全文获取类型
收费全文 | 4449篇 |
免费 | 391篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 70篇 |
综合类 | 4篇 |
化学工业 | 1069篇 |
金属工艺 | 107篇 |
机械仪表 | 146篇 |
建筑科学 | 151篇 |
矿业工程 | 6篇 |
能源动力 | 195篇 |
轻工业 | 968篇 |
水利工程 | 32篇 |
石油天然气 | 32篇 |
无线电 | 261篇 |
一般工业技术 | 704篇 |
冶金工业 | 448篇 |
原子能技术 | 33篇 |
自动化技术 | 620篇 |
出版年
2024年 | 18篇 |
2023年 | 44篇 |
2022年 | 76篇 |
2021年 | 207篇 |
2020年 | 153篇 |
2019年 | 188篇 |
2018年 | 218篇 |
2017年 | 221篇 |
2016年 | 223篇 |
2015年 | 135篇 |
2014年 | 203篇 |
2013年 | 373篇 |
2012年 | 293篇 |
2011年 | 295篇 |
2010年 | 239篇 |
2009年 | 259篇 |
2008年 | 214篇 |
2007年 | 168篇 |
2006年 | 137篇 |
2005年 | 100篇 |
2004年 | 85篇 |
2003年 | 75篇 |
2002年 | 81篇 |
2001年 | 62篇 |
2000年 | 43篇 |
1999年 | 55篇 |
1998年 | 132篇 |
1997年 | 96篇 |
1996年 | 84篇 |
1995年 | 60篇 |
1994年 | 31篇 |
1993年 | 35篇 |
1992年 | 20篇 |
1991年 | 32篇 |
1990年 | 15篇 |
1989年 | 27篇 |
1988年 | 17篇 |
1987年 | 17篇 |
1986年 | 13篇 |
1985年 | 12篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1978年 | 11篇 |
1976年 | 14篇 |
1975年 | 6篇 |
1972年 | 5篇 |
1969年 | 4篇 |
排序方式: 共有4846条查询结果,搜索用时 31 毫秒
1.
2.
A proper detection and classification of defects in steel sheets in real time have become a requirement for manufacturing these products, largely used in many industrial sectors. However, computers used in the production line of small to medium size companies, in general, lack performance to attend real-time inspection with high processing demands. In this paper, a smart deep convolutional neural network for using in real-time surface inspection of steel rolling sheets is proposed. The architecture is based on the state-of-the-art SqueezeNet approach, which was originally developed for usage with autonomous vehicles. The main features of the proposed model are: small size and low computational burden. The model is 10 to 20 times smaller when compared to other networks designed for the same task, and more than 700 times smaller than general networks. Also, the number of floating-point operations for a prediction is about 50 times lower than the ones used for similar tasks. Despite its small size, the proposed model achieved near-perfect accuracy on a public dataset of 1800 images of six types of steel rolling defects. 相似文献
3.
