全文获取类型
收费全文 | 90篇 |
免费 | 5篇 |
专业分类
化学 | 60篇 |
数学 | 12篇 |
物理学 | 23篇 |
出版年
2023年 | 1篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 8篇 |
2014年 | 3篇 |
2013年 | 7篇 |
2012年 | 7篇 |
2011年 | 5篇 |
2010年 | 4篇 |
2009年 | 4篇 |
2008年 | 2篇 |
2007年 | 9篇 |
2006年 | 2篇 |
2005年 | 6篇 |
2004年 | 8篇 |
2003年 | 2篇 |
2002年 | 2篇 |
1999年 | 3篇 |
1997年 | 3篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有95条查询结果,搜索用时 15 毫秒
1.
José M. Arrieta Neus Cónsul Anibal Rodríguez-Bernal 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2004,23(2):1-14
We prove the existence of nonconstant stable stationary
solutions of
an evolution problem with a nonlinear reaction acting on the
boundary. These solutions present layers at certain points of the
boundary. We also study the behavior of these solutions as the small
parameter appearing in the equation approaches zero and show some
stability properties of the profiles given by these equilibrium
solutions. 相似文献
2.
Ford RC Ruffle SV Ramirez-Cuesta AJ Michalarias I Beta I Miller A Li J 《Journal of the American Chemical Society》2004,126(14):4682-4688
We have previously used inelastic incoherent neutron scattering spectroscopy to investigate the properties of aqueous suspensions of biomolecules as a function of hydration. These experiments led to the identification of signals corresponding to interfacial (hydration) water at low water content. A prediction from these studies was that in the crowded environment inside living cells, a significant proportion of the water would be interfacial, with profound implications for biological function. Here we describe the first inelastic incoherent neutron scattering spectroscopy studies of living cells and tissues. We find that the interfacial water signal is similar to that observed for water interacting with purified biomolecules and other solutes, i.e., it is strongly perturbed in the librational and translational intermolecular optical regions of the spectrum at 20-150 meV. The ratio of interfacial water compared to total water in cells (approximately 30%) is in line with previous experimental data for hydration water and calculations based on simple assumptions. 相似文献
3.
Effective core potential (ECP) and full-electron (FE) calculations for MoS4?2, MoO4?2, and MoOCl4 compounds were analyzed. Geometry parameters, binding energies, charge distributions, and topological properties of the electronic density were studied for Mo? L bonds (L = S, O, Cl). Results clearly indicate that those approaches that include valence plus 4s and 4p electrons (ECP2 methods) are able to reproduce the topological properties of Mo? L bonds, charge distributions, and geometries with respect to those obtained by FE methods. ECP methods that consider only the 4d and 5s valence electrons (ECP1) fail in the calculation of molecular properties. The use of 5p functions in ECP1 approaches produces a negative Mulliken charge on Mo. Bader's charges give more consistent results than Mulliken's ones. A new parameter for measuring the degree of ionicity is proposed. © 1994 by John Wiley & Sons, Inc. 相似文献
4.
Summary A partitioning of theab initio total energy into one-center and two-center terms is proposed. The partitioning scheme is developed using the auxiliary function
(2, 1; 1, 2) = γ(2, 1)γ(1, 2) and the topological theory of atoms in molecules. It is shown that this scheme can be used at theoretical levels beyond
Hartree-Fock. The numerical results indicate that the two-center terms follow the experimental trend of the dissociation energies
for a series of related compounds. 相似文献
5.
Iain J. W. McKean Joanna C. Sadler Anibal Cuetos Amina Frese Luke D. Humphreys Gideon Grogan Paul A. Hoskisson Glenn A. Burley 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(49):17747-17752
A tandem enzymatic strategy to enhance the scope of C‐alkylation of small molecules via the in situ formation of S‐adenosyl methionine (SAM) cofactor analogues is described. A solvent‐exposed channel present in the SAM‐forming enzyme SalL tolerates 5′‐chloro‐5′‐deoxyadenosine (ClDA) analogues modified at the 2‐position of the adenine nucleobase. Coupling SalL‐catalyzed cofactor production with C‐(m)ethyl transfer to coumarin substrates catalyzed by the methyltransferase (MTase) NovO forms C‐(m)ethylated coumarins in superior yield and greater substrate scope relative to that obtained using cofactors lacking nucleobase modifications. Establishing the molecular determinants that influence C‐alkylation provides the basis to develop a late‐stage enzymatic platform for the preparation of high value small molecules. 相似文献
6.
