全文获取类型
收费全文 | 19867篇 |
免费 | 5249篇 |
国内免费 | 1002篇 |
专业分类
电工技术 | 2027篇 |
综合类 | 2623篇 |
化学工业 | 2604篇 |
金属工艺 | 533篇 |
机械仪表 | 1879篇 |
建筑科学 | 885篇 |
矿业工程 | 131篇 |
能源动力 | 350篇 |
轻工业 | 762篇 |
水利工程 | 383篇 |
石油天然气 | 329篇 |
武器工业 | 201篇 |
无线电 | 2465篇 |
一般工业技术 | 970篇 |
冶金工业 | 578篇 |
原子能技术 | 247篇 |
自动化技术 | 9151篇 |
出版年
2024年 | 4篇 |
2023年 | 132篇 |
2022年 | 406篇 |
2021年 | 379篇 |
2020年 | 385篇 |
2019年 | 435篇 |
2018年 | 577篇 |
2017年 | 437篇 |
2016年 | 528篇 |
2015年 | 366篇 |
2014年 | 3679篇 |
2013年 | 2570篇 |
2012年 | 3403篇 |
2011年 | 3659篇 |
2010年 | 3225篇 |
2009年 | 2872篇 |
2008年 | 1106篇 |
2007年 | 291篇 |
2006年 | 243篇 |
2005年 | 200篇 |
2004年 | 177篇 |
2003年 | 178篇 |
2002年 | 149篇 |
2001年 | 151篇 |
2000年 | 90篇 |
1999年 | 79篇 |
1998年 | 82篇 |
1997年 | 67篇 |
1996年 | 33篇 |
1995年 | 42篇 |
1994年 | 32篇 |
1993年 | 30篇 |
1992年 | 18篇 |
1991年 | 18篇 |
1990年 | 13篇 |
1989年 | 11篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 10篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 7篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
城市慢行交通系统是现代城市交通系统的重要组成部分,随着多模式城市交通发展,建立便捷和高效的城市慢行交通网络系统成为现代城市解决交通问题和提升交通运行效率的关键措施。基于此,文中应用统一建模语言(UML)和地理标识语言(GML)建立城市慢行交通网络数据模型,提出一种统一的和一致性的交通地理要素定义和性质描述方法,并阐述基于GML的城市慢行交通网络的地理要素和关系表达。研究成果促进了城市交通地理数据的组织、表达、集成、共享和操作,对建立高效的城市慢行交通网络系统具有重要的理论价值。 相似文献
62.
鲍蓉 《自动化与仪器仪表》2014,(1):27-29
运用线性回归对预测数据进行分析,剔除异常数据,用GM(1,1)模型进行预测,有效降低了数据相对误差,提高了预测数据的精度。选用印刷包衬压缩变形的压缩变形量值,用线性回归进行数据分析并剔除异常数据后用GM(1,1)进行预测,使得预测数据具有更高的准确性和适应性。实验及仿真结果表明,经过前期数据分析整理后的灰色预测模型,其预测期望值远优于单纯的回归模型和GM(1,1)模型。 相似文献
63.
王淑晶 《自动化与仪器仪表》2014,(12):152-153
LTE-R是国际铁路联盟(UIC)确定的铁路下一代宽带移动通信系统。本文从系统应用、系统架构、系统性能等方面对GSM-R和LTE-R进行对比分析,以珠三角某城际铁路为例,结合城际铁路特点,阐述了城际铁路GSM-R向LTE-R演进策略。 相似文献
64.
65.
Takatoshi Yamada Purayath Robert Vinod Doo-Sup Hwang Hiromichi Yoshikawa Shin-ichi Shikata Naoji Fujimori 《Diamond and Related Materials》2005,14(11-12):2047
This paper describes a self-aligned fabrication process for diamond gated field emitter array (FEA). Utilizing the non-conformal coverage sputtering conditions of silicon oxide, an interesting “sphere on cone” structure is formed on diamond nano tip array, which is the key point of gate hole opening process. This structure causes shadowing at certain regions of side-wall during Ti / Au gate metal deposition. Removal of “sphere” by wet etching leads to the successful fabrication of a single crystalline diamond gated FEA. Scanning electron microscope observations reveal the fabrication of a uniform emitter array with tip radius of curvature (20 nm) and gate hole (1.4 μm). We also confirmed that no noticeable physical damage exists on tip. In field emission characteristics of the fabricated single crystal diamond gated FEA, gate voltage control of field emission current is realized. 相似文献
66.
The fuzzy c-partition entropy has been widely adopted as a global optimization technique for finding the optimized thresholds for multilevel image segmentation. However, it involves expensive computation as the number of thresholds increases and often yields noisy segmentation results since spatial coherence is not enforced. In this paper, an iterative calculation scheme is presented for reducing redundant computations in entropy evaluation. The efficiency of threshold selection is further improved through utilizing the artificial bee colony algorithm as the optimization technique. Finally, instead of performing thresholding for each pixel independently, the presented algorithm oversegments the input image into small regions and uses the probabilities of fuzzy events to define the costs of different label assignments for each region. The final segmentation results is computed using graph cut, which produces smooth segmentation results. The experimental results demonstrate the presented iterative calculation scheme can greatly reduce the running time and keep it stable as the number of required thresholds increases. Quantitative evaluations over 20 classic images also show that the presented algorithm outperforms existing multilevel segmentation approaches. 相似文献
67.
《Pattern recognition》2014,47(2):789-805
This paper studies Fisher linear discriminants (FLDs) based on classification accuracies for imbalanced datasets. An optimal threshold is found out from a series of empirical formulas developed, which is related not only to sample sizes but also to distribution regions. A mixed binary–decimal coding system is suggested to make the very dense datasets sparse and enlarge the class margins on condition that the neighborhood relationships of samples are nearly preserved. The within-class scatter matrices being or approximately singular should be moderately reduced in dimensionality but not added with tiny perturbations. The weight vectors can be further updated by a kind of epoch-limited (three at most) iterative learning strategy provided that the current training error rates come down accordingly. Putting the above ideas together, this paper proposes a type of integrated FLDs. The extensive experimental results over real-world datasets have demonstrated that the integrated FLDs have obvious advantages over the conventional FLDs in the aspects of learning and generalization performances for the imbalanced datasets. 相似文献
68.
Lauro Cassio Martins de Paula Anderson da Silva Soares 《通讯和计算机》2014,(4):339-346
This paper presents a parallel implementation of the hybrid BiCGStab(2) (bi-conjugate gradient stabilized) iterative method in a GPU (graphics processing unit) for solution of large and sparse linear systems. This implementation uses the CUDA-Matlab integration, in which the method operations are performed in a GPU core using Matlab built-in functions. The goal is to show that the exploitation of parallelism by using this new technology can provide a significant computational performance. For the validation of the work, we compared the proposed implementation with a BiCGStab(2) sequential and parallelized implementation in the C and CUDA-C languages. The results showed that the proposed implementation is more efficient and can be viable for simulations being carried out with quality and in a timely manner. The gains in computational efficiency were 76x and 6x compared to the implementation in C and CUDA-C, respectively. 相似文献
69.
70.