全文获取类型
收费全文 | 449篇 |
免费 | 27篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 156篇 |
金属工艺 | 12篇 |
机械仪表 | 14篇 |
建筑科学 | 12篇 |
能源动力 | 14篇 |
轻工业 | 66篇 |
水利工程 | 4篇 |
石油天然气 | 2篇 |
无线电 | 21篇 |
一般工业技术 | 69篇 |
冶金工业 | 12篇 |
原子能技术 | 1篇 |
自动化技术 | 90篇 |
出版年
2024年 | 8篇 |
2023年 | 10篇 |
2022年 | 27篇 |
2021年 | 35篇 |
2020年 | 23篇 |
2019年 | 39篇 |
2018年 | 36篇 |
2017年 | 23篇 |
2016年 | 31篇 |
2015年 | 19篇 |
2014年 | 17篇 |
2013年 | 36篇 |
2012年 | 23篇 |
2011年 | 42篇 |
2010年 | 13篇 |
2009年 | 18篇 |
2008年 | 18篇 |
2007年 | 9篇 |
2006年 | 6篇 |
2005年 | 6篇 |
2004年 | 4篇 |
2003年 | 8篇 |
2002年 | 5篇 |
2001年 | 7篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
排序方式: 共有476条查询结果,搜索用时 15 毫秒
1.
Luccas M. Barata Eloísa H. Andrade Alessandra R. Ramos Oriel F. de Lemos William N. Setzer Kendall G. Byler Jos Guilherme S. Maia Joyce Kelly R. da Silva 《International journal of molecular sciences》2021,22(2)
This study evaluated the chemical compositions of the leaves and fruits of eight black pepper cultivars cultivated in Pará State (Amazon, Brazil). Hydrodistillation and gas chromatography–mass spectrometry were employed to extract and analyze the volatile compounds, respectively. Sesquiterpene hydrocarbons were predominant (58.5–90.9%) in the cultivars “Cingapura”, “Equador”, “Guajarina”, “Iaçará”, and “Kottanadan”, and “Bragantina”, “Clonada”, and “Uthirankota” displayed oxygenated sesquiterpenoids (50.6–75.0%). The multivariate statistical analysis applied using volatile composition grouped the samples into four groups: γ-Elemene, curzerene, and δ-elemene (“Equador”/“Guajarina”, I); δ-elemene (“Iaçará”/“Kottanadan”/“Cingapura”, II); elemol (“Clonada”/“Uthirankota”, III) and α-muurolol, bicyclogermacrene, and cubebol (“Bragantina”, IV). The major compounds in all fruit samples were monoterpene hydrocarbons such as α-pinene, β-pinene, and limonene. Among the cultivar leaves, phenolics content (44.75–140.53 mg GAE·g−1 FW), the enzymatic activity of phenylalanine-ammonia lyase (20.19–57.22 µU·mL−1), and carotenoids (0.21–2.31 µg·mL−1) displayed significant variations. Due to black pepper’s susceptibility to Fusarium infection, a molecular docking analysis was carried out on Fusarium protein targets using each cultivar’s volatile components. F. oxysporum endoglucanase was identified as the preferential protein target of the compounds. These results can be used to identify chemical markers related to the susceptibility degree of black pepper cultivars to plant diseases prevalent in Pará State. 相似文献
2.
Rinaldo Gregorio Luiz Francisco Malmonge Guilherme Fontes Leal Ferreira Wilson Nunes Dos Santos Luiz Henrique Capparelli Mattoso 《应用聚合物科学杂志》2003,87(5):752-758
The real (ε′) and imaginary (ε″) components of the complex permittivity of blends of PVDF [poly(vinylidene fluoride)] with POMA [poly(o‐methoxyaniline)] doped with toluenosulfonic acid (TSA) containing 1, 2.5, and 5 wt % POMA–TSA were determined in the frequency interval between 102 and 3 × 106 Hz and in the temperature range from ?120 up to 120°C. It was observed that the values of ε′ and ε″ had a greater increase with the POMA–TSA content and with a temperature in the region of frequencies below 10 kHz. This effect decreased with frequency and it was attributed to interfacial polarization. This polarization was caused by the blend heterogeneity, formed by conductive POMA–TSA agglomerates dispersed in an insulating matrix of PVDF. The equation of Maxwell–Garnett, modified by Cohen, was used to evaluate the permittivity and conductivity behavior of POMA–TSA in the blends. A strong decrease was observed in POMA–TSA conductivity in the blend, which was bigger the lower the POMA–TSA content in the blend. This decrease could have been caused either by the POMA dedoping during the blend preparation process or by its dispersion into the insulating matrix. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 752–758, 2003 相似文献
3.
