全文获取类型
收费全文 | 234篇 |
免费 | 8篇 |
国内免费 | 1篇 |
专业分类
化学 | 162篇 |
力学 | 5篇 |
数学 | 21篇 |
物理学 | 55篇 |
出版年
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 4篇 |
2014年 | 6篇 |
2013年 | 13篇 |
2012年 | 9篇 |
2011年 | 13篇 |
2010年 | 10篇 |
2009年 | 3篇 |
2008年 | 14篇 |
2007年 | 4篇 |
2006年 | 6篇 |
2005年 | 15篇 |
2004年 | 3篇 |
2003年 | 6篇 |
2002年 | 9篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1997年 | 6篇 |
1996年 | 16篇 |
1995年 | 4篇 |
1994年 | 10篇 |
1993年 | 7篇 |
1992年 | 10篇 |
1991年 | 8篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1959年 | 1篇 |
1958年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有243条查询结果,搜索用时 93 毫秒
241.
242.
Parikshit Goswami Richard S. Blackburn Jim Taylor Patrick White 《Cellulose (London, England)》2011,18(4):1063-1072
Cellulose is a linear 1,4-β-glucan polymer where the units are able to form highly ordered structures, as a result of extensive
interaction through intra- and intermolecular hydrogen bonding of the three hydroxyl groups in each cellulose unit. Alkali
has a substantial influence on morphological, molecular and supramolecular properties of cellulose II polymer fibres causing
changes in crystallinity. Lyocell fibres pre-treated with 0.0, 2.0, and 4.0 mol dm−3 aqueous NaOH solution were dyed with hydrolyzed reactive dyes that had different molecular shapes and sizes. Overall exhaustion
(q
e), value of K, and −ΔG increased for lyocell samples pre-treated with aqueous NaOH solution in the following order: 2.0 > 4.0 > 0.0 mol dm−3 NaOH. The same trends were observed for colour strength (K/S) values of the dyeings. Pre-treatment of lyocell with 2.0 mol dm−3 NaOH creates the substrate that achieves the most thermodynamically favourable system for sorption of hydrolyzed reactive
dyes, as at this concentration crystallinity decreases (with respect to 0.0 mol dm−3 NaOH treated lyocell) to afford higher sorption; however, at higher alkali concentrations the macro-sorbent forms a compacted
unit that limits diffusion within the sorbent interior. Molecular size of the sorbate dye has a significant effect on the
sorption process: for the largest dye structure the sorption isotherm is most closely correlated to a Langmuir isotherm; as
the size of the dye decreases correlation to a Langmuir isotherm is observed, but with good correlation to the Freundlich
isotherm; as the size of the dye is decreased further sorption is more typical of a Freundlich isotherm. 相似文献
243.
G. Michael Blackburn Peter R. Ashton Mao-Jun Guo Michael Rogers Graham Taylor Andrzej Guranowski Donald Watts 《Heteroatom Chemistry》1991,2(1):163-170
The enzymatic cleavage of a scissile P O bond can be blocked by recourse to phosphonate analogues of biological phosphate esters. α-Fluorophosphonates have an enhanced electronegativity at the bridging carbon, which, in many cases, makes them superior to simple methylene phosphonates for the study of enzyme reactions. Thus, the β,γ-difluoro-methylene analogue of ATP is a good substrate for the interferon-induced (2→5)An synthetase, which converts it into a (2→5)A4 species having a 5′-β,γ-difluoromethylenetriphosphate. This binds strongly to RNase L but does not activate it. The unsymmetrical Ap4Aases from Artemia and Lupin are strongly inhibited by P1,P4-dithiophosphate analogues of diadenosyl-5′,5‴-P1,P4-tetraphosphate although nonregiospecific cleavage of certain P2,P3-methylene analogues can be observed. Some of these analogues are remarkably effective inhibitors of platelet aggregation and are effective inhibitors in vivo of arterial blood-clotting in rabbits. Separation of all diastereoisomers of P1,P4-dithiophosphate analogues of Ap4A is achieved cleanly using reverse-phase hplc chromatography and this provides direct access to β,γ-CHF-bridged analogues of ATP with resolved stereochemistry at the CHF center. Lastly, growing cells of Dictyostelium discoideum not only tolerate a range of substituted methylene bisphosphonates in their growth medium but actually incorporate them into nucleotide analogues of ATP and Ap4A. 相似文献