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排序方式: 共有175条查询结果,搜索用时 15 毫秒
1.
Iliopoulou D Mihopoulos N Vagias C Papazafiri P Roussis V 《The Journal of organic chemistry》2003,68(20):7667-7674
Five new brominated diterpenes, along with two known, have been isolated from the organic extract of the red alga Laurencia obtusa, collected from the coastal rocks of Preveza in the Ionean Sea, Greece. The novel metabolites prevezols B-E possess two new carbon skeletons, to the best of our knowledge, unprecedented in the literature. The structures and the relative stereochemistry of the new natural products were established by means of spectral data analyses. The new metabolites were tested for their cytotoxic activity against five human cell lines. Two metabolites have exhibited significant cytotoxicity. 相似文献
2.
We present exact calculations of the spatial correlation of the blackbody radiation in the presence of spheres whose dimensions are smaller or comparable to the radiation wavelength. By going beyond the standard scalar coherence theory, we show that the spatial correlation function of a spherical thermal source is not universal but depends on the material properties of the source and exhibits near-field-induced features. Near-field effects are also manifested in the case of a linear chain of dielectric spheres where the correlation function probes the inhomogeneity of the chain. For this latter system we have established the conditions when the near-field effects cancel out and the correlation function takes the typical form of a conventional Lambertian source. For the case of a chain of metallic nanospheres, the increased spatial correlation of the far field leads to a directional thermal emission spectrum. 相似文献
3.
Imen Ben Atitallah Georgia Antonopoulou Ioanna Ntaikou Amaia Soto Beobide Vassilios Dracopoulos Tahar Mechichi Gerasimos Lyberatos 《Molecules (Basel, Switzerland)》2022,27(4)
The effect of different pretreatment approaches based on alkali (NaOH)/hydrogen peroxide (H2O2) on willow sawdust (WS) biomass, in terms of delignification efficiency, structural changes of lignocellulose and subsequent fermentation toward ethanol, was investigated. Bioethanol production was carried out using the conventional yeast Saccharomyces cerevisiae, as well as three non-conventional yeasts strains, i.e., Pichia stipitis, Pachysolen tannophilus, Wickerhamomyces anomalus X19, separately and in co-cultures. The experimental results showed that a two-stage pretreatment approach (NaOH (0.5% w/v) for 24 h and H2O2 (0.5% v/v) for 24 h) led to higher delignification (38.3 ± 0.1%) and saccharification efficiency (31.7 ± 0.3%) and higher ethanol concentration and yield. Monocultures of S. cerevisiae or W. anomalus X19 and co-cultures with P. stipitis exhibited ethanol yields in the range of 11.67 ± 0.21 to 13.81 ± 0.20 g/100 g total solids (TS). When WS was subjected to H2O2 (0.5% v/v) alone for 24 h, the lowest ethanol yields were observed for all yeast strains, due to the minor impact of this treatment on the main chemical and structural WS characteristics. In order to decide which is the best pretreatment approach, a detailed techno-economical assessment is needed, which will take into account the ethanol yields and the minimum processing cost. 相似文献
4.
Maria Harizani Dafni-Ioanna Diakaki Stamatios Perdikaris Vassilios Roussis Efstathia Ioannou 《Molecules (Basel, Switzerland)》2022,27(6)
The chemical diversity of the approximately 1,200 natural products isolated from red algae of the genus Laurencia, in combination with the wide range of their biological activities, have placed species of Laurencia in the spotlight of marine chemists’ attention for over 60 years. The chemical investigation of the organic (CH2Cl2/MeOH) extracts of Laurencia microcladia and Laurencia obtusa, both collected off the coasts of Tinos island in the Aegean Sea, resulted in the isolation of 32 secondary metabolites, including 23 C15 acetogenins (1–23), 7 sesquiterpenes (24–30) and 2 diterpenes (31 and 32). Among them, six new C15 acetogenins, namely 10-acetyl-sagonenyne (2), cis-sagonenyne (3), trans-thuwalenyne C (4), tinosallene A (11), tinosallene B (12) and obtusallene XI (17), were identified and their structures were elucidated by extensive analysis of their spectroscopic data. Compounds 1–3, 5–11, 13 and 15–32 were evaluated for their antibacterial activity against Staphylococcus aureus and Escherichia coli. 相似文献
5.
