全文获取类型
收费全文 | 150篇 |
免费 | 4篇 |
专业分类
化学 | 88篇 |
晶体学 | 1篇 |
力学 | 5篇 |
数学 | 20篇 |
物理学 | 40篇 |
出版年
2022年 | 3篇 |
2021年 | 1篇 |
2020年 | 4篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 5篇 |
2016年 | 8篇 |
2015年 | 7篇 |
2014年 | 6篇 |
2013年 | 6篇 |
2012年 | 10篇 |
2011年 | 8篇 |
2010年 | 8篇 |
2009年 | 5篇 |
2008年 | 9篇 |
2007年 | 6篇 |
2006年 | 5篇 |
2005年 | 8篇 |
2004年 | 10篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有154条查询结果,搜索用时 593 毫秒
21.
Leticia A. Montoya Xinggui Shen James J. McDermott Christopher G. Kevil Michael D. Pluth 《Chemical science》2015,6(1):294-300
Hydrogen sulfide (H2S) has emerged as an important biological signaling molecule in the last decade. During the growth of this field, significant controversy has arisen centered on the physiological concentrations of H2S. Recently, a monobromobimane (mBB) method has been developed for the quantification of different biologically-relevant sulfide pools. Based on the prevalence of the mBB method for sulfide quantification, we expand on this method to report the use of dibromobimane (dBB) for sulfide quantification. Reaction of H2S with dBB results in formation of highly-fluorescent bimane thioether (BTE), which is readily quantifiable by HPLC. Additionally, the reaction of sulfide with dBB to form BTE is significantly faster than the reaction of sulfide with mBB to form sulfide dibimane. Using the dBB method, BTE levels as low as 0.6 pM can be detected. Upon use of the dBB method in wild-type and CSE–/– mice, however, dBB reports significantly higher sulfide levels than those measured using mBB. Further investigation revealed that dBB is able to extract sulfur from other sulfhydryl sources including thiols. Based on mechanistic studies, we demonstrate that dBB extracts sulfur from thiols with α- or β-hydrogens, thus leading to higher BTE formation than from sulfide alone. Taken together, the dBB method is a highly sensitive method for H2S but is not compatible for use in studies in which other thiols are present. 相似文献
22.
Julio López Sebastián Maldonado Ricardo Montoya 《The Journal of the Operational Research Society》2017,68(11):1323-1334
Support vector machines (SVMs) have been successfully used to identify individuals’ preferences in conjoint analysis. One of the challenges of using SVMs in this context is to properly control for preference heterogeneity among individuals to construct robust partworths. In this work, we present a new technique that obtains all individual utility functions simultaneously in a single optimization problem based on three objectives: complexity reduction, model fit, and heterogeneity control. While complexity reduction and model fit are dealt using SVMs, heterogeneity is controlled by shrinking the individual-level partworths toward a population mean. The proposed approach is further extended to kernel-based machines, conferring flexibility to the model by allowing nonlinear utility functions. Experiments on simulated and real-world datasets show that the proposed approach in its linear form outperforms existing methods for choice-based conjoint analysis. 相似文献
23.
A.D. Brooke-Taylor V. Fischer S.D. Friedman D.C. Montoya 《Annals of Pure and Applied Logic》2017,168(1):37-49
We provide a model where for a supercompact cardinal κ. [10] provides a sketch of how to obtain such a model by modifying the construction in [6]. We provide here a complete proof using a different modification of [6] and further study the values of other natural generalizations of classical cardinal characteristics in our model. For this purpose we generalize some standard facts that hold in the countable case as well as some classical forcing notions and their properties. 相似文献
24.
Comini LR Montoya SC Páez PL Argüello GA Albesa I Cabrera JL 《Journal of photochemistry and photobiology. B, Biology》2011,102(2):108-114
Photosensitizing anthraquinones isolated from Heterophyllaea pustulata Hook f. (Rubiaceae), namely soranjidiol, rubiadin, damnacanthal and 5,5'-bisoranjidiol, showed antibacterial activity (bacteriostatic/bactericide) on Staphylococcus aureus. The mechanism of action seems to involve an increase in the levels of superoxide anion (O(2)(·-)) and/or singlet molecular oxygen ((1)O(2)). Moreover, the effect of actinic irradiation as a boosting agent for the production of both reactive species of oxygen as well as its influence on antibacterial activity was assessed. The routine susceptibility assay (minimum inhibitory concentration determination) was carried out by means of the broth macrodilution method. Bactericide activity was determined counting the colony-forming units per milliliter (cfu/mL) in plate. The O(2)(·-) production was determined by means of an indirect photobiological assay (Nitroblue Tetrazolium test), and the production of (1)O(2) was followed using an indirect steady-state method, with methionine as the (1)O(2) chemical quencher. 相似文献
25.
