全文获取类型
收费全文 | 3890篇 |
免费 | 251篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 43篇 |
综合类 | 2篇 |
化学工业 | 1069篇 |
金属工艺 | 61篇 |
机械仪表 | 108篇 |
建筑科学 | 100篇 |
矿业工程 | 6篇 |
能源动力 | 190篇 |
轻工业 | 536篇 |
水利工程 | 34篇 |
石油天然气 | 14篇 |
无线电 | 265篇 |
一般工业技术 | 684篇 |
冶金工业 | 111篇 |
原子能技术 | 31篇 |
自动化技术 | 898篇 |
出版年
2024年 | 7篇 |
2023年 | 66篇 |
2022年 | 171篇 |
2021年 | 196篇 |
2020年 | 141篇 |
2019年 | 137篇 |
2018年 | 157篇 |
2017年 | 154篇 |
2016年 | 179篇 |
2015年 | 127篇 |
2014年 | 195篇 |
2013年 | 304篇 |
2012年 | 252篇 |
2011年 | 331篇 |
2010年 | 212篇 |
2009年 | 224篇 |
2008年 | 186篇 |
2007年 | 172篇 |
2006年 | 126篇 |
2005年 | 126篇 |
2004年 | 79篇 |
2003年 | 66篇 |
2002年 | 70篇 |
2001年 | 51篇 |
2000年 | 40篇 |
1999年 | 30篇 |
1998年 | 38篇 |
1997年 | 25篇 |
1996年 | 38篇 |
1995年 | 26篇 |
1994年 | 18篇 |
1993年 | 12篇 |
1992年 | 13篇 |
1991年 | 22篇 |
1990年 | 10篇 |
1989年 | 11篇 |
1988年 | 12篇 |
1987年 | 6篇 |
1986年 | 12篇 |
1985年 | 14篇 |
1984年 | 16篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1977年 | 6篇 |
1975年 | 5篇 |
1973年 | 6篇 |
1972年 | 3篇 |
排序方式: 共有4152条查询结果,搜索用时 15 毫秒
21.
Vehicle detection by means of stereo vision-based obstacles features extraction and monocular pattern analysis. 总被引:2,自引:0,他引:2
Gwena?lle Toulminet Massimo Bertozzi Stéphane Mousset Abdelaziz Bensrhair Alberto Broggi 《IEEE transactions on image processing》2006,15(8):2364-2375
This paper presents a stereo vision system for the detection and distance computation of a preceding vehicle. It is divided in two major steps. Initially, a stereo vision-based algorithm is used to extract relevant three-dimensional (3-D) features in the scene, these features are investigated further in order to select the ones that belong to vertical objects only and not to the road or background. These 3-D vertical features are then used as a starting point for preceding vehicle detection; by using a symmetry operator, a match against a simplified model of a rear vehicle's shape is performed using a monocular vision-based approach that allows the identification of a preceding vehicle. In addition, using the 3-D information previously extracted, an accurate distance computation is performed. 相似文献
22.
23.
Juan S. Rocha-Ortiz Jianchang Wu Jonas Wenzel Andreas J. Bornschlegl Jose Dario Perea Salvador Leon Anastasia Barabash Anna-Sophie Wollny Dirk M. Guldi Jiyun Zhang Alberto Insuasty Larry Lüer Alejandro Ortiz Andreas Hirsch Christoph J. Brabec 《Advanced functional materials》2023,33(44):2304262
Dumbbell-shaped systems based on PAHs-BODIPY-triarylamine hybrids TM-(01-04) are designed as novel and highly efficient hole-transporting materials for usage in planar inverted perovskite solar cells. BODIPY is employed as a bridge between the PAH units, and the effects of the conjugated π-system's covalent attachment and size are investigated. Fluorescence quenching, 3D fluorescence heat maps, and theoretical studies support energy transfer within the moieties. The systems are extremely resistant to UVC 254 nm germicidal light sources and present remarkable thermal stability at degradation temperatures exceeding 350 °C. Integrating these systems into perovskite solar cells results in outstanding power conversion efficiency (PCE), with TM-02-based devices exhibiting a PCE of 20.26%. The devices base on TM-01, TM-03, and TM-04 achieve PCE values of 16.98%, 17.58%, and 18.80%, respectively. The long-term stability of these devices is measured for 600 h, with initial efficiency retention between 94% and 86%. The TM-04-based device presents noticeable stability of 94%, better than the reference polymer PTAA with 91%. These findings highlight the exciting potential of dumbbell-shaped systems based on PAHs-BODIPY-triarylamine derivatives for next-generation photovoltaics. 相似文献
24.
Manlio Bacco Marco Colucci Alberto Gotta Charilaos Kourogiorgas Athanasios D. Panagopoulos 《International Journal of Satellite Communications and Networking》2019,37(4):331-342
The use of unmanned aerial vehicles (UAVs) is rising in several application fields. This work deals with the communication challenges in UAV swarms, or flying ad hoc network (FANET), when taking into account non–line‐of‐sight scenarios. The use of satellites is a necessity in such operating conditions; thus, this work provides architectural considerations and performance assessments when several (FANETs) share an uplink random access satellite channel, fed with M2M/IoT traffic generated from on‐board sensors, to be reliably delivered to a remote ground destination. 相似文献
25.
26.
