全文获取类型
收费全文 | 632篇 |
免费 | 22篇 |
国内免费 | 4篇 |
专业分类
化学 | 417篇 |
晶体学 | 5篇 |
力学 | 14篇 |
数学 | 79篇 |
物理学 | 143篇 |
出版年
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 9篇 |
2019年 | 9篇 |
2018年 | 3篇 |
2017年 | 13篇 |
2016年 | 16篇 |
2015年 | 15篇 |
2014年 | 26篇 |
2013年 | 43篇 |
2012年 | 54篇 |
2011年 | 55篇 |
2010年 | 35篇 |
2009年 | 30篇 |
2008年 | 49篇 |
2007年 | 28篇 |
2006年 | 28篇 |
2005年 | 43篇 |
2004年 | 34篇 |
2003年 | 31篇 |
2002年 | 36篇 |
2001年 | 16篇 |
2000年 | 14篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 6篇 |
1995年 | 2篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1972年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有658条查询结果,搜索用时 31 毫秒
631.
Young Kyo Shin Chae Hwa Shon Woong Kim Jae Koo Lee 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1999,27(5):1366-1371
The effect of the voltage pulsing is simulated in AC plasma display panel using various two-dimensional simulation codes. The volume-averaged density increases rapidly because of the large electric field in the AC-plasma display panel cell as the peak voltage is raised. The ignition time and the decaying time of the discharge are related to the external voltage. The space and time variations of the charged particle densities and the potential profile are described for various voltage forms. The ion energy distribution near the cathode-side dielectric which plays an important role in the MgO lifetime and the secondary electron emission coefficient is concentrated to much lower energies than the applied voltage 相似文献
632.
Sung-Gon Kim Kyung-Hyun Kim Junyang Jung Seung Koo Shin Kyo Han Ahn 《Journal of the American Chemical Society》2002,124(4):591-596
The enantiomeric recognition of alpha-chiral primary ammonium ions has been studied with benzene-based tripodal tris(oxazoline) receptors. Contrary to the literature and our expectation, a good level of chiral discrimination is observed with one of the tripodal receptors, which provides a C3-symmetric chiral environment on guest binding. The chiral discrimination has been found to be general in the case of alpha-aryl substituted guests, suggesting pi-pi interactions as an important factor. This result raises a question with respect to the origin of the chiral discrimination since little steric or electronic difference is expected between the diastereomeric inclusion complexes. Binding studies by NMR titration and isothermal titration calorimetry show that the chiral discrimination results from the different thermodynamic stabilities between the diastereomeric complexes and that the host-guest complex formation is driven by favorable enthalpy changes with a minor negative contribution by entropy changes. The X-ray crystal structures for both of the diastereomeric inclusion complexes are resolved, which unambiguously show the binding mode and provide clues on the origin of the chiral discrimination. Bond angle analyses indicate that the minor complex experiences a larger steric strain, which is discernible when it is viewed from "three-body" interactions between the host and the guest. The guest and oxazoline phenyl rings are well stacked, indicating interplay of the pi-pi interactions. The pi-pi interactions are believed to stabilize host-guest complexes, thereby endowing the highly flexible receptors with a substantial enantio-discrimination. 相似文献
633.
[reaction: see text] It is shown that nanosized WO(3) particles supported on MCM-48 work as a highly efficient and selective heterogeneous catalyst for the oxidation of olefins, sulfides, and cyclic ketones using hydrogen peroxide or peracetic acid. The catalytic activity of the supported tungstate was dependent on the nature of the supporting materials and particle size. The catalyst system employs environmentally benign oxidants in halide-free solvents, and it does not require phase-transfer agents and pH control. 相似文献
634.
We report on the applicability of combining surface-enhanced Raman scattering (SERS) with coherent anti-Stokes Raman scattering for high-sensitivity detection of biological molecules. We found that this combination of techniques provides more than 3 orders of signal enhancement compared with SERS and permits monitoring of biological molecules such as deoxyguanosine monophosphate (dGMP) and deoxyadenosine monophosphate at the single-molecule level. This combined technique also improved detection sensitivity for angiotensin peptide. As this is believed to be the first report of detection of dGMP at the single-molecule level, we suggest that this approach can serve as a new tool for biological studies. 相似文献
635.
