全文获取类型
收费全文 | 237篇 |
免费 | 9篇 |
专业分类
化学 | 162篇 |
晶体学 | 5篇 |
力学 | 2篇 |
数学 | 36篇 |
物理学 | 41篇 |
出版年
2023年 | 1篇 |
2022年 | 6篇 |
2021年 | 7篇 |
2020年 | 8篇 |
2019年 | 9篇 |
2018年 | 9篇 |
2017年 | 13篇 |
2016年 | 14篇 |
2015年 | 7篇 |
2014年 | 9篇 |
2013年 | 23篇 |
2012年 | 18篇 |
2011年 | 21篇 |
2010年 | 16篇 |
2009年 | 16篇 |
2008年 | 13篇 |
2007年 | 16篇 |
2006年 | 10篇 |
2005年 | 7篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 1篇 |
2001年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1983年 | 2篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1956年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有246条查询结果,搜索用时 31 毫秒
91.
Prof. Dr. Muvaffak Seyhan Şeniz Kaban 《Monatshefte für Chemie / Chemical Monthly》1976,107(5):1185-1188
Two new heteroarylformazans with two complex forming carboxy groups in the ortho position relative to the formazan chain have been synthesized. These compounds form complexes with uranyl, cobalt and nickel ions. The ratio metal/formazan of these complexes has been investigated.
Teil der Dissertation,. Kaban, Univ. Istanbul 1975. 相似文献
Teil der Dissertation,. Kaban, Univ. Istanbul 1975. 相似文献
92.
Hakan Günaydin Seyhan Salman Nurcan enyurt Tüzün Duygu Avci Viktorya Aviyente 《International journal of quantum chemistry》2005,103(2):176-189
Acrylates have gained importance because of their ease of conversion to high‐molecular‐weight polymers and their broad industrial use. Methyl methacrylate (MMA) is a well‐known monomer for free radical polymerization, but its α‐methyl substituent restricts the chemical modification of the monomer and therefore the properties of the resulting polymer. The presence of a heteroatom in the methyl group is known to increase the polymerizability of MMA. Methyl α‐hydroxymethylacrylate (MHMA), methyl α‐methoxymethylacrylate (MC1MA), methyl α‐acetoxymethylacrylate (MAcMA) show even better conversions to high‐molecular‐weight polymers than MMA. In contrast, the polymerization rate is known to decrease as the methyl group is replaced by ethyl in ethyl α‐hydroxymethylacrylate (EHMA) and t‐butyl in t‐butyl α‐hydroxymethylacrylate (TBHMA). In this study, quantum mechanical tools (B3LYP/6‐31G*) have been used in order to understand the mechanistic behavior of the free radical polymerization reactions of acrylates. The polymerization rates of MMA, MHMA, MC1MA, MAcMA, EHMA, TBHMA, MC1AN (α‐methoxymethyl acrylonitrile), and MC1AA (α‐methoxymethyl acrylic acid) have been evaluated and rationalized. Simple monomers such as allyl alcohol (AA) and allyl chloride (AC) have also been modeled for comparative purposes. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 相似文献
93.
Benzoylthiourea immobilized on silica gel was prepared by two-step post-synthesis modification. The capacity of the chelating
silica gel, which was characterized by FTIR, was 3.21 mmol · g−1. The separation and enrichment of uranium(VI) from solutions was investigated. Effective extraction conditions were optimized
in both batch and column methods prior to determination by spectrophotometry using arsenazo(III). The optimum pH range for
quantitative adsorption is 4–7. Quantitative recovery of U(VI) was achieved by stripping with 0.1 mol · L−1 HCl. The sorption capacity of modified silica gel was 0.85 mmol · g−1 uranium(VI). Recovery of U(VI) was 99.1 ± 2.3% with a detection limit of 2 μg · L−1. The preconcentration factor was 250, and the relative standard deviation was 1.53% for a 1 μg · L−1 U(VI) solution. The method was used for the determination of uranium in synthetic samples and a soil sample. 相似文献
94.
