全文获取类型
收费全文 | 276篇 |
免费 | 3篇 |
专业分类
化学 | 194篇 |
晶体学 | 7篇 |
力学 | 14篇 |
数学 | 21篇 |
物理学 | 43篇 |
出版年
2022年 | 9篇 |
2021年 | 5篇 |
2020年 | 3篇 |
2019年 | 9篇 |
2018年 | 5篇 |
2017年 | 4篇 |
2016年 | 9篇 |
2015年 | 5篇 |
2014年 | 2篇 |
2013年 | 19篇 |
2012年 | 13篇 |
2011年 | 10篇 |
2010年 | 6篇 |
2009年 | 11篇 |
2008年 | 11篇 |
2007年 | 19篇 |
2006年 | 13篇 |
2005年 | 16篇 |
2004年 | 5篇 |
2003年 | 10篇 |
2002年 | 7篇 |
2001年 | 3篇 |
1998年 | 7篇 |
1997年 | 2篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1966年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有279条查询结果,搜索用时 156 毫秒
91.
Snehlata Yadav Balasubramanian Narasimhan Siong M. Lim Kalavathy Ramasamy Mani Vasudevan Syed Adnan Ali Shah Manikandan Selvaraj 《Chemistry Central journal》2017,11(1):137
Background
A series of 2-(1H-benzo[d]imidazol-2-ylthio)-N-(substituted 4-oxothiazolidin-3-yl) acetamides was synthesized and characterized by physicochemical and spectral means. The synthesized compounds were evaluated for their in vitro antimicrobial activity against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Candida albicans and Aspergillus niger by tube dilution method. The in vitro cytotoxicity study of the compounds was carried out against human colorectal (HCT116) cell line. The most promising anticancer derivatives (5l, 5k, 5i and 5p) were further docked to study their binding efficacy to the active site of the cyclin-dependent kinase-8.Results
All the compounds possessed significant antimicrobial activity with MIC in the range of 0.007 and 0.061 µM/ml. The cytotoxicity study revealed that almost all the derivatives were potent in inhibiting the growth of HCT116 cell line in comparison to the standard drug 5-fluorouracil. Compounds 5l and 5k (IC50 = 0.00005 and 0.00012 µM/ml, respectively) were highly cytotoxic towards HCT116 cell line in comparison to 5-fluorouracil (IC50 = 0.00615 µM/ml) taken as standard drug.Conclusion
The molecular docking studies of potent anticancer compounds 5l, 5k, 5i and 5p showed their putative binding mode and significant interactions with cyclin-dependent kinase-8 as prospective agents for treating colon cancer.92.
Mixed saturated-unsaturated alkyl-chain assemblies: solid solutions of zinc stearate and zinc oleate
The linear saturated stearic acid and the bent mono-unsaturated oleic acid do not mix and form solid solutions. However, the zinc salts of these acids can. From X-ray diffraction and DSC measurements we show that the layered zinc stearate and zinc oleate salts form a homogeneous solid solution at all composition ratios. The solid solutions exhibit a single melting endotherm, with the melting temperature varying linearly with composition but with the enthalpy change showing a minimum. By monitoring features in the infrared spectra that are characteristic of the global conformation of the hydrocarbon chain, and hence can distinguish between stearate and oleate chains, it is shown that solid solution formation is realized by the introduction of gauche defects in a fraction of the stearate chains that are then no longer linear. This fraction increases with oleate concentration. It has also been possible from the spectroscopic measurements to establish a quantitative relation between molecular conformational order and the thermodynamic enthalpy of melting of the solid solutions. 相似文献
93.
Cynodon dactylon (L.) is a potent medicinal plant in the traditional and current Indian medicinal systems. The objective of this research was to find out the levels of flavonoids, carotenoids and chlorophyll b in C. dactylon leaves by high-performance liquid chromatography (HPLC) equipped with a diode array detector. HPLC analysis revealed that total carotenoid and total flavonoid concentration were 62 mg/100 g and 249.1 μg/g, respectively. The mean chlorophyll b was 85.1 mg/100 g in C. dactylon. Among the flavonoids, quercetin (164.7 μg/g) was the major flavonoid followed by kaempferol (48.2 μg/g), rutin (18.4 μg/g), catechin (12.1 μg/g) and myricetin (5.7 μg/g). Of the carotenoids, β-carotene (35.2 mg/100 g) was predominant followed by lutein (17.0 mg/100 g), violaxanthin (5.8 mg/100 g) and zeaxanthin (4.2 mg/100 g). Chlorophyll b concentration was 85.1 mg/100 g in C. dactylon. The results of this investigation should be useful information for further pharmacological studies. 相似文献
94.
