全文获取类型
收费全文 | 125篇 |
免费 | 2篇 |
专业分类
化学 | 68篇 |
晶体学 | 2篇 |
力学 | 3篇 |
数学 | 17篇 |
物理学 | 37篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 6篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 8篇 |
2015年 | 3篇 |
2014年 | 5篇 |
2013年 | 10篇 |
2012年 | 9篇 |
2011年 | 14篇 |
2010年 | 8篇 |
2009年 | 12篇 |
2008年 | 6篇 |
2007年 | 3篇 |
2006年 | 4篇 |
2005年 | 3篇 |
2004年 | 3篇 |
2003年 | 2篇 |
2001年 | 1篇 |
1999年 | 1篇 |
1994年 | 1篇 |
1990年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1938年 | 1篇 |
排序方式: 共有127条查询结果,搜索用时 370 毫秒
51.
Havva Nur Demirtas Selahattin Bozkurt Mustafa Durmaz Mustafa Yilmaz Abdulkadir Sirit 《Tetrahedron: Asymmetry》2008,19(17):2020-2025
Two novel chiral calix[4]azacrown ethers 4 and 5 bearing a furfuryl group on the nitrogen atom were developed by the reaction of dibromo- or ditosyl derivatives of p-tert-butylcalix[4]arenes 2 and 3 with a chiral diol, 1. The enantioselective recognition of these receptors towards the enantiomers of racemic carboxylic acids has been studied by 1H NMR spectroscopy. The molar ratio and the association constants of the chiral compounds 4 and 5 with each of the enantiomers of guest molecules were determined by using Job plots and a nonlinear least-squares fitting method, respectively. The Job plots indicate that both of the hosts form 1:1 instantaneous complexes with (R)- or (S)-mandelic acid and (l)- or (d)-dibenzoyltartaric acid. The receptors exhibited different chiral recognition abilities towards the enantiomers of racemic guests. 相似文献
52.
Milovanovi Emina Bozkurt Altinda erife Burcu Mateji Marjan Milovanovi Igor 《Czechoslovak Mathematical Journal》2022,72(3):783-799
Czechoslovak Mathematical Journal - Let a = (a1,a2, …, an) be a nonincreasing sequence of positive real numbers. Denote by S = {1, 2, …, n} the index set and by Jk = {I = {r1, r2,... 相似文献
53.
54.
Burak Esat Ismail Fidan Sumeyye Bahceci Yusuf Yerli Levent Sari 《Magnetic resonance in chemistry : MRC》2009,47(8):641-650
Several novel benzimidazole‐3‐oxide‐1‐oxyl radicals with substituents at 5 and/or 6 position were synthesized. The ESR analysis of nitrogen hyperfine coupling constants (hfccs) revealed that substituents at 5 and 6‐position affect the spin density to greater extent than substituents on the phenyl ring at 2‐position. Density functional theory calculations of nitrogen hfccs were performed using several different Pople type basis sets, as well as double and triple zeta quality individual gauge for localized orbital (IGLO‐II, IGLO‐III) and electron paramagnetic resonance (EPR‐II, EPR‐II) basis sets. Experimental and theoretical hfccs are compared. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
55.
We have developed a cloud point extraction procedure based on room temperature ionic liquid for the preconcentration and determination of mercury in water samples. Mercury ion was quantitatively extracted with tetraethyleneglycol-bis(3- methylimidazolium) diiodide in the form of its complex with 5,10,15,20-tetra-(4-phenoxyphenyl)porphyrin. The complex was back extracted from the room temperature ionic liquid phase into an aqueous media prior to its analysis by spectrofluorimetry. An overall preconcentration factor of 45 was accomplished upon preconcentration of a 20?mL sample. The limit of detection obtained under the optimal conditions is 0.08?μg mL?1, and the relative standard deviation for 10 replicate assays (at 0.5?g mL?1 of Hg) was 2.4%. The method was successfully applied to the determination of mercury in tap, river and mineral water samples. Figure
In this work, a novel and sensitive analytical methodology for mercury preconcentration and determination in different water samples using ionic liquid was developed. The use of room temperature ionic liquid‘s biphasic systems as an alternative to conventional solvents offers several advantages including safety and high capacity to extract Hg(II) and other elements with high recoveries. ?onic liquid in combination with porphyrin complexing reagent was successfully applied in this study for the extraction and preconcentration of Hg(II). Likewise, a fast and quantitative back extraction of the analyte from room temperature ionic liquid phase into aqueous phase was possible, allowing its further determination by spectrofluorimetry. The preconcentration method allowed mercury determination in tap, river and mineral water samples at trace levels with high accuracy and reproducibility. 相似文献
56.
