全文获取类型
收费全文 | 827篇 |
免费 | 58篇 |
学科分类
工业技术 | 885篇 |
出版年
2024年 | 2篇 |
2023年 | 12篇 |
2022年 | 14篇 |
2021年 | 38篇 |
2020年 | 28篇 |
2019年 | 27篇 |
2018年 | 28篇 |
2017年 | 33篇 |
2016年 | 30篇 |
2015年 | 28篇 |
2014年 | 53篇 |
2013年 | 82篇 |
2012年 | 75篇 |
2011年 | 89篇 |
2010年 | 71篇 |
2009年 | 57篇 |
2008年 | 52篇 |
2007年 | 30篇 |
2006年 | 30篇 |
2005年 | 21篇 |
2004年 | 17篇 |
2003年 | 15篇 |
2002年 | 20篇 |
2001年 | 6篇 |
2000年 | 2篇 |
1999年 | 6篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1980年 | 3篇 |
排序方式: 共有885条查询结果,搜索用时 15 毫秒
61.
Sofia Pettersson Dr. Violeta I. Pérez‐Nueno Dr. Maria Pau Mena Dr. Bonaventura Clotet Dr. José A. Esté Dr. José I. Borrell Dr. Jordi Teixidó Dr. 《ChemMedChem》2010,5(8):1272-1281
The CXCR4 receptor has been shown to interact with the human immunodeficiency virus (HIV) envelope glycoprotein gp120, leading to fusion of viral and cell membranes. Therefore, ligands that can attach to this receptor represent an important class of therapeutic agents against HIV, thus inhibiting the first step in the cycle of viral infection: the virus–cell entry/fusion. Herein we describe the in silico design, synthesis, and biological evaluation of novel monocyclam derivatives as HIV entry inhibitors. In vitro activity testing of these compounds in cell cultures against HIV strains revealed EC50 values in the low micromolar range without cytotoxicity at the concentrations tested. Docking and molecular dynamics simulations were performed to predict the binding interactions between CXCR4 and the novel monocyclam derivatives. A binding mode of these compounds is proposed which is consistent with the main existing site‐directed mutagenesis data on the CXCR4 co‐receptor. Moreover, molecular modeling comparisons were performed between these novel monocyclams, previously reported non‐cyclam compounds from which the monocyclams are derived, and the well‐known AMD3100 bicyclam CXCR4 inhibitors. Our results suggest that these three structurally diverse CXCR4 inhibitors bind to overlapping but not identical amino acid residues in the transmembrane regions of the receptor. 相似文献
62.
Víctor Falguera Jordi PagánSalvador Garza Alfonso GarvínAlbert Ibarz 《Food research international (Ottawa, Ont.)》2011,44(6):1580-1588
The effectiveness of ultraviolet irradiation in inactivating microorganisms has been known for decades. Nevertheless, in the processing of foodstuff other important issues must be considered, such as organoleptic or nutritional properties preservation. Ultraviolet irradiation constitutes an alternative to thermal treatment that is being studied and developed to obtain a better final product sensory quality, but without neglecting microbial safety. Moreover, it has been proved that this technology can be useful to decompose some toxins that are not affected by thermal processing. In this piece of work, the effect of UV irradiation on all of these contaminants and components of liquid food has been reviewed. 相似文献
63.
Factors influencing the soil-air partitioning and the strength of soils as a secondary source of polychlorinated biphenyls to the atmosphere 总被引:2,自引:0,他引:2
Cabrerizo A Dachs J Moeckel C Ojeda MJ Caballero G Barceló D Jones KC 《Environmental science & technology》2011,45(11):4785-4792
Soils are a major reservoir of persistent organic pollutants, and soil-air partitioning and exchange are key processes controlling the atmospheric concentrations and regional fate of pollutants. Here, we report and discuss the concentrations of polychlorinated biphenyls (PCBs) in soils, their measured fugacities in soil, the soil-air partition coefficients (K(SA)) and soil-air fugacity gradients in rural background areas of N-NE Spain and N-NW England. Four sampling campaigns were carried out to assess seasonal and daily variability and differences between sampling sites. K(SA) values were significantly dependent on soil temperature and soil organic matter quantity, and to a minor extent organic matter type. All the PCB congeners in the soil are close to equilibrium with the atmosphere at rural Ebro sites, but soil fugacities tend to be higher than ambient air fugacities in early and late summer, consistent with the influence of temperature on soil-air partitioning. Therefore, during warm periods, soils increment their strength as secondary sources to the atmosphere. The mixture of PCBs found in the atmosphere is clearly strongly influenced by the mixture of PCBs which escape from soil, with significant correlations between them (R(2) ranging between 0.35 and 0.74 and p-level <0.001 for the Ebro sampling sites). Conversely, the close-to-equilibrium to net sink status of rural UK sites, suggest a close coupling of air and soil concentrations, but it is not possible to elucidate the importance of these soils as secondary sources yet, and presumably there are still significant primary sources to the regional/global environment. 相似文献
64.
65.
