全文获取类型
收费全文 | 960篇 |
免费 | 66篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 330篇 |
金属工艺 | 8篇 |
机械仪表 | 21篇 |
建筑科学 | 33篇 |
矿业工程 | 3篇 |
能源动力 | 23篇 |
轻工业 | 343篇 |
水利工程 | 8篇 |
石油天然气 | 10篇 |
无线电 | 47篇 |
一般工业技术 | 97篇 |
冶金工业 | 22篇 |
原子能技术 | 3篇 |
自动化技术 | 77篇 |
出版年
2024年 | 4篇 |
2023年 | 16篇 |
2022年 | 77篇 |
2021年 | 85篇 |
2020年 | 26篇 |
2019年 | 43篇 |
2018年 | 38篇 |
2017年 | 38篇 |
2016年 | 41篇 |
2015年 | 35篇 |
2014年 | 48篇 |
2013年 | 66篇 |
2012年 | 77篇 |
2011年 | 80篇 |
2010年 | 53篇 |
2009年 | 38篇 |
2008年 | 54篇 |
2007年 | 52篇 |
2006年 | 33篇 |
2005年 | 29篇 |
2004年 | 22篇 |
2003年 | 17篇 |
2002年 | 9篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 6篇 |
1993年 | 6篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1987年 | 2篇 |
1983年 | 2篇 |
1980年 | 1篇 |
排序方式: 共有1028条查询结果,搜索用时 15 毫秒
1.
Ana Piar-Gutierrez Cristina García-Fontana Beatriz García-Fontana Manuel Muoz-Torres 《International journal of molecular sciences》2022,23(15)
Recent scientific evidence has shown an increased risk of fractures in patients with obesity, especially in those with a higher visceral adipose tissue content. This contradicts the old paradigm that obese patients were more protected than those with normal weight. Specifically, in older subjects in whom there is a redistribution of fat from subcutaneous adipose tissue to visceral adipose tissue and an infiltration of other tissues such as muscle with the consequent sarcopenia, obesity can accentuate the changes characteristic of this age group that predisposes to a greater risk of falls and fractures. Other factors that determine a greater risk in older subjects with obesity are chronic proinflammatory status, altered adipokine secretion, vitamin D deficiency, insulin resistance and reduced mobility. On the other hand, diagnostic tests may be influenced by obesity and its comorbidities as well as by body composition, and risk scales may underestimate the risk of fractures in these patients. Weight loss with physical activity programs and cessation of high-fat diets may reduce the risk. Finally, more research is needed on the efficacy of anti-osteoporotic treatments in obese patients. 相似文献
2.
Luana Beatriz dos Santos Nascimento Massimiliano Tattini 《International journal of molecular sciences》2022,23(9)
Plants evolved an impressive arsenal of multifunctional specialized metabolites to cope with the novel environmental pressures imposed by the terrestrial habitat when moving from water. Here we examine the multifarious roles of flavonoids in plant terrestrialization. We reason on the environmental drivers, other than the increase in UV-B radiation, that were mostly responsible for the rise of flavonoid metabolism and how flavonoids helped plants in land conquest. We are reasonably based on a nutrient-deficiency hypothesis for the replacement of mycosporine-like amino acids, typical of streptophytic algae, with the flavonoid metabolism during the water-to-land transition. We suggest that flavonoids modulated auxin transport and signaling and promoted the symbiosis between plants and fungi (e.g., arbuscular mycorrhizal, AM), a central event for the conquest of land by plants. AM improved the ability of early plants to take up nutrients and water from highly impoverished soils. We offer evidence that flavonoids equipped early land plants with highly versatile “defense compounds”, essential for the new set of abiotic and biotic stressors imposed by the terrestrial environment. We conclude that flavonoids have been multifunctional since the appearance of plants on land, not only acting as UV filters but especially improving both nutrient acquisition and biotic stress defense. 相似文献
3.
Claudio Bernardazzi Morgana Teixeira Lima Castelo-Branco Beatriz Pêgo Beatriz Elias Ribeiro Siane Lopes Bittencourt Rosas Patrícia Teixeira Santana Joo Carlos Machado Camille Leal Fabiano Thompson Robson Coutinho-Silva Heitor Siffert Pereira de Souza 《International journal of molecular sciences》2022,23(9)
4.
Luna Karlos; Higham Philip A.; Martín-Luengo Beatriz 《Canadian Metallurgical Quarterly》2011,17(2):148
We report two experiments that investigated the regulation of memory accuracy with a new regulatory mechanism: the plurality option. This mechanism is closely related to the grain-size option but involves control over the number of alternatives contained in an answer rather than the quantitative boundaries of a single answer. Participants were presented with a slideshow depicting a robbery (Experiment 1) or a murder (Experiment 2), and their memory was tested with five-alternative multiple-choice questions. For each question, participants were asked to generate two answers: a single answer consisting of one alternative and a plural answer consisting of the single answer and two other alternatives. Each answer was rated for confidence (Experiment 1) or for the likelihood of being correct (Experiment 2), and one of the answers was selected for reporting. Results showed that participants used the plurality option to regulate accuracy, selecting single answers when their accuracy and confidence were high, but opting for plural answers when they were low. Although accuracy was higher for selected plural than for selected single answers, the opposite pattern was evident for confidence or likelihood ratings. This dissociation between confidence and accuracy for selected answers was the result of marked overconfidence in single answers coupled with underconfidence in plural answers. We hypothesize that these results can be attributed to overly dichotomous metacognitive beliefs about personal knowledge states that cause subjective confidence to be extreme. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
5.
