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   2855篇
  免费   173篇
  国内免费   1篇
电工技术   60篇
综合类   1篇
化学工业   942篇
金属工艺   17篇
机械仪表   79篇
建筑科学   106篇
矿业工程   2篇
能源动力   85篇
轻工业   423篇
水利工程   27篇
石油天然气   5篇
无线电   229篇
一般工业技术   391篇
冶金工业   90篇
原子能技术   12篇
自动化技术   560篇
  2023年   34篇
  2022年   171篇
  2021年   187篇
  2020年   91篇
  2019年   84篇
  2018年   109篇
  2017年   86篇
  2016年   136篇
  2015年   90篇
  2014年   117篇
  2013年   201篇
  2012年   169篇
  2011年   218篇
  2010年   153篇
  2009年   180篇
  2008年   128篇
  2007年   129篇
  2006年   109篇
  2005年   87篇
  2004年   65篇
  2003年   58篇
  2002年   59篇
  2001年   36篇
  2000年   29篇
  1999年   26篇
  1998年   34篇
  1997年   25篇
  1996年   30篇
  1995年   17篇
  1994年   27篇
  1993年   9篇
  1992年   11篇
  1991年   5篇
  1990年   18篇
  1989年   10篇
  1988年   7篇
  1987年   6篇
  1986年   4篇
  1985年   4篇
  1984年   10篇
  1983年   8篇
  1982年   10篇
  1981年   7篇
  1980年   11篇
  1977年   3篇
  1976年   2篇
  1975年   2篇
  1971年   2篇
  1965年   2篇
  1909年   2篇
排序方式: 共有3029条查询结果,搜索用时 0 毫秒
81.
82.
Engineering the electrical properties of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)holds great potential for various applications such a...  相似文献   
83.
84.
85.
86.
The beneficial health effects of extra virgin olive oil are due to both its high content of monounsaturated fatty acids and its high content of phenolic compounds, which have recently attracted research interest. In this context, the aim of this work was to examine the in vitro antioxidant and antiproliferative activities of the phenolic extract obtained from extra virgin olive oil from O. europea cultivar ‘Frantoio’ (samples 1–4), one of the main varieties cultivated in Italy. The total phenolic content was determined by Folin–Ciocalteu method and instead the phenolic profile was obtained by HPLC coupled to a diode array detector and mass spectrometry. Extra virgin olive oil extracts exhibited high antioxidant activity through different mechanisms of action and these activities are related to the phenolic content. Sample 3 demonstrated the strongest free radical scavenging activity with IC50 value of 56.5 μg/mL. The reducing ability measured with FRAP assay revealed that samples ranged from 91.3 to 156 μM Fe(II)/g. The same interesting trend was observed with Trolox equivalent antioxidant capacity value. Moreover, the virgin olive oils showed a good oxidative stability ranging between 19 to 32 h. Antiproliferative activity evaluated by SRB assay revealed that phenolic extracts from the cultivar ‘Frantoio’ showed a strong antiproliferative activity against CORL-23 cell line with an IC50 value of 14.5 and 55.9 μg/mL for samples 3 and 1, respectively, and these results are comparable to the positive control vinblastine. Overall, these results showed that extra virgin olive oils from the cultivar ‘Frantoio’, may represent an interesting source of phenolic compounds as functional components that could be consumed in diets and/or used for the elaboration of functional food and pharmaceutical industries.  相似文献   
87.
Astronomy has been at the forefront of the development of the techniques and methodologies of data intensive science for over a decade with large sky surveys and distributed efforts such as the Virtual Observatory. However, it faces a new data deluge with the next generation of synoptic sky surveys which are opening up the time domain for discovery and exploration. This brings both new scientific opportunities and fresh challenges, in terms of data rates from robotic telescopes and exponential complexity in linked data, but also for data mining algorithms used in classification and decision making. In this paper, we describe how an informatics-based approach—part of the so-called “fourth paradigm” of scientific discovery—is emerging to deal with these. We review our experiences with the Palomar-Quest and Catalina Real-Time Transient Sky Surveys; in particular, addressing the issue of the heterogeneity of data associated with transient astronomical events (and other sensor networks) and how to manage and analyze it.  相似文献   
88.
This paper proposes a new effective strategy for designing and implementing interactive systems overcoming culture, skill and situation hurdles in Human-Computer Interaction (HCI). The strategy to identify and reduce these hurdles is developed in the framework of a methodology based on a recently introduced model of HCI, and exploits the technological innovations of XML (Extensible Markup Language). HCI is modelled as a cyclic process in which the user and the interactive system communicate by materializing and interpreting a sequence of messages. The interaction process is formalized by specifying both the physical message appearance and the computational aspect of the interaction. This formalization allows the adoption of notation traditionally adopted by users in their workplaces as the starting point of the interactive system design. In this way, the human–system interaction language takes into account the users’ culture. Moreover, the methodology permits user representatives to build a hierarchy of systems progressively adapted to users’ situations, skills and habits, according to the work organization in the domain considered. The strategy is proved to be effective by describing how to implement it using BANCO (Browsing Adaptive Network for Changing user Operativity), a feasibility prototype based on XML, which allows the hierarchy implementation and system adaptations. Several examples from an environmental case under study are used throughout the paper to illustrate the methodology and the effectiveness of the technology adopted. Published online: 4 June 2002  相似文献   
89.
Boosting text segmentation via progressive classification   总被引:1,自引:4,他引:1  
A novel approach for reconciling tuples stored as free text into an existing attribute schema is proposed. The basic idea is to subject the available text to progressive classification, i.e., a multi-stage classification scheme where, at each intermediate stage, a classifier is learnt that analyzes the textual fragments not reconciled at the end of the previous steps. Classification is accomplished by an ad hoc exploitation of traditional association mining algorithms, and is supported by a data transformation scheme which takes advantage of domain-specific dictionaries/ontologies. A key feature is the capability of progressively enriching the available ontology with the results of the previous stages of classification, thus significantly improving the overall classification accuracy. An extensive experimental evaluation shows the effectiveness of our approach.  相似文献   
90.
A GIS-based procedure for predicting pesticide exposure in surface waters has been applied on a pilot river basin characterized by intensive agricultural activity. The predictive approach has been validated through experimental monitoring, performed by collecting manual and automatic water samples during the productive season. Five active ingredients (terbuthylazine, metolachlor, alachlor, linuron, fenitrothion) were selected for analysis to validate the predictive approach. Comparison between predicted and experimental values showed good agreement for terbuthylazine and metolachlor (used in large volumes within the basin), demonstrating the reliability of the approach. However, some anomalous results were obtained for some of the other chemicals, which serve to highlight the difficulties in getting reliable input data, in particular on application patterns (rate and time). Furthermore, the value of mapping pesticide exposure on the medium-large scale is described, and the limitations of the reported predictive approach are discussed.  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