全文获取类型
收费全文 | 188篇 |
免费 | 9篇 |
专业分类
化学 | 115篇 |
晶体学 | 1篇 |
力学 | 19篇 |
数学 | 15篇 |
物理学 | 47篇 |
出版年
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 9篇 |
2020年 | 7篇 |
2019年 | 3篇 |
2018年 | 5篇 |
2017年 | 6篇 |
2016年 | 7篇 |
2015年 | 4篇 |
2014年 | 8篇 |
2013年 | 17篇 |
2012年 | 10篇 |
2011年 | 8篇 |
2010年 | 8篇 |
2009年 | 5篇 |
2008年 | 4篇 |
2007年 | 10篇 |
2006年 | 7篇 |
2005年 | 4篇 |
2004年 | 8篇 |
2003年 | 2篇 |
2002年 | 8篇 |
2001年 | 9篇 |
2000年 | 8篇 |
1999年 | 5篇 |
1998年 | 1篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1993年 | 3篇 |
1991年 | 1篇 |
1988年 | 2篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有197条查询结果,搜索用时 31 毫秒
21.
Electron energy loss spectroscopy has been examined as a possible tool for measuring the atomic composition of polymers on a local scale in the transmission electron microscope. Thin films of nylon 6,6 and single crystal lamellae of poly(chlorotrifluorethylene) were investigated as model systems. Spectra were obtained using an 100 kV electron beam. Results for nylon 6,6 gave fairly good quantitative agreement between the measured relative atomic contents of carbon, nitrogen, and oxygen (77, 9, and 14%, ± 5%, respectively) and the calculated values (75, 12.5, and 12.5%, respectively). Spectra obtained for poly(chlorotrifluoroethylene) single crystals revealed significant mass loss of chlorine as a function of electron dose. The amount of chlorine decayed exponentially with a characteristic dose D* of 96 C/m2. Supporting the poly(chlorotrifluoroethylene) crystals on a continuous carbon film, a holey carbon film, or sandwiched between two carbon films did not effect the mass loss decay constant significantly but did effect the amount of chlorine remaining in the irradiated area at large electron doses. The poly(chlorotrifluorethylene) crystals sandwiched between two carbon films retained more chlorine at large doses, possibly due to the carbon film on both sides of the crystals, inhibiting surface diffusion of the chlorine. Analysis of the spectrum from a portion of a trilayer PCTFE crystal suspended over a hole in the support film gave the relative contents of C, Cl, and F (extrapolated to zero dose) as being 38, 15, and 47%, respectively. The calculated values are 33, 17, and 50%, respectively. 相似文献
22.
23.
Sabine El Khoury 《代数通讯》2013,41(9):3259-3277
In this article, we study height four graded Gorenstein ideals I in k[x, y, z, w] such that I 2 is of height one and generated by three quadrics. After a suitable linear change of variables, I ∩ k[x, y, z] is either Gorenstein or of type two. The former case was studied by Iarrobino and Srinivasan [8] where they give the structure of the ideal and its resolution. We study the latter case and give the structure of these ideals and their minimal resolution. We also explicitly write the form of the generators of I and the maps in the free resolution of R/I. 相似文献
24.
Enrico Falcone Ikhlas M. M. Ahmed Dr. Valentina Oliveri Dr. Francesco Bellia Dr. Bertrand Vileno Dr. Youssef El Khoury Prof. Petra Hellwig Prof. Peter Faller Prof. Graziella Vecchio 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(8):1871-1879
Mounting evidence supports the role of amyloidogenesis, oxidative stress, and metal dyshomeostasis in the development of neurodegenerative disorders. Parkinson's Disease is characterized by α-synuclein (αSyn) accumulation and aggregation in brain regions, also promoted by Cu2+. αSyn is modified by reactive carbonyl species, including acrolein (ACR). Notwithstanding these findings, the interplay between ACR, copper, and αSyn has never been investigated. Therefore, we explored more thoroughly the effects of ACR on αSyn using an approach based on LC-MS/MS analysis. We also evaluated the influence of Cu2+ on the protein carbonylation and how the ACR modification impacts the Cu2+ binding and the production of Reactive Oxygen Species (ROS). Finally, we investigated the effects of ACR and Cu2+ ions on the αSyn aggregation by dynamic light scattering and fluorescence assays. Cu2+ regioselectively inhibits the modification of His50 by ACR, the carbonylation lowers the affinity of His50 for Cu2+ and ACR inhibits αSyn aggregation both in the presence and in the absence of Cu2+. 相似文献
25.
