全文获取类型
收费全文 | 216篇 |
免费 | 1篇 |
国内免费 | 1篇 |
专业分类
化学 | 116篇 |
晶体学 | 1篇 |
力学 | 9篇 |
数学 | 40篇 |
物理学 | 52篇 |
出版年
2022年 | 2篇 |
2021年 | 1篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 2篇 |
2015年 | 5篇 |
2014年 | 8篇 |
2013年 | 4篇 |
2012年 | 16篇 |
2011年 | 17篇 |
2010年 | 10篇 |
2009年 | 6篇 |
2008年 | 16篇 |
2007年 | 20篇 |
2006年 | 14篇 |
2005年 | 19篇 |
2004年 | 7篇 |
2003年 | 5篇 |
2002年 | 12篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1988年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有218条查询结果,搜索用时 15 毫秒
11.
Konu J Chivers T Tuononen HM 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(43):12977-12987
The lithium salts of the chalcogenocarbonyl dianions [(E)C(PPh2S)2]2? (E=S ( 4 b ), Se ( 4 c )) were produced through the reactions between Li2[C(PPh2S)2] and elemental chalcogens in the presence of tetramethylethylenediamine (TMEDA). The solid‐state structure of {[Li(TMEDA)]2[(Se)C(PPh2S)2]}—[{Li(TMEDA)}2 4 c ]—was shown to be bicyclic with the Li+ cations bis‐S,Se‐chelated by the dianionic ligand. One‐electron oxidation of the dianions 4 b and 4 c with iodine afforded the diamagnetic complexes {[Li(TMEDA)]2[(SPh2P)2CEEC(PPh2S)2]} ([Li(TMEDA)]2 7 b (E=S), [Li(TMEDA)]2 7 c (E=Se)), which are formally dimers of the radical anions [(E)C(PPh2S)2]? . (E=S ( 5 b ), Se ( 5 c )) with elongated central E? E bonds. Two‐electron oxidation of the selenium‐containing dianion 4 c with I2 yielded the LiI adduct of a neutral selone {[Li(TMEDA)][I(Se)C(PPh2S)2]}—[{LiI(TMEDA)} 6 c ]—whereas the analogous reaction with 4 b resulted in the formation of 7 b followed by protonation to give {[Li(TMEDA)][(SPh2P)2CSS(H)C(PPh2S)2]}—[Li(TMEDA)] 8 b . Attempts to identify the transient radicals 5 b and 5 c by EPR spectroscopy in conjunction with DFT calculations of the electronic structures of these paramagnetic species and their dimers are also described. The crystal structures of [{Li(TMEDA)}2 4 c ], [{LiI(TMEDA)} 6 c ] ? C7H8, [Li(TMEDA)]2 7 b? (CH2Cl2)0.33, [Li(THF)2]2 7 b , [Li(TMEDA)]2 7 c , [Li(TMEDA)] 8 b? (CH2Cl2)2 and [Li([12]crown‐4)2] 8 b were determined and salient structural features are discussed. 相似文献
12.
[CoCl2{N,N′-Te2(NtBu)4}] (1) was obtained in good yields by the reaction of equimolar amounts of (tBu)NTe(μ-NtBu)2TeN(tBu) and CoCl2 in toluene under an argon atmosphere. The crystal structure of 1·CH2Cl2 showed that the dimeric tellurium diimide ligand is N,N′-chelated to cobalt. The related reaction of Se(NtBu)2 and CoCl2 affords a green product tentatively identified as a 1:1 adduct [CoCl2{N,N′-Se(NtBu)2}] (CHN analysis). However, recrystallization from thf produces the ion-separated complex [Co2(μ-Cl)3{N,N′-Se(NtBu)2}2(thf)2][CoCl3{NH2(tBu)}]·1½thf (2·1½thf), in which the monomeric selenium diimide ligand is N,N′-chelated to cobalt in the cation. A pathway for the formation of 2 from [CoCl2{N,N′-Se(NtBu)2}] in thf is proposed. 相似文献
13.
