全文获取类型
收费全文 | 1245篇 |
免费 | 56篇 |
专业分类
电工技术 | 19篇 |
综合类 | 4篇 |
化学工业 | 354篇 |
金属工艺 | 18篇 |
机械仪表 | 9篇 |
建筑科学 | 118篇 |
矿业工程 | 3篇 |
能源动力 | 33篇 |
轻工业 | 98篇 |
水利工程 | 5篇 |
石油天然气 | 2篇 |
无线电 | 93篇 |
一般工业技术 | 225篇 |
冶金工业 | 52篇 |
原子能技术 | 3篇 |
自动化技术 | 265篇 |
出版年
2024年 | 5篇 |
2023年 | 21篇 |
2022年 | 24篇 |
2021年 | 36篇 |
2020年 | 29篇 |
2019年 | 27篇 |
2018年 | 29篇 |
2017年 | 29篇 |
2016年 | 55篇 |
2015年 | 41篇 |
2014年 | 46篇 |
2013年 | 68篇 |
2012年 | 70篇 |
2011年 | 95篇 |
2010年 | 74篇 |
2009年 | 75篇 |
2008年 | 69篇 |
2007年 | 68篇 |
2006年 | 66篇 |
2005年 | 42篇 |
2004年 | 47篇 |
2003年 | 30篇 |
2002年 | 30篇 |
2001年 | 16篇 |
2000年 | 17篇 |
1999年 | 18篇 |
1998年 | 19篇 |
1997年 | 22篇 |
1996年 | 11篇 |
1995年 | 10篇 |
1994年 | 12篇 |
1993年 | 8篇 |
1992年 | 10篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 7篇 |
1987年 | 3篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1980年 | 3篇 |
1978年 | 3篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1939年 | 3篇 |
1938年 | 5篇 |
1937年 | 3篇 |
1930年 | 2篇 |
排序方式: 共有1301条查询结果,搜索用时 15 毫秒
11.
12.
In June 2003, a large scale injection experiment started at the Continental Deep Drilling site (KTB) in Germany. A tiltmeter array was installed which consisted of five high resolution borehole tiltmeters of the ASKANIA type, also equipped with three dimensional seismometers. For the next 11 months, 86 000 m(3) were injected into the KTB pilot borehole 4000 m deep. The average injection rate was approximately 200 l/min. The research objective was to observe and to analyze deformation caused by the injection into the upper crust at the kilometer range. A new data acquisition system was developed by Geo-Research Center Potsdam (GFZ) to master the expected huge amount of seismic and tilt data. Furthermore, it was necessary to develop a new preprocessing software called PREANALYSE for long-period time series. This software includes different useful functions, such as step and spike correction, interpolation, filtering, and spectral analysis. This worldwide unique installation offers the excellent opportunity of the separation of signals due to injection and due to environment by correlation of the data of the five stations with the ground water table and meteorological data. 相似文献
13.
Evaluation of a low-cost 3D sound system for immersive virtual reality training systems 总被引:2,自引:0,他引:2
Doerr KU Rademacher H Huesgen S Kubbat W 《IEEE transactions on visualization and computer graphics》2007,13(2):204-212
Since head mounted displays (HMD), datagloves, tracking systems, and powerful computer graphics resources are nowadays in an affordable price range, the usage of PC-based "virtual training systems" becomes very attractive. However, due to the limited field of view of HMD devices, additional modalities have to be provided to benefit from 3D environments. A 3D sound simulation can improve the capabilities of VR systems dramatically. Unfortunately, realistic 3D sound simulations are expensive and demand a tremendous amount of computational power to calculate reverberation, occlusion, and obstruction effects. To use 3D sound in a PC-based training system as a way to direct and guide trainees to observe specific events in 3D space, a cheaper alternative has to be provided, so that a broader range of applications can take advantage of this modality. To address this issue, we focus in this paper on the evaluation of a low-cost 3D sound simulation that is capable of providing traceable 3D sound events. We describe our experimental system setup using conventional stereo headsets in combination with a tracked HMD device and present our results with regard to precision, speed, and used signal types for localizing simulated sound events in a virtual training environment 相似文献
14.
Holger Fritze 《Journal of Electroceramics》2006,17(2-4):625-630
Langasite (La3Ga5SiO14, LGS) and gallium orthophosphate (GaPO4) resonators exhibit piezoelectrically exited bulk acoustic waves at temperatures of up to at least 1400∘C and 900∘C, respectively. Their mass sensitivity at elevated temperatures has been found to be about as high as that of quartz at room
temperature. Within its operation temperature range, GaPO4 shows significantly lower losses than LGS.
Factors restricting application relevant properties of LGS at elevated temperatures, such as the mass resolution, include
excessive viscous damping. Therefore, the effective viscosity is determined as a function of the temperature by fitting the
calculated complex impedance to the experimental data in the vicinity of the resonance frequency. The viscosity shows an Arrhenius-like
behavior if a temperature independent contribution is subtracted. The activation energies of the viscosity for LGS and GaPO4 correspond to those of the bulk electrical conductivity for each material. Viscosity and conductivity are obviously correlated.
Therefore, it is highly likely that the predominant conductivity mechanism also controls the mechanical damping. First attempts
to minimize the viscosity of LGS by doping are undertaken. Very light doping does, however, not change the conductivity and
viscosity of LGS. Higher doping levels have to be applied and tested.
