全文获取类型
收费全文 | 223篇 |
免费 | 11篇 |
专业分类
化学 | 145篇 |
晶体学 | 1篇 |
力学 | 8篇 |
数学 | 26篇 |
物理学 | 54篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 6篇 |
2020年 | 6篇 |
2019年 | 2篇 |
2018年 | 7篇 |
2017年 | 8篇 |
2016年 | 11篇 |
2015年 | 11篇 |
2014年 | 14篇 |
2013年 | 15篇 |
2012年 | 14篇 |
2011年 | 16篇 |
2010年 | 20篇 |
2009年 | 10篇 |
2008年 | 15篇 |
2007年 | 9篇 |
2006年 | 14篇 |
2005年 | 8篇 |
2004年 | 5篇 |
2003年 | 10篇 |
2002年 | 6篇 |
2001年 | 6篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1988年 | 1篇 |
排序方式: 共有234条查询结果,搜索用时 10 毫秒
91.
Jacek Gasiorowski Sameh Boudiba Kurt Hingerl Christoph Ulbricht Valeria Fattori Francesca Tinti Nadia Camaioni Reghu Menon Stefanie Schlager Louiza Boudida Niyazi Serdar Sariciftci Daniel Ayuk Mbi Egbe 《Journal of Polymer Science.Polymer Physics》2014,52(4):338-346
An anthracene‐containing poly(arylene‐ethynylene)‐alt‐poly(arylene‐vinylene) (PAE‐PAV) of general constitutional unit (? Ph? C?C? Anthr? C?C? Ph? CH?CH? Anthr? CH?CH)n bearing two 2‐ethylhexyloxy solubilizing side chains on each phenylene (Ph) unit has been synthesized and characterized. The basic electrochemical characterization was done, showing the existence of two non‐reversible oxidation and one reversible reduction peaks. The optical properties, the real and imaginary part of the dielectric function, were probed using spectroscopic ellipsometry (SE). The vibrational structure of the undoped/doped polymer was investigated using Fourier transformed infrared spectroscopy. A strong change in the polaronic absorption was observed during the doping, which after modeling revealed the existence of two separated transitions. The optical changes upon doping were additionally recorded using the SE technique. Similar to the results from FT‐IR spectroscopy, two new in‐the‐gap absorptions were found. Moreover, the electrical conductivity as well as the mobility of positive carriers were measured. In the undoped state, the conductivity of the polymer was found to be below the detection limit (<μS cm?1), after doping the conductivity increased to 0.69 S cm?1. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 338–346 相似文献
92.
L. Dreesen C. Humbert M. Celebi J.J. Lemaire A.A. Mani P.A. Thiry A. Peremans 《Applied physics. B, Lasers and optics》2002,74(7-8):621-625
Infrared-visible sum-frequency generation (SFG) spectroscopy is performed at different visible wavelengths between 450 and
650 nm in order to investigate the interaction between metallic substrates (Pt, Ag and Au) and 1-dodecanethiol self-assembled
monolayers. We show that such measurements provide a means to study the electronic properties of metals as well as the interference
phenomena between the SFG signals from the adsorbate and the substrate. The common features of the three interfaces are the
vibration modes of the terminal methyl groups. However, these resonances appear as peaks for Pt (111) and as dips in the case
of Ag (111). Their shape is not modified when the visible wavelength is tuned between 450 and 650 nm. Moreover, the metal
sum-frequency generation contribution is slightly modified in that spectral range. For Au (111) samples, the sum-frequency
generation spectrum drastically evolves with the visible wavelength: the peak resonant sum-frequency generation signal at
450 nm becomes rather dip-shaped at 650 nm. The non-linear response of gold is also enhanced when the wavelength associated
with the sum-frequency process is close to 480 nm. These results are interpreted on the basis of the metal electronic properties
that are responsible for the non-resonant contribution to the SFG signal.
Received: 15 October 2001 / Revised version: 27 March 2002 / Published online: 6 June 2002 相似文献
93.
Dibenzo[e,k]-2,3-bis(hydroxyimino)-1,4-dithia-7,10-diaza-2,3,8,9-tetrahydrocyclododecine (H2L) has been prepared from 1,2-bis(o-mercaptoanilino) ethane ( 4 ) and (E,E)-dichloroglyoxime. A mononuclear complex with a metal: ligand ratio of 1:2 has been isolated for cobalt(III). The CoIII complex of H2L has been prepared with L′ = 2,6-lutidine, and with a chlorine ion as axial ligands. In addition to that, the synthesis of a new cobalt complex which contains BF2+ bridges is achieved with the bis(E,E)-dioxime ligand. The trinuclear complex of this CoIII complex has been obtained by the reaction of BF2+ bridged CoIII complex with Pd[bis(benzonitrile)]Cl2. The structures of these complexes and (E,E)-dioxime were identified by using elemental analysis, 1H and 13C-NMR, IR and MS spectral data. 相似文献
94.
Mononuclear [Co(HL)2LCl)], [Co(LBF2)2LCl] or [Cu-(HL)2] H2L = {N,N-bis (4-N-phenylaza [15]crown-5)diaminoglyoxime} and a trinuclear, [Cu(L)2(CuL)2](NO3)2, complex of the ligand were synthesized and characterized. The mononuclear copper(II) species coordinates to two copper(II) ions through the deprotonated oximate oxygens to yield a trinuclear structure cis-bridged by the oximate groups, with 1,10-phenanthroline as an end-cap ligand. The terminal copper adopts an essentially planar configuration with the nitrogen atoms of H2L. The structure of the ligand and its complexes is proposed and formulated according to the elemental analyses, 1H- and 13C-n.m.r, i.r. and m.s. spectral data. 相似文献
95.
