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71.
72.
Miguel Guerrero Josefina Pons Mercè Font-Bardia Teresa Calvet Josep Ros 《Journal of chemical crystallography》2011,41(5):721-726
Abstract
The crystal structure of the title compound C22H30N4O2·H2O (L), has been determined using X-ray diffraction at 293 K. The crystal of 1,2-bis[4-(3,5-dimethyl-1H-pyrazol-1-yl)-2-oxobutyl]benzene is in triclinic crystal system with space group P(−1) (Z = 2), lattice parameters a = 8.225(6) ?, b = 10.967(6) ?, c = 12.903(6) ?, V = 1119.1(11) ?3. Analyses of single crystals of L, crystallized from dichloromethane/diethyl ether (1:1), revealed that the molecules are arranged in couples, which adopt a pseudo chair conformation, by means of intermolecular O–H···N hydrogen bonding interactions. Moreover, the extended structure revealed a 1D chain caused by several C–H···N intermolecular interactions. 相似文献73.
Pozo OJ Guerrero C Sancho JV Ibáñez M Pitarch E Hogendoorn E Hernández F 《Journal of chromatography. A》2006,1103(1):83-93
The potential of solid-phase extraction coupled on-line to liquid chromatography/electrospray tandem mass spectrometry (SPE-LC-ESI-MS/MS) has been investigated in this paper for the efficient sensitive quantification and confirmation of 16 antibiotics in water. The list of targeted analytes included 10 quinolones (oxolinic acid (OXO), nalidixic acid (NAL), flumequine (FLU), marbofloxacine (MAR), ofloxacine (OFLO), enrofloxacine (ENR), pefloxacine (PEF), ciprofloxacine (CIP), pipemidic acid (PIPE), norfloxacine (NOR)) and 6 penicillins (penicillin G (PEN), oxacillin (OXA), dicloxacillin (DIC), piperacillin (PIP), cloxacillin (CLO) and ampicillin (AMP)) that were determined in ground and surface water. The procedure is based on the injection of 9.8 mL of sample into the SPE-LC-MS/MS system and the measurement of antibiotics by selected reaction monitoring mode, using a triple quadrupole analyser. The method has been validated at realistic low concentrations that might be present in environmental water, i.e. 10 and 100 ng L(-1), obtaining recoveries between 74% and 123% with relative standard deviation lower than 14%. Matrix effects were not relevant in most of cases, except for ampicillin in surface water, where notable signal suppression was observed. The limits of detection were as low as 0.4-4.3 ng L(-1). The method developed allows the rapid screening and quantification of all the analytes selected by acquiring one MS/MS transition (normally the most sensitive) for each compound. It was applied to a number of actual surface and groundwater samples with several compounds being detected, mainly quinolones, at low ng L(-1) levels. Special attention was given to the confirmation of compounds detected in water due to the difficulties of obtaining confident confirmation at low ng L(-1). This matter has been of growing concern in the last few years as reflected by recent papers and correspondence. The acquisition of several MS/MS transitions for each compound detected in a second independent analysis allowed the unequivocal confirmation of identity, avoiding reporting false-positives. Finally, the potential of QTOF instruments to confirm positive samples has also been evaluated and compared with triple quadrupole analysers. 相似文献
74.
Bernardo?Nu?ez-MoraledaEmail author Joaquin?Pizarro Elisa?Guerrero Maria?P.?Guerrero-Lebrero Andres?Yá?ez Sergio?Ignacio?Molina Pedro?Luis?Galindo 《The European Physical Journal B - Condensed Matter and Complex Systems》2014,87(11):263
In this paper, stress fields at the surface of the capping layer of self-assembled InAsP quantum wires grown on an InP (001) substrate have been determined from atomistic models using molecular dynamics and Stillinger-Weber potentials. To carry out these calculations, the quantum wire compositional distribution was extracted from previous works, where the As and P distributions were determined by electron energy loss spectroscopy and high-resolution aberration-corrected Z-contrast imaging. Preferential sites for the nucleation of wires on the surface of the capping layer were studied and compared with (i) previous simulations using finite element analysis to solve anisotropic elastic theory equations and (ii) experimentally measured locations of stacked wires. Preferential nucleation sites of stacked wires were determined by the maximum stress location at the MD model surface in good agreement with experimental results and those derived from finite element analysis. This indicates that MD simulations based on empirical potentials provide a suitable and flexible tool to study strain dependent atom processes. 相似文献
75.
