012,19(1):37-44
The ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([emim][OAc]) readily dissolves high concentrations of cellulose.
However, the high viscosity of [emim][OAc] (162 cP at 20 °C) could limit its use as a solvent for cellulose. Dissolved CO2 has been shown to decrease the viscosity of ILs. In this study, a 50 psi CO2 environment was applied for the dissolution of cellulose in [emim][OAc] to determine if the cellulose dissolution could be
enhanced. Dissolution profiles of 4 wt% cellulose dissolved in [emim][OAc] were obtained over a 24 h period. A 75% increase
in the amount of dissolved cellulose was observed with the application of a 50 psi CO2 environment. 相似文献
92.
93.
Eugenia Poliakov Susan Gentleman Preethi Chander Francis X Cunningham Jr Bella L Grigorenko Alexander V Nemuhin T Michael Redmond 《BMC biochemistry》2009,10(1):31-13
Background
β-carotene 15,15'-monooxygenase (BCMO1) catalyzes the crucial first step in vitamin A biosynthesis in animals. We wished to explore the possibility that a carbocation intermediate is formed during the cleavage reaction of BCMO1, as is seen for many isoprenoid biosynthesis enzymes, and to determine which residues in the substrate binding cleft are necessary for catalytic and substrate binding activity. To test this hypothesis, we replaced substrate cleft aromatic and acidic residues by site-directed mutagenesis. Enzymatic activity was measured in vitro using His-tag purified proteins and in vivo in a β-carotene-accumulating E. coli system. 相似文献94.
ChristopherW. Cunningham Kellie Hom Chayan Acharya Angela Wilks AlexanderD. MacKerell Andrew Coop 《Helvetica chimica acta》2010,93(2):220-226
The Diels–Alder reaction was applied to 4,5‐epoxymorphinan opioids to generate a novel aromatic cycloadduct at C(7) C(8): Thermolytic cleavage of sultine 8 produced the reactive diene o‐quinodimethane 7 which condensed favorably with codeine ( 11 ), but not with codeinone ( 9 ) or 14‐hydroxycodeinone ( 10 ), producing the desired tetrahydronaphtho adduct 12 with (7R,8R) geometry (Scheme). The configuration of the cycloadduct was determined by 1D‐ and 2D‐NMR experiments. The unanticipated reactivity of these codeine derivatives was investigated by quantum‐mechanical calculations, and it was determined that steric effects of the 6‐keto and 14‐hydroxy group likely precluded condensation by raising the molecular energy of their respective transition states. 相似文献
95.
L. Cunningham P.G. Murray E.J. Elliffe K. Haughian M. Hendry I.W. Martin S. Rowan K.A. Strain C. Torrie A.A. van Veggel 《Physics letters. A》2010,374(39):3993-75
New measurements of the mechanical loss factors of hydroxide-catalysis bonds have been made and these have been found to be significantly lower than previously reported. We provide the first estimate for the resulting thermal noise limitation for a practical test mass geometry for next generation gravitational wave detectors. 相似文献
96.
We describe a spectroscopic comparative analysis based on the optoacoustic technique over the wavelength range from 410nm to 1000nm using a Q-switched Nd:YAG pumped optical parametric oscillator tunable source on a gold nanostructure solution located within a highly scattering medium. The advantages of this method over standard spectroscopy techniques are the possibility to localize and monitor the spectroscopic response of absorbing materials located within turbid media. The operation is confirmed using a comparative analysis with the spectroscopic results obtained from a reference measurement scheme, based on a highly sensitive collimated optical transmission setup in parallel and under the same experimental conditions as the optoacoustic technique. 相似文献
97.
Jordan Pohn Mourad Heniche Louis Fradette Michael Cunningham Timothy McKenna 《Macromolecular Symposia》2011,302(1):133-141
Summary: A hybrid multi-zonal/computational fluid dynamics (CFD) framework is currently being developed to aid in the scale-up of high solid content latex production and processing. Poly3D, a commercial laminar CFD code tailored to modelling the mixing of non-Newtonian fluids, has been coupled to a population balance model via a customized interface. CFD is used to generate flow fields inside a series of reactors; this information is then transferred to a multi-zone population balance model to assess the impact of non-homogenous mixing on the evolution of the latex particle size distribution (PSD) when concentrated latex suspension is altered via the addition of a coagulant. The rheological properties of high solid content latexes are sensitive to changes in the PSD, so the flow field is periodically updated if significant changes in the rheological properties of the latex are detected in any of the zones. The details of the models comprising the framework are presented and the utility of the framework is demonstrated. 相似文献
98.
Cunningham C Glish GL Burinsky DJ 《Journal of the American Society for Mass Spectrometry》2006,17(1):81-84
Collision induced dissociation (CID) in a quadrupole ion trap mass spectrometer using the conventional 30 ms activation time is compared with high amplitude short time excitation (HASTE) CID using 2 ms and 1 ms activation times. As a result of the shorter activation times, dissociation of the parent ions using the HASTE CID technique requires resonance excitation voltages greater than conventional CID. After activation, the rf trapping voltage is lowered to allow product ions below the low mass cut-off to be trapped. The HASTE CID spectra are notably different from those obtained using conventional CID and can include product ions below the low mass cut-off for the parent ions of interest. The MS/MS efficiencies of HASTE CID are not significantly different when compared with the conventional 30 ms CID. Similar results were obtained with a two-dimensional (linear) ion trap and a three-dimensional ion trap. 相似文献
99.
Bart Park A. A. Blair H. Kinder T. R. Cunningham und R. W. Coltman 《Fresenius' Journal of Analytical Chemistry》1927,71(3-4):132-133
Ohne Zusammenfassung 相似文献
100.