Based on the electromechanical properties given for undoped LGS, the applicability of this material as resonant gas sensor
at 600∘C is demonstrated. 相似文献
15.
Schwaibold Schormüller Beckel W. Sutthoff Lars Erlandsen v. Skramlik W. Schreiber Kanitz Bierotte M. Steiner W. Wodsak G. Steinhoff H. J. Steinbeck Frey-Wyssling M. Gordienko K. Dirr Pawletta Stelzer W. Wodsak W. Bartels Hoepke G. Stamm Brüning W. Hämmerle Schnetka K. Felix H. Schülke Kluge Krzywanek W. Brandt Gertraude Körner-Hennig K. J. Demeter Damm J. Ph. Bruno Roßmann W. Karlowa H. Ketterl L. W. Jirak W. Preiß Diemair W. Ludorff Jahr Griebel J. J. van Eck W. Preiß C. Pyriki K. Müller Jesser K. Boresch Fr. Bartschat 《European Food Research and Technology》1939,77(3):290-336
16.
Hannes M. Findeisen Vivienne C. Voges Laura C. Braun Jannik Sonnenberg Dennis Schwarz Helena Krner Holger Reinecke Yahya Sohrabi 《International journal of molecular sciences》2022,23(11)
Reprogramming of metabolic pathways in monocytes and macrophages can induce a proatherosclerotic inflammatory memory called trained innate immunity. Here, we have analyzed the role of the Liver X receptor (LXR), a crucial regulator of metabolism and inflammation, in oxidized low-density lipoprotein (oxLDL)-induced trained innate immunity. Human monocytes were incubated with LXR agonists, antagonists, and oxLDL for 24 h. After five days of resting time, cells were restimulated with the TLR-2 agonist Pam3cys. OxLDL priming induced the expression of LXRα but not LXRβ. Pharmacologic LXR activation was enhanced, while LXR inhibition prevented the oxLDL-induced inflammatory response. Furthermore, LXR inhibition blocked the metabolic changes necessary for epigenetic reprogramming associated with trained immunity. In fact, enrichment of activating histone marks at the IL-6 and TNFα promotor was reduced following LXR inhibition. Based on the differential expression of the LXR isoforms, we inhibited LXRα and LXRβ genes using siRNA in THP1 cells. As expected, siRNA-mediated knock-down of LXRα blocked the oxLDL-induced inflammatory response, while knock-down of LXRβ had no effect. We demonstrate a specific and novel role of the LXRα isoform in the regulation of oxLDL-induced trained immunity. Our data reveal important aspects of LXR signaling in innate immunity with relevance to atherosclerosis formation. 相似文献
17.
Holger Rhm Tobias Leonhard Michael J. Hoffmann Alexander Colsmann 《Advanced functional materials》2020,30(5)
Seemingly contradictory reports on polar domains and their origin have surrounded the controversial discussion about the ferroelectricity of the methyl ammonium lead iodide (MAPbI3) thin films that are commonly employed in perovskite solar cells. In this work, microscopic modulations of the polar domain patterns upon application of an electric poling field are correlated with macroscopic changes to the currents through the MAPbI3 layer. Piezoresponse force microscopy is used to monitor the widening, narrowing, generation or extinction of polar domains, as well as shifts of the domain walls at room temperature under an in‐plane electric poling field that is applied between two laterally organized electrodes. This poling leads to a net polarization of individual grains and the thin film itself. Macroscopically, this net polarization results in a persistent shift of the diode characteristics that is measured across the channel between the electrodes. Both the modulation of the polar domains upon electric poling and the concurrent persistent shift of the electric currents through the device are the unambiguous hallmarks of ferroelectricity, which demonstrate that MAPbI3 is a ferroelectric semiconductor. 相似文献
18.
Erick González-Rodríguez Holger Maune Yuliang Zheng Mohsen Sazegar Lufei Shen Ibrahim Asghar Shah Dirk Dahlhaus Klaus Hofmann Rolf Jakoby 《AEUE-International Journal of Electronics and Communications》2013,67(12):1107-1117
In this paper the bit error rate performance and error vector magnitude of a tunable impedance matching network is analyzed assuming QPSK, 16-QAM and 64-QAM digital modulation schemes. The characterized tunable impedance matching network is based on barium–strontium–titanate ferroelectric thick-film varactors. Inherent dispersive behavior is subsumed into the forward transmission of the passive device. Due to this nonlinear phase response, in general to maximize the overall system performance, an agile tuning of the varactor values is demonstrated, taking into account the phase and group delay of s21 parameter. Detailed signal simulation results based on measured data of a testbed are presented. The influence of varying matched impedances on the tuning behavior with different modulation bandwidths is discussed at a center frequency of 1.9 GHz. 相似文献
19.
20.
This paper presents a spatially distributed and dynamic billing, pricing and allocation mechanism for which a user terminal
requires Cognitive Radio abilities. That is, the Cognitive Radio abilities will be applied to the economical environment.
The radio resource goods are allocated to the users by a multi-unit sealed-bid auction. Intelligent entities like the bidding
strategy have to represent operator’s and users’ behavior and to make decisions for them in order to fulfill the preferences
and QoS. The main functionalities, used to execute the dynamic auction sequence and located in the MAC are described, assuming
the entities possess Cognitive Radio abilities.
相似文献
Friedrich JondralEmail: |