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排序方式: 共有163条查询结果,搜索用时 46 毫秒
21.
Distinguishing and quantification of the human visual pathways using high-spatial-resolution diffusion tensor tractography 总被引:1,自引:0,他引:1
Arash Kamali Khader M. Hasan Pavani Adapa Azadeh Razmandi Zafer Keser John Lincoln Larry A. Kramer 《Magnetic resonance imaging》2014
Quantification of the living human visual system using MRI methods has been challenging, but several applications demand a reliable and time-efficient data acquisition protocol. In this study, we demonstrate the utility of high-spatial-resolution diffusion tensor fiber tractography (DTT) in reconstructing and quantifying the human visual pathways. Five healthy males, age range 24–37 years, were studied after approval of the institutional review board (IRB) at The University of Texas Health Science Center at Houston. We acquired diffusion tensor imaging (DTI) data with 1-mm slice thickness on a 3.0-Tesla clinical MRI scanner and analyzed the data using DTT with the fiber assignment by continuous tractography (FACT) algorithm. By utilizing the high-spatial-resolution DTI protocol with FACT algorithm, we were able to reconstruct and quantify bilateral optic pathways including the optic chiasm, optic tract, optic radiations free of contamination from neighboring white matter tracts. 相似文献
22.
Renewability is not Enough: Recent Advances in the Sustainable Synthesis of Biomass‐Derived Monomers and Polymers
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Dr. Audrey Llevot Patrick‐Kurt Dannecker Marc von Czapiewski Lena C. Over Zafer Söyler Prof. Dr. Michael A. R. Meier 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(33):11510-11521
Taking advantage of the structural diversity of different biomass resources, recent efforts were directed towards the synthesis of renewable monomers and polymers, either for the substitution of petroleum‐based resources or for the design of novel polymers. Not only the use of biomass, but also the development of sustainable chemical approaches is a crucial aspect for the production of sustainable materials. This review discusses the recent examples of chemical modifications and polymerizations of abundant biomass resources with a clear focus on the sustainability of the described processes. Topics such as synthetic methodology, catalysis, and development of new solvent systems or greener alternative reagents are addressed. The chemistry of vegetable oil derivatives, terpenes, lignin, carbohydrates, and sugar‐based platform chemicals was selected to highlight the trends in the active field of a sustainable use of renewable resources. 相似文献
23.
The synthesis and photoconductivity properties of the alkylthia and triethyleneoxysulfonyl substituted oxotitanium(IV) phthalocyanines (1a and 2a) are reported for the first time. The new compounds have been characterized by elemental analysis, IR, 1H and 13C NMR spectroscopy, electronic spectroscopy and mass spectroscopy. The mesogenic properties of these new materials were studied by differential scanning calorimetry and optical microscopy. The electrical dark conductivities (σd) and photoconductivities (σph) of deposited films of 1a and 2a were investigated in various media with different concentrations of oxygen. Molecular oxygen increases photoconductivities (σph) significantly. The photoconductivity mechanism and formation of Pc+ which is positive charge carrier under the light irradiation of the phthalocyanine molecules are demonstrated using the theoretical calculations. The geometries of the oxotitanium(IV) phthalocyanines (TiOPc) are optimized with PM3 semi-empirical method, and their visible absorption maxima are calculated with ZINDO/S method. The results agree well with the observed values. It was found that for the calculation of visible absorption of neutral and positively charged substituted TiOPc molecules using ZINDO/S method could rapidly yield excellent results. Dipole moment, HOMO, LUMO energies and atomic charges are also calculated for clarification of the oxygen effect on the photoconductivity using PM3 and ZINDO/S methods. 相似文献
24.
Zafer Kandemir Selma Mayda Nejat Bulut 《The European Physical Journal B - Condensed Matter and Complex Systems》2016,89(5):113
We study the electronic structure and correlations of vitamin B12 (cyanocobalamine) by using theframework of the multi-orbital single-impurity Haldane-Anderson model of atransition-metal impurity in a semiconductor host. The parameters of the effectiveHaldane-Anderson model are obtained within the Hartree-Fock (HF) approximation. Thequantum Monte Carlo (QMC) technique is then used to calculate the one-electron andmagnetic correlation functions of this effective model. We observe that new states forminside the semiconductor gap found by HF due to the intra-orbital Coulomb interaction atthe impurity 3d orbitals. In particular, the lowest unoccupiedstates correspond to an impurity bound state, which consists of states from mainly the CNaxial ligand and the corrin ring as well as the Co eg-like orbitals. We alsoobserve that the Co?(3d) orbitals can develop antiferromagneticcorrelations with the surrounding atoms depending on the filling of the impurity boundstates. In addition, we make comparisons of the HF+QMC data with the density functionaltheory calculations. We also discuss the photoabsorption spectrum of cyanocobalamine. 相似文献
25.
Okan Zafer Yeşilel Dr. Hümeyra Paşaoğlu Kamber Akdağ Orhan Büyükgüngör 《无机化学与普通化学杂志》2007,633(10):1731-1734
The new orotate complex of cadmium(II) with quinoxaline, mer‐[Cd(HOr)(H2O)3(QX)]·2H2O, was synthesized and characterized by elemental analysis, FT–IR spectroscopy, thermal analysis and single crystal X–ray diffraction techniques. The complex crystallizes in the triclinic system, space group . The Cd2+ ion exhibits a distorted octahedral coordination by one bidentate orotate, one monodentate quinoxaline and three aqua ligands. The uncoordinated water molecules link the orotate, quinoxaline and aqua ligands via O–H···O, O–H···N hydrogen bonds. Thus, an extensive network of hydrogen bonds stabilizes the crystal structure and form an infinitive three dimensional lattice. The decomposition reaction takes place in the temperature range 20–700 °C in the static air atmosphere. 相似文献
26.