The ternary vanadium sulfide BaVS3 consists of VS3 chains made up of face sharing VS6 octahedra, and exhibits a number of structural, electrical and magnetic properties that are not explained in terms of the normal metallic state. Our analysis indicates that the spin ordering of BaVS3 taking place below 30 K is most probably random along the chain direction. Thus the puzzling properties of BaVS3 are explained in terms of the broken-symmetry electronic state in which pairs of nonmagnetic V atoms alternate with those of magnetic V atoms in each VS3 chain. The origin of this broken-symmetry state was discussed on the basis of cooperative Jahn-Teller distortion and lattice strain. 相似文献
636.
Ji S Song C Koo J Lee KB Park YJ Kim JY Park JH Shin HJ Rhyee JS Oh BH Cho BK 《Physical review letters》2003,91(25):257205
Resonant x-ray scattering experiments at the Gd L3 edge show interference between magnetic and anisotropic tensor susceptibility (ATS) reflections in GdB4. Energy profiles obtained from the magnetic and ATS resonances exhibited approximately 10 eV separation between the maximum resonance energies. The findings show that the Gd 5d band experienced hybridization giving rise to a significant split into isotropic lower energy band and distorted upper band states that account for the magnetic and ATS scattering, respectively. 相似文献
637.
L. Delimova I. Grekhov D. Mashovets S. Shin J. -M. Koo S. -P. Kim Y. Park 《Physics of the Solid State》2006,48(6):1182-1185
A method is developed for determining the trap density at the metal/ferroelectric interfaces in a completely depleted ferroelectric film with two Schottky barriers. The method is based on the recharging of traps induced by an external pulsed bias. The ranges of the bias fields and of the parameters of the metal/ferro-electric/metal structure for which analytical solution of the Poisson equation is possible are found. Using this method and measurements of the transient current, the density of the charge trapped at the upper and lower interfaces of Pt(Ir)/PZT/Ir(Ti/SiO2/Si) capacitors is determined. The interface charge as estimated from the trap density proved to be much smaller than the residual polarization of the PZT film. The observed correlation between the symmetry of the interface trap charges and the symmetry of the hysteresis loops and switching currents indicates the reliability of the estimation of the trap density determined using the proposed method. 相似文献
638.
J. P. Y. Ho C. W. Y. Yip V. S. Y. Koo D. Nikezic K. N. Yu 《Radiation measurements》2002,35(6):571-573
Equations for calculating track parameters have been proposed, which invariably involve the track etch rate Vt and the bulk etch rate Vb. The present study measured Vb for the LR115 solid-state nuclear track detector using atomic force microscopy (AFM). The detectors were partially masked using rubber cement and then etched in 2.5 N NaOH solution at 60°C for time periods ranging from 5 to 40 min. The rubber cement was then peeled off and cross-sectional images of the LR115 detectors were obtained by AFM. Vb has been found to have different values below and beyond the etching time of about 13.5 min, with the values of 0.0555 and 0.0875 μm min−1, respectively. The increase in Vb with the etching time can be explained by a diffusion-etch model, in which the additional damage of the detector material is due to those etchant ions diffused into the detector over time. Now that Vb has been determined, this can be combined with the track etch rate Vt to calculate track parameters. 相似文献
639.
Most work on supersingular potentials has focused on the study of the ground state. In this paper, a global analysis of the
ground and excited states for the successive values of the orbital angular momentum of the supersingular plus quadratic potential
is carried out, making use of centrifugal plus quadratic potential eigenfunction bases. First, the radially nodeless states
are variationally analyzed for each value of the orbital angular momentum using the corresponding functions of the bases;
the output includes the centrifugal and frequency parameters of the auxiliary potentials and their eigenfunction bases. In
the second stage, these bases are used to construct the matrix representation of the Hamiltonian of the system, and from its
diagonalization the energy eigenvalues and eigenvectors of the successive states are obtained. The systematics of the accuracy
and convergence of the overall results are discussed with emphasis on the dependence on the intensity of the supersingular
part of the potential and on the orbital angular momentum.
under the CNPq-CONACyT scientific exchange program. 相似文献
640.
Jobic S Brec R Chateau C Haines J Léger JM Koo HJ Whangbo MH 《Inorganic chemistry》2000,39(19):4370-4373
The new monoclinic IrTe2 phase m-IrTe2 was synthesized under pressure, and its structure was determined by X-ray powder diffraction. The relative stabilities of the three known and three hypothetical IrTe2 polymorphs were discussed on the basis of tight binding electronic band structure calculations. m-IrTe2 exhibits structural features of both CdI2- and pyrite-type IrTe2 phases and is expected to be nearly as stable as that of the CdI2-type IrTe2. The hypothetical IrS2- and ramsdellite-type IrTe2 phases are predicted to be more stable than the CdI2-type IrTe2. 相似文献