全文获取类型
收费全文 | 3174篇 |
免费 | 52篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 159篇 |
综合类 | 5篇 |
化学工业 | 565篇 |
金属工艺 | 57篇 |
机械仪表 | 99篇 |
建筑科学 | 65篇 |
矿业工程 | 4篇 |
能源动力 | 106篇 |
轻工业 | 222篇 |
水利工程 | 8篇 |
石油天然气 | 8篇 |
无线电 | 416篇 |
一般工业技术 | 553篇 |
冶金工业 | 750篇 |
原子能技术 | 80篇 |
自动化技术 | 136篇 |
出版年
2023年 | 9篇 |
2022年 | 25篇 |
2021年 | 57篇 |
2020年 | 19篇 |
2019年 | 34篇 |
2018年 | 38篇 |
2017年 | 44篇 |
2016年 | 37篇 |
2015年 | 30篇 |
2014年 | 51篇 |
2013年 | 121篇 |
2012年 | 91篇 |
2011年 | 94篇 |
2010年 | 87篇 |
2009年 | 86篇 |
2008年 | 115篇 |
2007年 | 99篇 |
2006年 | 92篇 |
2005年 | 80篇 |
2004年 | 84篇 |
2003年 | 111篇 |
2002年 | 90篇 |
2001年 | 83篇 |
2000年 | 60篇 |
1999年 | 84篇 |
1998年 | 323篇 |
1997年 | 190篇 |
1996年 | 129篇 |
1995年 | 116篇 |
1994年 | 85篇 |
1993年 | 84篇 |
1992年 | 54篇 |
1991年 | 38篇 |
1990年 | 39篇 |
1989年 | 43篇 |
1988年 | 40篇 |
1987年 | 36篇 |
1986年 | 35篇 |
1985年 | 27篇 |
1984年 | 29篇 |
1983年 | 32篇 |
1982年 | 23篇 |
1981年 | 27篇 |
1980年 | 21篇 |
1979年 | 19篇 |
1978年 | 15篇 |
1977年 | 28篇 |
1976年 | 39篇 |
1975年 | 10篇 |
1972年 | 6篇 |
排序方式: 共有3233条查询结果,搜索用时 690 毫秒
71.
72.
Ryo Tsujimoto Genki Terauchi Hisao Sasaki Shingo X. Sakamoto Shuhei Sawayama Shuji Sasa 《International journal of remote sensing》2016,37(24):5843-5863
Damage to seagrass and seaweed beds caused by the huge tsunami of the Great East Japan Earthquake on 11 March 2011 was investigated in Matsushima Bay, Miyagi Prefecture, Japan, by comparing satellite images taken before the tsunami in November 2009 and after the tsunami in May 2011. The results showed that the tsunami destroyed 220 ha of seagrass and seaweed beds, from 320 ha in 2009 to 100 ha just after the tsunami. Zostera marina beds on the sandy and muddy bottom were rather severely damaged compared with brown seaweed beds of Sargassum horneri on the rocky substrate. Substrates of the beds and directions of the tsunami seem to be responsible for the magnitude of the damage to the beds. Maps of the spatial distributions of the beds before and after the tsunami can provide information for the restoration of seagrass and seaweed beds as natural infrastructures of coastal fisheries resources. 相似文献
73.
Daichi Amagata Yuya Sasaki Takahiro Hara Shojiro Nishio 《Distributed and Parallel Databases》2016,34(2):259-287
A nearest neighbor (NN) query, which returns the most similar object to a user-specified query object, plays an important role in a wide range of applications and hence has received considerable attention. In many such applications, e.g., sensor data collection and location-based services, objects are inherently uncertain. Furthermore, due to the ever increasing generation of massive datasets, the importance of distributed databases, which deal with such data objects, has been growing. One emerging challenge is to efficiently process probabilistic NN queries over distributed uncertain databases. The straightforward approach, that each local site forwards its own database to the central server, is communication-expensive, so we have to minimize communication cost for the NN object retrieval. In this paper, we focus on two important queries, namely top-k probable NN queries and probabilistic star queries, and propose efficient algorithms to process them over distributed uncertain databases. Extensive experiments on both real and synthetic data have demonstrated that our algorithms significantly reduce communication cost. 相似文献
74.