Nieminen JO Vesanen PT Zevenhoven KC Dabek J Hassel J Luomahaara J Penttilä JS Ilmoniemi RJ 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2011,212(1):154-160
In ultra-low-field magnetic resonance imaging (ULF MRI), superconductive sensors are used to detect MRI signals typically in fields on the order of 10-100 μT. Despite the highly sensitive detectors, it is necessary to prepolarize the sample in a stronger magnetic field on the order of 10-100 mT, which has to be switched off rapidly in a few milliseconds before signal acquisition. In addition, external magnetic interference is commonly reduced by situating the ULF-MRI system inside a magnetically shielded room (MSR). With typical dipolar polarizing coil designs, the stray field induces strong eddy currents in the conductive layers of the MSR. These eddy currents cause significant secondary magnetic fields that may distort the spin dynamics of the sample, exceed the dynamic range of the sensors, and prevent simultaneous magnetoencephalography and MRI acquisitions. In this paper, we describe a method to design self-shielded polarizing coils for ULF MRI. The experimental results show that with a simple self-shielded polarizing coil, the magnetic fields caused by the eddy currents are largely reduced. With the presented shielding technique, ULF-MRI devices can utilize stronger and spatially broader polarizing fields than achievable with unshielded polarizing coils. 相似文献
14.
Gerhard Post Jeffrey H. Kingston Samad Ahmadi Sophia Daskalaki Christos Gogos Jari Kyngas Cimmo Nurmi Nysret Musliu Nelishia Pillay Haroldo Santos Andrea Schaerf 《Annals of Operations Research》2014,218(1):295-301
We present the progress on the benchmarking project for high school timetabling that was introduced at PATAT 2008. In particular, we announce the High School Timetabling Archive XHSTT-2011 with 21 instances from 8 countries and an evaluator capable of checking the syntax of instances and evaluating the solutions. 相似文献
15.
Kimmo Nurmi Dries Goossens Jari Kyngäs 《The Journal of the Operational Research Society》2014,65(11):1770-1779
This paper presents a method to schedule a triple round robin tournament, which involves minitournaments, each hosted by one team. A key issue is that at the end of the season the number of home games should be balanced over the teams, despite the fact that in minitournament matches only the host team plays at home. This format is played in the Finnish national ice hockey league for players under the age of 20 years, where the problem is further complicated by many other constraints, for example, preassigned matches resulting from away tours that should limit the distances travelled by the teams. To obtain a schedule for this league, we sequentially solve four distinct combinatorial problems. This method allows us to construct a schedule for the 2009–2010 season, which is superior to the official schedule: it has no hard constraint violations, and outperforms the official schedule on three of five soft constraints. 相似文献
16.
The use of a TDI camera is restricted to cases of viewing from the direction of the surface normal. Our previous work indicated that a TDI camera can be used with viewing angles up to 30° from the surface normal which extends the usability of TDI for visual inspection applications. The objective of this paper is to examine the use of a TDI camera at a non-zero viewing angle under vibration conditions. The effects caused by vibration of the surface to be viewed become critical when using a TDI camera at non-zero viewing angles. A method of approximating the TDI performance under vibration conditions was determined and evaluated experimentally. The resulting measurements support the approximating method developed here. 相似文献
17.
18.
Jari M. Kinaret Mats Jonson Robert I. Shekhter Sebastian Eggert 《Physica E: Low-dimensional Systems and Nanostructures》1998,1(1-4)
We consider a mesoscopic ring connected to external reservoirs by tunnel junctions. The ring is capacitively coupled to an external gate electrode and may be pierced by a magnetic field. Due to strong electron–electron interactions within the ring the conductance shows Coulomb blockade oscillations as a function of the gate voltage, while Aharonov–Bohm interference effects lead to a dependence on the magnetic flux. The Hamiltonian of the ring is given by a Luttinger model that allows for an exact treatment of both interaction and interference effects. We conclude that the positions of conductance maxima as a function the external parameters can be used to determine the interaction parameter
, and the shapes of conductance peaks are strongly affected by electron correlations within the ring. 相似文献
19.
Giuseppe Cardone Sergey A. Nazarov Jan Sokolowski Jari Taskinen 《Comptes Rendus Mecanique》2007,335(12):763-767
We construct the asymptotics (as ε→0) of solutions to the Neumann problem for the Laplace equation and of the corresponding Dirichlet integral. The problem concerns a three-dimensional domain having two connected components of the boundary at the distance ε>0. To cite this article: G. Cardone et al., C. R. Mecanique 335 (2007). 相似文献
20.
We characterize boundedness, compactness and weak compactness of Volterra operators acting between different weighted Banach spaces of entire functions with sup‐norms in terms of the symbol g; thus we complement recent work by Bassallote, Contreras, Hernández‐Mancera, Martín and Paul 3 for spaces of holomorphic functions on the disc and by Constantin and Peláez 16 for reflexive weighted Fock spaces. 相似文献