Marissa?K.?Geikie Zakery?R.?Carr Kareem?A. AhmedEmail author David?J.?Forliti 《Flow, Turbulence and Combustion》2017,99(2):487-509
This investigation considers the dynamics of flame-generated vorticity for a premixed, submerged bluff-body stabilized flame. Experimentation characterizes the far-field region in particular with a level of detail not previously afforded to this type of flow. Simultaneous particle imaging velocimetry (PIV), Mie scattering and CH ? chemiluminescence are used to obtain velocity fields and flame location. Mean static pressure measurements at the combustion chamber wall capture the pressure field. Analysis of the flame fronts in relation to the mean velocity and vorticity fields provides useful insight into the interaction of the flame and the flow. The unique nature of the velocity and vorticity fields and their effect on downstream flame structures are explained by the baroclinic torque generation of vorticity. The coupling that exists among pressure, heat release, and baroclinic generation is acknowledged and will influence strategies for control of the baroclinic mechanism. 相似文献
26.
Ahmad Aqel Abdulrhman M. Dhabbah Kareem Yusuf Nasser M. AL-Harbi Zeid A. Al Othman A. Yacine Badjah-Hadj-Ahmed 《Journal of Analytical Chemistry》2016,71(7):730-736
The identification of ignitable liquids is very important and challenging aspect in arson crime investigations. The detection of gasoline and diesel fuel components using solid phase micro-extraction prior to gas chromatography–mass spectrometry for the forensic analysis of fire debris has been carried out. Previous works show that the absorption characteristics of the substrate are one of the most important factors in determining the evaporation rate of the accelerants. In order to determine the presence of the fuel residues, four of the most common substrate materials were tested in this work; wool, cotton, silk and polyester. The obtained results indicate that both gasoline and diesel fuel accelerants persisted longer on wool and silk than on the other selected substrates. Such information illustrates the influence of fuel persistence times after extinguishing and the best materials to be scanned for ignitable liquids at the fire scene. 相似文献
27.
In this work, we address some important topological and algebraic aspects of two-qudit states evolving under local unitary operations. The projective invariant subspaces and evolutions are connected with the common elements characterizing the su(d) Lie algebra and their representations. In particular, the roots and weights turn out to be natural quantities to parametrize cyclic evolutions and fractional phases. This framework is then used to recast the coset contribution to the geometric phase in a form that generalizes the usual monopole-like formula for a single qubit. 相似文献
28.
There are many methods available to synthesize nanomaterials and the glow discharge plasma electrolysis is a novel and a green
method in this category. It is seen that most of the papers are published after 2005 and the interest in it is growing due
to its applicability in the industry for preparing nanomaterials at large scale. But, only few results are available yet and
most of them are on metal nanoparticle preparation, so that more studies are needed to understand the nature of growth of
the nanoparticles under glow discharge in liquid and its applicability in preparing semi-conductor nanomaterials. Many have
tried many methods to prepare nanoparticles by the glow discharge and a review like this is the need of the time to understand
its present status that helps to modify the present situation to a better one. This review classifies all the available methods
of nanomaterials synthesis in liquid by glow discharge in to three and it is discussed in detail. 相似文献
29.
Manganese doped zinc sulfide nanocrystalline powder was synthesized with sodium citrate and its films were formed by mixing it with polyvinyl alcohol to study optical absorption of Mn doped ZnS dispersed in polyvinyl alcohol. The characteristics of the prepared powder and film samples were studied by X-ray diffraction, transmission electron microscopy and UV–visible absorption spectroscopy. Samples exhibited optical absorption at lower wavelength region and particle sizes were calculated from X-ray diffractogram. 相似文献
30.
S. Yaacoub S. Calas J. Jabbour R. Tauk D. Zaouk A. Khoury P. Etienne 《Journal of Non》2012,358(22):3036-3041
This work investigates the mechanical properties of different scratch resistant coatings, namely, a mixture of 3-glycidoxypropyltrimethoxysilane (GPTMS) with either colloidal silica particles or tetraethoxysilane (TEOS). Coatings were prepared by the hydrolysis and the condensation of the precursor's alkoxide (sol–gel process) with thermally catalyzed polymerization of epoxy ring of GPTMS. Dip deposition techniques were used on silicon substrate.The nanoindentation technique was used to analyze the force required to indent the coating with a diamond tip. At low forces, this technique, based on indentation depth, predicts the hardness and the elastic modulus of the coating, while at higher forces, cracks appear. Another analysis based on geometric approach, namely, the crack length, allows the determination of both coating and interface toughness. 相似文献