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11.
Dr. N. Kodiah Beyeh Dr. Fangfang Pan Dr. Sandip Bhowmik Toni Mäkelä Prof. Robin H. A. Ras Acad. Prof. Kari Rissanen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(4):1355-1361
N‐Alkyl ammonium resorcinarene salts (NARYs, Y=triflate, picrate, nitrate, trifluoroacetates and NARBr) as tetravalent receptors, are shown to have a strong affinity for chlorides. The high affinity for chlorides was confirmed from a multitude of exchange experiments in solution (NMR and UV/Vis), gas phase (mass spectrometry), and solid‐state (X‐ray crystallography). A new tetra‐iodide resorcinarene salt (NARI) was isolated and fully characterized from exchange experiments in the solid‐state. Competition experiments with a known monovalent bis‐urea receptor ( 5 ) with strong affinity for chloride, reveals these receptors to have a much higher affinity for the first two chlorides, a similar affinity as 5 for the third chloride, and lower affinity for the fourth chloride. The receptors affinity toward chloride follows the trend K1?K2?K3≈ 5 >K4, with Ka=5011 m ?1 for 5 in 9:1 CDCl3/[D6]DMSO. 相似文献
12.
Effects of a flow field (E) on segregation and flow of polymer chains are studied in two dimensions using a hybrid (discrete‐to‐continuum) simulation. The flow rate (j) of polymer chains is found to increase monotonically with E, a linear response in the low field regime followed by a slow approach to saturation in the high field regime. The effective chain permeability (ϕc = j/E) varies nonmonotonically on increasing the field E, with a maximum (ϕcm) at a characteristic value of the field (in the range 0.2 < E < 2); ϕcm depends on the chain length. Chain aggregates exhibit an anisotropic mass distribution due to the field with a molecular bridging at high fields. The longitudinal component of the radius of gyration (Rgx) exhibits a crossover from a random walk (RW) (Rgx ˜ Lc1/2) at E = 0 to an elongated conformation (Rgx ˜Lc) at E ⪈ 0.2; the transverse component changes from Rgy ˜ Lc1/2 to Rgy ˜ Lc1/3. The width of the radial distribution function (ρ(r)) of the monomers increases while its peak varies nonmonotonically with E and is consistent with the observation of anisotropic mass distribution. 相似文献
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What is new in the field of neutrino detection? In addition to new projects probing both the low and high ends of the neutrino energy scale, an inexpensive, effective technique is being developed to allow tagging of antineutrinos in water Cherenkov (WC) detectors via the addition to water of a solute with a large neutron cross-section and energetic γ daughters. Gadolinium is an excellent candidate since in recent years it has become very inexpensive, now less than $8 per kilogram in the form of commercially available gadolinium trichloride. This non-toxic, non-reactive substance is highly soluble in water. Neutron capture on gadolinium yields an 8.0 MeV gamma cascade easily seen in detectors like Super-Kamiokande. The uses of GdCl3 as a possible upgrade for the Super-Kamiokande detector — with a view toward improving its performance as an antineutrino detector for supernova neutrinos and reactor neutrinos — are discussed, as are the ongoing R&;D efforts which aim to make this dream a reality within the next two years. 相似文献
15.
Maria Rosa Ras Francesc Borrull Rosa Maria Marcé 《Journal of separation science》2009,32(7):1051-1059
Pressurised liquid extraction (PLE) was applied to determine the atmospheric levels of 16 polycyclic aromatic hydrocarbons (PAHs) in the gas and particulate phases. The method involved high‐volume air sampling with quartz fibre filters (QFFs) and polyurethane foam (PUF) plugs and analytes were subsequently extracted from the samples by PLE, and determined with GC‐MS. We optimised the PLE conditions for the solvent, the number of cycles and extraction temperature. Recoveries were higher than 90% for most compounds. Method LODs and LOQs were between 0.001 and 0.02 ng/m3 and between 0.01 and 0.05 ng/m3. Air samples were taken from a site in the region of Tarragona in Catalonia, Spain, where one of the largest petrochemical complexes in southern Europe is located. The total concentration of PAHs were from 6.7 to 27.66 ng/m3, with predominant levels of PAHs appearing in the gas phase (48–81%), and an average level of benzo[a]pyrene, the most carcinogenic PAH, of 0.86 ng/m3. 相似文献
16.
Isabel Díez Dr. Matti Pusa Sakari Kulmala Prof. Hua Jiang Dr. Andreas Walther Anja S. Goldmann Axel H. E. Müller Prof. Olli Ikkala Prof. Robin H. A. Ras Dr. 《Angewandte Chemie (International ed. in English)》2009,48(12):2122-2125
Colorful clusters : Silver nanoclusters consisting of only a few atoms exhibit large chemical‐environment‐responsive shifts of their optical absorption and emission bands, that is, large solvatochromism (see picture). The photophysical characteristics and electrochemiluminescence of the Ag clusters give them remarkable advantages over larger nanoparticles in applications such as molecular sensing.
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A computer simulation model is used to study the percolation of random chains with a self-avoiding constraint. The percolation threshold is found to decay with the chain lengthL
c
with a power lawL
c
–0.1
, while the jamming coverage varies asL
c
–1/3
. 相似文献
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Shihai Yang Adam Seyfarth Samuel P. Bateman Ras B. Pandey 《Macromolecular theory and simulations》2006,15(3):263-271
Summary: A computer simulation model is proposed to study film growth and surface roughness in aqueous (A) solution of hydrophobic (H) and hydrophilic (P) groups on a simple three dimensional lattice of size with an adsorbing substrate. Each group is represented by a particle with appropriate characteristics occupying a unit cube (i.e., eight sites). The Metropolis algorithm is used to move each particle stochastically. The aqueous constituents are allowed to evaporate while the concentration of H and P is constant. Reactions proceed from the substrate and bonded particles can hop within a fluctuating bond length. The film thickness ( ) and its interface width ( ) are examined for hardcore and interacting particles for a range of temperature ( ). Simulation data show a rapid increase in and followed by its non‐monotonic growth and decay before reaching steady‐state and near equilibrium ( ) in asymptotic time step limit. The growth can be described by power laws, e.g., with a typical value of in initial time regime followed by at . For hardcore system, the equilibrium film thickness ( ) and surface roughness ( ) seem to scale linearly with the temperature, i.e., at low and at higher . For interacting functional groups in contrast, the long time (unsaturated) film thickness and surface roughness, and decay rapidly followed by a slow increase on raising the temperature.