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991.
Alvaro Castillo-García Andreas W. Hauser María Pilar de Lara-Castells Pablo Villarreal 《Molecules (Basel, Switzerland)》2021,26(19)
We present path integral molecular dynamics (PIMD) calculations of an electron transfer from a heliophobic Cs dimer in its () state, located on the surface of a He droplet, to a heliophilic, fully immersed C molecule. Supported by electron ionization mass spectroscopy measurements (Renzler et al., J. Chem. Phys. 2016, 145, 181101), this spatially quenched reaction was characterized as a harpoon-type or long-range electron transfer in a previous high-level ab initio study (de Lara-Castells et al., J. Phys. Chem. Lett. 2017, 8, 4284). To go beyond the static approach, classical and quantum PIMD simulations are performed at 2 K, slightly below the critical temperature for helium superfluidity (2.172 K). Calculations are executed in the NVT ensemble as well as the NVE ensemble to provide insights into real-time dynamics. A droplet size of 2090 atoms is assumed to study the impact of spatial hindrance on reactivity. By changing the number of beads in the PIMD simulations, the impact of quantization can be studied in greater detail and without an implicit assumption of superfluidity. We find that the reaction probability increases with higher levels of quantization. Our findings confirm earlier, static predictions of a rotational motion of the Cs dimer upon reacting with the fullerene, involving a substantial displacement of helium. However, it also raises the new question of whether the interacting species are driven out-of-equilibrium after impurity uptake, since reactivity is strongly quenched if a full thermal equilibration is assumed. More generally, our work points towards a novel mechanism for long-range electron transfer through an interplay between nuclear quantum delocalization within the confining medium and delocalized electronic dispersion forces acting on the two reactants. 相似文献
992.
993.
A. Lopez-Molinero J. R. Castillo Pilar Chamorro Pascual Asuncion Callizo 《Mikrochimica acta》1999,131(3-4):225-230
The generation of volatile species of As(III) as a means to introduce arsenic into a flame atomic absorption spectrometer
has been studied. The method is based on the reaction between As(III) and chloride ions in sulphuric acid medium. The reaction
is performed in a discontinuous or batch mode. With this method 130 μl of a solution containing 17.5% (w/v) sodium chloride
and As(III) are injected by a 500 ml.min−1 N2 carrier gas flow into 1 ml of concentrated sulphuric acid. The gaseous compounds generated are introduced into the spectrometer
through the nebulizer and As is determined.
Received October 3, 1998. Revision January 6, 1999. 相似文献
994.
Almudena García-Fernández Josefina Díez Ángel Manteca Jesús Sánchez M. Pilar Gamasa Elena Lastra 《Polyhedron》2008
A series of half-sandwich ruthenium(II) complexes containing κ3(N,N,N)-hydridotris(pyrazolyl)borate (κ3(N,N,N)-Tp) and the water-soluble phosphane 1,3,5-triaza-7-phosphaadamantane (PTA) [RuX{κ3(N,N,N)-Tp}(PPh3)2−n(PTA)n] (n = 2, X = Cl (1), n = 1, X = Cl (2), I (3), NCS (4), H (5)) and [Ru{κ3(N,N,N)-Tp}(PPh3)(PTA)L][PF6] (L = NCMe (6), PTA (7)) have been synthesized. Complexes containing 1-methyl-3,5-diaza-1-azonia-7-phosphaadamantane(m-PTA) triflate [RuCl{κ3(N,N,N)-Tp}(m-PTA)2][CF3SO3]2 (8) and [RuX{κ3(N,N,N)-Tp}(PPh3)(m-PTA)][CF3SO3] (X = Cl (9), H (10)) have been obtained by treatment, respectively, of complexes 1, 2 and 5 with methyl triflate. Single crystal X-ray diffraction analysis for complexes 1, 2 and 4 have been carried out. DNA binding properties by using a mobility shift assay and antimicrobial activity of selected complexes have been evaluated. 相似文献
995.
