全文获取类型
收费全文 | 1035篇 |
免费 | 87篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 7篇 |
综合类 | 2篇 |
化学工业 | 390篇 |
金属工艺 | 31篇 |
机械仪表 | 17篇 |
建筑科学 | 49篇 |
矿业工程 | 2篇 |
能源动力 | 32篇 |
轻工业 | 135篇 |
水利工程 | 20篇 |
石油天然气 | 48篇 |
无线电 | 48篇 |
一般工业技术 | 171篇 |
冶金工业 | 76篇 |
原子能技术 | 16篇 |
自动化技术 | 79篇 |
出版年
2023年 | 17篇 |
2022年 | 14篇 |
2021年 | 129篇 |
2020年 | 50篇 |
2019年 | 49篇 |
2018年 | 51篇 |
2017年 | 45篇 |
2016年 | 55篇 |
2015年 | 38篇 |
2014年 | 60篇 |
2013年 | 67篇 |
2012年 | 92篇 |
2011年 | 76篇 |
2010年 | 48篇 |
2009年 | 53篇 |
2008年 | 51篇 |
2007年 | 25篇 |
2006年 | 22篇 |
2005年 | 14篇 |
2004年 | 16篇 |
2003年 | 10篇 |
2002年 | 12篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 3篇 |
1998年 | 10篇 |
1997年 | 8篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 8篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1960年 | 2篇 |
排序方式: 共有1123条查询结果,搜索用时 46 毫秒
31.
A model-based approach to reconstruction of 3D human arm motion from a monocular image sequence taken under orthographic
projection is presented. The reconstruction is divided into two stages. First, a 2D shape model is used to track the arm silhouettes
and second-order curves are used to model the arm based on an iteratively reweighted least square method. As a result, 2D
stick figures are extracted. In the second stage, the stick figures are backprojected into the scene. 3D postures are reconstructed
using the constraints of a 3D kinematic model of the human arm. The motion of the arm is then derived as a transition between
the arm postures. Applications of these results are foreseen in the analysis of human motion patterns.
Received: 26 January 1996 / Accepted: 17 July 1997 相似文献
32.
Valentina V Zhurikhina Pavel N Brunkov Vladimir G Melehin Tommi Kaplas Yuri Svirko Victoria V Rutckaia Andrey A Lipovskii 《Nanoscale research letters》2012,7(1):676
We demonstrate that silver nanoisland film self-assembled on the surface of silver-containing glass in the course of thermal processing in hydrogen is capable to detect 10−7 M concentration of rhodamine 6G in water using surface enhanced Raman spectroscopy (SERS) technique. The film can be multiply restored on the same glass substrate via annealing of the glass in hydrogen. We showed that the film can be self-assembled after as much as ten circles of the substrate cleaning followed by annealing. The proposed technique of the silver nanoisland film formation enables multiple usage of the same glass substrate in SERS experiments. 相似文献
33.
Anna Bernasconi Valentina Ciriani Fabrizio Luccio Linda Pagli 《Theory of Computing Systems》2013,53(4):583-608
Given a Boolean function f on n variables, a Disjoint Sum-of-Products (DSOP) of f is a set of products (ANDs) of subsets of literals whose sum (OR) equals f, such that no two products cover the same minterm of f. DSOP forms are a special instance of partial DSOPs, i.e. the general case where a subset of minterms must be covered exactly once and the other minterms (typically corresponding to don’t care conditions of f) can be covered any number of times. We discuss finding DSOPs and partial DSOPs with a minimal number of products, a problem theoretically connected with various properties of Boolean functions and practically relevant in the synthesis of digital circuits. Finding an absolute minimum is hard, in fact we prove that the problem of absolute minimization of partial DSOPs is NP-hard. Therefore it is crucial to devise a polynomial time heuristic that compares favorably with the known minimization tools. To this end we develop a further piece of theory starting from the definition of the weight of a cube c as a functions of the number of fragments induced on other cubes by the selection of c, and show how cube weights can be exploited for building a class of minimization heuristics for DSOP and partial DSOP synthesis. A set of experiments conducted on major benchmark functions show that our method, with a family of variants, always generates better results than the ones of previous heuristics, including the method based on a BDD representation of f. 相似文献
34.
35.
36.
