全文获取类型
收费全文 | 601篇 |
免费 | 11篇 |
国内免费 | 2篇 |
专业分类
化学 | 418篇 |
晶体学 | 7篇 |
力学 | 9篇 |
数学 | 130篇 |
物理学 | 50篇 |
出版年
2022年 | 2篇 |
2021年 | 5篇 |
2020年 | 8篇 |
2019年 | 5篇 |
2018年 | 3篇 |
2017年 | 7篇 |
2016年 | 11篇 |
2015年 | 21篇 |
2014年 | 14篇 |
2013年 | 39篇 |
2012年 | 33篇 |
2011年 | 33篇 |
2010年 | 16篇 |
2009年 | 20篇 |
2008年 | 23篇 |
2007年 | 40篇 |
2006年 | 28篇 |
2005年 | 24篇 |
2004年 | 20篇 |
2003年 | 31篇 |
2002年 | 22篇 |
2001年 | 8篇 |
2000年 | 12篇 |
1999年 | 13篇 |
1998年 | 6篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 13篇 |
1994年 | 8篇 |
1993年 | 10篇 |
1992年 | 12篇 |
1991年 | 7篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 9篇 |
1981年 | 4篇 |
1980年 | 9篇 |
1979年 | 4篇 |
1978年 | 9篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1975年 | 7篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1966年 | 3篇 |
排序方式: 共有614条查询结果,搜索用时 15 毫秒
81.
Jean Pierre Majoral Monique Revel Raymond Kraemer Hlne Germa Jacques Navech 《Journal of heterocyclic chemistry》1977,14(5):749-755
The reaction of phosphodi- or trihydrazides with orthoesters affords mainly 2,3,4,5-tetrahydro-1,2,4,5,3-tetrazaphosphorines and sometimes 4-amino-1,2,4,3-triazaphospholidines. These 1,2,4,5,3-tetrazaphosphorines present a prototropy which explains different pathways of the reaction of these derivatives with formaldehyde or acetone, The structure of all heterocycles which were obtained was established by nmr spectra. 相似文献
82.
83.
Monique Combescot 《Applied Physics A: Materials Science & Processing》1991,53(6):547-551
We show that the exciton optical Stark effect is basically a dressed-exciton effect: excitons are dressed by the electromagnetic field in a way similar to the way atoms are dressed. The situation appears, however, much richer in semiconductor than in atomic physics due to both the complexity of the band structure and the Coulomb interaction between excitons. We show that the dressed-exciton effect can appear as either a blue or a red shift of the exciton line as well as a splitting of exciton levels, with an interesting dimensional effect in the absorption strength. We also relate the dressed-exciton to the polariton effect. 相似文献
84.
85.
A nonpreemptive single stage manufacturing process with parallel, unrelated machines and multiple job types with setups (PUMS) is considered. We propose a hybrid approximation procedure where a Lagrangean relaxation dual and a Lagrangean decomposition dual are solved one after the other to generate a good lower bound on the optimal makespan value. Computational results are reported. 相似文献
86.
For (initiator)/(monomer) ratios exceeding 10-3, the anionic polymerization of α-methyleneglutaronitrile in homogeneous solution in DMF (initiated by lithium-naphthalene at -35° or by diphenylmethyl-lithium at -70°) leads to fairly white polymers with yields higher than 75 per cent. Infra-red and u.v. spectrometric studies and flash pyrolysis experiments show that the nitrile functions are involved in the polymerization only to a very small extent. On the other hand, molecular weight and sedimentation measurements and hydrodynamic behaviour of the polymer in DMF solution suggest a broad polydispersity for the samples, and a very high branching density for their higher molecular weight fractions. These characteristic features are to be correlated with those of anionic polyacrylonitrile; they may be tentatively attributed to transfer to polymer at the acidic methylene group a to the nitrile function. 相似文献
87.
88.
Kinderman SS Wekking MM van Maarseveen JH Schoemaker HE Hiemstra H Rutjes FP 《The Journal of organic chemistry》2005,70(14):5519-5527
[reaction: see text] Catalytic Sn(OTf)2-induced cyclization of linear, aryl-containing allylic N,O-acetals produced vinyl-substituted tetrahydroisoquinolines and tetrahydro-1H-beta-carbolines. The usefulness of the vinyl moiety in the resulting products was demonstrated via the synthesis of various key building blocks for alkaloid structures. The alpha-vinyl moiety was utilized in a [2,3] sigmatropic rearrangement, in ring-closing metathesis and a cross-metathesis-based synthesis of vincantril, an antianoxia agent, and a synthetic member of the vincamine type natural products. 相似文献
89.
The Neumann realization for the Schr?dinger operator with magnetic field is considered in a bounded two-dimensional domain
with corners. This operator is associated with a small semi-classical parameter h or, equivalently, with a large magnetic field.We investigate the behavior of its eigenpairs as h tends to zero, like in a semi-classical limit. We prove, in the situation where the domain is a polygon and the magnetic
field is constant, that the lowest eigenvalues are exponentially close to those of model problems associated with the corners.
We approximate the corresponding eigenvectors by linear combinations of functions concentrated in corners at the scale
If the domain has curved sides and the magnetic field is smoothly varying, we exhibit a full asymptotics for eigenpairs in
powers of
Communicated by Christian Gérard
Submitted: October 13, 2005 Accepted: December 19, 2005 相似文献
90.
Elhamzaoui H Jousseaume B Toupance T Zakri C Biesemans M Willem R Allouchi H 《Chemical communications (Cambridge, England)》2006,(12):1304-1306
The hydrolysis of a bridged alpha,omega-bis(trialkynylstannylated) compound leads to a hybrid material ordered by self-assembly where the spacer forms two six-membered [1,2]oxastanninane rings by intramolecular coordination. 相似文献