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41.
Koeken AC Torres Galvis HM Davidian T Ruitenbeek M de Jong KP 《Angewandte Chemie (International ed. in English)》2012,51(29):7190-7193
Pressure leverage: A tapered-element oscillating microbalance was used to evaluate carbon deposition on a highly selective and active supported iron catalyst for the production of lower olefins. With increasing pressure, the H(2)/CO ratio had a profound effect on the carbon deposition rate and accordingly, conditions leading to minimal carbon deposition, low methane selectivity, and high olefin selectivity were identified. 相似文献
42.
Domingos SR Panman MR Bakker BH Hartl F Buma WJ Woutersen S 《Chemical communications (Cambridge, England)》2012,48(3):353-355
Vibrational circular dichroism is a powerful technique to study the stereochemistry of chiral molecules, but often suffers from small signal intensities. Electrochemical modulation of the energies of the electronically excited state manifold is now demonstrated to lead to an order of magnitude enhancement of the differential absorption. Quantum-chemical calculations show that increased mixing between ground and excited states is at the origin of this amplification. 相似文献
43.
TH van der Loop MR Panman S Lotze J Zhang T Vad HJ Bakker WF Sager S Woutersen 《The Journal of chemical physics》2012,137(4):044503
We study the structure and reorientation dynamics of nanometer-sized water droplets inside nonionic reverse micelles (water/Igepal-CO-520/cyclohexane) with time-resolved mid-infrared pump-probe spectroscopy and small angle x-ray scattering. In the time-resolved experiments, we probe the vibrational and orientational dynamics of the O-D bonds of dilute HDO:H(2)O mixtures in Igepal reverse micelles as a function of temperature and micelle size. We find that even small micelles contain a large fraction of water that reorients at the same rate as water in the bulk, which indicates that the polyethylene oxide chains of the surfactant do not penetrate into the water volume. We also observe that the confinement affects the reorientation dynamics of only the first hydration layer. From the temperature dependent surface-water dynamics, we estimate an activation enthalpy for reorientation of 45 ± 9 kJ mol(-1) (11?±?2 kcal mol(-1)), which is close to the activation energy of the reorientation of water molecules in ice. 相似文献
44.
De Vreese P Brooks NR Van Hecke K Van Meervelt L Matthijs E Binnemans K Van Deun R 《Inorganic chemistry》2012,51(9):4972-4981
A deep-eutectic solvent with the properties of an ionic liquid is formed when choline chloride is mixed with copper(II) chloride dihydrate in a 1:2 molar ratio. EXAFS and UV-vis-near-IR optical absorption spectroscopy have been used to compare the coordination sphere of the cupric ion in this ionic liquid with that of the cupric ion in solutions of 0.1 M of CuCl(2)·2H(2)O in solvents with varying molar ratios of choline chloride and water. The EXAFS data show that species with three chloride ions and one water molecule coordinated to the cupric ion as well as species with two chloride molecules and two water molecules coordinated to the cupric ion are present in the ionic liquid. On the other hand, a fully hydrated copper(II) ion is formed in an aqueous solution free of choline chloride, and the tetrachlorocuprate(II) complex forms in aqueous choline chloride solutions with more than 50 wt % of choline chloride. In solutions with between 0 and 50 wt % of choline chloride, mixed chloro-aquo complexes occur. Upon standing at room temperature, crystals of CuCl(2)·2H(2)O and of Cu(choline)Cl(3) formed in the ionic liquid. Cu(choline)Cl(3) is the first example of a choline cation coordinating to a transition-metal ion. Crystals of [choline](3)[CuCl(4)][Cl] and of [choline](4)[Cu(4)Cl(10)O] were also synthesized from molecular or ionic liquid solvents, and their crystal structures were determined. 相似文献
45.
Anderson N. Mendes Isabela Hubber Mônica Siqueira Gleyce Moreno Barbosa Davyson de Lima Moreira Carla Holandino José Carlos Pinto Marcio Nele 《Macromolecular Symposia》2012,319(1):34-40
Summary: This work aimed to produce poly(methyl methacrylate) nanoparticles for use in drug encapsulation. The polymer nanoparticles were produced using miniemulsion polymerization technique. Monomer miniemulsion showed moderate stability and polymer average particle size was about 90 nm. PMMA nanoparticles were tested for toxicity in human leukemic cell strain K562 and they did not show any adverse effect on cell viability. Therefore, poly(methyl methacrylate) nanoparticles are suitable to encapsulate antitumor agents. 相似文献
46.
