全文获取类型
收费全文 | 750篇 |
免费 | 52篇 |
国内免费 | 2篇 |
专业分类
化学 | 576篇 |
晶体学 | 7篇 |
力学 | 23篇 |
数学 | 80篇 |
物理学 | 118篇 |
出版年
2023年 | 9篇 |
2022年 | 8篇 |
2021年 | 11篇 |
2020年 | 21篇 |
2019年 | 14篇 |
2018年 | 24篇 |
2017年 | 5篇 |
2016年 | 38篇 |
2015年 | 22篇 |
2014年 | 28篇 |
2013年 | 37篇 |
2012年 | 62篇 |
2011年 | 81篇 |
2010年 | 39篇 |
2009年 | 47篇 |
2008年 | 64篇 |
2007年 | 69篇 |
2006年 | 56篇 |
2005年 | 54篇 |
2004年 | 25篇 |
2003年 | 29篇 |
2002年 | 23篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1988年 | 3篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1981年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有804条查询结果,搜索用时 234 毫秒
31.
Tailoring the Structure of Two‐Dimensional Self‐Assembled Nanoarchitectures Based on NiII–Salen Building Blocks 下载免费PDF全文
Dr. Marta Viciano‐Chumillas Dongzhe Li Dr. Alexander Smogunov Dr. Sylvain Latil Dr. Yannick J. Dappe Dr. Cyrille Barreteau Prof. Talal Mallah Dr. Fabien Silly 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(42):13566-13575
The synthesis of a series of NiII–salen‐based complexes with the general formula of [Ni(H2L)] (H4L=R2‐N,N′‐bis[R1‐5‐(4′‐benzoic acid)salicylidene]; H4L1: R2=2,3‐diamino‐2,3‐dimethylbutane and R1=H; H4L2: R2=1,2‐diaminoethane and R1=tert‐butyl and H4L3: R2=1,2‐diaminobenzene and R1=tert‐butyl) is presented. Their electronic structure and self‐assembly was studied. The organic ligands of the salen complexes are functionalized with peripheral carboxylic groups for driving molecular self‐assembly through hydrogen bonding. In addition, other substituents, that is, tert‐butyl and diamine bridges (2,3‐diamino‐2,3‐dimethylbutane, 1,2‐diaminobenzene or 1,2‐diaminoethane), were used to tune the two‐dimensional (2D) packing of these building blocks. Density functional theory (DFT) calculations reveal that the spatial distribution of the LUMOs is affected by these substituents, in contrast with the HOMOs, which remain unchanged. Scanning tunneling microscopy (STM) shows that the three complexes self‐assemble into three different 2D nanoarchitectures at the solid–liquid interface on graphite. Two structures are porous and one is close‐packed. These structures are stabilized by hydrogen bonds in one dimension, while the 2D interaction is governed by van der Waals forces and is tuned by the nature of the substituents, as confirmed by theoretical calculations. As expected, the total dipolar moment is minimized 相似文献
32.
Bernard Lavielle Bertrand Thomas Eric Gilabert Gregory Canchel Denis Horlait Sylvain Topin Fabien Pointurier Christophe Moulin 《Journal of mass spectrometry : JMS》2016,51(10):908-913
A double focusing sector field mass filter used in Nier–Johnson geometry has been built in order to perform Kr isotope enrichment for 81Kr and 85Kr isotopes. The principle consists in implanting Kr+ ions accelerated at 7 keV in Al foils after separation using the magnetic sector. A specific ion source has been designed capable of generating high Kr+ ion beams (>0.5 μA) to transfer into the collecting Al foils in 3 to 5 h significant fractions of large Kr samples (1015 to 1016 atoms) initially introduced in the instrument. Implanted Kr isotopes can be further selectively released from the Al foil by surface ablation using an infrared laser beam. Implantation yields and enrichment factors are measured using a conventional mass spectrometer. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
33.
34.
Thomas Krajewski Vincent Rivasseau Fabien Vignes-Tourneret 《Annales Henri Poincare》2011,12(3):483-545
We define a new topological polynomial extending the Bollobás–Riordan one, which obeys a four-term reduction relation of the
deletion/contraction type and has a natural behaviour under partial duality. This allows to write down a completely explicit
combinatorial evaluation of the polynomials, occurring in the parametric representation of the non-commutative Grosse–Wulkenhaar
quantum field theory. An explicit solution of the parametric representation for commutative field theories based on the Mehler
kernel is also provided. 相似文献
35.