Rheological properties of vinyl ester-polyester resin suspensions containing various amounts (0.05, 0.1 and 0.3 wt.%) of multi walled carbon nanotubes (MWCNT) with and without amine functional groups (-NH2) were investigated by utilization of oscillatory rheometer with parallel plate geometry. Dispersion of corresponding carbon nanotubes within the resin blend was accomplished employing high shear mixing technique (3-roll milling). Based on the dynamic viscoelastic measurements, it was observed that at 0.3 wt.% of CNT loadings, storage modulus (G′) values of suspensions containing MWCNTs and MWCNT-NH2 exhibited frequency-independent pseudo solid like behavior especially at lower frequencies. Moreover, the loss modulus (G″) values of the resin suspensions with respect to frequency were observed to increase with an increase in contents of CNTs within the resin blend. In addition, steady shear viscosity measurements implied that at each given loading rate, the resin suspensions demonstrated shear thinning behavior regardless of amine functional groups, while the neat resin blend was almost the Newtonian fluid. Furthermore, dynamic mechanical behavior of the nanocomposites achieved by polymerizing the resin blend suspensions with MWCNTs and MWCNT-NH2 was investigated through dynamic mechanical thermal analyzer (DMTA). It was revealed that storage modulus (E′) and the loss modulus (E″) values of the resulting nanocomposites increased with regard to carbon nanotubes incorporated into the resin blend. In addition, at each given loading rate, nanocomposites containing MWCNT-NH2 possessed larger loss and storage modulus values as well as higher glass transition temperatures (Tg) as compared to those with MWCNTs. These findings were attributed to evidences for contribution of amine functional groups to chemical interactions at the interface between CNTs and the resin blend matrix. Transmission electron microscopy (TEM) studies performed on the cured resin samples approved that the dispersion state of carbon nanotubes with and without amine functional groups within the matrix resin blend was adequate. This implies that 3-roll milling process described herein is very appropriate technique for blending of carbon nanotubes with a liquid thermoset resin to manufacture nanocomposites with enhanced final properties. 相似文献
95.
Celik SU Akbey U Graf R Bozkurt A Spiess HW 《Physical chemistry chemical physics : PCCP》2008,10(39):6058-6066
The synthesis, thermal and proton conducting properties of copolymers based on vinylphosphonic acid (VPA) and 1-vinyl-1,2,4-triazole (VTri) were investigated. The copolymers were synthesized by free-radical copolymerization of the corresponding monomers at several monomer feed ratios to obtain poly(VPA-co-VTri) copolymer electrolytes. The final structures of the copolymers were confirmed by spectroscopic methods. The composition of the low molecular weight copolymers was varied with the feed ratio of the monomers. The presence of triazole units in the copolymers suppresses the formation of phosphonic acid anhydrides up to 150 degrees C, as verified by both (31)P NMR and TGA. The observation of defined glass transition temperatures indicated that the ionic interactions do not prevent segmental relaxations of the polymer chains. In the absence of humidity, the copolymer electrolyte, poly(VPA-co-VTri), S2 (with 33% triazole content) showed proton conductivity of 10(-3) S cm(-1) at 120 degrees C, which is far higher than in imidazole based copolymers. Two different types of hydrogen-bonded protons were detected by (1)H MAS NMR in the solid copolymer systems, due to different arrangements of triazole and phosphonic acid units. 相似文献
96.
Serap Titretir Erdal Kendüzler Yasin Arslan İbrahim Kula Sezgin Bakırdere O. Yavuz. Ataman 《Spectrochimica Acta Part B: Atomic Spectroscopy》2008
An electrically heated tungsten coil was used as a trap in the determination of antimony. The technique consists of three steps. Initially, SbH3 is formed by hydride generation procedure; then the analyte species in vapor form are transported to W-coil trap heated at 370 °C. Following the preconcentration step, the trap is heated to 895 °C; analyte species are revolatilized and transported to the flame-heated quartz atom cell where atomization and the formation of signal take place. The experimental parameters were optimized both for trap and no-trap studies. The most important experimental parameters are concentrations of HCl and NaBH4 solutions, H2 and Ar gas flow rates, and collection and revolatilization temperatures of W-coil. Accuracy was tested using a certified reference material, waste water EU-L-1. Limit of detection for the system is 16 ng l− 1 using a sample of 36 ml collected in 4.0 min. Enhancement factor in sensitivity was 17. 相似文献
97.
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
98.
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
99.
A. Seyhan O. Karabulut B. G. Aknolu B. Aslan R. Turan 《Crystal Research and Technology》2005,40(9):893-895
Optical anisotropy of the layer semiconductor GaSe has been studied by photoluminescence (PL) and Fourier Transform Infrared Spectroscopy (FTIR). The PL spectra are dominated by two closely positioned emission bands resulting from the free exciton and the bound exciton connected direct band edge of GaSe. Photoluminescence and transmission spectra of GaSe crystals have been measured for two cases in which the propagation vector k is perpendicular (k ⟂ c) and parallel to the c‐axis (k // c). Peak position of the PL emission band and the onset of the transmission have been found to be significantly different for these two cases. This observed anisotropy is related to anisotropic band structure and the selection rules for the optical absorption in layered GaSe. FTIR transmission spectrum is in good agreement with PL results. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
100.
Tosun Serap Gençtürk Uzun Davut Yeşilot Serkan 《Journal of Solid State Electrochemistry》2021,25(4):1271-1281
Journal of Solid State Electrochemistry - A series of novel KxNa0.6-xMn0.35Fe0.35Co0.3O2 (x = 0, 0.005, 0.01, 0.05, 0.1) materials were successfully synthesized by the solid-state... 相似文献