Devis Tuia Jordi Muñoz-Marí Mikhail Kanevski Gustavo Camps-Valls 《Journal of Signal Processing Systems》2011,65(3):301-310
Traditional kernel classifiers assume independence among the classification outputs. As a consequence, each misclassification
receives the same weight in the loss function. Moreover, the kernel function only takes into account the similarity between
input values and ignores possible relationships between the classes to be predicted. These assumptions are not consistent
for most of real-life problems. In the particular case of remote sensing data, this is not a good assumption either. Segmentation
of images acquired by airborne or satellite sensors is a very active field of research in which one tries to classify a pixel
into a predefined set of classes of interest (e.g. water, grass, trees, etc.). In this situation, the classes share strong
relationships, e.g. a tree is naturally (and spectrally) more similar to grass than to water. In this paper, we propose a
first approach to remote sensing image classification using structured output learning. In our approach, the output space
structure is encoded using a hierarchical tree, and these relations are added to the model in both the kernel and the loss
function. The methodology gives rise to a set of new tools for structured classification, and generalizes the traditional
non-structured classification methods. Comparison to standard SVM is done numerically, statistically and by visual inspection
of the obtained classification maps. Good results are obtained in the challenging case of a multispectral image of very high
spatial resolution acquired with QuickBird over a urban area. 相似文献
66.
Jordi Cabana Laure Monconduit Dominique Larcher M. Rosa Palacín 《Advanced materials (Deerfield Beach, Fla.)》2010,22(35):E170-E192
Despite the imminent commercial introduction of Li‐ion batteries in electric drive vehicles and their proposed use as enablers of smart grids based on renewable energy technologies, an intensive quest for new electrode materials that bring about improvements in energy density, cycle life, cost, and safety is still underway. This Progress Report highlights the recent developments and the future prospects of the use of phases that react through conversion reactions as both positive and negative electrode materials in Li‐ion batteries. By moving beyond classical intercalation reactions, a variety of low cost compounds with gravimetric specific capacities that are two‐to‐five times larger than those attained with currently used materials, such as graphite and LiCoO2, can be achieved. Nonetheless, several factors currently handicap the applicability of electrode materials entailing conversion reactions. These factors, together with the scientific breakthroughs that are necessary to fully assess the practicality of this concept, are reviewed in this report. 相似文献
67.
Víctor Falguera Oriol Miarnau Jordi Pagán Albert Ibarz 《European Food Research and Technology》2011,233(6):1075-1079
In recent years, some beneficial effects on health of melanins that are formed as a result of polyphenol oxidase action have
been discovered. However, it is also known that similar polymers have a detrimental effect on proteases activity. Thus, the
aim of this work was to assay whether melanins from two different substrates act as carboxypeptidase A and carboxypeptidase
B inhibitors. It was found that melanin synthesized from l-tyrosine decreases both the apparent affinity between carboxypeptidases and their substrates and the maximum reaction rate.
Consequently, it is possible to conclude that these melanins inhibit CPA and CPB activity in a mixed way. On the contrary,
no inhibition was found in the case of melanin synthesized from 4-methylcatechol. 相似文献
68.
Regional economic dynamics and convergence in the European Union 总被引:4,自引:1,他引:3
Enrique López-Bazo Esther Vayá Antonio J. Mora Jordi Suriñach 《The Annals of Regional Science》1999,33(3):343-370
This paper uses an alternative approach to convergence analysis, which, in our opinion, is richer than those traditionally
proposed. We believe that the evolution of the whole regional distribution is what matters, not that of an average or representative economy, implicit in the or convergence concepts. Moreover, when analyzing inequality among regional economies, geographic space acquires a preeminent
role. We therefore apply spatial association tests recently developed in the spatial econometrics literature and relate them
to convergence analysis. Specifically, we apply this methodology to the analysis of regional dynamics and convergence in the
European Union (EU). In this context, the progress made in the integration process has highlighted the question of economic
disparities at regional level. The process of convergence came to an end in the late seventies, coinciding with major changes
in economic activity. This paper shows how these factors appear to have provoked a regionally differentiated response which,
though significant, did not, in all likelihood, exacerbate the decrease in regional inequalities. 相似文献
69.
The isothermal crystallization behavior of a segmented copolymer constituted by hard blocks of polyglycolide and soft segments derived from the copolymerization of glycolide and trimethylene carbonate was investigated. This polymer has applied relevance because it is one of the most widely used for bioabsorbable surgical sutures. Calorimetric, optical microscopy, and infrared techniques were combined to understand the thermal properties and the different factors that influence the crystallization process. Basically, only the hard blocks crystallized, although certain processing conditions allowed performing an additional crystallization associated with small lamellar domains of the soft segment. Crystallization from both the melt and the glass state rendered positive spherulites with a fibrillar texture. The observed unusual sign of birefringence was a consequence of the close packing structure of polyglycolide, which was also corroborated by electron diffraction patterns. Crystallization was characterized by an athermal nucleation, which allowed accurate estimation of the secondary nucleation parameter by using the calorimetric data only. Significant differences in the Avrami exponent (from 2.32 to 1.45) were found between the cold and hot isothermal crystallizations. The stronger geometric constraints observed in the crystallization from the glass state were also corroborated by FTIR analyses. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
70.
Xavier Ruiz Jordi Pallarés 《International Journal of Heat and Mass Transfer》2012,55(23-24):6966-6978
Three different shear cell arrangements are considered here in order to discuss and compare the accuracy of their measurements at low and moderate Rayleigh number, that is to say, in reduced gravity environments. To do so, specific numerical procedures have been designed in order to quantitatively estimate the corresponding associated errors as a function of time and at the end of the diffusive process. The present work clearly shows that the interdiffusion-couple configuration is, from the point of view of accuracy, the worst one. 相似文献