Fang L Demee M Sierra T Kshirsagar T Celebi AA Yan B 《Journal of combinatorial chemistry》2002,4(4):362-368
The kinetics of cleavage reactions of seven resin-bound thiophenol esters with three amines has been studied by single-bead FTIR. The reactivity of these seven thiophenol esters was dependent on their structures and could be summarized as follows: 5-benzimidazolecarboxylic thiophenol ester > alkyl thiophenol ester > aromatic thiophenol ester. The reactivity of three amines was summarized as follows: n-butylamine > 3,4-dimethoxyphenethylamine > 1-piperonylpiperazine. The rate of the cleavage reaction increased 2-fold per 10 degrees C rise in reaction temperature. Oxidation of the thiophenol linker increased the rate of the cleavage reaction by 580-fold. 相似文献
96.
Kapou A Benetis NP Durdagi S Nikolaropoulos S Mavromoustakos T 《Journal of chemical information and modeling》2008,48(11):2254-2264
Thirty-eight antileukemic steroidal esters possessing conformationally flexible nitrogen mustards were studied, and the 3D QSAR/CoMFA and CoMSIA methodologies were applied in order to derive the correlation between their structure and the in vivo antileukemic activity. These compounds show significantly reduced toxicity and possibly increased bioavailability compared to free nitrogen mustards and therefore constitute potent antileukemic drugs. Both the CoMFA and CoMSIA studies gave similar results indicating that the steric effect and the hydrophobic/hydrophilic balance especially in the steroidal part of the molecules probably determined their bioactivity. Of paramount interest is the observation that the orientation of the alkylating part of the SMEs toward the surface of ring B of the steroidal skeleton was related with increased activity. Concerning the steroidal part, the presence of hydrophobic groups in rings B and D was found to be important for enhanced activity. Enhancement of antileukemic potency is further observed if hydrophilic/H-bond acceptor groups are present at the positions 7 and 17 of the steroidal skeleton. Leapfrog simulations provided novel compounds which lead our future synthetic endeavor for obtaining SMEs with optimum bioactivity. 相似文献
97.
Serbest Kerim Karaböcek Serdar Değirmencioğlu İsmail Güner Saadettin Kormali Fatma 《Transition Metal Chemistry》2001,26(4-5):375-379
A new ligand incorporating a dioxime moiety, 3-{2-[2-(2-hydroxyimino-1-methylpropylideneamino)ethylamino]ethylimino}butan-2-one oxime, (H2mdo), has been synthesized and its mono-, di- and trinuclear copper(II), and hetero-dinuclear copper(II)–manganese(II) complexes have been prepared and characterized by elemental analyses, magnetic moments, 1H- and 13C-n.m.r., i.r. and mass spectral studies. A mononuclear copper(II) complex of H2mdo was found to have a 1:1 metal:ligand ratio. Elemental analyses, stoichiometric and spectroscopic data of the metal complexes indicated that the metal ions are coordinated to the oxime and imine nitrogen atoms (C=N); the data support the proposed structure of H2mdo and its complexes. 相似文献
98.
The constitutive theories intended to quantitatively account for the complicated material response exhibited by polymers include, in general, adjustable material parameters. These must be identified from experimental data obtained from the material under consideration. This contribution presents the complete procedure studying the behavior of polymers at large strains in three basic steps: i) Accomplishment of homogeneous and 3-D inhomogeneous experiments under different deformation conditions. ii) Identification of the material parameters of a constitutive model by means of gradient–based optimization methods with respect to the homogeneous experimental data. iii) Validation of the identified material parameters by comparing 3-D FE simulations to the inhomogeneous experimental data. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
99.
Summary The synthesis and characterization of new NiII, PdII, PtII and CoIII complexes, with the BF
inf2
sup+
-bridged,bis(-di-oximato) ligands are described. The initially formed six-coordinate hydrogen-bonded macrocycles, were used as metal templates to prepare the corresponding BF
inf2
sup+
- capped macrocycles. The complexes were characterized by1H-n.m.r. and i.r. spectroscopy, and by elemental analysis. 相似文献
100.
In this study, SnO2 nanoparticles (SNPs)-poly(vinylferrocenium) (PVF+) modified single-use graphite electrodes were developed for electrochemical monitoring of DNA hybridization. The surfaces of polymer modified and polymer-SNP modified pencil graphite electrodes (PGEs) were firstly characterized by using SEM analysis. The electrochemical behaviours of these electrodes were also investigated using the differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) techniques. The polymer-SNP modified PGEs were then tested for the electrochemical sensing of DNA based on the changes at the guanine oxidation signals. Experimental parameters, such as; different modifications in DNA oligonucleotides, DNA probe concentrations were examined to obtain more sensitive and selective electrochemical signals for nucleic acid hybridization. After optimization studies, DNA hybridization was investigated in the case of complementary of hepatitis B virus (HBV) probe, mismatch (MM), and noncomplementary (NC) sequences. 相似文献