全文获取类型
收费全文 | 122篇 |
免费 | 9篇 |
专业分类
化学 | 63篇 |
晶体学 | 7篇 |
力学 | 5篇 |
数学 | 11篇 |
物理学 | 45篇 |
出版年
2023年 | 6篇 |
2022年 | 7篇 |
2021年 | 12篇 |
2020年 | 8篇 |
2019年 | 8篇 |
2018年 | 6篇 |
2016年 | 9篇 |
2015年 | 7篇 |
2014年 | 7篇 |
2013年 | 5篇 |
2012年 | 4篇 |
2011年 | 6篇 |
2010年 | 5篇 |
2009年 | 6篇 |
2008年 | 4篇 |
2007年 | 7篇 |
2006年 | 2篇 |
2005年 | 6篇 |
2004年 | 3篇 |
2003年 | 3篇 |
2002年 | 1篇 |
2001年 | 1篇 |
1999年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1989年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有131条查询结果,搜索用时 15 毫秒
81.
Bagchi S Nebgen BT Loring RF Fayer MD 《Journal of the American Chemical Society》2010,132(51):18367-18376
Myoglobin (Mb) double mutant T67R/S92D displays peroxidase enzymatic activity in contrast to the wild type protein. The CO adduct of T67R/S92D shows two CO absorption bands corresponding to the A(1) and A(3) substates. The equilibrium protein dynamics for the two distinct substates of the Mb double mutant are investigated by using two-dimensional infrared (2D IR) vibrational echo spectroscopy and molecular dynamics (MD) simulations. The time-dependent changes in the 2D IR vibrational echo line shapes for both of the substates are analyzed using the center line slope (CLS) method to obtain the frequency-frequency correlation function (FFCF). The results for the double mutant are compared to those from the wild type Mb. The experimentally determined FFCF is compared to the FFCF obtained from molecular dynamics simulations, thereby testing the capacity of a force field to determine the amplitudes and time scales of protein structural fluctuations on fast time scales. The results provide insights into the nature of the energy landscape around the free energy minimum of the folded protein structure. 相似文献
82.
Sayan Bhattacharyya Sajith Kurian S. M. Shivaprasad N. S. Gajbhiye 《Journal of nanoparticle research》2010,12(4):1107-1116
A new ternary nitride, CoMoN2, was prepared in the nanosize regime of 9.0 ± 2.0 nm, by nitridation of the precursor intermetallic nitride Co3Mo3N. XRD–Rietveld analysis revealed the presence of 0.60 (±0.02) mass % of Co impurity phase. The calculated space groups of
CoMoN2 and Co are P6
3
/mmc and Fm-3m, respectively. The N atoms lie at the interstitial sites and the 12 calculated nitrogen sites indicate the presence of a
layered structure. The XPS studies indicated the presence of the nitride and surface oxynitride/oxide phases. CoMoN2 is an interstitial nitride with Co and Mo in the zero oxidation state. The room temperature susceptibility is estimated after
subtracting the ferromagnetic contribution from cobalt and found to be 2.7 × 10−4 emu g−1 Oe−1, indicating the Pauli-paramagnetic nature. The ferromagnetic exchange interactions between the Co atoms in CoMoN2 are reduced due to the presence of Mo and N in the crystal lattice. The hysteresis loop shift 19 Oe is attributed to the
demagnetizing dipolar fields created in the soft CoMoN2 phase by the hard Co phase. 相似文献
83.
84.
JPC – Journal of Planar Chromatography – Modern TLC - A simple, rapid, quantitative, and validated high-performance thin-layer chromatographic (HPTLC) method has been developed for the... 相似文献
85.
Surface fitting is one of the well‐known retrospective methods for bias field estimation from magnetic resonance imaging (MRI) images. Bias field in MRI images is primarily caused because of radio frequency–coil nonuniformity, improper image acquisition process, patient movement, and so on. The bias field can be characterized by any slow variant and smooth function because of its slow variant nature. In this paper, we present a comparative study between polynomial and Gaussian surface fitting methods. In particular, we have used both the second‐ and third‐order polynomial functions to estimate the bias field. In this study, we approximate the bias field in two different ways. In the first method, the surfaces are fitted on the anatomical tissue regions individually and then fused to estimate the bias field. Conversely, in the second method, we have done the same over the entire image region. We have tested on three volumes of simulated and one volume of real‐patient MRI brain images and validated the results by both the qualitative and quantitative analyses. The quantitative analyses are presented in standard deviation and coefficient of joint variation. The analysis of the simulation results show that the Gaussian surface fitting method yields better results in both the cases, where the surface fitting is done on entire image and individual tissue regions. 相似文献
86.
87.
Chitosan, a biopolymer obtained from chitin deacetylation, was solubilized by bipolar membrane electroacidification (BMEA). We showed earlier that limitation in solubilization process was mainly due to chitosan precipitation in the acidified compartment. If fouling can be reduced or prevented, BMEA could be an environmentally attractive method for chitosan solubilization. The purpose of the present work was to identify process conditions that could reduce chitosan fouling in BMEA. The factors studied were: the type of salt in the acidified compartment (NaCl or CH3COONa); the type of electrolyte in the basified compartment (KCl or HCl); and the current density (4 or 20 mA/cm2). Chitosan fouling was successfully reduced by a combination of NaCl salt and HCl electrolyte, while 98% chitosan solubilization yield was achieved by operating at a current density of 4 mA/cm2 with NaCl/KCl configuration with no apparent fouling. This work showed that water dissociation at the interface of the anionic membranes was the main factor responsible for chitosan precipitation. 相似文献
88.
The problem of time-variant reliability analysis of randomly driven linear/nonlinear vibrating structures is studied. The excitations are considered to be non-stationary Gaussian processes. The structure properties are modeled as non-Gaussian random variables. The structural responses are therefore non-Gaussian processes, the distributions of which are not generally available in an explicit form. The limit state is formulated in terms of the extreme value distribution of the response random process. Developing these extreme value distributions analytically is not easy, which makes failure probability estimations difficult. An alternative procedure, based on a newly developed improved response surface method, is used for computing exceedance probabilities. This involves fitting a global response surface which approximates the limit surface in regions which make significant contributions to the failure probability. Subsequent Monte Carlo simulations on the fitted response surface yield estimates of failure probabilities. The method is integrated with professional finite element software which permits reliability analysis of large structures with complexities that include material and geometric nonlinear behavior. Three numerical examples are presented to demonstrate the method. 相似文献
89.
The hyperfine interactions of six different PAC (perturbed angular correlations) probes in the ferromagnetic spinel semiconductor HgCr2Se4 have been investigated. Thereby the site occupation of the probes was determined and opposed to that in other comparable substances. All of the three lattice sites could be tested. Theoretically calculated hyperfine fields (WIEN97) were compared with the experimental values. 相似文献
90.
Sayan K. Chakrabarti Emmanuel N. Saridakis Anjan A. Sen 《General Relativity and Gravitation》2011,43(11):3065-3078
We investigate f (R)-gravity models performing the ADM-slicing of standard General Relativity. We extract the static, spherically-symmetric vacuum
solutions in the general case, which correspond to either Schwarzschild de-Sitter or Schwarzschild anti-de-Sitter ones. Additionally,
we study the cosmological evolution of a homogeneous and isotropic universe, which is governed by an algebraic and not a differential
equation. We show that the universe admits solutions corresponding to acceleration at late cosmological epochs, without the
need of fine-tuning the model-parameters or the initial conditions. 相似文献