Siew Ting Melissa Tan Alexander Giovannitti Armantas Melianas Maximilian Moser Benjamin L. Cotts Devan Singh Iain McCulloch Alberto Salleo 《Advanced functional materials》2021,31(19):2010868
Organic electrochemical transistors (OECTs) have exhibited promising performance as transducers and amplifiers of low potentials due to their exceptional transconductance, enabled by the volumetric charging of organic mixed ionic/electronic conductors (OMIECs) employed as the channel material. OECT performance in aqueous electrolytes as well as the OMIECs’ redox activity has spurred a myriad of studies employing OECTs as chemical transducers. However, the OECT's large (potentiometrically derived) transconductance is not fully leveraged in common approaches that directly conduct chemical reactions amperometrically within the OECT electrolyte with direct charge transfer between the analyte and the OMIEC, which results in sub-unity transduction of gate to drain current. Hence, amperometric OECTs do not truly display current gains in the traditional sense, falling short of the expected transistor performance. This study demonstrates an alternative device architecture that separates chemical transduction and amplification processes on two different electrochemical cells. This approach fully utilizes the OECT's large transconductance to achieve current gains of 103 and current modulations of four orders of magnitude. This transduction mechanism represents a general approach enabling high-gain chemical OECT transducers. 相似文献
27.
Intrinsic selectivities and yields in the catalytic hydrogenation of polyenoic fatty acid methyl esters 总被引:1,自引:0,他引:1
Ricardo J. Grau Alberto E. Cassano Miguel A. Balfanás 《Journal of the American Oil Chemists' Society》1990,67(4):226-232
Precise values of the intrinsic selectivities and yields for the hydrogenation products of methyl linolenate (Ln) and methyl
linoleate (L) obtained under carefully controlled conditions using a commercial Ni catalyst are presented and analyzed in
detail. The existence of a preferential adsorption of Ln and a significant co-hydrogenation of its double bonds are confirmed
as being the dominant features under typical vegetable oil processing conditions.
It is shown that the values of the selectivities that are obtained from the classical consecutive reactions network account
for the intrinsic selectivity of the catalyst only while hydrogenating feedstocks with moderate to low (<10%) contents of
Ln.
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional del Lltoral (U.N.L.) 相似文献
28.
Luis M. Contreras Alberto Solano Francisco Cano Jesus Folgueira 《International Journal of Network Management》2023,33(4):e2221
Video content consumption is currently dominating the mix of traffic observed in Internet service provider (ISP) networks. The distribution of that content is usually performed by means of content delivery network (CDN) caches storing and delivering multimedia. The advent of virtualization is calling attention to the CDN providers as a use case for virtualizing the cache function. In parallel, there is a trend for sharing network infrastructures as a way of reducing deployment costs by ISPs. Then, an interesting scenario emerges when considering the possibility of sharing virtualized cache functions among ISPs which are sharing a common physical infrastructure, mostly considering that those ISPs offer similar video content catalogs to end users. Furthermore, when deciding to share the caches among ISPs, it is interesting to understand the impacts due to limiting the storage capacity at the edge sites. This paper investigates through simulations the potential efficiencies that can be achieved when sharing a virtual cache function if compared with the classical approach of independent virtual caches operated per ISP, as well as the implications of limiting the storage capacity of the caches at the edge. 相似文献
29.
Calcium ion is vital for the regulation of many cellular functions and serves as a second messenger in the signal transduction pathways. Once the intracellular Ca2+ level exceeds the tolerance of cells (called Ca2+ overload), oxidative stress, mitochondrial damage, and cell/mitochondria apoptosis happen. Therefore, Ca2+ overload has started to be deeply exploited as a new strategy for cancer therapy due to its high efficiency and satisfactory safety. This review aims to highlight the recent development of Ca2+-based nanomaterials (such as Ca3(PO4)2, CaCO3, CaO2, CaH2, CaS, and others) able to trigger intracellular Ca2+ overload and apoptosis in cancer therapy. The intracellular mechanisms of varied Ca2+-based nanomaterials and the different types of strategies to enhance Ca2+ overload are discussed in detail. Moreover, the design of more efficient Ca2+ overload-mediated cancer therapies is prospected mainly based on 1) the enhanced cellular uptake by surface modification and morphology optimization of nanomaterials, 2) the accelerated Ca2+ release from nanomaterials by increasing the intracellular H+ level and by photothermal effect, and 3) the overload maintenance by Ca2+ efflux inhibition, Ca2+ influx promotion, or promoting Ca2+ release from the endoplasmic reticulum. 相似文献
30.
Artifact removal in magnetoencephalogram background activity with independent component analysis 总被引:2,自引:0,他引:2
Escudero J Hornero R Abásolo D Fernández A López-Coronado M 《IEEE transactions on bio-medical engineering》2007,54(11):1965-1973
The aim of this study was to assess whether independent component analysis (ICA) could be valuable to remove power line noise, cardiac, and ocular artifacts from magnetoencephalogram (MEG) background activity. The MEGs were recorded from 11 subjects with a 148-channel whole-head magnetometer. We used a statistical criterion to estimate the number of independent components. Then, a robust ICA algorithm decomposed the MEG epochs and several methods were applied to detect those artifacts. The whole process had been previously tested on synthetic data. We found that the line noise components could be easily detected by their frequency spectrum. In addition, the ocular artifacts could be identified by their frequency characteristics and scalp topography. Moreover, the cardiac artifact was better recognized by its skewness value than by its kurtosis one. Finally, the MEG signals were compared before and after artifact rejection to evaluate our method. 相似文献