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191.
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193.
COMPONENT ALLEE EFFECTS AND STAGE‐SPECIFIC PREDATION: A BRIEF INSIGHT INTO CONSERVATION AND BIOLOGICAL CONTROL ISSUES 下载免费PDF全文
In this paper, we propose a two‐stage structured population model subject to component Allee effects in fecundity and maturation, and with two disturbances (predation only and harvest and predation) acting on both stages. It is shown that this combination leads to a demographic Allee effect—a characteristic that could be exploited in pest biological control, but on the other hand, it represents a bane in conservation biology. The analysis is performed for disturbances with functional responses type 2 and 3, and the models show that they yield qualitatively similar results. This characteristic is discussed from the species conservation and biological control point of view, together with possible extensions of this work. 相似文献
194.
195.
Bayraktar H Ghosh PS Rotello VM Knapp MJ 《Chemical communications (Cambridge, England)》2006,(13):1390-1392
Functionalized gold nanoparticles bind selectively to cytochrome c or cytochrome c peroxidase and inhibit enzyme turnover. 相似文献
196.
Plastic microchip liquid chromatography-matrix-assisted laser desorption/ionization mass spectrometry using monolithic columns 总被引:1,自引:0,他引:1
A prototype array of monolithic liquid chromatography (LC) columns was prepared in a plastic microfluidic device for the off-line interface with matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The microfluidic channels were fabricated on a cyclic olefin copolymer (COC) plate by hot embossing. An array of methacrylate monolithic columns was prepared in the microfluidic channels by UV-initiated polymerization. The deposition system employed a pulsed electric field to transfer the effluents from multiple columns directly onto MALDI targets with a non-contact deposition method reported by Ericson et al. [C. Ericson, Q.T. Phung, D.M. Horn, E.C. Peters, J.R. Fitchett, S.B. Ficarro, A.R. Salmon, L.M. Brill, A. Brock, Anal. Chem. 75 (2003) 2309]. To characterize the off-line interface of the multiple-channel microchip LC and the MALDI-MS for the analysis of peptide mixtures, the separation efficiency and reproducibility tests in each column were carried out by separating a peptide mixture from tryptic digested proteins and depositing the multiple effluents simultaneously on the MALDI target plate. Using a MALDI-TOF mass spectrometer with a mass accuracy of +/-1 Da for peptide assignments of digested bovine serum albumin (BSA), amino acid sequence coverage of around 59% was obtained for the microchip LC-MALDI-MS compared to 23% obtained by the MALDI-MS method without LC separation. In sensitivity tests for the detection of low abundance proteins in the presence of high concentration protein mixtures, as low as 10 fmol/mul (S/N = 10) of a spiked peptide in 1 microg of digested BSA could be detected. In the analysis of a mixture of three digested proteins (BSA, myoglobin, and cytochrome c), more than twice the amino acid sequence coverage was obtained for the microchip LC-MALDI-MS compared to MALDI-MS alone. 相似文献
197.
The synthesis of a variety of new 1-thio-D-glucopyranose derivatives oxidized at the sulfur atom is described, including seven 1-C-sulfonic acids, three sulfonate esters, three sulfinate esters, an S,S'-diglycosyl thiolsulfonate and thiolsulfinate, four S-glycosyl sulfenamides, an S-glycosyl sulfinamide, and two S-glycosyl sulfonamides. These compounds possess unusual anomeric functionality that might be resistant or even inhibitory to normal enzymatic carbohydrate processing, and therefore, they may be of future use in studies of enzyme inhibition, structure, mechanism, and function. 相似文献
198.
Knapp S Thakur VV Madduru MR Malolanarasimhan K Morriello GJ Doss GA 《Organic letters》2006,8(7):1335-1337
[reaction: see text] Commercial 1,2:5,6-di-O-isopropylidene-alpha-d-allofuranose was converted to a protected bicyclic octosyl acid thioglycoside donor by a 10-step sequence that features an intramolecular ester enolate alkylation. Glycosylation of N-benzoyladenine and methyl uridine-5-carboxylate followed by deprotection gave the respective nucleosides "octosyl adenine" and octosyl acid A. 相似文献
199.
