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   8824篇
  免费   276篇
  国内免费   163篇
电工技术   308篇
技术理论   2篇
综合类   771篇
化学工业   960篇
金属工艺   428篇
机械仪表   596篇
建筑科学   1455篇
矿业工程   631篇
能源动力   370篇
轻工业   674篇
水利工程   245篇
石油天然气   648篇
武器工业   81篇
无线电   401篇
一般工业技术   316篇
冶金工业   403篇
原子能技术   53篇
自动化技术   921篇
  2024年   2篇
  2023年   38篇
  2022年   78篇
  2021年   101篇
  2020年   135篇
  2019年   80篇
  2018年   80篇
  2017年   97篇
  2016年   164篇
  2015年   180篇
  2014年   379篇
  2013年   378篇
  2012年   519篇
  2011年   583篇
  2010年   476篇
  2009年   431篇
  2008年   375篇
  2007年   565篇
  2006年   523篇
  2005年   494篇
  2004年   467篇
  2003年   464篇
  2002年   446篇
  2001年   436篇
  2000年   372篇
  1999年   331篇
  1998年   280篇
  1997年   204篇
  1996年   170篇
  1995年   141篇
  1994年   74篇
  1993年   52篇
  1992年   36篇
  1991年   19篇
  1990年   13篇
  1989年   11篇
  1988年   10篇
  1987年   7篇
  1986年   7篇
  1985年   5篇
  1984年   7篇
  1983年   4篇
  1982年   3篇
  1981年   9篇
  1980年   4篇
  1971年   2篇
  1963年   1篇
  1962年   1篇
  1961年   1篇
  1960年   1篇
排序方式: 共有9263条查询结果,搜索用时 140 毫秒
1.
To study the computational aspects of collecting available data in a systematically organized database is becoming a matter of urgency in Nutrition & Food Science. Indeed, major projects on developing big datasets have attempted to fill this gap, but so far with limitations on important facets of food composition such as its temporal variation and uncertainty quantification. The need for methodological data processing, from data acquisition, digital storage, statistics and visualization, via pattern recognition and modelling to prediction and optimization is key to make objective and knowledge-based decisions on scientific and technological issues for food industry, academy and regulation. This study aims to demonstrate the use of a recently developed database on the composition of human milk, the first and easily the most complex food in one's life. We show that the purpose-built ontology of the database, with novelties like considering the food composition as a temporal and stochastic response, can help to recognize patterns in the variation of its protein content.Industrial relevance textThis study highlights the need (i) for introducing ISO-like standards how to digitize food composition data; (ii) for computational methods to explore and utilize such databases to their full potentials.  相似文献   
2.
朱凤山 《福建电脑》2022,38(1):40-43
为简化不同软件开发技术处理界面中组件关系的算法,增强使用数学模型解决软件开发中算法设计的能力,全面分析和总结直角坐标系在界面设计中的应用十分必要。通过对不同开发技术处理界面设计的分析,界面中组件位置关系实质上都可以转化为坐标关系的计算。本文列举了直角坐标系在Python编程、Android编程、Java编程和Unity编程中的应用,以期给相应的算法设计提供借鉴思路。  相似文献   
3.
对煤的自燃倾向进行快速有效鉴别,有助于对煤的自燃倾向采取分级分类管理从而有效防治煤矿火灾,因而采用绝热式自燃测试方法对煤的自燃倾向进行准确分析很有必要。简要介绍绝热式自燃测试方法的测试原理及其仪器结构,模拟煤炭自燃的物理过程,通过采用包括反应器、气体预热铜管和跟踪温度控制方式等综合绝热措施以实现300 g煤样的自然发火实验,记录煤样从40℃上升到70℃的升温速率(或前30 h的升温速率),测试煤样的自燃特性曲线并分析曲线特征。即建立煤绝热氧化产热速率计算模型,结合实验数据计算所得的煤在绝热氧化条件下的升温速率和产热速率可鉴定煤自燃倾向性的强弱。采用绝热式自燃测试方法对不同煤的自燃倾向分析后表明,无烟煤和部分烟煤的自燃倾向较低,褐煤的自燃倾向较高,故而在煤矿开采时需特别注意褐煤的自燃倾向。  相似文献   
4.
