全文获取类型
收费全文 | 2270篇 |
免费 | 189篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 12篇 |
综合类 | 3篇 |
化学工业 | 933篇 |
金属工艺 | 20篇 |
机械仪表 | 45篇 |
建筑科学 | 66篇 |
矿业工程 | 6篇 |
能源动力 | 68篇 |
轻工业 | 481篇 |
水利工程 | 22篇 |
石油天然气 | 5篇 |
无线电 | 113篇 |
一般工业技术 | 315篇 |
冶金工业 | 100篇 |
原子能技术 | 7篇 |
自动化技术 | 264篇 |
出版年
2024年 | 3篇 |
2023年 | 35篇 |
2022年 | 138篇 |
2021年 | 227篇 |
2020年 | 76篇 |
2019年 | 100篇 |
2018年 | 83篇 |
2017年 | 81篇 |
2016年 | 103篇 |
2015年 | 89篇 |
2014年 | 96篇 |
2013年 | 169篇 |
2012年 | 146篇 |
2011年 | 185篇 |
2010年 | 164篇 |
2009年 | 117篇 |
2008年 | 103篇 |
2007年 | 88篇 |
2006年 | 80篇 |
2005年 | 54篇 |
2004年 | 39篇 |
2003年 | 39篇 |
2002年 | 42篇 |
2001年 | 21篇 |
2000年 | 13篇 |
1999年 | 20篇 |
1998年 | 24篇 |
1997年 | 13篇 |
1996年 | 10篇 |
1995年 | 14篇 |
1994年 | 10篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1967年 | 1篇 |
1965年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有2460条查询结果,搜索用时 883 毫秒
81.
Silvia Bierlich Timmy Reimann Frauke Gellersen Arne F. Jacob Jörg Töpfer 《Journal of the European Ceramic Society》2019,39(10):3077-3081
Sc3+ substituted M-type ferrites are effective microwave magnetic materials with a ferromagnetic resonance frequency in the range of 20 GHz–50 GHz. We report on the fabrication of oriented ferrite thick films as microwave components for application in the Ka-band at 30 GHz. Films of BaFe11.5.Sc0.5O19 were prepared by screen-printing on alumina substrates, drying in an external magnetic field, and sintering at 900 °C. Low-temperature sintering is achieved through use of a mixed BBSZ/CuO sintering aid. A strong anisotropy of the sintered ferrite films is revealed by XRD analysis. Microwave properties of the films were determined in a coplanar waveguide setup. The ferromagnetic resonance frequency of the films is at 30 GHz and the textured films possess good nonreciprocal properties which scale with film thickness. The films were tested in a Y-junction circulator, and represent promising materials for self-biased microwave components fabricated in thick film technology. 相似文献
82.
Silvia Vega-Rubín-de-Celis Lisa Kinch Samuel Pea-Llopis 《International journal of molecular sciences》2020,21(23)
Beclin 1 is a major regulator of autophagy, and it is a core component of the class III PI3K complexes. Beclin 1 is a highly conserved protein and its function is regulated in a number of ways, including post-translational modifications. Several studies indicate that receptor and non-receptor tyrosine kinases regulate autophagy activity in cancer, and some suggest the importance of Beclin 1 tyrosine phosphorylation in this process. Here we summarize the current knowledge of the mechanism whereby some oncogenic tyrosine kinases regulate autophagy through Beclin 1. 相似文献
83.
Iliescu Florina Silvia Teo Jeremy Choon Meng Vrtacnik Danilo Taylor Hayden Iliescu Ciprian 《Microsystem Technologies》2018,24(7):2905-2912
Microsystem Technologies - Cell transplantation traditionally employs needles to inject donor cells into tissues to treat certain diseases. However, it is difficult for the current method to... 相似文献
84.
85.
86.
87.
This paper introduces a joint planning and management optimization approach for cellular networks to limit energy consumption while guaranteeing QoS and minimizing operators Capex and Opex. The modeling framework shows that an effective energy-efficient operation depends on the planning decisions. Conversely, it also shows that planning with energy management operation in view yields more versatile topologies than more traditional models based only on Capex. Results for LTE networks are provided and show that savings up to 65% in energy expenses are possible with slight increases in capital investments. 相似文献
88.