Pierre-Yves Roger Fabien Blondeau David Bensa Thierry Constantieux Jean Rodriguez 《Molecular diversity》2009,13(4):469-473
A new one-pot domino reaction for a general entry to functionalised bridged bicyclo[n.2.1] ring systems from α ,α’-diactivated cyclic ketones and trans-1,4-dihalides is described. The sequence combines a base promoted C–O cycloalkylation reaction leading to fused polycyclic
enol ethers and their in situ palladium-catalysed isomerisation. 相似文献
36.
N‐(2‐Ethylhexyl)carbazole: A New Fluorophore Highly Suitable as a Monomolecular Liquid Scintillator 下载免费PDF全文
Eva Montbarbon Dr. Fabien Sguerra Dr. Guillaume H. V. Bertrand Élodie Magnier Dr. Romain Coulon Dr. Robert B. Pansu Dr. Matthieu Hamel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(34):12074-12080
The synthesis, photophysical properties, and applications in scintillation counting of N‐(2‐ethylhexyl)carbazole (EHCz) are reported. This molecule displays all of the required characteristics for an efficient liquid scintillator (emission wavelength, scintillation yield), and can be used without any extra fluorophores. Thus, its scintillation properties are discussed, as well as its fast neutron/gamma discrimination. For the latter application, the material is compared with the traditional liquid scintillator BC‐501 A, and other liquid fluorescent molecules classically used as scintillation solvents, such as xylene, pseudocumene (PC), linear alkylbenzenes (LAB), diisopropylnaphthalene (DIN), 1‐methylnaphthalene (1‐MeNapht), and 4‐isopropylbiphenyl (iPrBiph). For the first time, an excimeric form of a molecule has been advantageously used in scintillation counting. A moderate discrimination between fast neutrons and gamma rays was observed in bulk EHCz, with an apparent neutron/gamma discrimination potential half of that of BC‐501 A. 相似文献
37.
When certain trivalent rare-earth ions (Ln's) are co-doped in CaGa2S4:Mn2+ as sensitizers, the Mn red emission of the compound is strikingly enhanced. In this work, efficiency of each lanthanide is studied. The best efficiencies are achieved with La3+-, Pr3+-, and Tb3+- co-doped compounds, for each of which the effects of concentrations of the co-doped ions on the Mn2+ emission are investigated. The energy-transfer mechanisms and the location of electronic energy levels of both the trivalent and the divalent lanthanides in the energy band gap of the host material are discussed. Depending on Ln's, charge transfer or cross-relaxation should be taken into account. 相似文献
38.
[reaction: see text] The readily available N-(O-ethyl thiocarbonylsulfanyl)amides are powerful amidyl radical precursors that undergo 5-exo cyclization to give pyrrolidinone derivatives via a radical-chain reaction initiated by a small amount of lauroyl peroxide. 相似文献
39.
Impurity profiles of 3,4-methylenedioxymethylamphetamine (MDMA) tablets seized in France have been examined. The samples were extracted with methylene chloride under basic conditions and then analyzed by capillary gas chromatography. Almost 30 compounds were identified as precursors, intermediates and by-products. Palmitic and stearic acid were also found as tableting materials. The comparison of the different profiles obtained by the reported procedure provided very useful information about the synthetic processes used by clandestine laboratories and enabled a classification into several groups of profiles. According to these results, the reductive amination route appears to be the most common synthetic pathway in Western Europe. Furthermore, 3,4-methylenedioxyphenyl-2-propanone seems to be the most used precursor in clandestine laboratories. 相似文献
40.
We study the nature of the ground state of the two-dimensional extended boson Hubbard model on a square lattice by quantum Monte Carlo methods. We demonstrate that strong but finite on-site interaction U along with a comparable nearest-neighbor repulsion V result in a thermodynamically stable supersolid ground state for densities larger than 1/2, in contrast to fillings less than 1/2 or for very large U, where the checkerboard supersolid is unstable towards phase separation. We discuss the relevance of our results to realizations of supersolids using cold bosonic atoms in optical lattices. 相似文献