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   40582篇
  免费   14248篇
  国内免费   2篇
电工技术   727篇
综合类   1篇
化学工业   17547篇
金属工艺   317篇
机械仪表   718篇
建筑科学   1799篇
矿业工程   4篇
能源动力   848篇
轻工业   7416篇
水利工程   322篇
石油天然气   51篇
无线电   6921篇
一般工业技术   11814篇
冶金工业   1726篇
原子能技术   1篇
自动化技术   4620篇
  2024年   8篇
  2023年   29篇
  2022年   73篇
  2021年   296篇
  2020年   1475篇
  2019年   3205篇
  2018年   3157篇
  2017年   3484篇
  2016年   3944篇
  2015年   4014篇
  2014年   3948篇
  2013年   5105篇
  2012年   2818篇
  2011年   2586篇
  2010年   2822篇
  2009年   2664篇
  2008年   2265篇
  2007年   2089篇
  2006年   1818篇
  2005年   1515篇
  2004年   1448篇
  2003年   1408篇
  2002年   1352篇
  2001年   1160篇
  2000年   1121篇
  1999年   500篇
  1998年   65篇
  1997年   86篇
  1996年   50篇
  1995年   46篇
  1994年   39篇
  1993年   38篇
  1992年   27篇
  1991年   16篇
  1990年   26篇
  1989年   21篇
  1988年   13篇
  1987年   18篇
  1986年   17篇
  1985年   15篇
  1984年   11篇
  1983年   12篇
  1981年   7篇
  1980年   4篇
  1979年   2篇
  1978年   3篇
  1977年   3篇
  1975年   5篇
  1972年   1篇
  1890年   1篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
241.
242.
243.
244.
245.
The water bamboo husk is one of major agricultural wastes in Taiwan. In this study, the powder obtained from the water bamboo husk was added to poly(lactic acid) (PLA) to form novel reinforced biodegradable composites. Morphologies, mechanical properties, and heat resistance of these water bamboo powder reinforced composites were investigated. The results indicate that the char yields were increased as plant powder was incorporated to PLA. In addition, the mechanical properties were also enhanced due to the addition of powders. The increments of storage moduli of PLA were about 50–200%. Moreover, the increments of loss moduli of PLA were about 70–200%. On the other hand, the Tg of PLA was slightly decreased by the addition of powder, and this may improve the brittle characteristics of PLA. Furthermore, this type of reinforced PLA would be more environmental friendly than the artificial additive‐reinforced one. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers  相似文献   
246.
Seven linseed varieties were harvested at seven times before complete maturity. Microscale oilseed expressions were subsequently carried out on it. A pressure of 10 MPa was applied for 1 h under uniaxial stress. The results were characterized in terms of oil, water and mucilage content, harvest date and oil yield. The piston displacement versus time (creep curves) was described by a four‐Kelvin‐Voigt elements viscoelastic model. Parameters were derived from the model, such as the mechanical properties of seeds (compressibility moduli), showing that the viscoelastic model fits well the experimental data (R² ≈ 0.999). The modeling parameters were combined with some biochemical data in order to predict the kinetics of oil extraction.  相似文献   
247.
248.
Imperfection in information can be considered a crosscutting concern that manifests itself in diverse kinds of imprecision, uncertainty, or inconsistency in the data models of a software system. The extension of existing programming and querying interfaces for the different aspects of information imperfection requires a proper modularization of the different concerns of numerical imprecision handling, so that the extensions do not interfere with existing programming practices and do not obscure the original design. Aspect‐oriented design (AOD) enables such a form of nonintrusive extensions to be added to existing software libraries, clearly separating fuzziness or other imperfections in data as a differentiated concern that can be considered from the early phases of development. In this article, a general framework for aspect‐based extension of data models and fuzzy databases is described, and some design and implementation issues of such AOD‐based extensions on OJB database libraries are described as a case study. © 2006 Wiley Periodicals, Inc. Int J Int Syst 21: 1199–1216, 2006.  相似文献   
249.
BACKGROUND: Trichloroethylene (TCE) and perchloroethylene (PCE) are considered among the most important groundwater pollutants around the world. These compounds are usually found together in polluted environments but little is known about the ability of microorganisms to simultaneously degrade TCE and PCE. RESULTS: Data showed that several species of white‐rot fungi, including Trametes versicolor, Ganoderma lucidum, and Irpex lacteus, degrade substantial levels of TCE in pure culture. T. versicolor was chosen for further study since it degraded higher levels of TCE than the other organisms. Initial glucose concentration and reoxygenation of samples increased the amount of TCE dechlorination, but no significant difference in percentage TCE degradation was observed. T. versicolor was able to degrade 34.1 and 47.7% of PCE and TCE added as mixtures (containing 5 and 10 mg L−1, respectively). CONCLUSIONS: The degradation ability of TCE was extended to other species of white‐rot fungi. Percentage degradation as well as chloride release from mixtures of TCE and PCE showed that T. versicolor degrades mixtures of TCE and PCE almost as well as its ability to degrade individually added TCE or PCE. The results suggest the potential promise of T. versicolor for bioremediation of TCE and PCE in the environment. Copyright © 2008 Society of Chemical Industry  相似文献   
250.
The objective of this study is to determine the chemical kinetics of desulphurization of Thai limestone in an atmospheric fluidized bed combustor (AFBC). The experiments, which employed the batch technique using the limestone samples from six major sources in Thailand, were performed in a laboratory‐scale AFBC. The results obtained were analysed and correlated in the form of apparent reaction rate and deactivation rate constants as a function of operating conditions of the furnace and their properties, respectively. The formulae derived from these correlations were kept as general as possible in order that they could be used as input parameters for the selected mathematical model of desulphurization in an AFBC that is suitable for practical use. The predicted results were in good agreement with the experimental data reported in the literature. Copyright © 2003 John Wiley & Sons, Ltd.  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