Duygu Totur Serap Seyhan Bozkurt Melek Merdivan 《Journal of Radioanalytical and Nuclear Chemistry》2012,292(1):321-327
A sensitive and selective solid phase extraction procedure for the determination of trace of uranium(VI) has been developed.
An alumina-sodium dodecyl sulfate coated on with pyrocatechol violet was used for preconcentration and determination of uranyl
ions by spectrophotometry method using Arsenazo III reagent. Sorbed ions were quantitatively eluted using 5 mL of 0.25 mol L−1 HNO3. The effects of parameters such as pH, amount of alumina, amount of ligand, flow rate, type and concentration of elution
agent were examined. The capacity of the sorbent for U(VI) was found to be 0.92 mmol g−1. The relative standard deviation was 1.28% for 10 replicate determinations of U(VI) ion in a solution with a concentration
of 1.0 μg mL−1. The practical applicability of the developed sorbent was examined using synthetic and real samples such as standard reference
material 2709 (San Joaquin Soil) and 2711 (Montana Soil). 相似文献
57.
Mehtap Safak Boroglu Sevim Unugur Celik Ayhan Bozkurt Ismail Boz 《Polymer Science Series A》2012,54(3):231-239
In the present study, a new type of chemically cross-linked polymer blend membranes consisting of poly(vinyl alcohol) (PVA),
sulfosuccinic acid (SSA) and benzimidazole (BnIm), as a dopant, at different stoichometric ratios were prepared and used as
proton conducting polymer electrolytes. The proton conductivities of the membranes were investigated as a function of blending
composition and the temperature. TGA indicated that the blend polymers were thermally stable up to approximately 175°C; differential
scanning calorimetry (DSC) results illustrated the homogeneity of the materials. The local chain flexibility of the host polymer
increased with BnIm concentration. The methanol permeability values of the membranes were much lower than that of a Nafion-membrane.
The proton conductivity of these materials increased with BnIm and SSA concentration and the temperature. 相似文献
58.
Esat Bozkurt Bünyamin Karabulut 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,73(5):871-874
The electron paramagnetic resonance spectra of Cu2+ doped diaquabis(nicotinamide)bis(o-sulfobenzimidato-N)-cadmium(II) (hereafter, CdNAS) single crystals which were taken at room temperature are discussed. It was found from the analysis of the EPR data that the Cu2+ ions substitute for magnetically inequivalent Cd2+ ions. Two magnetically inequivalent Cu2+sites were observed. The principal values of the g and the hyperfine tensors were determined. The ground state wave functions of the unpaired electron of Cu2+ ions in two sites were constructed and type of the distortion was determined. 相似文献
59.
Diabetes Mellitus (DM) is a metabolic disorder, characterized by abnormally high blood glucose levels due to decreased secretion or effectiveness in function of insulin. Having a role in carbohydrate and lipid metabolism, skeletal muscle is affected by the absence of insulin in diabetic conditions. This current study reports the application of Fourier transform infrared (FTIR) spectroscopy in the determination of macromolecular alterations in streptozotocin (STZ)-induced diabetic rat skeletal Soleus (SOL) muscles, which highlight the promise of this technique in medical research. The results revealed that DM induced several alterations in macromolecular content and structure of slow-contracting SOL muscles. In diabetic SOL muscles, a decrease in the content of lipids, proteins and nucleic acids together with an increase in lipid order was observed. The decrease in the level of unsaturation and acyl chain length of lipids demonstrated the increased lipid peroxidation in DM. There were alterations in protein secondary structure in DM with a decrease in α-helix and β-sheet content of proteins, whereas the content of aggregated β-strands increased, which is generally seen when proteins denature. Besides, the integrity of collagen molecules was found to be decreased, demonstrating the alterations in its triple helical structure in diabetic muscles. Furthermore, the same alterations mentioned above were also observed in diabetic fast-contracting Extensor Digitorum Longus (EDL) muscles. However, having a high content of mitochondria and relying on an oxidative pathway, SOL muscle was found to be more affected by DM. 相似文献
60.
We determine bounds for the spectral and ??p norm of Cauchy–Hankel matrices of the form Hn=[1/(g+h(i+j))]ni,j=1≡ ([1/(g+kh)]ni,j=1), k=0, 1,…, n –1, where k is defined by i+j=k (mod n). Copyright © 2002 John Wiley & Sons, Ltd. 相似文献