全文获取类型
收费全文 | 123篇 |
免费 | 10篇 |
专业分类
化学 | 90篇 |
力学 | 11篇 |
数学 | 15篇 |
物理学 | 17篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 7篇 |
2018年 | 5篇 |
2017年 | 1篇 |
2016年 | 9篇 |
2015年 | 2篇 |
2014年 | 4篇 |
2013年 | 5篇 |
2012年 | 9篇 |
2011年 | 6篇 |
2010年 | 8篇 |
2009年 | 4篇 |
2008年 | 5篇 |
2007年 | 8篇 |
2006年 | 7篇 |
2005年 | 10篇 |
2004年 | 5篇 |
2003年 | 8篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1957年 | 1篇 |
1955年 | 1篇 |
1932年 | 2篇 |
排序方式: 共有133条查询结果,搜索用时 15 毫秒
1.
Accreditation and Quality Assurance - 相似文献
2.
3.
The incidence of the cutaneous malignant melanoma is increasing rapidly in the world [Ferlay J, Bray F, Pisani P, et al. GLOBOCAN 2000: Cancer incidence, mortality and prevalence worldwide, Version 1.0 IARC Cancer Base no. 5. Lyon: IARC Press, 2001]. The therapeutic address requires a method having high sensitivity and capability to diagnose such disease at an early stage. We introduce a new diagnostic method based on non-linear methodologies. In detail we suggest that fractal as well as noise and chaos dynamics are the most important components responsible for genetic instability of melanocytes. As consequence we introduce the new technique of the variogram and of fractal analysis extended to the whole regions of interest of skin in order to obtain parameters able to identify the malignant lesion. In a preliminary analysis, satisfactory results are reached. 相似文献
4.
Chiesa M Paganini MC Spoto G Giamello E Di Valentin C Del Vitto A Pacchioni G 《The journal of physical chemistry. B》2005,109(15):7314-7322
Paramagnetic centers at the surface of ionic oxides in the form of trapped electrons can be generated by exposure of the material to alkali metal or hydrogen atoms or of molecular hydrogen under UV irradiation. For many years, it has been assumed that the resulting paramagnetic centers consist of oxygen vacancies filled by one electron. High-resolution electron spin resonance spectra and ab initio quantum chemical calculations show that the paramagnetic centers consist of (H(+))(e(-)) electron pairs formed at morphological irregularities of the surface. At least three different kinds of (H(+))(e(-)) centers, [A], [B], and [C], have been identified with abundances of 80%, 10%, and 8%, respectively. In this work, we compare a wide set of measured and computed g-factors and hyperfine coupling constants of the unpaired electron with the surrounding (25)Mg, (17)O, and (1)H nuclei and we propose a general assignment of the centers. (H(+))(e(-)) pairs formed at Mg(4c) ions at steps and edges account for species [A], centers formed at Mg(4c) ions at reverse corners correspond to species [B], and species [C] originates from (H(+))(e(-)) pairs formed at Mg(3c) ions at corners and kinks. 相似文献
5.
Mercury-mercurous acetate indicator electrode for potentiometric titrations in anhydrous acetic acid
The authors describe a metallic mercury electrode covered with a mercurous acetate coating, its preparation, its use as an indicator electrode in anhydrous acetic acid neutralization titrations and its properties as compared with other electrodes used for the same purpose. 相似文献
6.
Mario Chiesa Maria Cristina Paganini Elio Giamello Cristiana Di Valentin Gianfranco Pacchioni 《Chemphyschem》2006,7(3):728-734
(H+)(e-) pairs generated at the surface of polycrystalline CaO are analyzed for the first time in terms of the interaction of the unpaired electron spin with the nuclear spin of the 17O anions of the surface. CaO crystals enriched in the 17O isotope are prepared and the corresponding hyperfine coupling constants are measured in electron paramagentic resonance (EPR) spectra. The results are analyzed on the basis of cluster model density functional theory calculations. The computed hyperfine coupling constants for (H+)(e-) pairs formed on the edge, corner, and reverse corner sites of the CaO surface allow a tentative assignment of two observed spectral features to specific morphological surface sites. 相似文献
7.
In research laboratories ultraviolet radiation is widely used, particularly in photochemistry and photobiology, as a sterilizing agent and for the characterization of samples. The results of a survey conducted near several university laboratories are presented with the aim of quantifying exposure levels to UV-incoherent radiation and to assess individual risk for researchers and students. It has been shown that exposure is not negligible, especially if safety procedures are neglected and personal protective equipments, described in this study, are not used. 相似文献
8.
9.
The paper presents an interphase cohesive zone model (CZM) incorporating stress multi-axiality devised to capture, by simplified micro-modeling, the influence of the in-plane strain and stress state in the mechanical response of the CZM. Moreover, the model is able to account for the Poisson-related effect in the interphase, which can play an important role in the modeling of heterogeneous masonry elements. From the constitutive point of view, the proposed formulation couples damage and friction by addressing a smooth transition from a quasi-brittle response to a residual frictional behavior described by a Coulomb law with unilateral contact. As in-plane stresses are accounted for, damage activation and evolution are governed by a Drucker–Prager law with linear softening. A predictor-corrector procedure based on a backward Euler scheme is detailed for integrating the nonlinear evolutive problem together with the related tangent operator which consistently linearizes the algorithmic strategy. This framework is embedded into a kinematically-enriched finite element interphase formulation incorporating stress multi-axiality. The modeling features of the resulting numerical tool are tested both at the local level, for the typical interphase point, and in meso-structural tests consisting of brick-mortar triplets, investigating the capability of the proposed model and numerical procedure to simulate the brick-mortar decohesion mechanism during confined slip tests. 相似文献
10.
A mass‐conservative staggered immersed boundary model for solving the shallow water equations on complex geometries 下载免费PDF全文
Alberto Canestrelli Aukje Spruyt Bert Jagers Rudy Slingerland Mart Borsboom 《国际流体数值方法杂志》2016,81(3):151-177
In this work, an approach is proposed for solving the 3D shallow water equations with embedded boundaries that are not aligned with the underlying horizontal Cartesian grid. A hybrid cut‐cell/ghost‐cell method is used together with a direction‐splitting implicit solver: Ghost cells are used for the momentum equations in order to prescribe the correct boundary condition at the immersed boundary, while cut cells are used in the continuity equation in order to conserve mass. The resulting scheme is robust, does not suffer any time step limitation for small cut cells, and conserves fluid mass up to machine precision. Moreover, the solver displays a second‐order spatial accuracy, both globally and locally. Comparisons with analytical solutions and reference numerical solutions on curvilinear grids confirm the quality of the method. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献