A.I. Figueroa J. Bartolomé J.M. García del Pozo A. Arauzo E. Guerrero P. Téllez F. Bartolomé L.M. García 《Journal of magnetism and magnetic materials》2012
A transverse susceptibility (TS) measurement system based on a simple inverter CMOS cell oscillator cross-coupled to a LC tank is presented. The system has been implemented to operate at a Quantum Design Physical Properties Measurement System (PPMS). We introduce several improvements with respect to similar currently operating TS measurement equipments. The electronics have been redesigned to use CMOS transistors as active devices, which simplifies the circuit design and enlarge the tuning range, thus making the proposed electronic block more feasible, predictable, and precise. Additionally, we propose a newly designed sample holder, which facilitates the procedure to change a sample and improves reproducibility of the circuit. Our design minimizes the thermal leak of the measuring probe by one order of magnitude, allowing to measure from 1.8 K in standard PPMS systems, thanks to the use of a low temperature beryllium–copper coaxial cable instead of the conventional RG402 Cu coaxial cable employed in the insert for the PPMS in similar systems. The data acquisition method is also simplified, so that the measuring sequences are implemented directly in the PPMS controller computer by programming them in the Quantum Design MultiVu software that controls the PPMS. We present the test measurements performed on the system without sample to study the background signal and stability of the circuit. Measurements on a Gd2O3 calibrating sample yield to the estimation of the system sensitivity, which is found to be on the order of 10−6 emu. Finally, measurements on a TmCo2 Laves phase sample with a ferrimagnetic transition temperature around 4 K are described, demonstrating that the developed system is well suited to explore interesting magnetic phenomena at this temperature scale. 相似文献
76.
Dávalos JZ Herrero R Chana A Guerrero A Jiménez P Santiuste JM 《The journal of physical chemistry. A》2012,116(9):2261-2267
We have studied the energetics and structural properties of trans-cinnamic acid (CA), o-, m-, and p-coumaric acids (2-, 3-, and 4-hydroxycinnamic acids), caffeic acid (3,4-dihydroxycinnamic acid), ferulic acid (4-hydroxy-3-methoxycinnamic acid), iso-ferulic acid (3-hydroxy-4-methoxycinnamic acid), and sinapic acid (3,5-dimethoxy-4-hydroxycinnamic acid). The experimental values of Δ(f)H(m)°(g), determined (in kJ·mol(-1)) for CA (-229.8 ± 1.9), p-coumaric acid (-408.0 ± 4.4), caffeic acid (-580.0 ± 5.9), and ferulic acid (-566.4 ± 5.7), allowed us to derive Δ(f)H(m)°(g) of o-coumaric acid (-405.6 ± 4.4), m-coumaric acid (-406.4 ± 4.4), iso-ferulic acid (-565.2 ± 5.7), and sinapic acid (-698.8 ± 4.1). From these values and by use of isodesmic/homodesmotic reactions, we studied the energetic effects of π-donor substituents (-OH and -OCH(3)) in cinnamic acid derivatives and in the respective benzene analogues. Our results indicate that the interaction between -OCH(3) and/or -OH groups in hydroxycinnamic acids takes place without significant influence of the propenoic fragment. 相似文献
77.
