首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   5334篇
  免费   154篇
  国内免费   14篇
电工技术   78篇
综合类   17篇
化学工业   1192篇
金属工艺   139篇
机械仪表   230篇
建筑科学   165篇
矿业工程   21篇
能源动力   838篇
轻工业   303篇
水利工程   41篇
石油天然气   87篇
无线电   429篇
一般工业技术   844篇
冶金工业   128篇
原子能技术   38篇
自动化技术   952篇
  2024年   6篇
  2023年   99篇
  2022年   78篇
  2021年   139篇
  2020年   165篇
  2019年   219篇
  2018年   191篇
  2017年   342篇
  2016年   447篇
  2015年   355篇
  2014年   494篇
  2013年   499篇
  2012年   313篇
  2011年   282篇
  2010年   213篇
  2009年   238篇
  2008年   93篇
  2007年   130篇
  2006年   138篇
  2005年   90篇
  2004年   63篇
  2003年   56篇
  2002年   77篇
  2001年   79篇
  2000年   52篇
  1999年   122篇
  1998年   42篇
  1997年   42篇
  1996年   41篇
  1995年   42篇
  1994年   34篇
  1993年   30篇
  1992年   14篇
  1991年   11篇
  1990年   15篇
  1989年   12篇
  1988年   30篇
  1987年   39篇
  1986年   48篇
  1985年   33篇
  1984年   21篇
  1983年   16篇
  1982年   12篇
  1981年   8篇
  1979年   9篇
  1978年   4篇
  1977年   7篇
  1976年   4篇
  1975年   2篇
  1974年   2篇
排序方式: 共有5502条查询结果,搜索用时 15 毫秒
51.
52.
The study of criminal networks using traces from heterogeneous communication media is acquiring increasing importance in nowadays society. The usage of communication media such as mobile phones and online social networks leaves digital traces in the form of metadata that can be used for this type of analysis. The goal of this work is twofold: first we provide a theoretical framework for the problem of detecting and characterizing criminal organizations in networks reconstructed from phone call records. Then, we introduce an expert system to support law enforcement agencies in the task of unveiling the underlying structure of criminal networks hidden in communication data. This platform allows for statistical network analysis, community detection and visual exploration of mobile phone network data. It enables forensic investigators to deeply understand hierarchies within criminal organizations, discovering members who play central role and provide connection among sub-groups. Our work concludes illustrating the adoption of our computational framework for a real-word criminal investigation.  相似文献   
53.
A new architecture of intelligent audio emotion recognition is proposed in this paper. It fully utilizes both prosodic and spectral features in its design. It has two main paths in parallel and can recognize 6 emotions. Path 1 is designed based on intensive analysis of different prosodic features. Significant prosodic features are identified to differentiate emotions. Path 2 is designed based on research analysis on spectral features. Extraction of Mel-Frequency Cepstral Coefficient (MFCC) feature is then followed by Bi-directional Principle Component Analysis (BDPCA), Linear Discriminant Analysis (LDA) and Radial Basis Function (RBF) neural classification. This path has 3 parallel BDPCA + LDA + RBF sub-paths structure and each handles two emotions. Fusion modules are also proposed for weights assignment and decision making. The performance of the proposed architecture is evaluated on eNTERFACE’05 and RML databases. Simulation results and comparison have revealed good performance of the proposed recognizer.  相似文献   
54.
In this paper, an improved global-best harmony search algorithm, named IGHS, is proposed. In the IGHS algorithm, initialization based on opposition-based learning for improving the solution quality of the initial harmony memory, a new improvisation scheme based on differential evolution for enhancing the local search ability, a modified random consideration based on artificial bee colony algorithm for reducing randomness of the global-best harmony search (GHS) algorithm, as well as two perturbation schemes for avoiding premature convergence, are integrated. In addition, two parameters of IGHS, harmony memory consideration rate and pitch adjusting rate, are dynamically updated based on a composite function composed of a linear time-varying function, a periodic function and a sign function in view of approximate periodicity of evolution in nature. Experimental results tested on twenty-eight benchmark functions indicate that IGHS is far better than basic harmony search (HS) algorithm and GHS. In further study, IGHS has also been compared with other eight well known metaheuristics. The results show that IGHS is better than or at least similar to those approaches on most of test functions.  相似文献   
55.
