全文获取类型
收费全文 | 299篇 |
免费 | 14篇 |
国内免费 | 4篇 |
专业分类
化学 | 254篇 |
晶体学 | 3篇 |
力学 | 16篇 |
数学 | 16篇 |
物理学 | 28篇 |
出版年
2023年 | 2篇 |
2022年 | 10篇 |
2021年 | 12篇 |
2020年 | 12篇 |
2019年 | 13篇 |
2018年 | 13篇 |
2017年 | 10篇 |
2016年 | 17篇 |
2015年 | 13篇 |
2014年 | 11篇 |
2013年 | 28篇 |
2012年 | 22篇 |
2011年 | 28篇 |
2010年 | 15篇 |
2009年 | 26篇 |
2008年 | 17篇 |
2007年 | 13篇 |
2006年 | 9篇 |
2005年 | 7篇 |
2004年 | 8篇 |
2003年 | 3篇 |
2002年 | 5篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1997年 | 3篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1976年 | 2篇 |
1973年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有317条查询结果,搜索用时 578 毫秒
51.
Central composite design (CCD) and response surface methodology (RSM) were developed as experimental strategies for modeling and optimization of the influence of some variables on the performance of a new PVC membrane triiodide ion-selective electrode. This triiodide sensor is based on triiodide-clozapine ion-pair complexation. PVC, plasticizers, ion-pair amounts and pH were investigated as four variables to build a model to achieve the best Nernstian slope (59.9 mV) as response. The electrode is prepared by incorporating the ion-exchanger in PVC matrix plasticized with 2-nitrophenyl octal ether, which is directly coated on the surface of a graphite electrode. The influence of foreign ions on the electrode performance was also investigated. The optimized membranes demonstrate Nernstian response for triiodide ions over a wide linear range from 5.0 x 10(-6) to 1.0 x 10(-2)mol L(-1) with a limit of detection 2.0 x 10(-6) mol L(-1) at 25 degrees C. The electrodes could be used over a wide pH range 4-8, and have the advantages of easy to prepare, good selectivity and fast response time, long lifetime (over 3 months) and small interferences from hydrogen ion. The proposed electrode was successfully used as indicator electrode in potentiometric titration of triiodide ions and ascorbic acid. 相似文献
52.
53.
Mousa Al-Noaimi Ismail I. Fasfous Firas F. Awwadi Deeb Taher Abdallah Alfayyoumi Obadah S. Abdel-Rahman 《Transition Metal Chemistry》2016,41(7):795-805
Five octahedral ruthenium(II) complexes with azoimine–quinoline (Azo) and α-diimine (L) ligands having the general formula [RuII(L)(Azo)Cl](PF6) (1–5) {Azo: PhN=NC(COMe)=NC9H6N, L = 4,4′-dimethoxy-2,2′-bipyridine (dmeb) (1), 4,4′-di-tertbutyl-2,2′-bipyridine (dtb) (2), 1,10-phenanthroline (phen) (3), 5-chlorophenanthroline (Clphen) (4), or 3,4,7,8-tetramethyl-1,10-phenanthroline (tmphen) (5)} were prepared by stepwise addition of the tridentate azoimine (H2Azo) and α-diimine (L) pro-ligands to RuCl3 in refluxing EtOH. The tridentate azoimine–quinoline ligands coordinate to ruthenium via the Azo-N′, N′-imine and N″-quinolone nitrogen atoms. The spectroscopic properties (IR, UV/Vis, 1H, 13C and 19F NMR) and electrochemical behavior of complexes 1–5 and the X-ray crystal structures of complexes 2 and 3 are presented. The coordination of Ru(II) to these strong π-acceptor ligands (Azo and L) results in a large anodic shift for the Ru(III/II) couples of 1.63–1.72 V versus NHE. The electronic spectra in MeCN and IR spectra in CH2Cl2 for complex 3 in its oxidized 3 + and reduced 3 ? forms were investigated. The calculated absorption spectrum of 3 in MeCN was used to assign the UV–Vis absorption bands. 相似文献
54.
55.
A new convenient colorimetric sensor for fructose based on anti-aggregation of citrate-capped gold nanoparticles(Au NPs) is presented. 4-Mercaptophenylboronic acid(MPBA) induces the aggregation of Au NPs, leading to a color change from red to blue. Fructose as a potent competitor has strong affinity for MPBA and a borate ester is formed between MPBA and fructose. There is an obvious color change from blue to red with increasing the concentration of fructose. The anti-aggregation effect of fructose on Au NPs was seen by the naked eye and monitored by UV–vis spectra. Our results showed that the absorbance ratio(A_(519)/A_(640)) was linear with fructose concentration in the range of 0.032–0.96 μmol/L(R~2= 0.996), with a low detection limit of 0.01 μmol/L(S/N = 3). Notably, a highly selective recognition of fructose was shown against other monosaccharide and disaccharide(glucose, mannose, galactose,lactose and saccharose). With anti-aggregation assays higher selectivity is achievable. The results of this work provide a rapid method for evaluating the quantitative analysis of fructose in human plasma at physiologically meaningful concentrations and at neutral pH. The proposed procedure can be used as an efficient method for the precise and accurate determination of fructose. 相似文献
56.