Elaine C. Lopes Pereira Bluma G. Soares Adriana A. Silva Guilherme M. O. Barra 《应用聚合物科学杂志》2021,138(39):51164
Conducting polymer composites constituted by co-continuous poly (vinylidene fluoride) (PVDF)/ ethylene- vinyl acetate copolymer (EVA) blends with multiwalled carbon nanotube (CNT) were prepared by melt mixing using different procedures. The effect of the master batch approach on the conductivity, morphology, mechanical, thermal and rheological properties of PVDF/EVA/CNT nanocomposites was compared with that based on one step mixing strategy. The selective extraction experiments revealed that CNT was preferentially localized in the EVA phase in all situations, even when PVDF@CNT master batch was employed. Nanocomposites prepared with EVA@CNT master batch displayed higher conductivity, whose value reached around 10−1 S m−1 with the addition of 0.56 vol% of CNT. The better electrical performance was attributed to the better distribution of the filler, as indicated by transmission electron microscopy and rheological behavior. The electrical and rheological behavior were also investigated as a function of the CNT content. 相似文献
4.
Guilherme T. de Assis Alberto H. F. Laender Marcos André Gonçalves Altigran S. da Silva 《World Wide Web》2009,12(3):285-319
Focused crawlers have as their main goal to crawl Web pages that are relevant to a specific topic or user interest, playing
an important role for a great variety of applications. In general, they work by trying to find and crawl all kinds of pages
deemed as related to an implicitly declared topic. However, users are often not simply interested in any document about a
topic, but instead they may want only documents of a given type or genre on that topic to be retrieved. In this article, we
describe an approach to focused crawling that exploits not only content-related information but also genre information present
in Web pages to guide the crawling process. This approach has been designed to address situations in which the specific topic
of interest can be expressed by specifying two sets of terms, the first describing genre aspects of the desired pages and
the second related to the subject or content of these pages, thus requiring no training or any kind of preprocessing. The
effectiveness, efficiency and scalability of the proposed approach are demonstrated by a set of experiments involving the
crawling of pages related to syllabi of computer science courses, job offers in the computer science field and sale offers
of computer equipments. These experiments show that focused crawlers constructed according to our genre-aware approach achieve
levels of F1 superior to 88%, requiring the analysis of no more than 65% of the visited pages in order to find 90% of the
relevant pages. In addition, we experimentally analyze the impact of term selection on our approach and evaluate a proposed
strategy for semi-automatic generation of such terms. This analysis shows that a small set of terms selected by an expert
or a set of terms specified by a typical user familiar with the topic is usually enough to produce good results and that such
a semi-automatic strategy is very effective in supporting the task of selecting the sets of terms required to guide a crawling
process. 相似文献
5.
Guilherme Ferreira Gomes Camila Aparecida Diniz Sebastião Simões da CunhaJr. Antonio Carlos AncelottiJr. 《Journal of Failure Analysis and Prevention》2017,17(4):740-749
The investigation of possible failures in composite materials is a matter of very great importance, and the Tsai-Wu criterion is an effective criterion for analyzing those flaws in anisotropic materials and defining whether the material at a given load will or will not suffer structural failure. In this study, an optimization procedure is proposed to minimize the maximum value of Tsai-Wu of laminated composite tubes subject to axial loading. Artificial neural networks and genetic algorithms are chosen as optimization tools. The results of this study show that the developed algorithm converges faster. Then, the maximum Tsai-Wu value is used as the objective function and the fiber orientations are the constraints in the optimization process. The results yielded by them are compared and discussed. Optimal results are compared with respect to the usual initial design. The design approach is recommended for structures where composites are the key load-carrying members such as orthopedic prosthesis. 相似文献
6.
Caroline ConcattoAuthor VitaeJoão AlmeidaAuthor Vitae Guilherme FachiniAuthor VitaeMarcos HervéAuthor Vitae Fernanda KastensmidtAuthor Vitae Érika CotaAuthor VitaeMarcelo LubaszewskiAuthor Vitae 《Journal of Parallel and Distributed Computing》2011,71(5):664-674
We propose an effective and low cost method to increase the yield and the lifetime of torus NoCs. The method consists in detecting and diagnosing NoC interconnect faults using BIST structures and activating alternative paths for the faulty links. Alternative paths use the inherent redundancy of the torus topology, thus leading to minimal performance, area, and power overhead. We assume an extended interconnect fault model comprising stuck-at and pairwise shorts within a single link or between any two links in the network. Experimental results for a 3×3 NoC show that the proposed approach can correctly diagnose 93% of all possible interconnect faults and can mitigate 42% of those faults (representing 94.4% of the solvable faults) with a worst case performance penalty of 8% and 1% of area overhead. We also demonstrate the scalability of the method by presenting its application to larger NoCs. 相似文献
7.
