全文获取类型
收费全文 | 134526篇 |
免费 | 15000篇 |
国内免费 | 10888篇 |
专业分类
电工技术 | 11981篇 |
综合类 | 14809篇 |
化学工业 | 17797篇 |
金属工艺 | 8916篇 |
机械仪表 | 9157篇 |
建筑科学 | 9418篇 |
矿业工程 | 5391篇 |
能源动力 | 3507篇 |
轻工业 | 16619篇 |
水利工程 | 3981篇 |
石油天然气 | 4583篇 |
武器工业 | 1671篇 |
无线电 | 13363篇 |
一般工业技术 | 11692篇 |
冶金工业 | 5122篇 |
原子能技术 | 2061篇 |
自动化技术 | 20346篇 |
出版年
2024年 | 830篇 |
2023年 | 2233篇 |
2022年 | 5410篇 |
2021年 | 6796篇 |
2020年 | 4864篇 |
2019年 | 3404篇 |
2018年 | 3649篇 |
2017年 | 4332篇 |
2016年 | 3913篇 |
2015年 | 6231篇 |
2014年 | 7607篇 |
2013年 | 9282篇 |
2012年 | 11267篇 |
2011年 | 11839篇 |
2010年 | 10950篇 |
2009年 | 10765篇 |
2008年 | 10718篇 |
2007年 | 10500篇 |
2006年 | 8821篇 |
2005年 | 7173篇 |
2004年 | 5109篇 |
2003年 | 3559篇 |
2002年 | 3230篇 |
2001年 | 2869篇 |
2000年 | 2308篇 |
1999年 | 854篇 |
1998年 | 354篇 |
1997年 | 253篇 |
1996年 | 175篇 |
1995年 | 161篇 |
1994年 | 108篇 |
1993年 | 117篇 |
1992年 | 100篇 |
1991年 | 77篇 |
1990年 | 75篇 |
1989年 | 76篇 |
1988年 | 49篇 |
1987年 | 36篇 |
1986年 | 36篇 |
1985年 | 29篇 |
1984年 | 18篇 |
1983年 | 28篇 |
1982年 | 12篇 |
1981年 | 36篇 |
1980年 | 41篇 |
1979年 | 21篇 |
1977年 | 4篇 |
1976年 | 11篇 |
1959年 | 32篇 |
1951年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
931.
HAN MengDi ZHANG XiaoSheng LIU Wen SUN XuMing PENG XuHua ZHANG HaiXia 《中国科学:技术科学(英文版)》2013,(8):1835-1841
Recently,hybrid energy harvester has been considered as an attractive potential approach to response the worldwide energy crisis due to the combination of advantages from different harvesting mechanism.In this paper,a novel low-frequency wide-band hybrid energy harvester based on piezoelectric and triboelectric mechanism is presented and systematically studied including structural design,fabrication process,working principle simulation and measurement.With a vibrational excitation,the polyvinylidene fluoride(PVDF) cantilevers will vibrate and impact the polydimethylsiloxane(PDMS) film on the substrate,producing a piezoelectric output as well as a triboelectric output.The structural parameters of each cantilever are optimized using finite element simulation,and the well-designed PVDF cantilevers with controllable PDMS mass not only reduce the device working frequency but also enlarge the bandwidth.Under a sweep-frequency test,three voltage peaks induced by the piezoelectric part are observed at 15,32.5 and 47.5 Hz,with the value of 320,288 and 264 mV,respectively.With the combined triboelectric part,a 20 V peak-peak voltage is generated at 15 Hz.The electrical driving ability of this hybrid energy harvester also has been demonstrated by lighting up a commercial light emitting diode(LED). 相似文献
932.
933.
十七大以来农村改革发展理论与实践的深化 总被引:1,自引:0,他引:1
农村改革发展事关党和国家的工作大局,是全面建成小康社会的关键环节和重要领域。十七大以来,党对农村改革发展的历史和作用有了更加清晰的认识,强化了农村改革、加快发展对国民经济发展的战略性作用,明确了农业现代化的发展路径,制定了一系列农业现代化和加快推进农村改革发展的制度体系,提出了一系列重要的科学论断,进一步深化和完善了党的农村改革理论。 相似文献
934.
Xiao-chuan SUN Hong-yan CUI Ren-ping LIU Jian-ya CHEN Yun-jie LIU 《浙江大学学报(英文版)(C辑:计算机与电子)》2012,13(9)
Echo state network (ESN),which efficiently models nonlinear dynamic systems,has been proposed as a special form of recurrent neural network.However,most of the proposed ESNs consist of complex reservoi... 相似文献
935.