Paola Songia Mattia Chiesa Valentina Alfieri Ilaria Massaiu Donato Moschetta Veronika Myasoedova Vincenza Valerio Laura Fusini Paola Gripari Marco Zanobini Paolo Poggio 《International journal of molecular sciences》2021,22(4)
Mitral valve prolapse (MVP) associated with severe mitral regurgitation is a debilitating disease with no pharmacological therapies available. MicroRNAs (miRNA) represent an emerging class of circulating biomarkers that have never been evaluated in MVP human plasma. Our aim was to identify a possible miRNA signature that is able to discriminate MVP patients from healthy subjects (CTRL) and to shed light on the putative altered molecular pathways in MVP. We evaluated a plasma miRNA profile using Human MicroRNA Card A followed by real-time PCR validations. In addition, to assess the discriminative power of selected miRNAs, we implemented a machine learning analysis. MiRNA profiling and validations revealed that miR-140-3p, 150-5p, 210-3p, 451a, and 487a-3p were significantly upregulated in MVP, while miR-223-3p, 323a-3p, 340-5p, and 361-5p were significantly downregulated in MVP compared to CTRL (p ≤ 0.01). Functional analysis identified several biological processes possible linked to MVP. In addition, machine learning analysis correctly classified MVP patients from CTRL with high accuracy (0.93) and an area under the receiving operator characteristic curve (AUC) of 0.97. To the best of our knowledge, this is the first study performed on human plasma, showing a strong association between miRNAs and MVP. Thus, a circulating molecular signature could be used as a first-line, fast, and cheap screening tool for MVP identification. 相似文献
37.
Virgínia C. Fernandes Valentina F. Domingues Victor de Freitas Cristina Delerue-Matos Nuno Mateus 《Food chemistry》2012
Consumer awareness, pesticide and fertilizer contaminations and environmental concerns have resulted in significant demand for organically grown farm produce. Consumption of berries has become popular among health-conscious consumers due to the high levels of valuable antioxidants, such as anthocyanins and other phenolic compounds. The present study evaluated the influence that organic farming (OF) and integrated pest management (IPM) practise exert on the total phenolic content in 22 strawberry samples from four varieties. Postharvest performance of OF and IPM strawberries grown in the same area in the centre of Portugal and harvested at the same maturity stage were compared. Chemical profiles (phenolic compounds) were determined with the aid of HPLC-DAD/MS. Total phenolic content was higher for OF strawberry extracts. This study showed that the main differences in bioactive phytochemicals between organically and IPM grown strawberries concerned their anthocyanin levels. Organically grown strawberries were significantly higher in antioxidant activity than were the IPM strawberries, as measured by DPPH and FRAP assays. 相似文献
38.
Commiphora myrrha (Nees) Engl. extracts: evaluation of antioxidant and antiproliferative activity and their ability to reduce microbial growth on fresh‐cut salad 下载免费PDF全文
Luisa Boffa Arianna Binello Valentina Boscaro Margherita Gallicchio Gabriella Amisano Stefania Fornasero Giancarlo Cravotto 《International Journal of Food Science & Technology》2016,51(3):625-632
With the aim to develop natural preservatives displaying also chemopreventive activity, different Commiphora myrrha (Nees) Engl. extracts were studied. Myrrh essential oils, obtained by steam distillation and microwave‐assisted hydrodistillation, and several other extracts, obtained by sequential procedures with petroleum ether (PE), ethanol, ethyl acetate and butanol, have been screened for their antioxidant (DPPH· scavenging assay) and antiproliferative activity (on both nontumour and colon cancer cell lines) without previous purification. Considering that the colon cancer cell lines were more sensitive to PE and ethanol extracts, the latter of which showed the highest antioxidant activity (EC50 = 0.160 ± 0.008 mg mL?1), both have been selected for further antibacterial/antifungal activity tests using an antimicrobial diffusion test and a growth inhibition test on salads. Results showed that the ethanol extract possessed the higher antibacterial and antifungal activity. Compared to untreated product, fresh‐cut salads treated with these two myrrh extracts displayed a significant lower bacterial growth. Although further investigation is required, these promising results offer hints as how to improve the shelf life of fresh‐cut salad. 相似文献
39.
40.
Valentina Medri Francesca Servadei Riccardo Bendoni Annalisa Natali Murri Angelo Vaccari Elena Landi 《Journal of the European Ceramic Society》2019,39(7):2453-2462
Cold Sintering Process (CSP) was applied on commercial nanopowders to produce nanostructured TiO2 anatase with nano-to-macro porosity. Nanoporous TiO2 based materials were obtained by applying CSP at 150 °C and pressures up to 500 MPa on three TiO2 nanopowders with different specific surface area (s.s.a. = 50, 90 and 370 m2/g), using water as transient aqueous environment. Although TiO2 is insoluble in water, a density of 68% and s.s.a. = 117 m2/g were achieved from the powder with the highest specific surface area. A post annealing process at 500 °C increased the density up to 73% with a s.s.a. = 59 m2/g, and the crystallites dimensions passed from 110 Å in the powder to 130 Å in CSP material and 172 Å after post annealing. Finally, macroporosity was produced by using thermoplastic polymer beads as sacrificial templates within TiO2 nanopowder during CSP, followed by a debonding at 500 °C. 相似文献