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991.
992.
Barbara Turchi Simone Mancini Luisa Pistelli Basma Najar 《Natural product research》2019,33(10):1509-1513
Fourteen Staphylococcus aureus wild strains were stressed with sub-inhibitory concentration of five essential oils: Leptospermum scoparium (manuka), Origanum majorana (marjoram), Origanum vulgare (oregano), Satureja montana (winter savoury) and Thymus vulgaris (thyme). Antibiotics susceptibility profiles of the strains were determined by agar disk diffusion method before and after EOs treatment. The following antibiotics were employed: amoxicillin-clavulanic acid, amikacin, ampicillin, amoxicillin, aztreonam, ceftazidime, cephalothin, ciprofloxacin, colistin, cefotaxime, doxycycline, enrofloxacin, erythromycin, gentamicin, cephalexin, neomycin, piperacillin, rifampin, streptomycin, trimethoprim-sulphamethoxazole, tetracycline and tobramycin. Before EOs treatment, strains were susceptible to all antibiotics except for aztreonam and colistin. After exposure to sub-inhibitory EOs concentration of manuka, marjoram and oregano, several modifications in antibiotics susceptibility profiles were detected. Conversely, few modifications were induced by winter savoury and thyme EOs. Moreover, occurrence of resistances seems uncorrelated with drug classes as low concentration of EO could induce phenotypic changes in susceptible bacteria leading to antibiotic resistance phenomena. 相似文献
993.
994.
Letters in Mathematical Physics - We consider the Rosenzweig–Porter model $$H = V + \sqrt{T}\, \varPhi $$ , where V is a $$N \times N$$ diagonal matrix, $$\varPhi $$ is drawn from the $$N... 相似文献
995.
Kaja Schubert Dr. Lucas Schwob Simon Dörner Dr. Marion Girod Dr. Luke MacAleese Dr. Cornelius L. Pieterse Dr. Thomas Schlathölter Prof. Dr. Simone Techert Dr. Sadia Bari 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(48):12371-12379
We investigated the photoionization and fragmentation of isolated metal protoporphyrin IX cations (MPPIX+ with M=Fe, Co, Zn) by means of vacuum-ultraviolet (VUV) action spectroscopy in the energy range of 8.5–35 eV. Experiments were carried out in the gas phase by interfacing an electrospray ionization tandem mass spectrometer with a synchrotron beamline. The mass spectra and partial ion yields show that photoexcitation of the precursor ions predominantly leads to .CH2COOH radical side-chain losses of the macrocycle with additional methyl radical (.CH3) side-chain losses. Ionization, in contrast, leads to the formation of the intact ionized precursor and various doubly charged fragments which are mostly due to side-chain cleavages. Although statistical fragmentation dominates, we found evidence for non-statistical processes such as new fragments involving for example single and double H2O losses, indicating that different relaxation mechanisms are at play upon photoionization compared to photoexcitation. The measured ionization energies were 9.6±0.2 eV, 9.4±0.2 eV and 9.6±0.2 eV for FePPIX+, CoPPIX+ and ZnPPIX+, respectively. 相似文献
996.
Curis E Dubar F Nicolis I Bénazeth S Biot C 《The journal of physical chemistry. A》2012,116(23):5577-5585
Antimalarial compounds ruthenoquine and methylruthenoquine were studied by X-ray absorption spectroscopy both in solid state and in solution, in normal (aqueous or CH(2)Cl(2) solutions) and oxidative (aqueous solution with H(2)O(2), either equimolar or in large excess) conditions, to detect small changes in the coordination sphere of the ruthenium atom. Since changes in the EXAFS spectra of these compounds are quite subtle, a complete procedure was developed to assess the different sources of uncertainties in fitted structural parameters, including the use of multivariate statistic methods for simultaneous comparison of edge energy correction ΔE(0) and distances, which can take into account the very strong correlation between these two parameters. Factors limiting the precision of distance determination depend on the recording mode. In transmission mode, the main source of uncertainty is the data reduction process, whereas in fluorescence mode, experimental noise is the main source of variability in the fitted parameters. However, it was shown that the effects of data reduction are systematic and almost identical for all compounds; hence, they can be ignored when comparing distances. Consequently, for both fluorescence and transmission recorded spectra, experimental noise is the limiting factor for distance comparisons, which leads to the use of statistical methods for comparing distances. Univariate methods, focusing on the distance only, are shown to be less powerful in detecting changes in distances than bivariate methods making a simultaneous comparison of ΔE(0) and distances. This bivariate comparison can be done either by using the Hotelling's T(2) test or by using a graphical comparison of Monte Carlo simulation results. We have shown that using these methods allows for the detection of very subtle changes in distances. When applied to ruthenoquine compounds, it suggests that the implication of the nonbinding doublet of the aminoquine nitrogen in either protonation or methylation enhances the tilt of the two cyclopentadienyls. It also suggests that ruthenoquine and methylruthenoquine are, at least partially, oxidized in the presence of H(2)O(2), with a small decrease in the Ru-C bond length and increase in the edge energy. 相似文献
997.
