全文获取类型
收费全文 | 2640篇 |
免费 | 144篇 |
国内免费 | 2篇 |
学科分类
工业技术 | 2786篇 |
出版年
2023年 | 27篇 |
2022年 | 24篇 |
2021年 | 110篇 |
2020年 | 63篇 |
2019年 | 54篇 |
2018年 | 63篇 |
2017年 | 74篇 |
2016年 | 91篇 |
2015年 | 55篇 |
2014年 | 86篇 |
2013年 | 163篇 |
2012年 | 133篇 |
2011年 | 170篇 |
2010年 | 115篇 |
2009年 | 133篇 |
2008年 | 118篇 |
2007年 | 91篇 |
2006年 | 86篇 |
2005年 | 74篇 |
2004年 | 53篇 |
2003年 | 65篇 |
2002年 | 52篇 |
2001年 | 36篇 |
2000年 | 32篇 |
1999年 | 47篇 |
1998年 | 196篇 |
1997年 | 116篇 |
1996年 | 97篇 |
1995年 | 44篇 |
1994年 | 52篇 |
1993年 | 46篇 |
1992年 | 22篇 |
1991年 | 14篇 |
1990年 | 9篇 |
1989年 | 22篇 |
1988年 | 10篇 |
1987年 | 9篇 |
1986年 | 17篇 |
1985年 | 17篇 |
1984年 | 8篇 |
1983年 | 10篇 |
1982年 | 8篇 |
1981年 | 12篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1977年 | 8篇 |
1976年 | 15篇 |
1974年 | 3篇 |
1969年 | 3篇 |
1967年 | 7篇 |
排序方式: 共有2786条查询结果,搜索用时 19 毫秒
121.
Paola Riolo Roxana L. Minuz Gianfranco Anfora Marco V. Rossi Stacconi Silvia Carlin Nunzio Isidoro Roberto Romani 《Journal of chemical ecology》2012,38(8):1017-1030
The Palearctic planthopper Hyalesthes obsoletus is the natural vector of the grapevine yellow disease Bois noir. Grapevine is an occasional host plant of this polyphagous planthopper. To deepen our knowledge of the role of plant volatile organic compounds for H. obsoletus host plant searching, we carried out behavioral, morphological, and electrophysiological studies. We tested the attraction of H. obsoletus to nettle, field bindweed, hedge bindweed, chaste tree, and grapevine by using a Y-shaped olfactometer. The results showed a significant attraction of male H. obsoletus to chaste tree, and of the females to nettle. Male H. obsoletus were repelled by odor from hedge bindweed. Ultrastructural studies of the antennae showed at least two types of olfactory sensilla at the antennal pedicel: plaque organs and trichoid sensilla. Volatile organic compounds from nettle and chaste tree were collected, and the extracts were analyzed by coupling gas-chromatography to both mass-spectrometry and electroantennography. The volatile organic compounds that elicited electrophysiological responses in male and female antennae were identified. These findings are discussed with respect to behavior of H. obsoletus males and females in the field. 相似文献
122.
Dario Imbraguglio Andrea Mario Giovannozzi Annalisa Nastro Andrea Mario Rossi 《Nanoscale research letters》2012,7(1):530
Three-dimensional submicrometric structures and biomolecular patterns have been fabricated on a porous silicon film by an electron beam-based functionalization method. The immobilized proteins act as a passivation layer against material corrosion in aqueous solutions. The effects'' dependence on the main parameters of the process (i.e., the electron beam dose, the biomolecule concentration, and the incubation time) has been demonstrated. 相似文献
123.
124.
Davide Giglio Riccardo Minciardi Simona Sacone Silvia Siri 《Discrete Event Dynamic Systems》2014,24(3):339-352
A class of production systems are considered in this paper with the aim of determining closed-loop strategies providing the production effort as functions of the system state. The key feature of the considered class of systems is that the demand and the way it is satisfied are asynchronous sequences of part requests and instantaneous withdrawals, respectively, generated by discrete-event processes, whereas the production process has continuous-time dynamics. The optimization problem, whose objective is to minimize inventory and lateness costs, is restated as an optimal control problem by exploiting some structural properties of the optimal solution. Then, optimal closed-loop strategies are found with dynamic programming techniques. 相似文献
125.