兰建国 《现代矿业》2020,36(7):13-16
为深入贯彻生态文明思想,促进矿产资源全面节约和高效利用,对招远市展开了金矿矿产资源开发利用水平调查评价,对2018年度数据进行整理和实地核查后,进行了单个矿山评价和多矿山评价,包括矿种评价、地区评价、行业评价。招远市16个矿山实际数据和基准值指标对比显示,单个矿山评价和多矿山评价的达标率均为100%。在此基础上,分析了金矿矿产资源资源开发利用水平调查评价的意义和存在问题。  相似文献   
5.
随着电子信息技术的进步,推土机正在向自动化、智能化方向发展。从行走系统智能控制、工作装置智能控制、故障诊断等方面介绍了推土机智能化控制技术的现状,从数字化机械施工、工作装置智能引导与自动控制、互联网大数据共享、机群智能化控制管理等方面分析了推土机智能化控制技术的发展趋势。  相似文献   
6.
The hot cracking tendency of 7075 semi-solid alloy under different conditions was studied by critical diameter method. The experiment and simulation results show that the dendrite arms of the rod grow from the edge to the center. The smaller the diameter of the rod is, the more obvious the directional growth of dendrite is, and the greater the tendency of hot cracking is. Compared with ordinary melt, for semi-solid slurry, increasing mould temperature or decreasing pouring temperature can significantly decrease hot cracking tendency of 7075 alloy, decreasing hot cracking grade from 256 to 100 mm2. Furthermore, based on the RDG criterion, the effects of solidification conditions on the hot cracking tendency were discussed combined with simulation. At the same time, the application and development of RDG criterion were also researched.  相似文献   
7.
对2014年我国冷却设备行业的发展状况进行了较为全面的叙述,对目前行业发展面临的一些问题做了比较客观的概括和总结,对行业发展趋势提出了一些观点及看法。  相似文献   
8.
The present contribution addresses the results of a longitudinal study in a ‘bioenergy-region’ concerning the public acceptance of biomass plants and the corresponding influencing factors. Using a standardized questionnaire, 423 persons were polled between 2009 and 2011 on three points of measurement in four places in the bioenergy-region Altmark. One main result of the study is that the reported public acceptance remains constantly high over time; nevertheless it became evident that the respective influencing factors differ in their strength, whereas the perceived regional benefit shows a strong connection to the reported public acceptance of biomass plants at each point of measurement. Concluding the research results, the acceptance of biomass plants doesn't seem to be a fixed construct, but has to be seen in context of the respective experiences with plants on a local level over time.In addition to the local population, key actors of the regional biomass sector were also interviewed (N = 26). The analyses show significant differences in the perception and evaluation of the current informational level between the population and the key actors. Furthermore, the key actors estimated the utilisation of biomass even more positively and expected a greater ‘signal function’ of the bioenergy-region-project compared to the population.  相似文献   
9.
In the first critical assessment of knowledge economy dynamic paths in Africa and the Middle East, but for a few exceptions, we find overwhelming support for diminishing cross-country disparities in knowledge-based economy dimensions. The paper employs all the four components of the World Bank's Knowledge Economy Index (KEI): economic incentives, innovation, education, and information infrastructure. The main finding suggests that sub-Saharan African (SSA) and the Middle East and North African (MENA) countries with low levels of KE dynamics and catching-up their counterparts of higher KE levels. We provide the speeds of integration and time necessary to achieve full (100%) integration. Policy implications are also discussed.  相似文献   
10.
The development of a sustainable energy system throughout an enterprise is a complex task, which requires an agile holistic approach. Such an approach needs to include a variety of objectives including energy strategy formation and strategic decision-making, which are directly related to the analysis and management of the main areas of sustainable development:The economic, technological, environmental, and social. These multidimensional requirements of sustainability are often difficult to achieve within the enterprise, because these aspects are interrelated and influenced by various internal and external environment factors. This paper first reviews the main challenges for an energy system, and then demonstrates how a strategic agile enterprise architecture driven approach could effectively guide the sustainable energy system development. The study presented in this paper provides a holistic approach that contributes to the advancement and usage of literature dealing with issues of sustainable energy system development and agile enterprise architecture, which has not been discussed before to any great extent.  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