Diogo P. Moraes Juliana S. F. Pereira Liange O. Diehl Márcia F. Mesko Valderi L. Dressler José Neri G. Paniz Guenter Knapp Érico M. M. Flores 《Analytical and bioanalytical chemistry》2010,397(2):563-570
In this work, three sample preparation methods were evaluated for further halogen determination in elastomers containing high
concentrations of carbon black. Samples of nitrile-butadiene rubber, styrene-butadiene rubber, and ethylene-propylene-diene
monomer elastomers were decomposed using oxygen flask combustion and microwave-induced combustion (MIC) for further Br and
Cl determination by ion chromatography (IC), inductively coupled plasma optical emission spectrometry (ICP OES), and inductively
coupled plasma mass spectrometry (ICP-MS). Extraction assisted by microwave radiation in closed vessels was also evaluated
using water or alkaline solution. Digestion by MIC was carried out using 50 mmol l−1 (NH4)2CO3 as the absorbing solution. The effect of the reflux step was also evaluated. Accuracy was evaluated using certified reference
materials with polymeric matrix composition and by comparison of results using neutron activation analysis. Agreement for
Br and Cl was better than 95% by MIC using 5 min of reflux, and no statistical difference was found using IC, ICP OES, and
ICP-MS for determination of both analytes. For MIC, the relative standard deviation (RSD) was lower than 5%. Using extraction
in closed vessels, a high amount of residues was observed, and recoveries were lower than 45% for both analytes. For oxygen
flask combustion, the agreement was similar using MIC but RSD was higher (20%). The residual carbon content, an important
parameter used to evaluate the digestion efficiency, was always below 1% for MIC. Using MIC, it was possible to digest elastomers
with high efficiency, resulting in a single solution suitable for halogen determination by different techniques. 相似文献
200.
Webb LJ Michalak DJ Biteen JS Brunschwig BS Chan AS Knapp DW Meyer HM Nemanick EJ Traub MC Lewis NS 《The journal of physical chemistry. B》2006,110(46):23450-23459
High-resolution soft X-ray photoelectron spectroscopy was used to investigate the oxidation of alkylated silicon(111) surfaces under ambient conditions. Silicon(111) surfaces were functionalized through a two-step route involving radical chlorination of the H-terminated surface followed by alkylation with alkylmagnesium halide reagents. After 24 h in air, surface species representing Si(+), Si(2+), Si(3+), and Si(4+) were detected on the Cl-terminated surface, with the highest oxidation state (Si(4+)) oxide signal appearing at +3.79 eV higher in energy than the bulk Si 2p(3/2) peak. The growth of silicon oxide was accompanied by a reduction in the surface-bound Cl signal. After 48 h of exposure to air, the Cl-terminated Si(111) surface exhibited 3.63 equivalent monoleyers (ML) of silicon oxides. In contrast, after exposure to air for 48 h, CH(3)-, C(2)H(5)-, or C(6)H(5)CH(2)-terminated Si surfaces displayed <0.4 ML of surface oxide, and in most cases only displayed approximately 0.20 ML of oxide. This oxide was principally composed of Si(+) and Si(3+) species with peaks centered at +0.8 and +3.2 eV above the bulk Si 2p(3/2) peak, respectively. The silicon 2p SXPS peaks that have previously been assigned to surface Si-C bonds did not change significantly, either in binding energy or in relative intensity, during such air exposure. Use of a high miscut-angle surface (7 degrees vs < or =0.5 degrees off of the (111) surface orientation) yielded no increase in the rate of oxidation nor change in binding energy of the resultant oxide that formed on the alkylated Si surfaces. Scanning Auger microscopy indicated that the alkylated surfaces formed oxide in isolated, inhomogeneous patches on the surface. 相似文献