Cornelia Lanz Moritz Schlötter Nele Klinkenberg Patricia Besirske Prof. Dr. Sebastian Polarz 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(23):8987-8991
Amphiphiles alter the energy of surfaces, but the extent of this feature is typically constant. Smart systems with amphiphilicity as a function of an external, physical trigger are desirable. As a trigger, the exposure to a magnetic field, in particular, is attractive because it is not shielded in water. Amphiphiles like surfactants are well known, but the magnetic response of molecules is typically weak. Vice-versa, magnetic particles with strong response to magnetic triggers are fully established in nanoscience, but they are not amphiphilic. In this work colloids with Janus architecture and ultra-small dimensions (25 nm) have been prepared by spatial control over the thiol-yne click modification of organosilica-magnetite core–shell nanoparticles. The amphiphilic properties of these anisotropically modified particles are proven. Finally, a pronounced and reversible change in interfacial stabilization results from the application of a weak (<1 T) magnetic field. 相似文献
47.
Paul E Sijens Matthijs Oudkerk Pieter van Dijk Peter C Levendag Charles J Vecht 《Magnetic resonance imaging》1998,16(10):1273-1280
Fifteen percent loss in the peak area of choline containing compounds (Cho) was recently observed in 1H MR spectra of contrast-enhancing tumor at 5–10 min after Gd-contrast administration [Magn. Reson. Med. 37:222–225, 1997]. In this study, chemical shift imaging (CSI, 1500/135 ms PRESS) was used to assess the spectral changes in 47 Gd-enhancing glial brain tumors and metastatic brain tumors measured at 0–5, 5–10, and/or 10–15 min after administration of Gd-contrast. Percent Cho peak area losses measured at these times, 3 ± 3, 12 ± 2, and 14 ± 3 SEM, respectively, coincided with trends of line narrowing and up-field shift of the Cho peak. Significant changes in creatine and N-acetyl acetate signals were not observed. It is concluded that the Gd-induced loss of tumor Cho signal measured after 5 min, typically required for post contrast-MRI and the positioning of the CSI volume on tumor, shows little further change with time, if any. 相似文献
48.
Stokvis E Nan-Offeringa LG Ouwehand M Tibben MM Rosing H Schnaars Y Grigat M Romeis P Schellens JH Beijnen JH 《Rapid communications in mass spectrometry : RCM》2004,18(13):1465-1471
The development of a liquid chromatography/tandem mass spectrometric assay for the quantitative analysis of the novel tubulin inhibitor D-24851 in human plasma and urine is described. D-24851 and the deuterated internal standard were extracted from 250 microL of plasma or urine using hexane/ether (1:1, v/v). Subsequently, 10-microL aliquots of reconstituted extracts were injected onto an Inertsil ODS analytical column (50 x 2.0 mm i.d., 5 microm particle size). An eluent consisting of methanol/5 mM ammonium acetate, 0.004% formic acid in water (80:20, v/v) was pumped at a flow rate of 0.2 mL/min. An API 365 triple quadrupole mass spectrometer was used in the multiple reaction monitoring mode for sensitive detection. For human plasma a dynamic range of 1-1000 ng/mL was validated, and for human urine a range of 0.25-50 ng/mL. Validation was performed according to the most recent FDA guidelines and all results were within requirements. The assay has been successfully applied to support a phase I clinical trial with orally administered D-24851. 相似文献
49.
Matthijs P. de Haas John M. Warman Pierre P. Infelta Andries Hummel 《Chemical physics letters》1975,31(2):382-386
The electrical conductivity induced by pulse irradiation of liquid cyclohexane has been studied by means of microwave absorption. The conductivity in pure cyclohexane, due principally to the excess electron, is reduced to less than 10% of the initial value on addition of 5 × 10?4 M of the electron scavenger SF6. The conductivity remaining after addition of SF6 is however more than an order of magnitude larger than expected for massive ions in cyclohexane and, since it is almost completely removed by the addition of 4 × 10?3 M of the positive ion scavenger NH3, is attributed mainly to the high mobility of the positive hole in this liquid. The ratio of the electron to hole mobility is determined to be 15. The mean lifetime of the hole under the present conditions is 86 ns. The rate constant for reaction of the hole with NH3 is determined to be 1.8 × 1011 M?1 s?1. From the conductivity remaining after removal of both the electron and the hole the sum of the mobilities of the resulting molecular ions is determined to be 8.4 × 10?4 cm2 V?1 s?1. 相似文献
50.
F. de Jong H. J. M. Sinnige Matthijs J. Janssen 《Journal of mass spectrometry : JMS》1970,3(12):1539-1548
The mass spectra of 13C-labelled thiophenes were studied and the label-distributions for the C3H3⊕, HCS⊕, C2H2S⊕ and [M ? CH3]⊕ ions are interpreted in terms of a carbon skeletal rearrangement. From a comparison of the results of 13C-labelling and D-labelling, a concurrent hydrogen migration process is demonstrated. The production of HCS⊕ ions is preceded by partial carbon scrambling and hydrogen migration is of minor importance. In contrast, hydrogen scrambling predominates over carbon scrambling in the loss of acetylene. 相似文献