全文获取类型
收费全文 | 2895篇 |
免费 | 174篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 63篇 |
综合类 | 2篇 |
化学工业 | 945篇 |
金属工艺 | 24篇 |
机械仪表 | 85篇 |
建筑科学 | 107篇 |
矿业工程 | 2篇 |
能源动力 | 86篇 |
轻工业 | 429篇 |
水利工程 | 27篇 |
石油天然气 | 5篇 |
无线电 | 230篇 |
一般工业技术 | 383篇 |
冶金工业 | 103篇 |
原子能技术 | 12篇 |
自动化技术 | 567篇 |
出版年
2023年 | 34篇 |
2022年 | 172篇 |
2021年 | 190篇 |
2020年 | 94篇 |
2019年 | 86篇 |
2018年 | 112篇 |
2017年 | 87篇 |
2016年 | 137篇 |
2015年 | 93篇 |
2014年 | 118篇 |
2013年 | 205篇 |
2012年 | 172篇 |
2011年 | 223篇 |
2010年 | 154篇 |
2009年 | 180篇 |
2008年 | 126篇 |
2007年 | 129篇 |
2006年 | 108篇 |
2005年 | 87篇 |
2004年 | 65篇 |
2003年 | 59篇 |
2002年 | 61篇 |
2001年 | 38篇 |
2000年 | 28篇 |
1999年 | 25篇 |
1998年 | 37篇 |
1997年 | 28篇 |
1996年 | 35篇 |
1995年 | 16篇 |
1994年 | 28篇 |
1993年 | 8篇 |
1992年 | 11篇 |
1991年 | 5篇 |
1990年 | 18篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 10篇 |
1983年 | 8篇 |
1982年 | 10篇 |
1981年 | 6篇 |
1980年 | 11篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1971年 | 2篇 |
1965年 | 2篇 |
1909年 | 2篇 |
排序方式: 共有3070条查询结果,搜索用时 15 毫秒
61.
Water resources management may be improved through the activities of organizations devoted to practice-oriented research, continuing education, and technical assistance. The experience carried out in southern Italy by CSEI Catania during 13 years of activity is presented. Two main activities are discussed: the research and training program on regional pollution control plans and the development of a water data bank. 相似文献
62.
Serena Bianchi Sara Bernardi Antonella Mattei Loredana Cristiano Leonardo Mancini Diana Torge Giuseppe Varvara Guido Macchiarelli Enrico Marchetti 《International journal of molecular sciences》2022,23(9)
Several types of deproteinised bovine bone mineral (DBBM) are available on the market, and each one is obtained with a thermic and chemical process that can differ, achieving different results. Currently, several protocols using low temperature are suggested to reduce the possible particle crystallisation during the production process. This study aimed to evaluate the biomorphological reaction of periodontal fibroblast cultures in contact with different DBBM particles treated with a low-temperature protocol (Thermagen®) and without exposure to sodium hydroxide (NaOH). Morphological evaluation was performed using light, confocal laser, and scanning electron microscopy, and the biological reaction in terms of proliferation was performed using an XTT proliferation assay at 24 h (T1), 72 h (T2), and 7 days (T3). The morphological analysis highlighted how the presence of the materials stimulated a change in the morphology of the cells into a polygonal shape, surface reactions with the thickening of the membrane, and expression of actin. In particular, the morphological changes were appreciable from T1, with a progressive increase in the considered morphological characteristics at T2 and T3 follow-ups. The proliferation assay showed a statistical significance between the different experimental materials and the negative control in T2 and T3 follow-ups. The post hoc analysis did not reveal any differences between the materials. In conclusion, the grafts obtained with the low-temperature extractions protocol and not exposed to NaOH solution showed positive morphological reactions with no differences in the sizes of particles. 相似文献
63.