L.L. Oliveira J.A. Cortés B.S. Caldeira T. Strusch U. Wiedwald A.Z. Simoes 《Ceramics International》2021,47(15):20768-20780
In this work, praseodymium (Pr) doped cerium oxide (CeO2) was prepared using the microwave-assisted hydrothermal method (MAH) and the properties were investigated by X-ray diffraction analysis (XRD), Raman spectroscopy, Field Emission Gun Scanning Electron Microscope (FEG-SEM), BET method, Photoluminescence spectroscopy (PL), Fourier-transform infrared spectroscopy (FTIR), Ultraviolet–visible spectroscopy (UV–Vis), Electron paramagnetic resonance spectroscopy (EPR) and Magnetometry. The results showed that increasing the Pr-doping promotes a structural disorder due to increased oxygen vacancies. XRD confirmed a cubic structure without deleterious phases with modifications in the structure caused by alteration in the cerium oxidation state as well as changes in the crystallite size and strain obtained by Wellinson-Hall method. Raman spectroscopy shows that changing the Pr content results in samples with different defect densities at short range. FEG-SEM showed that the nanocrystals are agglomerated with small particles tend to aggregate spontaneously to decrease the surface energy. BET method showed that the Pr doping results in a gain of specific surface area. PL indicated that Pr3+ leads to distinct emissions; red emission associated to oxygen vacancies located near the conduction band (shallow defects), green emission associated to electron-hole recombination and orange emission associated to shallow defects and electron-hole recombination. FTIR indicated the complete process of nucleation with no other phase. UV–Vis showed the transitions between oxygen 2p, cerium 4f and praseodymium 4f states. The EPR signal shows events occurring around 344 mT. These events can be related due the presence of paramagnetic elements containing unpaired electrons, such as Ce (III), which is indicative of cerium reduction caused by Pr ions, as evidenced by Rietveld data. Regardless of the Pr concentration used in this research, the magnetic measurements show a superparamagnetic system below the blocking temperature of ~20 K and a paramagnetic system above this temperature, which indicates no significant changes in the average size of the nanoparticles. Surface area, crystallite size and the temperature are important parameters, which control the magnetic properties of such N-type semiconductors. 相似文献
4.
Lipase production by solid‐state fermentation of olive pomace in tray‐type and pressurized bioreactors 下载免费PDF全文
5.
The , and mixed dynamic output feedback control of Markov jump linear systems in a partial observation context is studied through an iterative approach. By partial information, we mean that neither the state variable x(k) nor the Markov chain θ(k) are available to the controller. Instead, we assume that the controller relies only on an output y(k) and a measured variable coming from a detector that provides the only information of the Markov chain θ(k). To solve the problem, we resort to an iterative method that starts with a state‐feedback controller and solves at each iteration a linear matrix inequality optimization problem. It is shown that this iterative algorithm yields to a nonincreasing sequence of upper bound costs so that it converges to a minimum value. The effectiveness of the iterative procedure is illustrated by means of two examples in which the conservatism between the upper bounds and actual costs is significantly reduced. 相似文献
6.
de Siqueira Gustavo Oliveira Canuto Sérgio Gonçalves Marcos André Laender Alberto H. F. 《International Journal on Digital Libraries》2020,21(1):61-73
International Journal on Digital Libraries - Throughout the history of science, different knowledge areas have collaborated to overcome major research challenges. The task of associating a... 相似文献
7.
Biogenic amines assessment during different stages of the canning process of skipjack tuna (Katsuwonus pelamis) 下载免费PDF全文
Roberta Garcia Barbosa Luciano Valdemiro Gonzaga Eduarda Lodetti Gisele Olivo Ana Carolina Oliveira Costa Santiago Pedro Aubourg Roseane Fett 《International Journal of Food Science & Technology》2018,53(5):1236-1245
The present research focused on the biogenic amines (BAs) formation in skipjack tuna (Katsuwonus pelamis) throughout the whole canning process. In agreement with its wide employment on this species, on‐board brine immersion freezing (BIF) was tested as post‐mortem processing. The study included fish samples corresponding to different stages of the canning process such as frozen, thawed, cooked and canned; after cooking, two kinds of tuna muscles were considered, that is, whole fillets (main product) and grated muscle (off‐product arising from small pieces). For the BAs (tryptamine, putrescine, cadaverine, histamine, spermidine and spermine) assessment, an HPLC‐DAD method was developed and validated in skipjack tuna samples, in agreement with different parameters such as suitability, linearity, limits of detection and quantification, precision, accuracy and robustness. Tuna submitted on‐board to BIF procedure provided low levels of spermine and spermidine (up to 27.6 mg kg?1), while contents on the remaining BAs maintained below the limit of detection. Throughout the different stages of the canning process, skipjack tuna showed a low formation of most BAs; interestingly, histamine content was found below 10.6 mg kg?1 level. The highest values were obtained for spermidine, these related to cooked grated tuna (from 22.6 to 66.7 mg kg?1) and canned grated tuna (from 70.6 to 104.4 mg kg?1). Values for pH assessment in all kinds of tuna samples corroborated the results obtained for BAs determination. BIF procedure proved to be an amenable post‐mortem processing to guarantee the quality of canned skipjack tuna. 相似文献
8.
