全文获取类型
收费全文 | 211篇 |
免费 | 6篇 |
国内免费 | 2篇 |
专业分类
化学 | 169篇 |
晶体学 | 1篇 |
数学 | 27篇 |
物理学 | 22篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 2篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 4篇 |
2014年 | 4篇 |
2013年 | 28篇 |
2012年 | 9篇 |
2011年 | 15篇 |
2010年 | 9篇 |
2009年 | 6篇 |
2008年 | 10篇 |
2007年 | 9篇 |
2006年 | 8篇 |
2005年 | 6篇 |
2004年 | 8篇 |
2003年 | 3篇 |
2002年 | 8篇 |
2001年 | 2篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1969年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有219条查询结果,搜索用时 15 毫秒
21.
Fischer P Gruner M Jäger A Kataeva O Metz P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(47):13334-13340
The first total synthesis of the macrodiolide antibiotic pamamycin-649B (1) was achieved by using sultone methodology. The diethyl substituted larger hydroxy acid fragment was constructed in a concise fashion through domino elimination/alkoxide-directed 1,6-additions of ethyllithium to sultones derived from intramolecular Diels-Alder reaction of furan-containing vinylsulfonates. Intermolecular Yamaguchi esterification of the two hydroxy acid building blocks and subsequent Yamaguchi cyclization eventually provided the target macrocycle 1. Since the final lactonization with formation of the ester linkage between C1' and the C8 oxygen proceeded with complete C2' epimerization, the more readily available C2' epimeric smaller fragment could be used to streamline the synthetic sequence. 相似文献
22.
Synthesis and characterization of nanomagnetite particles and their polymer coated forms 总被引:1,自引:0,他引:1
Utkan GG Sayar F Batat P Ide S Kriechbaum M Pişkin E 《Journal of colloid and interface science》2011,353(2):372-379
Superparamagnetic nanoparticles were prepared by coprecipitation of ferrous (Fe(2+)) and ferric (Fe(3+)) aqueous solution by a base. Nanomagnetite particles were coated with poly(St/PEG-EEM/DMAPM) and poly(St/PEG-MA/DMAPM) layer by emulsifier-free emulsion polymerization. Chemical structure of nanoparticles was characterized by both FTIR and (1)H NMR. Particle morphologies were determined by Zeta Sizer, DLS, XRD and SAXS. Structural analysis showed that after polymer coating nanomagnetite particles kept their superparamagnetic property. Besides the synthesized magnetites, polymer coated forms of these particles are more biocompatible, well dispersable and uniform. These properties make them a very strong candidate for bioengineering applications, such as bioseparation, gene transfer. 相似文献
23.
24.
Margit Voigt 《Discrete Mathematics》1996,150(1-3):457-460
A graph G = G(V, E) with lists L(v), associated with its vertices v V, is called L-list colourable if there is a proper vertex colouring of G in which the colour assigned to a vertex v is chosen from L(v). We say G is k-choosable if there is at least one L-list colouring for every possible list assignment L with L(v) = k v V(G).
Now, let an arbitrary vertex v of G be coloured with an arbitrary colour f of L(v). We investigate whether the colouring of v can be continued to an L-list colouring of the whole graph. G is called free k-choosable if such an L-list colouring exists for every list assignment L (L(v) = k v V(G)), every vertex v and every colour f L(v). We prove the equivalence of the well-known conjecture of Erd s et al. (1979): “Every planar graph is 5-choosable” with the following conjecture: “Every planar graph is free 5-choosable”. 相似文献
25.
26.
Ana Brăileanu Susana Mihaiu Margit Bán J. Madarász G. Pokol 《Journal of Thermal Analysis and Calorimetry》2005,80(3):613-618
Summary Oxide materials belonging to the Sn-Ce-O system are very interesting due to their use as solid electrolytes in fuel cells, catalysts, sensors and photoanodes in solar cells. The aim of the present work is to investigate the thermal behaviour of some tin and cerium salt mixtures. Mixtures with different representative Sn:Ce atomic ratio were prepared by classical ceramic method using SnC2O4, Ce(SO4)2·4H2O and (NH4)2Ce(NO3)6 as starting compounds. The samples were investigated by means of TG/DTA methods in flowing and static air atmosphere. SnO2 and/or CeO2 were identified by X-ray diffraction and IR spectroscopy in the final decomposition products, depending on the initial composition of the both series. A different crystallinity degree of the solid products was observed depending on the Ce precursor. 相似文献
27.
Margit Imre 《Acta Mathematica Hungarica》1964,15(1-2):115-121
Ohne Zusammenfassung
Vorgelegt von
L. Fejes Tóth 相似文献
28.
Amides are the dominating products in some nitrilase catalyzed conversions of alpha-activated nitriles, but unexpectedly this hydrolytic reaction is also catalyzed by 1,4-dithio-dl-threitol (DTT), a standard antioxidizing enzyme stabilizer. 相似文献
29.
We prove the existence and study properties of the Green function of the unit ball for the Dunkl Laplacian △ k in \(\mathbb {R}^{d}\). As applications we derive the Poisson-Jensen formula for △ k -subharmonic functions and Hardy-Stein identities for the Poisson integrals of △ k . We also obtain sharp estimates of the Newton potential kernel, Green function and Poisson kernel in the rank one case in \(\mathbb {R}^{d}\). These estimates contrast sharply with the well-known results in the potential theory of the classical Laplacian. 相似文献
30.
Abdulrafiu Tunde Raji Sandro Scandolo Riccardo Mazzarello Schadrack Nsengiyumva Margit Härting David Thomas Britton 《哲学杂志》2013,93(20):1629-1645
By means of an ab initio plane-wave pseudopotential method, monovacancy, divacancy and self-interstitials in hcp titanium are investigated. The calculated monovacancy formation energy is 1.97 eV, which is in excellent agreement with other theoretical calculations, and agrees qualitatively with published experimental results. The relaxation of the atoms around a single vacancy is observed to be small. Two divacancy configurations, the in-plane and the off-plane, have also been shown to be equally stable. With regards to the interstitials, of the eight configurations studied, two (octahedral and basal octahedral) have relatively lower formation energies and are, thus, the most likely stable configurations. We find small energy differences between them, suggesting their possible co-existence. It is also observed that the tetrahedral configuration decays to a split dumbbell configuration, whereas both the basal tetrahedral and the basal pseudocrowdion interstitials decay to the basal octahedral configuration. Using the nudged elastic band method (NEB), we determine a possible minimum energy path (MEP) for the diffusion of self-interstitial titanium atoms from an octahedral site to the nearest octahedral site. The energy barrier for this migration mechanism is shown to be about 0.20 eV. 相似文献