Simone Cerreia-Vioglio Fabio Maccheroni Massimo Marinacci Luigi Montrucchio 《Journal of Mathematical Analysis and Applications》2012,385(2):895-912
We establish integral representation results for suitably pointwise continuous and comonotonic additive functionals of bounded variation defined on Stone lattices. As an application, we prove a comonotonic version of the Daniell–Stone Theorem. 相似文献
998.
Dr. Viktor Moberg Robin Duquesne Dr. Simone Contaldi Oliver Röhrs Jonny Nachtigall Llewellyn Damoense Dr. Alan T. Hutton Dr. Michael Green Prof. Magda Monari Daniela Santelia Prof. Matti Haukka Dr. Ebbe Nordlander 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(39):12458-12478
The new clusters [H4Ru4(CO)10(μ‐1,2‐P‐P)], [H4Ru4(CO)10(1,1‐P‐P)] and [H4Ru4(CO)11(P‐P)] (P‐P=chiral diphosphine of the ferrocene‐based Josiphos or Walphos ligand families) have been synthesised and characterised. The crystal and molecular structures of eleven clusters reveal that the coordination modes of the diphosphine in the [H4Ru4(CO)10(μ‐1,2‐P‐P)] clusters are different for the Josiphos and the Walphos ligands. The Josiphos ligands bridge a metal–metal bond of the ruthenium tetrahedron in the “conventional” manner, that is, with both phosphine moieties coordinated in equatorial positions relative to a triangular face of the tetrahedron, whereas the phosphine moieties of the Walphos ligands coordinate in one axial and one equatorial position. The differences in the ligand size and the coordination mode between the two types of ligands appear to be reflected in a relative propensity for isomerisation; in solution, the [H4Ru4(CO)10(1,1‐Walphos)] clusters isomerise to the corresponding [H4Ru4(CO)10(μ‐1,2‐Walphos)] clusters, whereas the Josiphos‐containing clusters show no tendency to isomerisation in solution. The clusters have been tested as catalysts for asymmetric hydrogenation of four prochiral α‐unsaturated carboxylic acids and the prochiral methyl ester (E)‐methyl 2‐methylbut‐2‐enoate. High conversion rates (>94 %) and selectivities of product formation were observed for almost all catalysts/catalyst precursors. The observed enantioselectivities were low or nonexistent for the Josiphos‐containing clusters and catalyst (cluster) recovery was low, suggesting that cluster fragmentation takes place. On the other hand, excellent conversion rates (99–100 %), product selectivities (99–100 % in most cases) and good enantioselectivities, reaching 90 % enantiomeric excess (ee) in certain cases, were observed for the Walphos‐containing clusters, and the clusters could be recovered in good yield after completed catalysis. Results from high‐pressure NMR and IR studies, catalyst poisoning tests and comparison of catalytic properties of two [H4Ru4(CO)10(μ‐1,2‐P‐P)] clusters (P‐P=Walphos ligands) with the analogous mononuclear catalysts [Ru(P‐P)(carboxylato)2] suggest that these clusters may be the active catalytic species, or direct precursors of an active catalytic cluster species. 相似文献
999.
Cristoni S Zingaro L Rota C Cariani E Trenti T 《Rapid communications in mass spectrometry : RCM》2012,26(3):231-235
1000.
Chen X Luais E Darwish N Ciampi S Thordarson P Gooding JJ 《Langmuir : the ACS journal of surfaces and colloids》2012,28(25):9487-9495
The preparation of self-assembled monolayers (SAMs) of organophosphonic acids on indium tin oxide (ITO) surfaces from different solvents (triethylamine, ethyl ether, tetrahydofuran (THF), pyridine, acetone, methanol, acetonitrile, dimethyl sulfoxide (DMSO), or water) has been performed with some significant differences observed. Cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy (STM), and contact angle measurement demonstrated that the quality of SAMs depends critically on the choice of solvents. Higher density, more stable monolayers were formed from solvents with low dielectric constants and weak interactions with the ITO. It was concluded low dielectric solvents that were inert to the ITO gave monolayers that were more stable with a higher density of surface bound molecules because higher dielectric constant solvents and solvents that coordinate with the surface disrupted SAM formation. 相似文献