Balbás IM Mendoza BE Fernández-Zertuche M Ordoñez M Linzaga-Elizalde I 《Molecules (Basel, Switzerland)》2011,17(1):151-162
We describe a protocol developed for the preparation of β-enaminoketones derived from 1,3-cyclohexanediones, and their subsequent reduction by sodium in THF-isopropyl alcohol to afford cis- and trans-3-aminocyclohexanols. 相似文献
26.
A Mixed Heuristic for Circuit Partitioning 总被引:5,自引:0,他引:5
C. Gil J. Ortega M.G. Montoya R. Baños 《Computational Optimization and Applications》2002,23(3):321-340
As general-purpose parallel computers are increasingly being used to speed up different VLSI applications, the development of parallel algorithms for circuit testing, logic minimization and simulation, HDL-based synthesis, etc. is currently a field of increasing research activity. This paper describes a circuit partitioning algorithm which mixes Simulated Annealing (SA) and Tabu Search (TS) heuristics. The goal of such an algorithm is to obtain a balanced distribution of the target circuit among the processors of the multicomputer allowing a parallel CAD application for Test Pattern Generation to provide good efficiency. The results obtained indicate that the proposed algorithm outperforms both a pure Simulated Annealing and a Tabu Search. Moreover, the usefulness of the algorithm in providing a balanced workload distribution is demonstrated by the efficiency results obtained by a topological partitioning parallel test-pattern generator in which the proposed algorithm has been included. An extented algorithm that works with general graphs to compare our approach with other state of the art algorithms has been also included. 相似文献
27.
在前文工作的基础上,结合MNDO/EHMO分子轨道方法和自然杂化轨道方法,具体计算了CC键和CP键的核自旋偶合常数.计算结果表明,1JCC和1JCP主要由成键原子的轨道杂化作用和键极性这两种结构因素所决定.为从简单价键理论角度解释和计算1JCC和1JCP值提供了简便直观的方法. 相似文献
28.
E. Piscopiello A. Rosenauer A. Passaseo E. H. Montoya Rossi G. Van Tendeloo 《哲学杂志》2013,93(32):3857-3870
Using quantitative high-resolution transmission electron microscopy we studied the chemical morphology of wetting layers in In x Ga1? x As/GaAs quantum dot structures which were optimized for applications to optical devices operating around 1.3?µm. The samples are grown by low-pressure metal–organic chemical vapour deposition on GaAs substrates. The In concentration profiles of the wetting layers are evaluated with the composition evaluation by lattice fringe analysis method. The profiles reveal a clear signature of segregation. A fit of the profiles with the Muraki et al. model for segregation reveals a segregation efficiency R?=?0.65?±?0.05 at the growth temperature of 550°C, which is significantly lower than segregation efficiencies observed in samples grown by molecular beam epitaxy at similar temperatures. 相似文献
29.
Azide telechelics of poly(dimethylsiloxane) (PDMS), polypropylene oxide (PPO), and polyethylene oxide (PEO) were synthesized from the corresponding epoxy telechelics and characterized. These oligomeric azides were chain extended by reaction with bispropargyl ether of bisphenol A (BPEBA) through a copper‐catalyzed azide‐alkyne cycloaddition (CuAAC) reaction. PDMS manifested a faster reaction in contrast to PPO or PEO. The chain‐extended polymers underwent cross‐linking above 170°C through thermal cleavage of residual (terminal) azide groups. This was manifested in their rheograms and was further substantiated by FTIR and NMR spectroscopic analyses. Dynamic mechanical analyses of the cross‐linked polymers exhibited characteristic transitions of hard and soft segments, implying microphase separation in the system. Microscopic evaluation of the thermally cross‐linked sample revealed a porous morphology with microsized to nanosized pores. 相似文献
30.
Kenkera Rayappa Naveen Dr. Keshavananda Prabhu CP Dr. Ramanaskanda Braveenth Prof. Jang Hyuk Kwon 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(12):e202103532
Pure organic molecules based thermally activated delayed fluorescence (TADF) emitters have been successfully developed in recent years for their propitious application in highly efficient organic light emitting diodes (OLEDs). In the case of orange red emitters, the non-radiative process is known to be a serious issue due to its lower lying singlet energy level. However, recent studies indicate that there are tremendous efforts put to develop efficient orange red TADF emitters. In addition, the external quantum efficiency (EQE) of heteroaromatic based orange red TADF OLEDs surpassed 30 %. Such heteroaromatic type emitters showed wide emission spectra; therefore, more attention is being paid to develop highly efficient orange red TADF emitters along with good color purity. Herein, the recent progress of orange red TADF emitters based on molecular structures, such as cyanobenzene, heteroaromatic, naphthalimide, and boron-based acceptors, are reviewed. Further, our insight on these acceptors has been provided by their photophysical studies and device performances. Future perspectives of orange red TADF emitters for real practical applications are discussed. 相似文献