Sergio Benini Michele Svanera Nicola Adami Riccardo Leonardi András Bálint Kovács 《Multimedia Tools and Applications》2016,75(23):16499-16527
The scale of shot, i.e. the apparent distance of the camera from the main subject of a scene, is one of the main stylistic and narrative functions of audiovisual products, conveying meaning and inducing the viewer’s emotional state. The statistical distribution of different shot scales in a film may be an important identifier of an individual film, an individual author, and of various narrative and affective functions of a film. In order to understand at which level shot scale distribution (SSD) of a movie might become its fingerprint, it is necessary to produce automatic recognition of shot scale on a large movie corpus. In our work we propose an automatic framework for estimating the SSD of a movie by using inherent characteristics of shots containing information about camera distance, without the need to recover the 3D structure of the scene. In the experimental investigation, the comparison of obtained results with manual SSD annotations proves the validity of the framework. Experiments conducted on movies by Michelangelo Antonioni taken from different stylistic periods (1950–57, 1960–64, 1966–75, 1980–82) show a strong similarity in shot scale distributions within each period, thus opening interesting research lines regarding the possible aesthetic and cognitive sources of such a regularity. 相似文献
126.
Giordana Feriotto Federico Tagliati Riccardo Giriolo Fabio Casciano Claudio Tabolacci Simone Beninati Mahmud Tareq Hassan Khan Carlo Mischiati 《International journal of molecular sciences》2021,22(4)
Among the phenolic acids tested on the K562 cell line, a model of chronic myeloid leukemia (CML), caffeic acid (CA) was biologically active on sensitive and imatinib (IM)-resistant cells at micro-molar concentration, either in terms of reduction of cell proliferation or triggering of apoptosis. The CA treatment provoked mitochondrial membrane depolarization, genomic DNA fragmentation and phosphatidylserine exposure, hallmarks of apoptosis. Cell cycle analysis following the treatment with comparable cytotoxic concentrations of IM or CA showed marked differences in the distribution profiles. The reduction of cell proliferation by CA administration was associated with increased expression of two cell cycle repressor genes, CDKN1A and CHES1, while IM at a cytotoxic concentration increased the CHES1 but not the CDKN1A expression. In addition, CA treatment affected the proliferation and triggered the apoptosis in IM-resistant cells. Taken together, these data suggested that CA induced the anti-proliferative effect and triggered apoptosis of CML cells by a different mechanism than IM. Finally, the combined administration of IM and CA at suboptimal concentrations evidenced a synergy of action in determining the anti-proliferative effect and triggering apoptosis. The ability of CA to potentiate the anti-leukemic effect of IM highlighted the nutraceutical potential of CA in CML. 相似文献
127.
128.
129.
Filippo Fabbri Francesca Rossi Manuela Melucci Ilse Manet Giovanni Attolini Laura Favaretto Massimo Zambianchi Giancarlo Salviati 《Nanoscale research letters》2012,7(1):680
A new class of nanostructured hybrid materials is developed by direct grafting of a model thiophene-based organic dye on the surface of 3C-SiC/SiO2 core/shell nanowires. TEM-EDX analysis reveals that the carbon distribution is more spread than it would be, considering only the SiC core size, suggesting a main contribution from C of the oligothiophene framework. Further, the sulfur signal found along the treated wires is not detected in the as-grown samples. In addition, the fluorescent spectra are similar for the functionalized nanostructures and T3Pyr in solution, confirming homogeneous molecule grafting on the nanowire surface. Chemical and luminescence characterizations confirm a homogeneous functionalization of the nanowires. In particular, the fluorophore retains its optical properties after functionalization. 相似文献