全文获取类型
收费全文 | 6894篇 |
免费 | 520篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 81篇 |
综合类 | 2篇 |
化学工业 | 2001篇 |
金属工艺 | 114篇 |
机械仪表 | 208篇 |
建筑科学 | 292篇 |
矿业工程 | 24篇 |
能源动力 | 267篇 |
轻工业 | 989篇 |
水利工程 | 62篇 |
石油天然气 | 35篇 |
无线电 | 435篇 |
一般工业技术 | 1077篇 |
冶金工业 | 351篇 |
原子能技术 | 47篇 |
自动化技术 | 1438篇 |
出版年
2024年 | 23篇 |
2023年 | 99篇 |
2022年 | 280篇 |
2021年 | 328篇 |
2020年 | 213篇 |
2019年 | 237篇 |
2018年 | 287篇 |
2017年 | 297篇 |
2016年 | 292篇 |
2015年 | 238篇 |
2014年 | 325篇 |
2013年 | 588篇 |
2012年 | 463篇 |
2011年 | 559篇 |
2010年 | 382篇 |
2009年 | 425篇 |
2008年 | 351篇 |
2007年 | 319篇 |
2006年 | 273篇 |
2005年 | 202篇 |
2004年 | 151篇 |
2003年 | 173篇 |
2002年 | 142篇 |
2001年 | 81篇 |
2000年 | 86篇 |
1999年 | 68篇 |
1998年 | 64篇 |
1997年 | 70篇 |
1996年 | 59篇 |
1995年 | 41篇 |
1994年 | 35篇 |
1993年 | 32篇 |
1992年 | 18篇 |
1991年 | 21篇 |
1990年 | 12篇 |
1989年 | 22篇 |
1988年 | 12篇 |
1987年 | 11篇 |
1986年 | 13篇 |
1985年 | 14篇 |
1984年 | 9篇 |
1983年 | 8篇 |
1982年 | 14篇 |
1981年 | 6篇 |
1980年 | 9篇 |
1979年 | 10篇 |
1978年 | 19篇 |
1976年 | 8篇 |
1975年 | 6篇 |
1973年 | 5篇 |
排序方式: 共有7423条查询结果,搜索用时 15 毫秒
81.
Antonio M. Ortiz Fernando Royo Teresa Olivares Jose Carlos Castillo Luis Orozco‐Barbosa 《Expert Systems》2014,31(2):154-162
ZigBee is the primary standard solution for wireless sensor networks, implementing the Ad hoc On‐Demand Distance Vector (AODV) protocol in the network layer and supported by the standard IEEE 802.15.4. This study is focused on mesh topologies and the critical problems encountered when AODV is executed in conjunction with the Carrier Sense Multiple Access with Collision Avoidance protocol. These problems are mainly related to the packet overhead required to carry out route creation. To perform preliminary experiments to be able to implement AODV in a real network, a new metric is proposed herein. This metric uses fuzzy logic to help in the decision‐making process. The objective of the fuzzy routine is to determine, during the route‐discovery process, the best node to forward request/reply packets, with the aim of reducing packet overhead and energy consumption. Moreover, minor changes are also added to the discovery procedure of AODV to improve the performance of the route‐creation process. This intelligent version of AODV has provided promising experimental results, greatly reducing the number of packets required, with the consequent energy saving while selecting the best nodes to be part of the routes. 相似文献
82.
Carlos H. González Basilio B. Fraguela 《International journal of parallel programming》2014,42(6):948-967
The parallelization of irregular algorithms has not been as widely studied as the one of regular codes. In particular, while there are many proposals of parallel skeletons and libraries very well suited to regular algorithms, this is not the case for irregular ones. This is probably due to the complexity of finding common patterns, behaviors and semantics in these algorithms. This is unfortunate, as the parallelization of irregular algorithms would benefit even more than that of regular codes from the higher degree of abstraction provided by skeletons. This work proposes to exploit the concept of domain defined on some property of the elements to process in order to enable the simple and effective parallelization of irregular applications. Namely, we propose to use such domains both to decompose the computations in parallel tasks and to detect and avoid conflicts between these tasks. A generic C++ library providing a skeleton for multicore systems built on this idea is described and evaluated. Our experimental results show that this library is a very practical tool for the parallelization of irregular algorithms with little programming effort. 相似文献
83.
