全文获取类型
收费全文 | 134篇 |
免费 | 5篇 |
国内免费 | 3篇 |
专业分类
化学 | 80篇 |
晶体学 | 2篇 |
力学 | 1篇 |
数学 | 34篇 |
物理学 | 25篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 6篇 |
2019年 | 10篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 7篇 |
2015年 | 3篇 |
2014年 | 1篇 |
2013年 | 5篇 |
2012年 | 10篇 |
2011年 | 9篇 |
2010年 | 11篇 |
2009年 | 8篇 |
2008年 | 15篇 |
2007年 | 10篇 |
2006年 | 7篇 |
2005年 | 5篇 |
2004年 | 5篇 |
2003年 | 6篇 |
2002年 | 4篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有142条查询结果,搜索用时 15 毫秒
101.
João C.M. Barreira Amilcar L. Antonio Tugba Günaydi Hasan Alkan Albino Bento M. Luisa Botelho Isabel C.F.R. Ferreira 《Radiation Physics and Chemistry》2012,81(9):1520-1524
Chestnut (Castanea sativa Miller) is a valuable natural resource, with high exportation levels. Due to their water content, chestnuts are susceptible to storage problems like dehydration or development of insects and microorganisms. Irradiation has been revealing interesting features to be considered as an alternative conservation technology, increasing food products shelf-life. Any conservation methodology should have a wide application range. Hence, and after evaluating Portuguese cultivars, the assessment of irradiation effects in foreign cultivars might act as an important indicator of the versatility of this technology. In this work, the effects of gamma irradiation (0.0, 0.5 and 3.0 kGy) on proximate composition, sugars, fatty acids (FA) and tocopherols composition of Turkish chestnuts stored at 4 °C for different periods (0, 15 and 30 days) were evaluated. Regarding proximate composition, the storage time (ST) had higher influence than the irradiation dose (ID), especially on fat, ash, carbohydrates and energetic value. Sucrose exhibited similar behavior in response to the assayed ST and ID. The prevalence of ST influence was also verified for FA, tocopherols and sucrose. Lauric, palmitoleic and linolenic acids were the only FA that underwent some differences with ID. Saturated, monounsaturated and polyunsaturated fatty acids levels were not affected either by storage or irradiation. α-Tocopherol was the only vitamer with significant differences among the assayed ST and ID. Overall, Turkish cultivars showed a compositional profile closely related with Portuguese cultivars, and seemed to confirm that gamma irradiation in the applied doses did not change chestnut chemical and nutritional composition. 相似文献
102.
Cirpan A Alkan S Toppare L Hepuzer Y Yagci Y 《Bioelectrochemistry (Amsterdam, Netherlands)》2003,59(1-2):29-33
Immobilization of invertase in conducting copolymer matrices of 3-methylthienyl methacrylate with pyrrole and thiophene was achieved by constant potential electrolysis using sodium dodecyl sulfate (SDS) as the supporting electrolyte. Polythiophene (PTh) was also used in entrapment process for comparison. Kinetic parameters, Michaelis-Menten constant, K(m), and the maximum reaction rate, V(max), were investigated. Operational stability and temperature optimization of the enzyme electrodes were also examined. 相似文献
103.
Emre Alkan Maosheng Xiong Alexandru Zaharescu 《Journal of Mathematical Analysis and Applications》2009,356(2):752-763
We prove the existence of the pair correlation measure associated to torsion points on the real locus E(R) of an elliptic curve E and provide an explicit formula for the limiting pair correlation function. 相似文献
104.
Sibel Alkan Bülent Zeybek Alev Doğan Rahmi Kasımoğulları Yunus Erdoğan Esma Kılıç 《Monatshefte für Chemie / Chemical Monthly》2009,140(4):381-386
Abstract Stoichiometric ionization constants of some pyrazole carboxylic acids [4-benzoyl-1-(3-nitrophenyl)-5-phenyl-1H-pyrazole-3-carboxylic
acid, 4-benzoyl-1-(4-nitrophenyl)-5-phenyl-1H-pyrazole-3-carboxylic acid, 4-(ethoxycarbonyl)-1,5-diphenyl-1H-pyrazole-3-carboxylic
acid, 4-(ethoxycarbonyl)-1-(3-nitrophenyl)-5-phenyl-1H-pyrazole-3-carboxylic acid, 4-(ethoxycarbonyl)-1-(4-nitrophenyl)-5-phenyl-1H-pyrazole-3-carboxylic
acid] were determined in ethanol–water mixtures of 50, 60, 70% ethanol (v/v) by a potentiometric titration method. Titrations
were performed in an ionic strength of 0.10 M NaCl at 25.0 ± 0.1 °C using an Orion 960 automatic titrator under a nitrogen
atmosphere. Using the potentiometric titration data, ionization constants were calculated in three different ways. The effects
of structure and solvent on the acidity of pyrazole carboxylic acids are also discussed.
Graphical abstract
相似文献
105.
Çiğdem Hopa Mahir Alkan Canan Kazak N. Burcu Arslan Raif Kurtaran 《Transition Metal Chemistry》2009,34(4):403-407
A mononuclear iron(III) complex with 2,6-bis(3,4,5-trimethyl-N-pyrazolyl)pyridine (btmpp) has been synthesized, and characterized by X-ray crystallography, IR, UV–Vis and TGA–DTA methods.
