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   3420篇
  免费   215篇
  国内免费   4篇
电工技术   47篇
综合类   28篇
化学工业   987篇
金属工艺   90篇
机械仪表   72篇
建筑科学   233篇
矿业工程   8篇
能源动力   77篇
轻工业   202篇
水利工程   16篇
石油天然气   1篇
无线电   258篇
一般工业技术   717篇
冶金工业   142篇
原子能技术   30篇
自动化技术   731篇
  2024年   6篇
  2023年   57篇
  2022年   87篇
  2021年   138篇
  2020年   109篇
  2019年   118篇
  2018年   115篇
  2017年   119篇
  2016年   151篇
  2015年   119篇
  2014年   190篇
  2013年   227篇
  2012年   223篇
  2011年   296篇
  2010年   208篇
  2009年   183篇
  2008年   202篇
  2007年   178篇
  2006年   140篇
  2005年   117篇
  2004年   73篇
  2003年   65篇
  2002年   63篇
  2001年   32篇
  2000年   51篇
  1999年   45篇
  1998年   51篇
  1997年   26篇
  1996年   24篇
  1995年   28篇
  1994年   17篇
  1993年   24篇
  1992年   19篇
  1991年   16篇
  1990年   14篇
  1989年   15篇
  1988年   15篇
  1987年   9篇
  1986年   5篇
  1985年   11篇
  1984年   5篇
  1983年   4篇
  1982年   4篇
  1981年   6篇
  1980年   4篇
  1979年   6篇
  1976年   5篇
  1975年   4篇
  1974年   4篇
  1966年   3篇
排序方式: 共有3639条查询结果,搜索用时 0 毫秒
211.
OpenSocial     
Zusammenfassung  OpenSocial definiert eine Menge von Programmierschnittstellen für Anwendungen von Drittanbietern im Kontext sozialer Netzwerke. Unter der Verwendung von Standardtechnologien wie HTML und JavaScript k?nnen Entwickler interoperable Anwendungen erstellen, die auf den sozialen Graphen des jeweiligen Netzwerks zugreifen.  相似文献   
212.
213.
Theory suggests that providing consumers with an estimated life-cycle cost (LCC) may make them buy more energy-efficient household appliances in cases where energy efficiency is cost effective. This article evaluates the link between the provision of LCC and consumer behavior by using an online field experiment for cooling appliances. Internet users arriving at a commercially operating price comparison website were randomly assigned to two experimental groups, and the groups were exposed to different visual stimuli. The control group received regular product price information, whereas the treatment group was offered additional information about estimated operating cost and total LCC. Consumers’ click behavior was evaluated with multiple regression controlling for several product characteristics (n = 1,969 clicks). We find that LCC disclosure reduces the mean specific energy use of chosen cooling appliances by 2.5% (p < 0.01), making it a potentially interesting approach for environmental policy regarding the market transformation toward more energy-efficient household appliances. However, LCC disclosure also decreases the number of clicks from the price comparison website to final retailers by about 23% (p < 0.01), which makes it—in the format chosen here—undesirable from a business perspective. Therefore, future research should clarify under what (if any) conditions can monetary energy cost disclosure be associated with more positive effects for price comparison websites.  相似文献   
214.
Scientometrics - At the Leibniz Institute for Baltic Sea Research Warnemünde (the home institute of this paper), scientists have been exploring the common denominator between microplastics and...  相似文献   
215.
216.
Mixing of titanium powder and thermoplastic binders creates a feedstock that is injection molded similar to plastic, has a chemical and thermal debinding process, and then is sintered to form a net-shape or near-net shape part. TiJet Medizintechnik GmbH (TiJet) developed and uses its own feedstock and powder processing technology to achieve desired mechanical properties. This paper explains the theory of the process and the possibilities that result from the development of this new powder processing technology, such as new alloys, design possibilities, etc. Discussed will be the microstructure, chemical composition, and mechanical properties of the manufactured parts.  相似文献   
217.
218.
This study examines the impacts of energy price changes resulting from different carbon-pricing policies on the competitiveness of selected US energy-intensive industries. It further examines possible industry responses, and identifies and provides a preliminary evaluation of potential opportunities to mitigate these impacts. The industry sectors investigated – steel, aluminum, chemicals and paper – are among the largest industrial users of fossil fuels in the US economy. The results of this examination show that climate policies that put a price on carbon could have substantial impacts on the competitiveness of US energy-intensive manufacturing sectors over the next two decades, if climate regulations are applied only in the United States, and no action is taken to invest in advanced low- and no-carbon technologies. The extent of these impacts will vary across industries, depending on their energy intensities, the mix of energy sources they rely on and how energy is used in production activities (heat and power, feedstock). Of relevance is also the speed and rigor with which industries adopt new technologies and retire (or replace) old ones. Other factors affecting these impacts include an industry's vulnerability to foreign imports and its ability to pass through cost increases to its customers in the face of international market competition.  相似文献   
219.
The analysis and classification of data is a common task in multiple fields of experimental research such as bioinformatics, medicine, satellite remote sensing or chemometrics leading to new challenges for an appropriate analysis. For this purpose different machine learning methods have been proposed. These methods usually do not provide information about the reliability of the classification. This, however, is a common requirement in, e.g. medicine and biology. In this line the present contribution offers an approach to enhance classifiers with reliability estimates in the context of prototype vector quantization. This extension can also be used to optimize precision or recall of the classifier system and to determine items which are not classifiable. This can lead to significantly improved classification results. The method is exemplarily presented on satellite remote spectral data but is applicable to a wider range of data sets.  相似文献   
220.
For 30 yr, a persistent foam cover has been observed during the summer months in the Rhine River beneath the Rhine Fall, a waterfall near Schaffhausen, Switzerland. This phenomenon has been a matter of public concern ever since its first appearance, but all previous attempts to clarify the origin of this foam had remained inconclusive. With the aid of electrospray LC-MS,triterpene saponins and mono- and digalactosyldiacylglycerolipids (MGDAG and DGDAG), two classes of tensioactive metabolites occurring in the aquatic plant Ranunculus fluitans Lamk. (Ranunculaceae), were detected in river water and foam samples. Saponin concentrations in water and foam samples were monitored at regular intervals during the years 1998 and 2000. Other compound classes with surfactant properties such as proteins, humic acids, and synthetic detergents were also analyzed. Foam occurrence paralleled with saponin concentration and with the amounts of detached Ranunculus biomass accumulating at the dam of the hydroelectric power plant of Schaffhausen located just above the Rhine Fall but not with the concentration of synthetic detergents. The ecotoxicological potential of Ranunculus constituents, water, and foam samples was checked with a representative range of aquatic indicator organisms. No acute toxicity was observed at concentrations that were at least 50-fold higher than those found in the environmental samples.  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