全文获取类型
收费全文 | 84篇 |
免费 | 1篇 |
国内免费 | 2篇 |
专业分类
化学 | 53篇 |
力学 | 1篇 |
数学 | 15篇 |
物理学 | 18篇 |
出版年
2022年 | 1篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2014年 | 2篇 |
2013年 | 4篇 |
2012年 | 4篇 |
2011年 | 10篇 |
2010年 | 3篇 |
2009年 | 4篇 |
2008年 | 6篇 |
2007年 | 2篇 |
2006年 | 8篇 |
2005年 | 4篇 |
2004年 | 1篇 |
2003年 | 5篇 |
2002年 | 1篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1989年 | 1篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1867年 | 2篇 |
排序方式: 共有87条查询结果,搜索用时 15 毫秒
31.
2-(pent-4-ynyl)norbornadienes undergo an intramolecular [2+2+2] cycloaddition in the presence of (nbd)RuCl2(PPh3)2 as a catalyst affording annelated deltacyclenes in good to excellent yields. The usefulness of the reaction is illustrated by the straighforward conversion of pentacyclene 2a into the angularly fused triquinane 19. 相似文献
32.
Stanis?aw Tokarzewski Alphonse Ph. Magnus 《Journal of Computational and Applied Mathematics》2009,233(3):835-841
Taylor series expansions of a Stieltjes function f in various complex conjugate points are used to construct the so called unified continued fractions (UCF) terminated on P-th step by a remainder named tail of f. We prove that, if f is a Stieltjes function then its tail is also a Stieltjes function. The estimations of f are obtained in what follows. Numerical calculations of the new complex bounds on f generated by complex conjugate input data are carried out. 相似文献
33.
cariocal is a new seco-diterpene isolated from a cardioactive fraction of the false boldo, Coleus barbatus. The structure was deduced from chemical and spectral data. 相似文献
34.
The phase diagram of the two-dimensional ANNNI model is investigated by the cluster variation method (CVM). We confirm the stability of the disordered phase down toT=0 and the absence of a Lifshitz point at finite temperature forK<1/2, whereK the ratio of the second to the first neighbor pair interactions. Two different modulation regimes for the correlation functions of the disordered phase are separated by a disorder line along which theq vector of the susceptibility maximum undergoes a lock-in transition. The study in reciprocal space of the stability of the disordered phase allows us to define a critical line in the phase diagram along which theq vector characterizing the instability is incommensurate. Finally, we show the existence of another Lifshitz point forK tending to infinity. 相似文献
35.
Electron-rich half-sandwich ruthenium complex CpRuI(PPh3)2, generated in situ, catalyzed the coupling reaction of 7-azabenzonorbornadienes with alkynes to form 3a,9b-dihydrobenzo[g]indoles. This transformation involves the cleavage of one C-N bond of the bicyclic alkene and formation of two (C-C and C-N) bonds at the acetylenic carbons. The scope and limitations of the reaction are addressed according to the substitution patterns of the alkyne and of the substituent at the nitrogen atom of the azabenzonorbornadiene. 相似文献
36.
The electron-rich cyclopentadienylruthenium complex CpRuCl(PPh3)2 turns out to be an efficient catalyst for the regio- and stereoselective cyclopropanation of bicyclic alkenes with tertiary propargylic carboxylates. The reaction provides 1,2,3-trisubstituted cyclopropanes in high yields as a single stereoisomer instead of the expected cyclobutenes via [2 + 2] cycloaddition. Functional groups such as ethers, esters, alcohols, phenols, ketones, esters, carboxylic anhydrides, nitriles, halides, sulfones, imides, carbamates, and azines are tolerated with the catalyzed reaction. An efficient cyclopropanation of cyclobutenes was also demonstrated, providing the strained bicyclo[2.1.0(1,3)]pentane framework. 相似文献
37.
Pierre Alphonse Aneesha Varghese Claire Tendero 《Journal of Sol-Gel Science and Technology》2010,56(3):250-263
The optimum processing parameters required to synthesize, by hydrolysis of titanium isopropoxide (TIP), highly stable hydrosols
composed of nanoparticles of the smallest possible size, are deduced both from data available in literature and from our own
experiments. The colloids prepared in these conditions are composed of aggregates of anatase (~90%) and brookite crystallites
(5–6 nm). They are suitable for coatings and have long-term stability (more than one year) in terms of polymorphic composition,
crystallite and agglomerate size. Stable sols composed solely of anatase crystallites (4 nm) can be prepared by partially
complexing the TIP by acetylacetone before hydrolysis. It is not possible to produce porous films with these colloids because
they are stabilized by electrostatic repulsion which causes the particles to organize themselves, during the drying step,
to form materials with a close packed structure. However, coatings with controlled porosity can be prepared from these stable
sols through the post addition of polymers, like PEG or block copolymers. 相似文献
38.
39.
40.
Necessary and sufficient conditions for the extendability of residual designs of Steiner systems S(t,t + 1,v) are studied. In particular, it is shown that a residual design with respect to a single point is uniquely extendable, and the extendability of a residual design with respect to a pair of points is equivalent to a bipartition of the block graph of a related design. © 1993 John Wiley & Sons, Inc. 相似文献