Fac‐bis(ethanolamine)orotatonickel(II), [Ni(HOr)(ea)2] and mer‐bis(ethanolamine)orotatocopper(II) dihydrate, [Cu(HOr)(ea)2]· 2H2O were synthesized and characterized by elemental analysis, FT‐IR, UV‐Vis Spectroscopy and thermal analysis. In addition, their solid‐state structures were determined by single crystal X‐ray diffraction studies. Both the fac‐[Ni(HOr)(ea)2] (1) and mer‐[Cu(HOr)(ea)2]·2H2O (2) complexes are isomorphous and crystallize in the triclinic space group . The Ni2+ and Cu2+ ions are coordinated by two neutral ea ligands and one orotate dianion in a distorted octahedral fashion. The ea ligand acts as a bidentate donor through the amine N and hydroxyl O atoms, while orotate dianion is coordinated through deprotonated N3 pyrimidine atom and carboxylate oxygen atom as a bidentate ligand. Thermal decompositions of the complexes are studied in over the range 20–600 °C on heating in a static air atmosphere. 相似文献
27.
Gözde Murat Saltan Deniz Aykut Kıymaz Ceylan Zafer Haluk Dinçalp 《Journal of fluorescence》2017,27(6):1975-1984
The riboflavin dye 2,3,4,5-tetra-O-acetyl-1-[3-(6-bromohexyl)-7,8-dimethyl-2,4-dioxo-3,4-dihydrobenzo[g]pteridin-10(2H)-yl]-1-deoxypentitol and its pyridinium salt were synthesized, and studied by absorption and fluorescence spectroscopy in solutions and on thin film states. The first absorption band of riboflavin-pyridinium salt derivative is red-shifted by 10 nm compared to neutral one on film. Cationic riboflavin derivative shows significant wavelength changes on its fluorescence emission spectrum in the excited state depending on the solvent polarity and the electronic environment. The fluorescence quantum yields of cationic riboflavin gave much higher values as compared to that of its neutral form. The fluorescence lifetimes were found to be in the range of 5.5–6.6 ns with mono ? exponential behavior. These dyes possess low-lying HOMO energy levels which are suitable to be able to inject holes to donor polymers so that they can be used as acceptor component in the active layer of bulk heterojunction solar cells (BHJ-SCs). Photovoltaic responses are reported for P3HT:riboflavin active layer wherein the synthesized dyes are used as acceptor component. Also, neutral riboflavin shows greater electron mobility value of 1.3 × 10?3 cm2/V?s compared to its cationic derivative. 相似文献
28.
Ahmet Bulut brahim Uar Okan Zafer Yeilel Hasan budak Halis
lmez Orhan Büyükgüngr 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(10):m526-m528
The title mononuclear [Cu(sq)(phen)2]·3H2O complex [sq is squarate (C4O4) and phen is 1,10‐phenanthroline (C12H8N2)] has been synthesized and the structure consists of a neutral mononuclear [Cu(sq)(phen)2] unit and three solvate water molecules. The CuII ion has distorted square‐pyramidal coordination geometry, comprised of one carboxylate O atom from a monodentate squarate ligand and four N atoms from two chelating phen ligands. An extensive three‐dimensional network of OW—H⋯O/OW hydrogen bonds, face‐to‐face π–π interactions between the 1,10‐phenanthroline aromatic rings and a weak π–ring interaction are responsible for crystal stabilization. 相似文献
29.
Güneş Süheyla Kürkçüoğlu Dr. Okan Zafer Yeşilel Ilkan Kavlak Orhan Büyükgüngör 《无机化学与普通化学杂志》2009,635(1):175-178
The heteronuclear polymeric complex, [Zn(teta)Ni(μ‐CN)2(CN)2]n (teta: triethylenetetramine), was synthesized and characterized by elementel analysis, FT‐IR spectroscopy, thermal analysis and single crystal X–ray diffraction techniques. The complex crystallizes in the monoclinic system, space group P21/c and in which the ZnII ion exhibits a distorted octahedral coordination by one tetradentate teta ligand and two bridging cyano groups as a trans position, whereas the NiII ion has square planer coordination and is coordinated by four cyano ligands. The decomposition reaction takes places in the temperature range 30–600 °C in the static air atmosphere. 相似文献
30.
Okan Zafer Yeşilel Prof. Dr. Hakan Erer Necmi Dege Orhan Büyükgüngör 《无机化学与普通化学杂志》2009,635(3):577-581
Two nickel(II) complexes of vitamin B13 (H3Or) with N,N,N′,N′‐tetramethylethylenediamine (tmen) and 2,2‐dimethylpropane‐1,3‐diamine (dmpen) were synthesized and characterized by means of elemental and thermal analyses, magnetic susceptibility, and IR and UV/Vis spectroscopic studies. The crystal structures of mer‐[Ni(HOr)(H2O)2(tmen)] · H2O ( 1 ) and [Ni(HOr)(dmpen)2] ( 2 ) were determined by using single‐crystal X‐ray diffraction. In the complexes, which crystallize in the triclinic system (space group for 1 ) and the monoclinic system (space group P21/c for 2 ), the NiII ions exhibit a distorted octahedral coordination. NiII ions are chelated by the deprotonated nitrogen atom of the pyrimidine ring and the oxygen atom of the carboxylate group, the distorted octahedral coordination completed by one tmen and two aqua ligands for 1 or two dmpen ligands for 2 . 相似文献