Caroline ML Prakash M Geetha D Vasudevan S 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,79(5):1936-1940
Bulk single crystals of l-alanine alaninium nitrate [abbreviated as LAAN], an intriguing material for frequency conversion has been grown from its aqueous solution by both slow solvent evaporation and by slow cooling techniques. The optimized pH value to grow good quality LAAN single crystal was found to be 2.5. The grown crystals were subjected to single crystal X-ray diffraction studies to determine the unit cell dimensions and morphology. Vibrational frequencies of the grown crystals by Fourier transform infrared spectroscopic technique were investigated. Also, the presence of hydrogen and carbon atoms in the grown sample was confirmed using proton and carbon NMR analyses. The dielectric constant and dielectric loss measurements of the as grown crystal at different temperatures and frequencies of the applied field are measured and reported. LAAN has good optical transmission in the entire visible region with cutoff wavelength within the UV region confirms its suitability for device fabrications. The existence of second harmonic generation signals was observed using Nd:YAG laser with fundamental wavelength of 1064 nm. Its Laser Damage Threshold (LDT) was measured and also tested by using a Q-switched Nd:YAG laser and the value of LDT of LAAN is 17.76GW/cm2 respectively, is found to be better than certain organic and semiorganic materials. 相似文献
95.
96.
Prathibha Vasudevan Sunil Thomas P. R. Biju C. Sudarsanakumar N. V. Unnikrishnan 《Journal of Sol-Gel Science and Technology》2012,62(1):41-46
Non hydrolytic sol–gel method was employed to synthesize pure anatase TiO2 nanocrystals using tetra isopropyl orthotitanate and poly vinylpyrrolidone as precursors. The structural analyses of the
prepared samples were carried out using Fourier transform infrared spectroscopy (FT-IR), thermo gravimetric and differential
thermal analysis (TG–DTA), X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM) and energy-dispersive
X-ray spectroscopy (EDS). The capping of PVP around TiO2 nanoparticles was confirmed by FT-IR spectroscopy, the interaction being via bridging oxygens of the carbonyl (C=O) and the
nanoparticle surface. The XRD, Raman and TEM results indicate that the prepared samples had a pure anatase nano-TiO2 structure. The particle size analysed by TEM ranged between 7 and 12 nm. The size of the nanocrystals evaluated from the
XRD spectra and TEM micrograph is well in agreement. The spacing for the crystal planes was also determined using the ImageJ
program applied to the TEM micrographs. 相似文献
97.
The host-guest chemistry of most inorganic layered solids is limited to ion-exchange reactions. The guest species are either cations or anions to compensate for the charge deficit, either positive or negative, of the inorganic layers. Here, we outline a strategy to include neutral molecules like ortho- and para-chloranil, that are known to be good acceptors in donor-acceptor or charge-transfer complexes, within the galleries of a layered solid. We have succeeded in including neutral ortho- and para-chloranil molecules within the galleries of an Mg-Al layered double hydroxide (LDH) by using charge-transfer interactions with preintercalated p-aminobenzoate ions as the driving force. The p-aminobenzoate ions are introduced in the Mg-Al LDH via ion exchange. The intercalated LDH can adsorb ortho- and para-chloranil from chloroform solutions by forming charge-transfer complexes with the p-aminobenzoate anions present in the galleries. We use X-ray diffraction, spectroscopy, and molecular dynamics simulations to establish the nature of interactions and arrangement of the charge-transfer complex within the galleries of the layered double hydroxide. 相似文献
98.
Vasudevan KV Smith NA Scott BL Bennett BL Muenchausen RE Gordon JC 《Dalton transactions (Cambridge, England : 2003)》2012,41(7):1924-1927
The preparation of a series of CeBr(3) molecular adducts supported by the polydentate oxygen donor ligands diglyme, dimethoxyethane and tetraglyme is reported. The new complexes are characterized structurally by X-ray diffraction and optically by photoluminescence studies. 相似文献
99.
Vasudevan KV Findlater M Vargas-Baca I Cowley AH 《Journal of the American Chemical Society》2012,134(1):176-178
The differences in redox behavior of the monofunctional bis(imino)acenaphthene (BIAN) and bifunctional tetrakis(imino)pyracene (TIP) ligands have been explored by treatment of the latter with PI(3), TeI(4), or BI(3). These reactions result in the formation of products involving the transfer of three or four electrons. Accompanying DFT calculations reveal that in each case the extent of electron transfer from each p-block element into the TIP ligand is dependent upon the element-TIP bonding interactions. 相似文献
100.
K. Ragavendran D. Sherwood D. Vasudevan Bosco Emmanuel 《Physica B: Condensed Matter》2009,404(16):2166-2171
Two batches of poly-crystalline lithium manganate were prepared by a fuel assisted solution combustion method. LiMn2O4(S) was prepared using starch as the fuel and LiMn2O4(P) was prepared using poly vinyl alcohol (PVA) as the fuel. XRD studies indicated a significant and consistent shift in the 2θ values of all the hkl peaks to higher values in LiMn2O4(P) compared to LiMn2O4(S) indicating a lattice contraction in the former. TG/DTA studies indicated a higher formation temperature (∼25 °C higher) for LiMn2O4(P). The higher formation temperature most likely promotes the oxidation of some Mn3+ to Mn4+ with a lower ionic radius causing a lattice contraction. This hypothesis is confirmed through XPS studies which indicated the presence of a higher fraction of Mn4+ in LiMn2O4(P) than that present in LiMn2O4(S). A crystal shape algorithm was used to generate the crystal habits of lithium manganate from their XRD data leading to an understanding on the exposed hkl planes in these materials. From the atomic arrangement on the exposed hkl planes it is predicted that LiMn2O4(P) would be less prone to manganese dissolution and hence would possess a higher cycle life when compared to LiMn2O4(S). 相似文献