Palimécio G. Guerrero Jr. Paulo R. de OliveiraAdriano C.M. Baroni Francisco A. MarquesRicardo Labes Gabriela R. HurtadoMiguel J. Dabdoub 《Tetrahedron letters》2012,53(39):5302-5305
An efficient and novel total synthesis of the two bioactive retinoids temarotene and arotinoid acid (TTNPB) is described. The key steps in this process include the regio and stereoselective hydrotelluration of thioacetylene 9 and Te/Li transmetalation of mixed (Z)-1,2-bis(organylchalcogene)-1-alkene (Z)-3. The subsequent reaction involving the β-phenylthio vinyl lithiated intermediate 10 with dimethyl sulfate gave the (E)-vinyl sulfide 11. The Ni+2 cross-coupling of 11 with the corresponding phenylzinc bromide and p-oxazoline phenylzinc bromide 12 afforded the respective temarotene 2 and retinoid-oxazoline substituted 13. Finally, compound 13 was deprotected with HCl to furnish arotinoid acid (TTNPB) 1. 相似文献
78.
Francisco J. Enríquez‐Medrano Martín Hernández‐Valdez Hortensia Maldonado‐Textle Patrick Lacroix‐Desmazes Ramiro Guerrero‐Santos 《先进技术聚合物》2012,23(3):375-381
S‐allyl‐4‐methyldithiobenzoate was synthesized and used as a chain transfer agent for the RAFT polymerization of butyl acrylate to produce a functionalized acrylic rubber. A solution of 8 wt% of this functionalized rubber was prepared in styrene and polymerized to generate a material called acrylic rubber‐modified polystyrene (AMP) constituted by well‐dispersed particles of poly(butyl acrylate)‐block‐poly(styrene) into a polystyrene matrix. Impact strength of injection‐molded samples of AMP was measured and compared with the general purpose polystyrene (GPPS) and the high impact polystyrene (HIPS). AMP itself showed an impact strength value similar to GPPS; however, when AMP was blended with conventional HIPS, the resulting material exhibited an improvement of 76–91% as compared to HIPS by itself, without affecting negatively tensile properties. Transmission electron microscopy analysis revealed both kinds of dispersed phases, i.e. the typical salami particles of polybutadiene coming from HIPS (size: 0.5–2 µ) and small particles from poly(butyl acrylate)‐block‐poly(styrene) (size: ~50 nm). We clearly showed that such a bimodality of the particle size distribution caused the positive synergistic effect on impact strength. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
79.
S. J. Guerrero A. Keller P. L. Soni P. H. Geil 《Journal of Macromolecular Science: Physics》2013,52(2):161-166
The main body of the present work is a summary of the extensive account in Ref. 1 to which we have to refer the reader for most of the details. Additional material is being included where explicitly stated. 相似文献
80.
Claude St. Thomas Hortensia Maldonado‐Textle Antal Rockenbauer Laszlo Korecz Nora Nagy Ramiro Guerrero‐Santos 《Journal of polymer science. Part A, Polymer chemistry》2012,50(14):2944-2956
Two different initiator/transfer agents (inifers) containing an alkoxyamine and a dithiobenzoate were synthetized and used to trigger out either reversible addition‐fragmentation chain transfer (RAFT) polymerization or nitroxide‐mediated polymerization (NMP). α‐Dithiobenzoate‐ω‐alkoxyamine‐difunctional polymers were produced in both cases which were subsequently used as precursors in the formation of block copolymers. This synthetic approach was applied to N‐isopropylacrylamide (NIPAM) or polyethylene oxide methacrylate (EOMA) to form α,ω‐heterodifunctional homopolymers via RAFT at 60°C which were chain extended with styrene by activating the alkoxyamine moiety at 120°C. Under such temperature conditions, it is proposed that a tandem NMP/RAFT polymerization is initiated producing a simultaneous growth of polystyrene blocks at both chain‐ends. Self‐assembled nanostructures of these amphiphilic block copolymers were evidenced by scanning electron microscopy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献