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971.
972.
Claire Bouvy Evgeny Chelnokov Wladimir Marine Robert Sporken Bao-Lian Su 《Journal of Non》2009,355(18-21):1152-1156
ZnO@mesoporous silica nanocomposite was prepared by the impregnation of a CMI-1 material in a Zn(NO3)2 solution followed by calcination under O2. Intensive characterization was carried out by N2 adsorption–desorption measurements, scanning and transmission electron microscopy. The optical properties of the ZnO@mesoporous silica nanocomposite were studied by photoluminescence spectroscopy. Quantum Size Effect was firstly demonstrated by subjecting the sample to a 254 nm excitation light, and was further confirmed by using a 680 nm excitation laser beam, which implies a two-photon absorption process. By focusing the 680 nm laser beam on different places in the sample, a very localized random laser effect, also induced by a two-photon absorption process, was detected. 相似文献
973.
Yong Wang Pascal Pigeon Siden Top Juan SanzGarcía Claire Troufflard Ilaria Ciofini Michael J. McGlinchey Grard Jaouen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(25):8509-8513
Ferrociphenols, especially those possessing a heterocycle at the terminus of an aliphatic chain, display strong anticancer activity through a novel redox mechanism that generates active metabolites such as quinone methides (QMs). X‐ray crystallography and UV/Vis spectroscopy reveal that the specific lone pair (lp)–π interaction between a carbonyl group of the imide and the quinone motif of the QM plays an important role in the exceptional cytotoxic behaviour of their imido‐ferrociphenol precursors. This intramolecular lp–π interaction markedly enhanced the stability of the QMs and lowered the pKa values of the corresponding phenol/phenolate couples. As the first example of such a non‐covalent interaction that stabilizes QMs remotely, it not only expands the scope of the lp–π interaction in supramolecular chemistry, but also represents a new mode of stabilization of a QM. This unprecedented application of lp–π interactions in imido‐ferrociphenol anticancer drug candidates may also have great potential in drug discovery and organocatalyst design. 相似文献
974.
Turibio Kuiate Tabopda Anne‐Claire Mitaine‐Offer Tomofumi Miyamoto Chiaki Tanaka Bonaventure Tchaleu Ngadjui Jean‐François Mirjolet Olivier Duchamp Marie‐Aleth Lacaille‐Dubois 《Helvetica chimica acta》2011,94(5):914-922
Three new medicagenic acid saponins, micranthosides A–C ( 1 – 3 ), were isolated from the roots of Polygala micrantha Guill . & Perr ., along with six known presenegenin saponins. Their structures were elucidated on the basis of extensive 1D‐ and 2D‐NMR experiments (1H, 13C, DEPT, COSY, TOCSY, NOESY, HSQC, and HMBC) and mass spectrometry as 3‐O‐β‐D ‐glucopyranosylmedicagenic acid 28‐[O‐β‐D ‐galactopyranosyl‐(1→4)‐O‐β‐D ‐xylopyranosyl‐(1→4)‐O‐α‐L ‐rhamnopyranosyl‐(1→2)‐β‐D ‐fucopyranosyl] ester ( 1 ), 3‐O‐β‐D ‐glucopyranosylmedicagenic acid 28‐[O‐6‐O‐acetyl‐β‐D ‐galactopyranosyl‐(1→4)‐O‐β‐D ‐xylopyranosyl‐(1→4)‐O‐α‐L ‐rhamnopyranosyl‐(1→2)‐β‐D ‐fucopyranosyl] ester ( 2 ), and 3‐O‐{O‐β‐D ‐glucopyranosyl‐(1→3)‐O‐[β‐D ‐glucopyranosyl‐(1→6)]‐β‐D ‐glucopyranosyl}medicagenic acid 28‐{O‐β‐D ‐apiofuranosyl‐(1→3)‐O‐β‐D ‐xylopyranosyl‐(1→4)‐O‐[β‐D ‐apiofuranosyl‐(1→3)]‐O‐α‐L ‐rhamnopyranosyl‐(1→2)‐β‐D ‐fucopyranosyl} ester ( 3 ). Compounds 1 – 3 were evaluated against HCT 116 and HT‐29 human colon cancer cells, but they did not show any cytotoxicity. 相似文献
975.
976.
Griffete N Frederich H Maître A Ravaine S Chehimi MM Mangeney C 《Langmuir : the ACS journal of surfaces and colloids》2012,28(1):1005-1012
Inverse opal films of molecularly imprinted polymers (MIP) were elaborated using the colloidal crystal template method. The colloidal crystals of silica particles were built by the Langmuir-Blodgett technique, allowing a perfect control of the film thickness. Polymerization in the interspaces of the colloidal crystal in the presence of bisphenol A (BPA) and removal of the used template provides 3D-ordered macroporous methacrylic acid-based hydrogel films in which nanocavities derived from bisphenol A are distributed within the thin walls of the inverse opal hydrogel. The equilibrium swelling properties of the nonimprinted (NIPs) and molecularly imprinted polymers (MIPs) were studied as a function of pH and bisphenol A concentration, while the molecular structures of the bulk hydrogels were analyzed using a cross-linked network structure theory. This study showed an increase in nanopore (mesh) size in the MIPs after BPA extraction as compared to NIPs, in agreement with the presence of nanocavities left by the molecular imprints of the template molecule. The resulting inverse opals were found to display large responses to external stimuli (pH or BPA) with Bragg diffraction peak shifts depending upon the hydrogel film thickness. The film thickness was therefore shown to be a critical parameter for improving the sensing capacities of inverse opal hydrogel films deposited on a substrate. 相似文献
977.