A complete and efficient CUDA-sharing solution for HPC clusters 总被引:1,自引:0,他引:1
Antonio J. Peña Carlos Reaño Federico Silla Rafael Mayo Enrique S. Quintana-Ortí José Duato 《Parallel Computing》2014
In this paper we detail the key features, architectural design, and implementation of rCUDA, an advanced framework to enable remote and transparent GPGPU acceleration in HPC clusters. rCUDA allows decoupling GPUs from nodes, forming pools of shared accelerators, which brings enhanced flexibility to cluster configurations. This opens the door to configurations with fewer accelerators than nodes, as well as permits a single node to exploit the whole set of GPUs installed in the cluster. In our proposal, CUDA applications can seamlessly interact with any GPU in the cluster, independently of its physical location. Thus, GPUs can be either distributed among compute nodes or concentrated in dedicated GPGPU servers, depending on the cluster administrator’s policy. This proposal leads to savings not only in space but also in energy, acquisition, and maintenance costs. The performance evaluation in this paper with a series of benchmarks and a production application clearly demonstrates the viability of this proposal. Concretely, experiments with the matrix–matrix product reveal excellent performance compared with regular executions on the local GPU; on a much more complex application, the GPU-accelerated LAMMPS, we attain up to 11x speedup employing 8 remote accelerators from a single node with respect to a 12-core CPU-only execution. GPGPU service interaction in compute nodes, remote acceleration in dedicated GPGPU servers, and data transfer performance of similar GPU virtualization frameworks are also evaluated. 相似文献
84.
J. Javier Gutiérrez J. Carlos Palencia Michael González Harbour 《Real-Time Systems》2014,50(2):230-269
The ARINC-664, Part 7 (AFDX) standard defines a communication network based on Ethernet and the UDP/IP protocols. Contrary to general-purpose Ethernet, the timing behavior in AFDX is deterministic due to the use of special network switches and end systems with static routing tables and traffic policing at the sending end through mechanisms called virtual links. Even though the latencies in this network are bounded, there are scheduling and contention effects that need to be analyzed. In this paper we develop a response-time analysis for multipacket messages transmitted through an AFDX network including the scheduling of the virtual links and sub-virtual links, and also the contention in the end systems and in the switches. This analysis allows us to obtain worst-case latencies and output jitter for the network messages with a precise modeling of the sending and receiving ends. These results can be integrated in a holistic approach with the response time analysis of the threads in the processing nodes to obtain end-to-end response times in heterogeneous distributed systems. 相似文献
85.
Maria Luz Fernandez A. Karin Conde Laura R. Ruiz Carlos Montano John Ebner Donald J. McNamara 《Lipids》1995,30(7):619-626
To test the effects of exchanging dietary complex and simple carbohydrate for fat calories on lipoprotein metabolism, guinea
pigs were fed two different fat/carbohydrate ratios: 2.5∶58% (w/w) or 25∶29% (w/w) with either sucrose or starch as the carbohydrate
source. Animals fed high-fat had higher plasma low-density lipoprotein (LDL) and hepatic cholesterol concentrations than animals
fed low-fat diets (P<0.01). The cholesteryl ester content per particle was higher, and the number of triacylglycerol (TAG) molecules was lower
in very low density lipoprotein (VLDL) and LDL from animals fed high-fat diets. Intake of high-fat/sucrose resulted in higher
plasma LDL concentrations than intake of high-fat/starch, and animals fed low-fat/starch had the highest plasma TAG concentrations
associated with VLDL particles containing more TAG molecules, as well as a TAG-enriched LDL. The activity of plasma lecithin
cholesteryl:acyl transferase (LCAT) was highest in animals fed high-fat/sucrose, and heart lipoprotein lipase (LPL) activity
was higher in animals fed high-fat diets. Hepatic apoprotein B/E (apo B/E) receptor number (Bmax) was increased 21% with low-fat diets (P<0.01). These results suggest that the hypercholesterolemia induced by high-fat and by sucrose intake are associated with
a higher plasma LCAT activity which results in a cholesteryl ester-enriched VLDL which, by the action of LPL, might be more
readily converted to LDL through the delipidation cascade leading to downregulation of hepatic apo B/E receptors. The hypertriglyceridemia
associated with low-fat intake may result from increased production of VLDL TAG, which would explain the increased TAG content
and the higher TAG/CE ratio of VLDL from animals fed the low-fat/starch diet. 相似文献
86.