The Fe(III/II) couple was characterized by way of cyclic voltammetry using DMF solvent, where the complex was observed to
have an irreversible behaviour. 相似文献
106.
Emre Alkan 《Proceedings of the American Mathematical Society》2003,131(6):1673-1680
Let be a cusp form with integer weight that is not a linear combination of forms with complex multiplication. For , let
Improving on work of Balog, Ono, and Serre we show that for almost all , where is any good function (e.g. such as ) monotonically tending to infinity with . Using a result of Fouvry and Iwaniec, if is a weight 2 cusp form for an elliptic curve without complex multiplication, then we show for all that . We also obtain conditional results depending on the Generalized Riemann Hypothesis and the Lang-Trotter Conjecture.
Improving on work of Balog, Ono, and Serre we show that for almost all , where is any good function (e.g. such as ) monotonically tending to infinity with . Using a result of Fouvry and Iwaniec, if is a weight 2 cusp form for an elliptic curve without complex multiplication, then we show for all that . We also obtain conditional results depending on the Generalized Riemann Hypothesis and the Lang-Trotter Conjecture.
107.
Magnetic resonance spectroscopy study of proton metabolite level changes in sensorimotor cortex after upper limb replantation-revascularization 总被引:1,自引:0,他引:1
Ertem K Alkan A Sarac K Onal C Bostan H Yologlu S Bora A 《Magnetic resonance imaging》2005,23(1):105-109
We aimed to investigate the changes in proton metabolite levels at the motor and somatosensory cortex by magnetic resonance spectroscopy (MRS) after upper extremity replantation or revascularization. Nine patients who referred to our clinic suffering from major total (two) and subtotal (seven) amputation of the upper extremity were enrolled in this study. Mean time value between the injury and operation was 5.1 h. Mean follow-up period or mean time between the injury and MRS analysis was 26.2 months (ranging from 7 to 41 months). Voxels (TR: 2000; TE: 136 ms) were placed onto locations in the bilateral precentral and postcentral cortex area of the cerebral hemispheres that represent the upper extremity. Contralateral sides of the brain hemisphere that represent the injured extremity were accounted as control groups. Metabolite ratios [NAA (N-acetyl aspartate)/Cr (creatine) and Cho (choline)/Cr] of the motor and somatosensory cortex were calculated. The NAA/Cr and Cho/Cr metabolite ratios between the two groups were found to be insignificant, and these results may indicate that there is no remarkable somatosensorial cortex disruption or demyelination in these patients. Fifty-six percent of patients were found as functional according to Chen's scale. 相似文献
108.
The synthesis and analytical applications of N,N'-bis(2-hydroxy-5-bromo-benzyl)1,2 diaminopropane (HBDAP) are described. This compound reacts with Fe(III) in the range of pH 3-6 to produce a red complex (2:3 mol ratio of Fe(III)/HBDAP) soluble in chloroform. The investigation included a study of the characteristics that are essential for solvent extraction and for spectrophotometric determination and speciation of iron. A highly sensitive, selective and rapid spectrophotometric method is described for the determination of trace amounts of iron(III) by HBDAP. The complex obeys Beer's law from 0.056 to 1.68 mg l(-1) with an optimum range. The detection limit (taken as three times the standard deviation of the reagent blank) is approximately 1.23x10(-7) M Fe(III) and the limit of quantitation (taken as ten times the standard deviation of the reagent blank) is about 4.11x10(-7) M Fe(III). A single extraction gave a good separation of iron(III) from iron(II). Good separation of Fe(III) from Ni(II), Fe(II), Co(II), Cd(II), Mn(II), Zn(II), Pb(II) was also achieved at pH 3-5. 相似文献
109.
Four novel 3-alkyl(aryl)-4-(4-methoxycarbonylbenzylidenamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (2) were synthesized by the reactions of 3-alkyl(aryl)-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones (1) with methyl 4-formylbenzoate and characterized by elemental analyses and IR, 1H NMR, 13C NMR and UV spectral data. In addition, isotropic 1H and 13C nuclear magnetic shielding constants of 2 were obtained by the gauge-including-atomic-orbital (GIAO) method at the B3LYP density functional level. The geometry of each compound was optimized using the 6-311G basis set. 相似文献
110.
Ayberk Özden Hüseyin Şar Aydan Yeltik Büşra Madenoğlu Cem Sevik Feridun Ay Nihan Kosku Perkgöz 《固体物理学:研究快报》2016,10(11):792-796
In this letter, we report on the fluorescence lifetime imaging and accompanying photoluminescence properties of a chemical vapour deposition (CVD) grown atomically thin material, MoS2. µ‐Raman, µ‐photoluminescence (PL) and fluorescence lifetime imaging microscopy (FLIM) are utilized to probe the fluorescence lifetime and photoluminescence properties of individual flakes of MoS2 films. Usage of these three techniques allows identification of the grown layers, grain boundaries, structural defects and their relative effects on the PL and fluorescence lifetime spectra. Our investigation on individual monolayer flakes reveals a clear increase of the fluorescence lifetime from 0.3 ns to 0.45 ns at the edges with respect to interior region. On the other hand, investigation of the film layer reveals quenching of PL intensity and lifetime at the grain boundaries. These results could be important for applications where the activity of edges is important such as in photocatalytic water splitting. Finally, it has been demonstrated that PL mapping and FLIM are viable techniques for the investigation of the grain‐boundaries.