Lazarides T Easun TL Veyne-Marti C Alsindi WZ George MW Deppermann N Hunter CA Adams H Ward MD 《Journal of the American Chemical Society》2007,129(13):4014-4027
We show in this paper how the 3MLCT luminescence of [Ru(bipy)(CN)4]2-, which is known to be highly solvent-dependent, may be varied over a much wider range than can be achieved by solvent effects, by interaction of the externally directed cyanide ligands with additional metal cations both in the solid state and in solution. A series of crystallographic studies of [Ru(bipy)(CN)4]2- salts with different metal cations Mn+ (Li+, Na+, K+, mixed Li+/K+, Cs+, and Ba2+) shows how the cyanide/Mn+ interaction varies from the conventional "end-on" with the more Lewis-acidic cations (Li+, Ba2+) to the more unusual "side-on" interaction with the softer metal cations (K+, Cs+). The solid-state luminescence intensity and lifetime of these salts is highly dependent on the nature of the cation, with Cs+ affording the weakest luminescence and Ba2+ the strongest. A series of titrations of the more soluble derivative [Ru(tBu2bipy)(CN)4]2- in MeCN with a range of metal salts showed how the cyanide/Mn+ association results in a substantial blue-shift of the 1MLCT absorptions, and 3MLCT energies, intensities, and lifetimes, with the complex varying from essentially non-luminescent in the absence of metal cation to showing strong (phi = 0.07), long-lived (1.4 micros), and high-energy (583 nm) luminescence in the presence of Ba2+. This modulation of the 3MLCT energy, over a range of about 6000 cm-1 depending on the added cation, could be used to reverse the direction of photoinduced energy transfer in a dyad containing covalently linked [Ru(bipy)3]2+ and [Ru(bipy)(CN)4]2- termini. In the absence of a metal cation, the [Ru(bipy)(CN)4]2- terminus has the lower 3MLCT energy and thereby quenches the [Ru(bipy)3]2+-based luminescence; in the presence of Ba2+ ions, the 3MLCT energy of the [Ru(bipy)(CN)4]2- terminus is raised above that of the [Ru(bipy)3]2+ terminus, resulting in energy transfer to and sensitized emission from the latter. 相似文献
978.
Lahootun V Besson C Villanneau R Villain F Chamoreau LM Boubekeur K Blanchard S Thouvenot R Proust A 《Journal of the American Chemical Society》2007,129(22):7127-7135
The ruthenium-nitrido POM derivative [PW11O39{RuVIN}]4- has been synthesized by reaction between [PW11O39]7- and [RuVINCl5]2- or [RuVINCl4]-. Its molecular structure has been confirmed from multinuclear 31P and 183W NMR spectroscopy together with an EXAFS study, while the oxidation state of the ruthenium bearing the nitrido ligand has been inferred both from 183W NMR and XANES analysis at the Ru-K edge. The potential of [PW11O39{RuVIN}]4- in N-atom transfer reactions has been demonstrated through reaction with triphenylphosphine, which ultimately leads to the release of the bis(triphenylphosphane)iminium cation [PPh3=N=PPh3]+ through several intermediates, among which the phosphoraniminato derivative [PW11O39{RuVNPh3}]3- has been structurally characterized. Its unusual oxidation state is in accordance with its EPR spectrum. 相似文献
979.
980.
Kevers C Jacques P Gaspar T Thonart P Dommes J 《Journal of chromatographic science》2004,42(10):554-558
The ginsenoside content of different ginseng species (Panax ginseng, P. quinquefolium, and P. vietnamensis) from different sources (roots from field-grown plants or from in vitro cultures, cells from solid calluses or from liquid cultures, commercial powders, and suspensions) is evaluated by means of a new high-performance thin-layer chromatography (HPTLC) technique combining an automatic TLC sampler and scanner. The results are compared with those obtained through more classical gross spectrometric and high-performance liquid chromatography (HPLC) techniques. HPTLC and HPLC allow the separation and estimation of the different ginsenosides. For this, HPTLC is faster and simpler than HPLC. Both techniques determine less amounts of ginsenosides than spectrophotometry, which displays overestimated values caused by light absorption by contaminating osides. In vitro cultured cells and roots contain the same ginsenosides as those produced by their mother plants, although at quite lower levels. The culture media also accumulates ginsenosides. 相似文献