基于流映射的负载均衡调度算法研究 总被引:1,自引:0,他引:1
网络管理者需要能够提供可扩展性、吞吐率保证及报文顺序的高性能路由器体系结构.目前基于Crossbar的集中式路由器体系结构难以实现性能和规模的可扩展,基于两级Mesh网络的负载均衡交换结构成为扩展Internet路由器容量的有效的途径.负载均衡路由器存在严重的报文乱序现象,输出端报文重定序复杂度为O(N2).文中提出一种区域均等的负载均衡交换结构,每k个连续的中间级输入端口划分为一个区域,输入端采用基于流映射的负载分配算法UFFS-k(Uniform Fine-grain Frame Spreading,k为聚合粒度,简称UFFS-k),在k个连续的外部时间槽,以细粒度的方式将同一条流的k个信元分派到固定的映射区域,通过理论证明,该调度策略可获得100%吞吐率并能够保证报文的顺序.为避免流量区域集中现象,采用双循环(dual-rotation)方式构建不同输入端口的流到区域的映射关系;为实现负载在中间级输入端口的均衡分布,每个输入端口维护全局统一视图的流量分布矩阵,UFFS-k调度算法根据流量分布矩阵调度单位帧,可以证明,对任意输出端口j,同一区域OQj队列长度相同且不同区域OQj队列长度至多差1,从而实现了100%负载均衡度.UFFS-k调度算法分布于每个输入端口独立执行,根据流到区域的映射关系及负载分布状态分派信元,模拟结果显示,当聚合粒度k=2时,UFFS-k算法在同类维序算法中表现出最优延迟性能. 相似文献
936.
Juan Carlos Gomez Erik Boiy Marie-Francine Moens 《Knowledge and Information Systems》2012,31(1):23-53
This paper reports on email classification and filtering, more specifically on spam versus ham and phishing versus spam classification,
based on content features. We test the validity of several novel statistical feature extraction methods. The methods rely
on dimensionality reduction in order to retain the most informative and discriminative features. We successfully test our
methods under two schemas. The first one is a classic classification scenario using a 10-fold cross-validation technique for
several corpora, including four ground truth standard corpora: Ling-Spam, SpamAssassin, PU1, and a subset of the TREC 2007
spam corpus, and one proprietary corpus. In the second schema, we test the anticipatory properties of our extracted features
and classification models with two proprietary datasets, formed by phishing and spam emails sorted by date, and with the public
TREC 2007 spam corpus. The contributions of our work are an exhaustive comparison of several feature selection and extraction
methods in the frame of email classification on different benchmarking corpora, and the evidence that especially the technique
of biased discriminant analysis offers better discriminative features for the classification, gives stable classification
results notwithstanding the amount of features chosen, and robustly retains their discriminative value over time and data
setups. These findings are especially useful in a commercial setting, where short profile rules are built based on a limited
number of features for filtering emails. 相似文献
937.
José María Moreno-Jiménez Juan Aguarón Jesús Cardeñosa María Teresa Escobar José Luis Salazar Adrián Toncovich Alberto Turón 《Computers in human behavior》2012
Two key aspects of the Knowledge Society are the interconnection between the actors involved in the decision making processes and the importance of the human factor, particularly the citizen’s continuous learning and education. This paper presents a new module devoted to knowledge extraction and diffusion that has been incorporated into a previously developed decision making tool concerning the Internet and related with the multicriteria selection of a discrete number of alternatives (PRIOR-Web). Quantitative and qualitative procedures using data and text mining methods have been employed in the extraction of knowledge. Graphical visualisation tools have been incorporated in the diffusion stage of the methodological approach suggested when dealing with decision making in the Knowledge Society. The resulting collaborative platform is being used as the methodological support for the cognitive democracy known as e-cognocracy. 相似文献
938.
Juan L. Mata-Machuca Rafael Martínez-Guerra 《Computers & Mathematics with Applications》2012,63(6):1072-1078
In this paper we deal with the observer-based asymptotic synchronization problem for a class of chaotic oscillators. Some results based on a differential algebraic approach are used in order to determine the algebraic observability of unknown variables. The strategy consists of proposing a slave system (observer) which tends to follow asymptotically the master system. The methodology is tested in the real-time asymptotic synchronization of the Colpitts oscillator by means of a proportional reduced order observer (PROO) of free-model type. 相似文献
939.
This paper presents F-MPJ (Fast MPJ), a scalable and efficient Message-Passing in Java (MPJ) communication middleware for
parallel computing. The increasing interest in Java as the programming language of the multi-core era demands scalable performance
on hybrid architectures (with both shared and distributed memory spaces). However, current Java communication middleware lacks
efficient communication support. F-MPJ boosts this situation by: (1) providing efficient non-blocking communication, which
allows communication overlapping and thus scalable performance; (2) taking advantage of shared memory systems and high-performance
networks through the use of our high-performance Java sockets implementation (named JFS, Java Fast Sockets); (3) avoiding
the use of communication buffers; and (4) optimizing MPJ collective primitives. Thus, F-MPJ significantly improves the scalability
of current MPJ implementations. A performance evaluation on an InfiniBand multi-core cluster has shown that F-MPJ communication
primitives outperform representative MPJ libraries up to 60 times. Furthermore, the use of F-MPJ in communication-intensive
MPJ codes has increased their performance up to seven times. 相似文献
940.