Assessment of pharmacokinetic interaction between piracetam and l‐carnitine in healthy subjects 下载免费PDF全文
Gustavo D. Mendes Gabriela Traldi Zaffalon Antonio Sérgio Silveira Juliana Cama Ramacciato Rogério Heládio Lopes Motta Thiago Gagliano‐Jucá Anibal Gil Lopes José Cássio de Almeida Magalhães Gilberto De Nucci 《Biomedical chromatography : BMC》2016,30(4):536-542
A rapid, sensitive and specific method for quantifying piracetam in human plasma using Piracetam d‐8 as the internal standard (IS) is described. The analyte and the IS were extracted from plasma by one‐step precipitation of protein using an acetonitrile (100%). The extracts were analyzed by high‐performance liquid chromatography coupled with electrospray tandem mass spectrometry (HPLC‐MS/MS). The method had a chromatographic run time of 3.8 min and a linear calibration curve over the range 0.5–50 µg/mL (r > 0.99). This LC‐MS‐MS procedure was used to assess the bioavailability of two piracetam formulations: piracetam + l‐carnitine (Piracar®; 270/330 mg tablet) and piracetam (Nootropil®; 800 mg tablet) in healthy volunteers of both sexes. The geometric means with corresponding 90% confidence interval (CI) for test/reference percentage ratios were 88.49% (90% CI = 81.19 – 96.46) for peak concentration/dose and 102.55% (90% CI = 100.62 – 104.51) for AUCinf/dose. The limit of quantitation of 0.5 µg/mL is well suited for pharmacokinetic studies in healthy volunteers. It was concluded that piracetam (Piracar®; 270/330 mg tablet) has a bioavailability equivalent to the piracetam (Nootropil®; 800 mg tablet) formulation with regard to both the rate and the extent of absorption. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
7.
L. Martínez E. RománJ.L. de Segovia S. PoupardJ. Creus F. Pedraza 《Applied Surface Science》2011,257(14):6202-6207
A surface study of electrodeposited cerium oxide based coatings is presented. Different surface analytical techniques were used in order to obtain complementary information to fully characterize such complex systems. X-ray Photoelectron Spectroscopy was used as the main technique to determine the surface composition of the coating. The analysis of the core level peaks of the elements provides additional information about the functional groups present on the surface. A mixture of Ce (III) and Ce (IV) was found in the coating and their proportion was calculated at different depths. The analysis of the O 1s core level peak revealed a triple structure whose origin will be discussed. To support the results obtained, electron stimulated desorption was performed. The study was completed with Auger electron spectroscopy and Raman spectroscopy, both techniques having different surface sensitivities. From all these results, it is derived that incomplete electrochemical reactions occurred during the growth of the coatings. This led to rather complex compositions, in which defective cerium oxides are the major species. In addition, hydroxides, carbonates and nitrates are also present, together with adsorbed water. 相似文献
8.
Theodore?J?Price Michael?D?Louria Damaries?Candelario-Soto Gregory?O?Dussor Nathanial?A?Jeske Amol?M?Patwardhan Anibal?Diogenes Amanda?A?Trott Kenneth?M?Hargreaves Christopher?M?FloresEmail author 《BMC neuroscience》2005,6(1):4
Background
Nerve growth factor (NGF), glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) all play important roles in the development of the peripheral sensory nervous system. Additionally, these growth factors are proposed to modulate the properties of the sensory system in the adult under pathological conditions brought about by nerve injury or inflammation. We have examined the effects of NGF, GDNF and BDNF on adult rat trigeminal ganglion (TG) neurons in culture to gain a better understanding of how these growth factors alter the cytochemical and functional phenotype of these neurons, with special attention to properties associated with nociception. 相似文献9.
We present a new method of measuring the guided, radiated, and total decay rates in uniform waveguides. It is also shown theoretically that large modifications of the total decay rate can be achieved in realistic erbium-doped fiber amplifiers and erbium-doped waveguide amplifiers with effective mode area radii smaller than approximately 1 microm. 相似文献
10.
Surface nanostructuring of silicon 总被引:1,自引:0,他引:1
A.J. Pedraza J.D. Fowlkes Y.-F. Guan 《Applied Physics A: Materials Science & Processing》2003,77(2):277-284
Irradiation with polarized laser light of 248-nm wavelength induces the formation of periodic undulations ∼10-nm-highon flat
silicon substrates. The wavelength of these periodic structures is a function of the light wavelength and the angle of incidence
of the laser beam. Linear arrays of silicon nanoparticles with fairly uniform size that extended up to a millimeter were formed
if the irradiation was performed using polarized light. When non-polarized laser light with the same fluence was used to illuminate
an initially flat surface, non-aligned nanoparticle strings were obtained. However, if part of the irradiated area was microstructured,
nanoparticle linear arrays resulted in the vicinity of the microstructured region. An analysis on the evolution of these nanostructures
is presented. Nanocolumns could be grown on top of every cone of a microstructured surface upon cumulative laser irradiation
with non-polarized light, reaching a height of ∼3 μm and a diameter of 100–200 nm. The mechanisms of nanocolumn origin and
growth are analyzed.
Received: 16 December 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +1-865/974-4115, E-mail: apedraza@utk.edu 相似文献