Konstantina A. Kounavi Constantina Papatriantafyllopoulou Anastasios J. Tasiopoulos Spyros P. Perlepes Vassilios Nastopoulos 《Polyhedron》2009
An investigation of the MII/X−/L [MII = Co, Ni, Cu, Zn; X− = Cl−, Br−, I−, NCS−, NO3−, N3−, CH3COO−; L = 1-methyl-4,5-diphenylimidazole] general reaction system towards the detailed study of the intermolecular interactions utilized for controlling the supramolecular organization and the structural consequences on the structures produced has been initiated. Three representative complexes with the formulae [Co(NO3)2(L)2] (1), [Zn(NO3)2(L)2] (2) and [Co(NCS)2(L)2]·EtOH (3·EtOH) have been synthesized and characterized by spectroscopic methods and single-crystal X-ray analysis. Compounds 1 and 2 are isomorphous (tetragonal, I41cd) with their metal ions in a severely distorted octahedral Co/ZnN2O4 environment, while 3·EtOH crystallizes in P21/c with a tetrahedral CoN4 coordination. The structural analysis of 1, 2 and 3·EtOH reveals a common mode of packing among neighbouring ligands (expressed through intramolecular π–π interactions between the 4,5-diphenylimidazole moieties), enhancing thus the rigidity and stability of the complexes. The bent coordination of the two isothiocyanates in 3 [Co–NCS angles of 173.8(2) and 160.8(2)°] seems to be caused by intermolecular hydrogen bonding and crystal packing effects. 相似文献
6.
Tony Tite Vassilios Myrianthopoulos Emmanuel Mikros Roxane Tenta Tzortzis Nomikos 《Tetrahedron》2010,66(50):9620-9628
A number of new pyrazolo[3,4-c] and [4,3-b]pyridine C-nucleosides, which can be viewed as 4- or 6-deazaformycin analogues were synthesized and examined as potential adenosine deaminase (ADA) inhibitors. The compounds were prepared through the condensation of a suitably substituted, lithiated 2- or 4-methylpyridine with tri-O-benzyl-d-ribonolactone, followed by borohydride reduction of the resulting hemiacetals, intramolecular Mitsunobu cyclisation of the derived diols, formation of the pyrazolopyridine ring system and subsequent removal of the protecting groups. These derivatives were designed on the structural basis provided by docking simulations performed within the enzyme catalytic site, however they demonstrated weak ADA inhibitory activity. Theoretical calculations assisted in the interpretation of the obtained biological data, thus providing guidance for rational structural modifications within this molecular scaffold. 相似文献
7.
8.
Couladouros EA Pitsinos EN Moutsos VI Sarakinos G 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,11(1):406-421
A general strategy for the synthesis of twenty naturally occurring bastadins (all but bastadin 3) is presented. A key retrosynthetic disconnection of the two amide bonds, common in all target molecules, bisects the macrocyclic core into two diaryl ether fragments, an alpha,omega-diamine (western part) and an alpha,omega-dicarboxylic acid (eastern part). Efficient preparation of the synthetically challenging o-mono or dibromo-substituted diaryl ether linkages was achieved employing the diaryl iodonium salt method. Regarding the western part, variations of the aliphatic chain were more efficiently secured by the preparation of two different alpha,omega-aminonitrile moieties. Cobalt boride mediated reduction of the nitrile functionality established the required diamines and, at the same time, provided the necessary variation of the aromatic-ring bromination pattern. Regarding the eastern part, two different dicarboxyl precursors had to be prepared in order to accommodate bromination-pattern variations. Coupling and subsequent macrolactamization of different combinations of these key intermediates may lead at will to any member of this family of marine natural products. Four bastaranes (bastadins 5, 10, 12 and 16) and two isobastaranes (bastadins 20 and 21) were synthesized as a demonstration of the flexibility and efficiency of the approach presented. 相似文献
9.
George Cordoyiannis Patricia Losada-Pérez Chandra Shekhar Pati Tripathi Brigita Rožič Uroš Tkalec Vassilios Tzitzios 《Liquid crystals》2013,40(11):1419-1426
The phase transition behaviour of the chiral liquid crystal CE6 doped with spherical surface-functionalised CdSe nanoparticles has been examined by means of high-resolution adiabatic scanning calorimetry and polarising microscopy. The addition of nanoparticles results in an essentially stabilised blue phase III. The phase diagram is displayed upon heating and cooling and the enthalpy changes involved in the conversion between the blue phases are determined. The dispersion of functionalised nanoparticles is prominent for the stabilisation of blue phase III, which is potentially useful for applications, especially if applied on liquid crystals that exhibit blue phases close to room temperature. 相似文献
10.
(S)-7-Hydroxy-3-amino-3,4-dihydro-2H-1-benzopyran, a key synthetic intermediate towards the total synthesis of (+)-scyphostatin, has been prepared in >98% ee. Key synthetic steps were (i) the oxidative dearomatization of an l-tyrosine derived phenol, (ii) the transformation of the resulting p-quinol acetate to the corresponding resorcinol upon exposure to Thiele reaction conditions and, (iii) the direct formation of the benzopyran ring upon treatment of an N-Boc protected 4-(2-acetoxybenzyl)oxazolidin-2-one with sodium methoxide. 相似文献