Cristina Dai Prá Martens Franklin Jean Machado Mauro Luiz Martens Filipe Quevedo Pires de Oliveira e Silva Henrique Mello Rodrigues de Freitas 《International Journal of Project Management》2018,36(2):255-266
Entrepreneurial orientation (EO) is a strategic posture of an organization, and it is related to basic policies and practices for the development of entrepreneurial actions looking for creating competitive advantages. This study develops and tests a model of the relationship between entrepreneurial orientation and project success in Brazilian context. As quantitative research, a survey was used to collect data. A sample of 100 valid answers from project practitioners was treated through the structural equation modeling method. As research implications, the main result points out the positive correlation between the entrepreneurial orientation and the project success, contributing to the development of this research subject and helping to minimize the gap in the literature that addresses the relationship between project success and EO. In practical terms, understanding that innovativeness, risk taking, proactiveness, autonomy and competitive aggressiveness (the dimensions of the EO) can contribute to project success and can also indirectly impact on organizational performance, could help organizations get competitive advantage when developing correlate factors. Finally, the results suggest that practices of project management can be aligned to the firm's entrepreneurial orientation to enable firms to attain better results in their projects and generate a competitive advantage. On other hand, given the proportion of the impact of EO on project success (20.3%) identified in this study, it is critical that project management professionals expand their horizon to recognize other factors that affect project success. 相似文献
9.
Ana Rita Gomes Nasim Bahram Sangani Tiago G. Fernandes M. Margarida Diogo Leopold M. G. Curfs Chris P. Reutelingsperger 《International journal of molecular sciences》2020,21(24)
The central nervous system (CNS) is the most complex structure in the body, consisting of multiple cell types with distinct morphology and function. Development of the neuronal circuit and its function rely on a continuous crosstalk between neurons and non-neural cells. It has been widely accepted that extracellular vesicles (EVs), mainly exosomes, are effective entities responsible for intercellular CNS communication. They contain membrane and cytoplasmic proteins, lipids, non-coding RNAs, microRNAs and mRNAs. Their cargo modulates gene and protein expression in recipient cells. Several lines of evidence indicate that EVs play a role in modifying signal transduction with subsequent physiological changes in neurogenesis, gliogenesis, synaptogenesis and network circuit formation and activity, as well as synaptic pruning and myelination. Several studies demonstrate that neural and non-neural EVs play an important role in physiological and pathological neurodevelopment. The present review discusses the role of EVs in various neurodevelopmental disorders and the prospects of using EVs as disease biomarkers and therapeutics. 相似文献
10.
Ariana de Souza Soares Afonso Mota Ramos Érica Nascif Rufino Vieira Ellen Silva Lago Vanzela Patrícia Martins de Oliveira Daniele de Almeida Paula 《International Journal of Food Science & Technology》2018,53(9):2229-2238
The goal of this research was to evaluate the use of vacuum impregnation (VI) and soaking techniques (ST) in the application of edible coatings of chitosan and chitosan + lauric acid to minimally processed pumpkins (MPP). The vacuum impregnation method led to greater component incorporation (5.9% and 1.75%, respectively) in the pumpkins when compared to soaking and consequently the formation of more uniform, thicker coatings (25.6 and 22.3 μm, respectively). However, VI caused greater changes in pH, acidity, colour and firmness. Relating to water content and carotenoid content, noncoated pumpkins presented greater losses during the storage period, regardless of impregnation method. The pumpkins with edible coatings, regardless of method, presented lower numbers of psychrotrophic micro‐organisms and coliforms during the storage period. Therefore, soaking was considered the best method for the application of chitosan‐based edible coatings to minimally processed pumpkins, as it led to smaller changes in the properties of the product. 相似文献