Takashi Soga Akihiro Musa Koki Okabe Kazuhiko Komatsu Ryusuke Egawa Hiroyuki Takizawa Hiroaki Kobayashi Shun Takahashi Daisuke Sasaki Kazuhiro Nakahashi 《Computers & Fluids》2011,45(1):215-221
The building-cube method (BCM) is a new generation algorithm for CFD simulations. The basic idea of BCM is to simplify the algorithm in all stages of flow computation to achieve large-scale simulations. Calculation of a pressure field using the Successive Over Relaxation (SOR) method consumes most of the total execution time required for BCM. In this paper, effective implementations on modern vector and scalar processors are investigated. NEC SX-9 and Intel Nehalem-EX are the latest vector and scalar processors. Those processors have much higher peak performances than their previous-generation processors. However, their memory bandwidth improvement cannot catch up with the performance improvement of processors. This is the so-called memory wall problem. In our paper, we discuss optimization techniques for implementation of the SOR method based on architectural characteristics of these modern processors, and evaluate their effects on the sustained performances of these processors for BCM. 相似文献
75.
Abstract. This paper proposes a highly parallel Hough transform algorithm for real-time straight-line extraction and its hardware implementation
on a content-addressable memory (CAM). To achieve high-speed processing, incrementation for voting, which composes the Hough
transform, and calculations for coordinate updating are carried out for the every scan line, not every edge pixel, and extracting
maxima in Hough space is executed by parallel comparing. Moreover, variously weighted voting achieves more accurate line extraction
in spite of the quantization error and noise in the image space. In the implementation, the CAM acts as a PE (processing-element)
array that effectively performs highly parallel processing for the Hough transform and also as a memory for two-dimensional
Hough space, and both voting and peak extraction are directly executed by the CAM. Evaluations of CAM hardware size, processing
time and the accuracy of line extraction show that a real-time and high-resolution Hough transform for a 256256 picture can be achieved using a single CAM chip with current VLSI technology. This CAM-based Hough transform algorithm
promises to be an important step towards the realization of a real-time and compact image-understanding system.
Received: 15 August 1998 / Accepted: 15 March 2000 相似文献
76.
Obayashi S. Sasaki D. Takeguchi Y. Hirose N. 《Evolutionary Computation, IEEE Transactions on》2000,4(2):182-187
This paper discusses the design optimization of a wing for supersonic transport (SST) using a multiple-objective genetic algorithm (MOGA). Three objective functions are used to minimize the drag for supersonic cruise, the drag for transonic cruise, and the bending moment at the wing root for supersonic cruise. The wing shape is defined by 66 design variables. A Euler flow code is used to evaluate supersonic performance, and a potential flow code is used to evaluate transonic performance. To reduce the total computational time, flow calculations are parallelized on an NEC SX-4 computer using 32 processing elements. The detailed analysis of the resulting Pareto front suggests a renewed interest in the arrow wing planform for the supersonic wing 相似文献
77.
78.
79.
The relationship between striation spacing and fatigue crack propagation rate up to 70 m/cycle was investigated for a ductile structural steel, qualified as JIS SM58Q. A modified compact-type specimen 400 mm wide and a centre-cracked specimen 200 mm wide were tested at a stress ratio, R, of 0 and 0.8. The fracture surface of the specimen was examined in detail under a scanning electron microscope. The crack propagation rate was expressed by a power function of the range of stress intensity factor from 0.1 to 70 m/cycle for R=0 and to 0.5 m/cycle for R=0.8. The striation spacing coincided with the fatigue crack propagation rate over the range 0.1 to 70 m/cycle. The profile of striation was found to be a ridge and valley type, and the ridges on one fracture surface coincided with those on the matching surface. It is suggested that the striation is formed by a plastic blunting mechanism. 相似文献
80.
Ranasinghe PD Satoh H Oshiki M Oshima K Suda W Hattori M Mino T 《Water science and technology》2012,66(10):2155-2161
The diversity of bacterial groups in activated sludge from large- and small-scale wastewater treatment plants was explored by barcoded pyrosequencing of 16S rRNA gene. Activated sludge samples (three small and 17 large scale) were collected from 12 wastewater treatment plants to clarify precise taxonomy and relative abundances. DNA was extracted, and amplified by 4 base barcoded 27f/519r primer set. The 454 Titanium (Roche) pyrosequences were obtained and analyses performed by Quantitative Insight Into Microbial Ecology (QIIME) with around 100,000 reads. Sequence statistics were computed, while constructing a phylogenetic tree and heatmap. Computed results explained total microbial diversity at phylum and class level and resolution was further extended to Operational Taxonomic Unit (OTU) based taxonomic assignment for investigating community distribution based on individual sample. Composition of sequence reads were compared and microbial community structures for large- and small-scale treatment plants were identified as major phyla (Proteobacteria and Bacteroidetes) and classes (Betaproteobacteria and Bacteroidetes). Also, family level breakdowns were explained and differences in family Nitrospiraceae and phylum Actinobacteria found at their species level were also illustrated. Thus, the pyrosequencing method provides high resolution insight into microbial community structures in activated sludge that might have been unnoticed with conventional approaches. 相似文献