8.
Arilo Claudio Dias-Neto Guilherme Horta Travassos 《Information and Software Technology》2009,51(11):1487-1504
Selecting software technologies for software projects represents a challenge to software engineers. It is known that software projects differ from each other by presenting different characteristics that can complicate the selection of such technologies. This is not different when considering model-based testing. There are many approaches with different characteristics described in the technical literature that can be used in software projects. However, there is no indication as to how they can fit a software project. Therefore, a strategy to select model-based testing approaches for software projects called Porantim is fully described in this paper. Porantim is based on a body of knowledge describing model-based testing approaches and their characterization attributes (identified by secondary and primary experimental studies), and a process to guide by adequacy and impact criteria regarding the use of this sort of software technology that can be used by software engineers to select model-based testing approaches for software projects. 相似文献
9.
Celina M.H. de Figueiredo Guilherme D. da Fonseca Vinicius G.P. de Sa Jeremy Spinrad 《Algorithmica》2006,46(2):149-180
A homogeneous set is a non-trivial module of a graph, i.e. a non-empty,
non-unitary, proper subset of a graph's vertices such that all its elements
present exactly the same outer neighborhood. Given two graphs
the Homogeneous Set Sandwich Problem (HSSP) asks whether there
exists a sandwich graph
which
has a homogeneous set. In 2001 Tang et al. published
an all-fast
algorithm which was recently proven wrong, so that the HSSP's known upper bound would have been reset
thereafter at the former
determined by Cerioli et al. in 1998. We present, notwithstanding, new deterministic
algorithms which have it established at
We give as
well two even faster
randomized algorithms, whose simplicity might
lend them didactic usefulness. We believe that, besides providing efficient
easy-to-implement procedures to solve it, the study of these new approaches
allows a fairly thorough understanding of the problem. 相似文献
10.
Mariane Severino Mohammed Gagaoua Welder Baldassini Richard Ribeiro Juliana Torrecilhas Guilherme Pereira Rogrio Curi Luis Artur Chardulo Pedro Padilha Otvio Machado Neto 《International journal of molecular sciences》2022,23(20)
Proteomics has been widely used to study muscle biology and meat quality traits from different species including beef. Beef proteomics studies allow a better understanding of the biological processes related to meat quality trait determination. This study aimed to decipher by means of two-dimensional electrophoresis (2D-PAGE), mass spectrometry and bioinformatics the changes in post-mortem muscle with a focus on proteins differentially expressed in the Longissimus thoracis (LT) muscle of immunocastrated young heifers and steers. Carcass traits, chemical composition, pH, instrumental color (L*, a*, b*), cooking loss and Warner-Bratzler shear force (WBSF) of meat from F1 Montana-Nellore cattle were also evaluated. Backfat thickness (BFT) and intramuscular fat content (IMF) were 46.8% and 63.6% higher in heifers (p < 0.05), respectively, while evaporation losses (EL) were 10.22% lower compared to steers. No differences (p > 0.05) were observed for tenderness evaluated by WBSF (3, 10, and 17 days post-mortem), pH, and color traits (L*, a* and b*) between the experimental groups. The study revealed several proteins to be differentially expressed proteins in heifers compared steers (p < 0.05). In heifers, proteins involved in nutrient transport (TF, ALB, and MB), energy metabolism (ALDOA, GAPDH, and PKM), and oxidative stress and response to stress (HSPA8 and CA3) were associated with a greater BFT and IMF deposition. The higher expression of these proteins indicated greater oxidative capacity and lower glycolytic activity in the LT muscle of heifers. In steers, there was greater abundance of protein expression related to muscle contraction and proteins of structure (ACTA1, TPM2 and TNNT3), energy metabolism (ENO1, ENO3, PYGM, PGM1 and TPI1) and ATP metabolism (ATP5F1B, PEBP1 and AK1), indicating greater glycogenolysis in LT muscle, suggesting a shift in the glycolytic/oxidative fibers of steers. 相似文献