Consumer complaints on online social network quickly become online groups complaints through many people’s aggregation and looking on, interaction and word-of-mouth communication. Therefore, assessing and managing online complain influence has become a new problem for enterprise to listen to and manage online group complaints. This paper analyzed the complaint information feature of consumer group on online social network, from three-dimensional perspective of complaint text’s quality, transmission timeliness and user interaction degree. We built the influence measure model of online complaint theme based on entropy weight model by monitoring and analyzing real-time the static and dynamic properties of complaint information, explored the measure method of complaint theme influence, employed empirical method to verify the validity and provided scientific decision-making tools and methods for enterprise listening to and managing online group complains.  相似文献   
56.
Cloud computing aims to provide dynamic leasing of server capabilities as scalable virtualized services to end users. However, data centers hosting cloud applications consume vast amounts of electrical energy, thereby contributing to high operational costs and carbon footprints. Green cloud computing solutions that can not only minimize the operational costs but also reduce the environmental impact are necessary. This study focuses on the Infrastructure as a Service model, where custom virtual machines (VMs) are launched in appropriate servers available in a data center. A complete data center resource management scheme is presented in this paper. The scheme can not only ensure user quality of service (through service level agreements) but can also achieve maximum energy saving and green computing goals. Considering that the data center host is usually tens of thousands in size and that using an exact algorithm to solve the resource allocation problem is difficult, the modified shuffled frog leaping algorithm and improved extremal optimization are employed in this study to solve the dynamic allocation problem of VMs. Experimental results demonstrate that the proposed resource management scheme exhibits excellent performance in green cloud computing.  相似文献   
57.
Results of performance, emission and tribological evaluations of palm oil methyl ester and its blends with conventional diesel in an automobile diesel engine test bed are presented. Polymerization and carbon deposits on the fuel injector were monitored. CO, CO2, O2, combustion efficiency and temperature of exhaust gases were also measured. Palm oil methyl ester and its blends have great potential as alternative diesel fuel. Performance and exhaust gas emission for palm oil methyl ester and its blends with conventional diesel are comparable with those of conventional diesel fuel. Palm oil methyl ester does not pose a severe environmental problem and will not deteriorate engine and bearing components.  相似文献   
58.
Rapid synthesis of high-purity MAG from refined, bleached, and deodorized palm stearin (RBDPS) via chemical glycerolysis in the presence of pyridine was developed to obviate the conventional molecular distillation in the production of pure MAG. The optimal reaction for the sodium methoxide-catalyzed glycerolyis of RBDPS was recorded at 110°C using a 3 wt% catalyst concentration based on the weight of RBDPS, with an RBDPS/glycerol ratio of 1∶2 and an RBDPS/pyridine ratio of 1∶4. High yields of over 99% were achieved rapidly in 15 min, and increases in DAG and FFA were observed after a prolonged reaction time.  相似文献   
59.
This work studies the enzymatic degradation of polyurethanes (PUs) and segmented polyurethane ureas (SPUUs) derived from lysine diisocyanate (LDI) by various proteases. Thiol proteases, such as papain, bromelain, and ficin, showed high activity on PUs. Protease K and chymotrypsin also hydrolyzed the PUs. For almost all SPUUs, papain showed high activity. For example, LDI/poly(caprolactone) diol (Mw = 1250)/ethylene diamine (2/1/1) was hydrolyzed to 43% under the same conditions. The water-soluble degradation products of a polyurethane, LDI/BD (1/1), and two model compounds treated with papain were studied with NMR and GPC analysis. From the results, it was evident that the pendant methyl ester group in LDI was rapidly hydrolyzed, followed by slow hydrolysis of urethane bonds in the backbone chain.  相似文献   
60.
Early diagnosis of Alzheimer’s disease (AD) is essential if treatments are to be administered at an earlier point in time before neurons degenerate to a stage beyond repair. In order for early detection to occur tools used to detect the disorder must be sensitive to the earliest of cognitive impairments. Virtual reality technology offers opportunities to provide products which attempt to mimic daily life situations, as much as is possible, within the computational environment. This may be useful for the detection of cognitive difficulties. We develop a virtual simulation designed to assess visuospatial memory in order to investigate cognitive function in a group of healthy elderly participants and those with a mild cognitive impairment (MCI). Participants were required to guide themselves along a virtual path to reach a virtual destination which they were required to remember. The preliminary results indicate that this virtual simulation has the potential to be used for detection of early AD since significant correlations of scores on the virtual environment with existing neuropsychological tests were found. Furthermore, the test discriminated between healthy elderly participants and those with a MCI.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号