Fathi A. Abu‐Shanab A. M. Hessen S. A. S. Mousa 《Journal of heterocyclic chemistry》2007,44(4):787-791
57.
58.
Priti Tagde Pooja Tagde Fahadul Islam Sandeep Tagde Muddaser Shah Zareen Delawar Hussain Md. Habibur Rahman Agnieszka Najda Ibtesam S. Alanazi Mousa O. Germoush Hanan R. H. Mohamed Mardi M. Algandaby Mohammed Z. Nasrullah Natalia Kot Mohamed M. Abdel-Daim 《Molecules (Basel, Switzerland)》2021,26(23)
Curcumin is the primary polyphenol in turmeric’s curcuminoid class. It has a wide range of therapeutic applications, such as anti-inflammatory, antioxidant, antidiabetic, hepatoprotective, antibacterial, and anticancer effects against various cancers, but has poor solubility and low bioavailability. Objective: To improve curcumin’s bioavailability, plasma concentration, and cellular permeability processes. The nanocurcumin approach over curcumin has been proven appropriate for encapsulating or loading curcumin (nanocurcumin) to increase its therapeutic potential. Conclusion: Though incorporating curcumin into nanocurcumin form may be a viable method for overcoming its intrinsic limitations, and there are reasonable concerns regarding its toxicological safety once it enters biological pathways. This review article mainly highlights the therapeutic benefits of nanocurcumin over curcumin. 相似文献
59.
Mahmoud H. Saleh Nidal M. Ershaidat Mais Jamil A. Ahmad Basim N. Bulos Mousa M. Abdul-Gader Jafar 《Optical Review》2017,24(3):260-277
Spectral dispersions of index of refraction \({n(\lambda )}\) and extinction coefficient \({\kappa (\lambda )}\) of undoped amorphous selenium (a-Se) films of three thicknesses (d?≈?0.5, 0.75, and 1.0 µm) were evaluated by analyzing experimental room-temperature normal-incidence transmittance-wavelength (\({{T_{{\text{exp}}}}(\lambda )} - \lambda\)) data (λ =?400–1100 µm) of their air-supported {a-Se film/thick glass slide}-stacks using Swanepoel’s transmission envelope theory of uniform films. Above a wavelength \({{\lambda _c}\,\, \approx \,\,640\;{\text{nm}}}\), as-measured \({{T_{{\text{exp}}}}(\lambda )}\,\, - \,\lambda\) spectra display well-resolved maxima and minima, with minor shrinkage in transparent and weak absorption regions (750–1100 nm). Below \({\lambda _{\text{c}}}\), a smeared sharp decline of \({{T_{{\text{exp}}}}(\lambda )}\) with decreasing λ, signifying strong absorption in a-Se films and existence of band-tail localized states. For λ > λ c, the \({n\,(\lambda )}\, - \,\lambda\) data retrieved from algebraic envelope procedures followed a Sellmeier-like dispersion relation, with the best-fit values of high-frequency dielectric constant \({{\varepsilon _\infty }\, \approx \,\,{\text{4.9}}}\), static index of refraction \({{n_{\text{0}}} = n\left( {E\, \to \,{\text{0}}} \right)\,\, \approx \,\,{\text{2.43}}}\), and resonance wavelength \({{\lambda _0}\, \approx \,490\,\,{\text{nm}}}\), which may be assigned to onset of photogeneration in a-Se. Urbach-like dependency of absorption coefficient \({\alpha (h{{\nu }})}\) of a-Se films on photon energy \({h{{\nu }}}\) was realized with an Urbach-tail breadth of 85 meV. All achieved optical parameters were found to be slightly dependent on film thickness. Findings of present algebraic analysis are consistent with reported literature results obtained on the basis of other optical analytical approaches. 相似文献
60.
Ramin Maleki Nasim Mohammad Nezhad Naser Samadi Khalil Farhadi 《Mikrochimica acta》2009,165(1-2):97-101
Dispersive liquid–liquid microextraction (DLLME) in conjunction with high-performance liquid chromatography-diode array detection (HPLC-DAD) has been applied to the extraction and determination of EDTA in sediments and water samples. The effect of extraction, nature and volume of disperser solvent, pH value of sample solution, extraction time and extraction temperature were investigated. Under the optimal conditions the analytical range of EDTA was from 3.0 to 50.0 μg L?1 with a correlation coefficient of 0.9982 and a detection limit of 1.7 μg L?1. The relative standard deviation (RSD) was less than 5.4% (n?=?5), and the recovery values were in the range of 89–95%. The simplicity, high enrichment, high recovery and good repeatability are the main advantages of the method presented. The DLLME-HPLC-DAD method was successfully applied to the analysis of EDTA in aqueous samples. 相似文献