Carlos Díaz María Luisa Valenzuela 《Journal of Inorganic and Organometallic Polymers and Materials》2006,16(2):123-128
Pyrolysis in air at 800°C of [{NP(OC12H10)}0.6{NP(OC6H4PPh2·(π-CH3C5H4)−Mn(CO)2)2}0.4]
n
(1) in the solid state affords product 2 containing nanoclusters of Mn2P2O7 with sizes ranging from 50 to 90 nm and averaging about 74 nm. The egg-shape of the unpyrolyzed organometallic polymer is
retained but with increased particle size after pyrolysis. The pyrolytic material shows near-infrared photoluminescence attributed
to the emission of tetrahedral Mn2+ embedded in a matrix of Mn2P2O7. The solid-state pyrolysis of organometallic derivatives of polyphosphazenes may be a useful and general route to nano-structured
Mn2P2O7.
An erratum to this article can be found at 相似文献
87.
Pablo Giménez Benjamín Molina Jaime Calvo-Gallego Manuel Esteve Carlos E. Palau 《Computers in Industry》2014
Sensor Web Enablement (SWE) technologies have been successfully applied to a great variety of outdoor scenarios but, in practical terms, little effort has been applied for indoor environments, and even less in the field of industrial applications. This article presents an intelligent SWE application for an indoor and industrial scenario, with the aim of improving and increasing the levels of human safety. The base low-level architecture is built on top of wireless sensor networks (WSN) connected to a Sensor Observation Service (SOS). Higher layers in the architecture include services that make real time decisions based on the collected data. Both simulation and experimental results are presented. The paper shows the viability of our approach in terms of performance, scalability, modularity and safety. 相似文献
88.
The exponential growth of Internet during the last decade leads us to make more efforts in the researching and developing of sustainable Web servers in order to decrease the global energy demand. In this paper, we cover, as a first step, a proper review of the literature related to the energy efficiency research in Web server systems to depict the state of the art to plan further contributions as more research in sustainable Web systems. We also propose and implement an energy metric that permits to establish a relation between the Quality of Service (QoS) obtained by the system and the power it consumes. 相似文献
89.
Fernando A. Oliveira Neri Alves José A. Giacometti Carlos J. L. Constantino Luiz H. C. Mattoso Ana M. O. A. Balan Aldo E. Job 《应用聚合物科学杂志》2007,106(2):1001-1006
This work describes the preparation and characterization of composite materials obtained by the combination of natural rubber (NR) and carbon black (CB) in different percentages, aiming to improve their mechanical properties, processability, and electrical conductivity, aiming future applications as transducer in pressure sensors. The composites NR/CB were characterized through optical microscopy (OM), DC conductivity, thermal analysis using differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMA), thermogravimetry (TGA), and stress–strain test. The electrical conductivity varied between 10?9 and 10 S m?1, depending on the percentage of CB in the composite. Furthermore, a linear (and reversible) dependence of the conductivity on the applied pressure between 0 and 1.6 MPa was observed for the sample with containing 80 wt % of NR and 20% of CB. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 相似文献
90.
Rinaldo Gregorio Luiz Francisco Malmonge Guilherme Fontes Leal Ferreira Wilson Nunes Dos Santos Luiz Henrique Capparelli Mattoso 《应用聚合物科学杂志》2003,87(5):752-758
The real (ε′) and imaginary (ε″) components of the complex permittivity of blends of PVDF [poly(vinylidene fluoride)] with POMA [poly(o‐methoxyaniline)] doped with toluenosulfonic acid (TSA) containing 1, 2.5, and 5 wt % POMA–TSA were determined in the frequency interval between 102 and 3 × 106 Hz and in the temperature range from ?120 up to 120°C. It was observed that the values of ε′ and ε″ had a greater increase with the POMA–TSA content and with a temperature in the region of frequencies below 10 kHz. This effect decreased with frequency and it was attributed to interfacial polarization. This polarization was caused by the blend heterogeneity, formed by conductive POMA–TSA agglomerates dispersed in an insulating matrix of PVDF. The equation of Maxwell–Garnett, modified by Cohen, was used to evaluate the permittivity and conductivity behavior of POMA–TSA in the blends. A strong decrease was observed in POMA–TSA conductivity in the blend, which was bigger the lower the POMA–TSA content in the blend. This decrease could have been caused either by the POMA dedoping during the blend preparation process or by its dispersion into the insulating matrix. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 752–758, 2003 相似文献