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61.
Prakash M Geetha D Caroline ML Ramesh PS 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,82(1):461-466
The mineral crandallite CaAl3(PO4)2(OH)5·(H2O) has been identified in deposits found in the Jenolan Caves, New South Wales, Australia by using a combination of X-ray diffraction and Raman spectroscopic techniques. A comparison is made between the vibrational spectra of crandallite found in the Jenolan Caves and a standard crandallite. Raman and infrared bands are assigned to PO43− and HPO42− stretching and bending modes. The predominant features are the internal vibrations of the PO43− and HPO42− groups. A mechanism for the formation of crandallite is presented and the conditions for the formation are elucidated. 相似文献
62.
Prakash M Geetha D Lydia Caroline M 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,81(1):48-52
Tris(L-phenylalanine)L-phenylalaninium nitrate, C(9)H(12)NO(2)(+)·NO(3)(-)·3C(9)H(11)NO(2) (TPLPN), a new organic nonlinear optical material was grown from aqueous solution by slow evaporation solution growth at room temperature. The grown crystals were subjected to powder X-ray diffraction and single crystal X-ray diffraction studies to confirm the crystalline nature and crystal structure. The modes of vibration of different molecular groups present in TPLPN have been identified by FTIR spectral analysis. The presence of hydrogen and carbon in the grown crystal were confirmed by using proton and carbon nuclear magnetic resonance (NMR) spectral analyses. The optical transmission spectral study establishes good transmitting ability of the crystal in the entire visible region. The thermogravimetric (TG) and differential thermal analyses (DTA) were carried out to understand the thermal stability of the sample. The nonlinear optical property of the compound observed using Kurtz powder second harmonic generation test assets the suitability of the grown material for the frequency conversion of laser radiation of Nd:YAG. 相似文献
63.
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
64.
The mechanism of biocidal action of nano titania on Escherichia coli and Staphylococcus aureus has been evaluated by various biochemical techniques like lipid peroxidation, hydrolysis of orthonitrophenol β-D-galactopyranoside, estimation of protein-amino acid and bacterial nucleic acids leakage into solution, in addition to morphology studies by electron microscopy (TEM and SEM) and K(+) ion leakage by inductively coupled plasma optical emission spectrometry. The active anatase phase of nano titania has been synthesized by sol-gel and pulverization techniques to obtain particle sizes averaging around 11 nm. The nano semiconductor with a bandgap of 3.2 eV responds well to the UV source to liberate reactive oxygen species (ROS). Gram negative bacteria easily succumb to the ROS at a faster rate than gram-positive bacteria with an observable difference in the mode of attack. The use of analytical techniques revealed the release of peroxidized lipid (26 nmol mL(-1) ) and protein content (370 μg mL(-1)) with a K(+) ion concentration of 22 000 ppb on complete destruction of E. coli. 相似文献
65.
S. Krishna prasad Geetha G. Nair Gurumurthy Hegde K. L. Sandhya D. S. Shankar Rao Chethan V. Lobo 《Phase Transitions》2013,86(6):443-455
Temperature, concentration of the solvent and pressure are the parameters that are well known to bring about phase transitions in liquid-crystalline systems. In recent years a new parameter has been added to this list: light. The principle behind these photoinduced transitions is the light-driven shape transformation of certain photoactive materials like, e.g., azobenzene. In this article, we present results of various aspects of our recent investigations on such photoinduced transitions in the nematic phase and highlight the feature that light is a new tool to study phase transitions and the associated critical phenomena. 相似文献
66.
Base-catalyzed reaction of the nitroketene N,S-acetals and the ring substituted 2-hydroxybenzaldehydes afforded a combinatorial library of the 2-alkylamino-3-nitro-4-alkylsulfanyl 4H-chromenes in excellent yields. Nucleophilic displacement of the C4 alkylsulfanyl group with different thiols afforded 4H-chromenes with structural diversity. 相似文献
67.
Amrutha P. Bakkyaraj T. Balasubramanian Krishnan Geetha T. 《Journal of mathematical chemistry》2022,60(4):733-751
Journal of Mathematical Chemistry - Let $$D_n$$ denotes the dihedral group of order 2n. In this article, given any subgroup H of $$D_n$$ , we describe the direct sum decomposition of... 相似文献
68.
69.
R. Geetha A. Torikai S. Yashida S. Nagaya K. Fueki 《Journal of polymer science. Part A, Polymer chemistry》1989,27(5):1653-1663
The fourth type of polyethylene—very low density polyethylene (VLDPE)—has been developed very recently. VLDPE is a copolymer of ethylene and 1-butene. The radiation and photo degradation of VLDPE was studied using gel, FT-IR, and UV spectral measurements. Mechanical tests were also done; the rate of gel and carbonyl formation was high. End methyl ? CH3 group was found to increase in the case of radiation degradation. The initial modulus was very low indicating the rubbery nature in the copolymer. VLDPE was found to be highly resistant to radiation-induced degradation than linear low density polyethylene. VLDPE is highly susceptible to thermal effects. 相似文献
70.