Molero G Aranjuelo I Teixidor P Araus JL Nogués S 《Rapid communications in mass spectrometry : RCM》2011,25(5):599-607
We have developed a method based on a double labeling with stable isotopes and gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) analyses to study amino acid exchange in a symbiotic plant-microbe association. Isotopic precision was studied for 21 standards including 15 amino acid derivatives, three N-protected amino acid methyl esters, three amines and one international standard. High correlations were observed between the δ(13)C and δ(15)N values obtained by GC/C/IRMS and those obtained by an elemental analyzer (EA) coupled to an isotope ratio mass spectrometer (R(2) = 0.9868 and 0.9992, respectively). The mean precision measured was 0.04‰ for δ(13)C and 0.28‰ for δ(15)N (n = 15). This method was applied in vivo to the symbiotic relationship between alfalfa (Medicago sativa L.) and N(2)-fixing bacteria. Plants were simultaneously labeled over 10 days with (13)C-depleted CO(2) ((12)CO(2)), which was assimilated through photosynthesis by leaves, and (15)N(2) fixed via nodules. Subsequently, the C and N isotope compositions (i.e. δ(13)C and δ(15)N) of free amino acids were analyzed in leaves and nodules by GC/C/IRMS. The method revealed the pattern of C and N exchange between leaves and nodules, highlighting that γ-aminobutanoic acid and glycine may represent an important form of C transport from leaves to the nodules. The results confirmed the validity, reliability and accuracy of the method for assessing C and N fluxes between plants and symbiotic bacteria and support the use of this technique in a broad range of metabolic and fluxomic studies. 相似文献
996.
Beatriz Fernández-Band Pilar Linares M. D. Luque de Castro Miguel Valcárcel 《Fresenius' Journal of Analytical Chemistry》1990,338(6):752-754
Summary A kinetic photometric method for the determination of creatinine in biological fluids based on the Jaffé reaction and the use of a flow injection manifold where the reacting plug is halted prior to detection is proposed. The wide linear range of the calibration curve obtained (between 3 and 150 g ml–1) allows the determination of the analyte in serum and urine. The kinetic measurements require no sample pretreatment (urine samples need dilution). The proposed method compares favourably with the standard recommended procedure. 相似文献
997.
998.
Juan M. Antelo Florencio Arce Marí C. Castro Juan Crugeiras Juan C. Prez-Moure Pilar Rodríguez 《国际化学动力学杂志》1995,27(7):703-717
The formation of N-chlorobutylamines is a reaction of order one with respect to hypochlorite and amine, and order ?1 with respect to OH?. Kinetic studies show that N-chlorobutylamines undergo decomposition in basic aqueous media, and disproportination (with formation of N,N-dichloramines) in acidic media, mechanisms are put forward for both these processes. © 1995 John Wiley & Sons, Inc. 相似文献
999.
Susana Meseguer-Lloret Pilar Campíns-Falcó Luis A. Tortajada-Genaro Francisco Blasco-Gómez 《International journal of environmental analytical chemistry》2013,93(5):405-416
Cr(III) and/or Cr(VI) determinations based on light emission produced by luminol oxidation by hydrogen peroxide in basic aqueous solution catalyzed by Cr(III) were studied in order to diagnose and/or avoid method bias. The calibration step was optimized, and the usefulness of the method for speciating chromium was tested. The use of the standard addition method in the linear interval concentration range made it possible to diagnose the accuracy of the method for real samples. Good results were obtained for several real water samples containing chromium at different concentrations. The proposed protocol made the method traceable with an appropriate certified reference material and with the reference method. 相似文献
1000.
Miguel A. Rodríguez-Carvajal Leandro Gonzalez Manuel Bernabe Juan F. Espinosa José L. Espartero Pilar Tejero-Mateo 《Journal of carbohydrate chemistry》2013,32(8):891-903
ABSTRACT The conformational behaviour of the major trisaccharide repeating unit (α-D-Galp-(1→2)-β-D-Ribf-(1→9)-α-5-O-Me-Kdnp-) of the polysaccharide from Sinorhizobium fredii SVQ293, a mutant derivative has been analysed by NMR spectroscopy and extensive molecular dynamics simulations. The results obtained indicate that the five-membered ring adopts an almost unique conformation as do the pyranose rings. The Ribf-(1→9)-α-5-O-Me-Kdnp linkage may adopt a variety of conformations while the α-D-Galp-(1→2)-β-D-Ribf- also populates an extended surface of the Φ/Ψ map. Two 10 ns MD simulations using the GB/SA continuum solvent model for water and the MM3* force field provides a population distribution of conformers which satisfactorily agrees with the experimental NMR data for both the glycosidic linkages and the hydroxymethyl groups. 相似文献