Gian-Pietro Di Sansebastiano Silvia Fornaciari Fabrizio Barozzi Gabriella Piro Laura Arru 《International journal of molecular sciences》2014,15(3):4565-4582
We investigated the effect of auxin and acetylcholine on the expression of the tomato expansin gene LeEXPA2, a specific expansin gene expressed in elongating tomato hypocotyl segments. Since auxin interferes with clathrin-mediated endocytosis, in order to regulate cellular and developmental responses we produced protoplasts from tomato elongating hypocotyls and followed the endocytotic marker, FM4-64, internalization in response to treatments. Tomato protoplasts were observed during auxin and acetylcholine treatments after transient expression of chimerical markers of volume-control related compartments such as vacuoles. Here we describe the contribution of auxin and acetylcholine to LeEXPA2 expression regulation and we support the hypothesis that a possible subcellular target of acetylcholine signal is the vesicular transport, shedding some light on the characterization of this small molecule as local mediator in the plant physiological response. 相似文献
89.
Francesca Palombo C. Peter Winlove Ryan S. Edginton Ellen Green Nick Stone Silvia Caponi Marco Madami Daniele Fioretto 《Journal of the Royal Society Interface》2014,11(101)
Brillouin light scattering (BLS) spectroscopy is a technique that is able to detect thermally excited phonons within a material. The speed of propagation of these phonons can be determined from the magnitude of the Brillouin frequency shift between incident and scattered light, thereby providing a measure of the mechanical properties of the material in the gigahertz range. The mechanical properties of the extracellular matrices of biological tissues and their constituent biopolymers are important for normal tissue function and disturbances in these properties are widely implicated in disease. BLS offers the prospect of measuring mechanical properties on a microscopic scale in living tissues, thereby providing insights into structure–function relationships under normal and pathological conditions. In this study, we investigated BLS in collagen and elastin—the fibrous proteins of the extracellular matrix (ECM). Measurements were made on type I collagen in rat tail tendon, type II collagen in articular cartilage and nuchal ligament elastin. The dependence of the BLS spectrum on fibre orientation was investigated in a backscattering geometry using a reflective substrate. Two peaks, a bulk mode arising from phonon propagation along a quasi-radial direction to the fibre axis and a mode parallel to the surface, depending on sample orientation relative to the fibre axis, could be distinguished. The latter peak was fitted to a model of wave propagation through a hexagonally symmetric elastic solid, and the five components of the elasticity tensor were combined to give axial and transverse Young''s, shear and bulk moduli of the fibres. These were 10.2, 8.3, 3.2 and 10.9 GPa, and 6.1, 5.3, 1.9 and 8 GPa for dehydrated type I collagen and elastin, respectively. The former values are close to those previously reported. A microfocused BLS approach was also applied providing selection of single fibres. The moduli of collagen and elastin are much higher than those measured at lower frequency using macroscopic strains, and the difference between them is much less. We therefore believe, like previous investigators, that molecular-scale viscoelastic effects are responsible for the frequency dependence of the fibre biomechanics. Combining BLS with larger-scale mechanical testing methods therefore should, in the future, provide a means of following the evolution of mechanical properties in the formation of the complex structures found in the ECM. 相似文献
90.
Silvia Curteanu Ciprian-George Piuleac Jose J. Linares Pablo Cañizares Manuel A. Rodrigo Justo Lobato 《International Journal of Hydrogen Energy》2014
A multi-objective optimization strategy, based on stacked neural network–genetic algorithm (SNN–GA) hybrid approach, was applied to study the C/PBI content on a high temperature PEMFC performance. The operating conditions of PEMFC were correlated with power density and electrochemical active surface area for electrodes. The structure of the stack was determined in an optimal form related to the contribution of individual neural networks, after applying an interpolation based procedure. Multi-objective optimization using SNN as model and GA as solving procedure provides optimal working conditions which lead to a high PEMFC performance. Simulation results were in agreement with experimental data, both for model validation and system optimization (the C/PBI content in the range of 17–21%). 相似文献