Alessandro Di Minno Monica Gelzo Marianna Caterino Michele Costanzo Margherita Ruoppolo Giuseppe Castaldo 《International journal of molecular sciences》2022,23(9)
Metabolomics helps identify metabolites to characterize/refine perturbations of biological pathways in living organisms. Pre-analytical, analytical, and post-analytical limitations that have hampered a wide implementation of metabolomics have been addressed. Several potential biomarkers originating from current targeted metabolomics-based approaches have been discovered. Precision medicine argues for algorithms to classify individuals based on susceptibility to disease, and/or by response to specific treatments. It also argues for a prevention-based health system. Because of its ability to explore gene–environment interactions, metabolomics is expected to be critical to personalize diagnosis and treatment. Stringent guidelines have been applied from the very beginning to design studies to acquire the information currently employed in precision medicine and precision prevention approaches. Large, prospective, expensive and time-consuming studies are now mandatory to validate old, and discover new, metabolomics-based biomarkers with high chances of translation into precision medicine. Metabolites from studies on saliva, sweat, breath, semen, feces, amniotic, cerebrospinal, and broncho-alveolar fluid are predicted to be needed to refine information from plasma and serum metabolome. In addition, a multi-omics data analysis system is predicted to be needed for omics-based precision medicine approaches. Omics-based approaches for the progress of precision medicine and prevention are expected to raise ethical issues. 相似文献
64.
Artistic edge and corner enhancing smoothing. 总被引:1,自引:0,他引:1
Giuseppe Papari Nicolai Petkov Patrizio Campisi 《IEEE transactions on image processing》2007,16(10):2449-2462
Two important visual properties of paintings and painting-like images are the absence of texture details and the increased sharpness of edges as compared to photographic images. Painting-like artistic effects can be achieved from photographic images by filters that smooth out texture details, while preserving or enhancing edges and corners. However, not all edge preserving smoothers are suitable for this purpose. We present a simple nonlinear local operator that generalizes both the well known Kuwahara filter and the more general class of filters known in the literature as "criterion and value filter structure." This class of operators suffers from intrinsic theoretical limitations which give rise to a dramatic instability in presence of noise, especially on shadowed areas. Such limitations are discussed in the paper and overcome by the proposed operator. A large variety of experimental results shows that the output of the proposed operator is visually similar to a painting. Comparisons with existing techniques on a large set of natural images highlight conditions on which traditional edge preserving smoothers fail, whereas our approach produces good results. In particular, unlike many other well established approaches, the proposed operator is robust to degradations of the input image such as blurring and noise contamination. 相似文献
65.
Nicola Barbieri Giuseppe Manco Ettore Ritacco Marco Carnuccio Antonio Bevacqua 《Machine Learning》2013,93(1):5-29
Probabilistic topic models are widely used in different contexts to uncover the hidden structure in large text corpora. One of the main (and perhaps strong) assumption of these models is that generative process follows a bag-of-words assumption, i.e. each token is independent from the previous one. We extend the popular Latent Dirichlet Allocation model by exploiting three different conditional Markovian assumptions: (i) the token generation depends on the current topic and on the previous token; (ii) the topic associated with each observation depends on topic associated with the previous one; (iii) the token generation depends on the current and previous topic. For each of these modeling assumptions we present a Gibbs Sampling procedure for parameter estimation. Experimental evaluation over real-word data shows the performance advantages, in terms of recall and precision, of the sequence-modeling approaches. 相似文献
66.
Chiara Manneschi Paola Fanzio Elena Angeli Giuseppe Firpo Luca Ceseracciu Valentina Mussi Luca Repetto Ugo Valbusa 《Microfluidics and nanofluidics》2013,14(1-2):21-30
Peculiar transport phenomena appear at nanoscale, since surface effects strongly affect the behaviour of fluids. Electrostatic and steric interactions, capillary forces and entropic effects play a key role in the behaviour of fluids and biomolecules. Since these effects strongly depend on the size of the nanofluidic system, a careful characterization of the fluidic environment is necessary. Moreover, the possibility to dynamically modulate the size of nanochannels is very appealing in the field of biomolecule manipulation. Recently, we have developed a lab-on-chip made of poly(dimethylsiloxane) (PDMS). This polymeric device is based on a tuneable nanochannel able to dynamically change its dimension in order to fit the application of interest. In fact, a mechanical compression applied on the top of the elastomeric device squeezes the nanochannel, reducing the channel cross section and allowing a dynamical optimization of the nanostructures. In this paper, this squeezing process is fully characterized both numerically and experimentally. This analysis provides information on the reduction of the nanochannel dimensions induced by compression as a function of the work of adhesion and of the stiffness of the materials composing the device. Moreover, calculations demonstrate the possibility to predict the change of the nanochannel size and shape induced by the compression. The possibility to dynamically tune the channel size opens up new opportunities in biomolecular sensing or sieving and in the study of new hydrodynamics effects. 相似文献
67.
