全文获取类型
收费全文 | 108篇 |
免费 | 1篇 |
国内免费 | 2篇 |
专业分类
化学 | 17篇 |
力学 | 1篇 |
数学 | 34篇 |
物理学 | 59篇 |
出版年
2020年 | 2篇 |
2019年 | 1篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2014年 | 5篇 |
2013年 | 1篇 |
2012年 | 2篇 |
2011年 | 9篇 |
2010年 | 2篇 |
2009年 | 3篇 |
2008年 | 1篇 |
2006年 | 1篇 |
2005年 | 6篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 1篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 4篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 7篇 |
1989年 | 8篇 |
1988年 | 10篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有111条查询结果,搜索用时 15 毫秒
101.
102.
John M. Peltier Richard W. Smith David B. Maclean Walter A. Szarek 《Journal of mass spectrometry : JMS》1992,27(1):31-36
The ammonia desorption chemical ionization (NH3-DCI) mass spectra of peracetylated gentiobiose (1) and two isotopically labelled gentiobioses (2 and 3) were examined. Compound 2 is labelled with trideuteroacetyl groups in the non-reducing moiety and 3 with trideuteroacetyl groups in the reducing moiety. It is shown that the [M + NH4 – 42]+ ion is not formed direct from [M + NH4]+ by loss of ketene but appears to be formed by way of a nucleophilic acyl substitution reaction resulting in a neutral species which complexes with NH4+. The disaccharides undergo cleavage at either side of the glycosidic oxygen joining the two sugar residues, a process which is accompanied by addition of H or CH3CO to afford neutral species which complex with NH4+. The structures of the ions resulting from H transfer have been inferred by comparison of their mass-analysed ion kinetic energy (MIKE) spectra with MIKE spectra of the [M + NH4]+ ions of compounds of established structure. A ring fragmentation reaction of 1, 2 and 3 is reported. 相似文献
103.
104.
105.
106.
S.?Artsteinartstein@math.princeton.edu" title="artst@post.tau.ac.il artstein@math.princeton.edu" itemprop="email" data-track="click" data-track-action="Email author" data-track-label="">Email author V.?Milman S.?Szarek N.?Tomczak-Jaegermann 《Geometric And Functional Analysis》2004,14(5):1134-1141
No Abstract. . 相似文献
107.
We show the existence of a sequence (λ
n
) of scalars withλ
n
=o(n) such that, for any symmetric compact convex bodyB ⊂R
n
, there is an affine transformationT satisfyingQ ⊂T(B) ⊂λ
n
Q, whereQ is then-dimensional cube. This complements results of the second-named author regarding the lower bound on suchλ
n
. We also show that ifX is ann-dimensional Banach space andm=[n/2], then there are operatorsα:l
2
m
→X andβ:X→l
∞
m
with ‖α‖·‖β‖≦C, whereC is a universal constant; this may be called “the proportional Dvoretzky-Rogers factorization”. These facts and their corollaries
reveal new features of the structure of the Banach-Mazur compactum.
Research performed while this author was visiting IHES. Supported in part by the NSF Grant DMS-8702058 and the Sloan Research
Fellowship. 相似文献
108.
Let be the euclidean norm on R
n
and let γ
n
be the (standard) Gaussian measure on R
n
with density . Let be defined by and let L be a lattice in R
n
generated by vectors of norm ≤ϑ. Then, for any closed convex set V in R
n
with , we have (equivalently, for any . The above statement can also be viewed as a ``nonsymmetric' version of the Minkowski theorem.
Received March 6, 1995, and in revised form January 26, 1996. 相似文献
109.
B. Mario Pinto Walter A. Szarek T. Bruce Grindley 《Magnetic resonance in chemistry : MRC》1984,22(11):676-692
Analogs of N-acetyl- and N-benzoyl-azacyclohex-2-enes having an oxygen atom, a methylene-d2 group or a carbonyl group in place of the C-4 methylene group have been synthesized. The amide rotational barriers in these compounds have been measured by the total line-shape analysis of variable-temperature 1H NMR spectra. The free energies of activation for both the N-acetyl and N-benzoyl series decrease in the sequence O?CD2 > C?O. The barriers for the first two compounds in each series are similar to those of the corresponding saturated analogs, a result which confirms recent reports that the long accepted barrier-decreasing effect of an α-olefinic substituent on nitrogen is counteracted. Evidence is presented that resonance stabilization of the rotational transition state in the unsaturated compounds still obtains. It is suggested that the introduction of an α-olefinic substituent on nitrogen has a negligible effect on the amide rotational barriers in the cases of the oxygen and methylene-d2 analogs, since any increase in the stabilization of the transition state by resonance is offset by the accompanying decrease in the sp3 character of the nitrogen atom. In cases in which a substituent on the olefinic group can interact directly with the lone pair on nitrogen, for example in the carbonyl analogs, then the resonance stabilization of the transition state is dominant. 相似文献
110.
Walter A. Szarek Osman Achmatowicz Jan Plenkiewicz Bruno K. Radatus 《Tetrahedron》1978,34(10):1427-1433
The photochemistry of glycosyl azides has been studied. Some of the azides, for example, β-d-glucopyranosyl or α-d-mannopyranosyl azide, were found to afford in good yield, on irradiation with UV light, the corresponding next-lower aldose. In other cases, for example, β-maltosyl or β-d-ribofuranosyl azide, there was observed the formation of an intermediate which, on standing in the dark, reverts back to starting material. A rationalization of the two types of behavior is suggested. 相似文献