Marilena Isabella Zappia Gabriele Bianca Sebastiano Bellani Michele Serri Leyla Najafi Reinier Oropesa‐Nuez Beatriz Martín‐García Daniel Boua David Sedmidubský Vittorio Pellegrini Zdenk Sofer Anna Cupolillo Francesco Bonaccorso 《Advanced functional materials》2020,30(10)
Gallium selenide (GaSe) is a layered compound, which has been exploited in nonlinear optical applications and photodetectors due to its anisotropic structure and pseudodirect optical gap. Theoretical studies predict that its 2D form is a potential photocatalyst for water splitting reactions. Herein, the photoelectrochemical (PEC) characterization of GaSe nanoflakes (single‐/few‐layer flakes), produced via liquid phase exfoliation, for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in both acidic and alkaline media is reported. In 0.5 m H2SO4, the GaSe photoelectrodes display the best PEC performance, corresponding to a ratiometric power‐saved metric for HER (Φsaved,HER) of 0.09% and a ratiometric power‐saved metric for OER (Φsaved,OER) of 0.25%. When used as PEC‐type photodetectors, GaSe photoelectrodes show a responsivity of ≈0.16 A W?1 upon 455 nm illumination at a light intensity of 63.5 µW cm?2 and applied potential of ?0.3 V versus reversible hydrogen electrode (RHE). Stability tests of GaSe photodetectors demonstrated a durable operation over tens of cathodic linear sweep voltammetry scans in 0.5 m H2SO4 for HER. In contrast, degradation of photoelectrodes occurred in both alkaline and anodic operation due to the highly oxidizing environment and O2‐induced (photo)oxidation effects. The results provide new insight into the PEC properties of GaSe nanoflakes for their exploitation in photoelectrocatalysis, PEC‐type photodetectors, and (bio)sensors. 相似文献
6.
Beatriz Marcotegui Ferran MarquÉs Joseph Ramon Morros Montse PardÀs Philippe Salembier 《电信纪事》1997,52(7-8):380-387
This paper deals with the relation between segmentation for coding and rate control. The efficiency of a segmentation-based coding scheme heavily relies on this step that defines how many and which regions have to be segmented. In this paper, we show that this problem can be formulated as a rate/distortion problem. The proposed solution not only controls the segmentation, but also defines the coding strategy to be used in each region. Together with the general approach, several simplified versions of the segmentation control are proposed and discussed. 相似文献
7.
A bottom-up segmentation method is presented as a first step of object based coding. An initial partition is created based on connected filters. The iterative fusion algorithm merges the most similar regions until the target is reached. As the regions become bigger, more complex criterion, like similarity of texture or of motion are used. The algorithm offers a good balance between time stability and the ability to cope with the apparition of new regions. 相似文献
8.
Jesús Agudelo José Antonio Suárez Agustín Olano María Jesús Callejo María Beatriz Colomo 《European Food Research and Technology》1994,199(1):26-28
Gas chromatography was used to study the polysaccharides present in samples that exhibited significant microbially induced viscosity values. Alterations in the media considered were related to the percentage glucose content and the total polysaccharide content. 相似文献
9.
Jaime Pitarch José M Catalá-Civera Felipe L Pe?aranda-Foix Beatriz García-Ba?os 《The Journal of microwave power and electromagnetic energy》2007,41(4):46-61
Waveguide structures are very popular in the microwave power industry due to their power handling capabilities. Modal expansion of the waveguide fields and application of the circuit theory allow for the division of a complex device into several simpler sections which can be analyzed separately with the best suited method. The modal techniques can be divided into two groups--those which analyze junctions or discontinuities and those which examine propagation characteristics. In this paper, a review of modal techniques for high power applications is given. Modal expansion of the fields in the waveguides is then performed and applied to modeling of k-furcated waveguides. The modal analysis based on the Coupled Mode Method is described for the waveguides partially filled with isotropic materials. A hybrid modal analysis coupled with Finite Element Method suitable for more complex waveguide structures is also described. Computational results obtained for some real-life microwave devices are presented. Excellent agreement was found when comparing the results with those generated with a commercial FDTD simulator demonstrates the validity and reliability of the proposed method. 相似文献
10.
P.M. Santos Vitor Costa M.C. Gomes Beatriz Borges Mário Lança 《Microelectronics Journal》2007,38(1):35-40
This work presents the design of LDMOS transistors fully compatible with a standard CMOS process, only requiring mask layout manipulation. A conventional 0.35 μm CMOS process was elected to demonstrate the viability of the approach. The prototyped LDMOS transistor exhibits a breakdown voltage of 24 V, which represents an improvement of 31% when compared with the high-voltage extended-drain NMOS available in the process library, while other static parameters remain in the same range. Furthermore, this solution enables the CMOS integration of a high-voltage pass-transistor, as a consequence of the formation of an isolated lightly doped p-type region inside the n-well. 相似文献