Antonio Iera Antonella Molinaro Stefano Yuri Paratore Giuseppe Ruggeri Antonella Zurzolo 《Ad hoc Networks》2011,9(8):1414-1429
This paper aims at answering the question whether it is practical to build a mesh-phone or not. A mesh-phone is a smartphone acting as a mesh router, i.e. either actively participating in the process of packet forwarding towards a mesh gateway, or acting itself as a gateway toward the Internet. Technical aspects of the mesh-phone implementation, such as design constraints and implementation details, are addressed. The technical feasibility is validated by describing the implementation of a prototype of the mesh-enabled phone over the OpenmokoTM open platform. Besides technical feasibility also convenience of the addressed solution is analyzed in terms of the consumed power, and some “energy-saving” related enhancements are suggested to be applied to future user’s devices. 相似文献
68.
This paper investigates the optimum design of tuned mass dampers (TMDs) for the seismic protection of inelastic structures. A single linear TMD is treated and is assumed to be applied to a single nonlinear degree of freedom system, described by the Bouc–Wen hysteretic model. The seismic load is modelled by a stationary filtered stochastic process to consider its intrinsic stochastic nature. The optimization problem is set by taking into consideration three different possible objective functions (OFs): the maximum of the peak structural displacement standard deviation, the average hysteretic dissipated energy of a protected building with reference to an unprotected one, and a functional damage that considers the two indexes previously described. Different numerical examples and parametric analysis are shown to confront the three optimization criteria and to determine the best tuning frequency and damping ratio of the TMDs to be used in the structure. Results confirm that the application of a TMD system reduces the amount of the hysteretic dissipated energy, which is a direct measure of damage in the structure, and so it is beneficial for the protection of buildings that develop a nonlinear behaviour under severe dynamic loadings. 相似文献
69.
The technical quality of two compositionally different groups of solid bricks fired between 800 and 1000 °C was evaluated. Five weight percentage of fly ash was added to both groups and they were compared with similar bricks with no added fly ash.The textures of the bricks with fly ash were very similar to the textures of those without it, except that the samples with the additive contained spherical fly ash particles with diameters ranging from 0.1 to 10 μm. These particles led to a reduction in the density of the bricks and a substantial improvement in their durability, with less decay being caused by salt crystallization in the pores. This is because fly ash causes a reduction in the number of micropores, the pores that make porous materials most vulnerable to salt-induced decay. Use of this additive could have practical implications as a means of recycling and for achieving cost savings in brick production. 相似文献
70.
Francesco Malara Alessandro Cannavale Giuseppe Gigli 《Progress in Photovoltaics: Research and Applications》2015,23(3):290-301
In the last few years, a new class of smart multifunctional photoelectrochemical devices has been attracting the interest of several academic institutions and industrial companies: photovoltachromic cells, combining the features of photoelectrochromic cells with those of dye‐sensitized solar cells. Here, we report the results of a detailed electrochemical analysis aiming at investigating the electrochemical behavior of these complex photoelectrochemical devices. In particular, we have been focused on the effect of Li+ ions displacement during the coloration of the electrochromic tungsten oxide on the performances of the photovoltaic unit. As we had previously observed striking differences between the performances of the barely photovoltaic mode (with the tungsten oxide in the bleached state) and the photovoltachromic mode (with the tungsten oxide in the colored state), we thus attempted to provide a reasonable physical interpretation to the observed phenomena. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献