全文获取类型
收费全文 | 193篇 |
免费 | 10篇 |
国内免费 | 25篇 |
专业分类
系统科学 | 8篇 |
丛书文集 | 3篇 |
教育与普及 | 5篇 |
综合类 | 212篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 14篇 |
2018年 | 20篇 |
2017年 | 4篇 |
2016年 | 2篇 |
2015年 | 6篇 |
2014年 | 6篇 |
2013年 | 18篇 |
2012年 | 32篇 |
2011年 | 22篇 |
2010年 | 6篇 |
2009年 | 11篇 |
2008年 | 11篇 |
2007年 | 5篇 |
2006年 | 2篇 |
2005年 | 14篇 |
2004年 | 3篇 |
2003年 | 13篇 |
2002年 | 3篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1992年 | 1篇 |
排序方式: 共有228条查询结果,搜索用时 250 毫秒
102.
103.
Land cover classification is one of the most wide ly used applications of remote sensing. The use ofmultitemporal remote sensing data in land cover clas sification is one of the effective methods of obtainingaccurate land cover/land use data. For a particularimage, different land cover types often show a similarspectral response and are difficult to separate. Theadvantage of using multitemporal data is that differentvegetation types show different spectral characteristicsin… 相似文献
104.
Inmostcomputeraideddesign(CAD)andcom puteraidedgeometricdesign(CAGD)systems,the BernsteinpolynomialsrepresentationofB啨ziercurves andsurfaceshasbeenastandard.Legendrepolynomi alshavesomeremarkableproperties.Firstly,Legen drepolynomialsconstituteanorthogonalbasisandthe degreeoftheLegendrebasisfunctionsgraduallyin creases,whichallowsthecoefficientsoftheapproxi mationtobedetermineddirectlywithoutneedingto solvealinearsysteminmanygeometricoperations whereapproximationisinvolved.Forexample,Lie… 相似文献
105.
106.
SincethepublicationoftheclassicalworkofChan[1] andHilliard[2 ] ,therehavebeenextensiveex perimentalandtheoreticalstudiesonthethermody namicsandkineticsofprecipitation process .Recentresearchworkhasbeenconcentratedoncomputersimulation ,mostofwhichwerereviewedbyChen[3] .Mostcomputersimulationswerecarriedoutinbinarysystems[4— 8] .However ,theternaryormulti compo sitionsystemsaremoreimportantinindustries .MechanicalpropertiesofNi Albasedsuperalloyscanbestronglyaffectedbythemorphology ,distribu … 相似文献
107.
R. H. Liu* Q. Zhang* 《系统科学与复杂性》2001,(2)
1 IntroductionMarkov decision processes (MDP) have drawn much sttention because of their capabilityin dealing with a wide range of application under UnCertainty. Many problems in operationsresearch such as resource allocation, queueing networks, and maChine replaCement etc., fit wellin the framework of Markov decision processes. Classical aPProaChes of discrete-time MDPmodels can be foUnd in Dermanll], RDssIZ], and ~e[3] among others.Because most of the systems in real life are large a… 相似文献
108.
ZHU Huanzhang* CHEN Xiaoguang* LI Feng GONG Juli & XUE Jinglun State Key Laboratory of Genetic Engineering Institute of Genetics School of Life Sciences Fudan University Shanghai China *The authors made equal contributions to this report. Correspondence should be addressed to Xue Jinglun 《科学通报(英文版)》2003,48(20)
Hemophilia B, a serious bleeding disorder, is an inherited X chromosome-linked disease for the deficiency or inactivity of human clotting factor Ⅸ (hFⅨ). Though factor substitution therapy has greatly improved the lives of hemophiliac patients, there are still limitations to the current treatment, which have triggered interest in alternative treatments by gene therapy[1]. Based on preclinical studies in rabbits[2], our lab had first initiated an ex vivo gene therapy clinical trial whereby a… 相似文献
109.
星*宝贝 《大众科学.科学研究与实践》2002,(2)
66岁的她静静地站着。“这是我在这个世界里的最后一天了,等到今天过去,我会永远的离开这个世界。”她这样想着,并留恋地看着自己的影子、自己亲手一砖一瓦建起来的城邦和曾经每天陪着自己练功的那150个女仆。“不要再想了,都已经决定了的事。”她勉强地给自己一个笑容。“直的决定了吗?”他问。 相似文献
110.
ZUO XinXin * & Lü HouYuan Key Laboratory of Cenozoic Geology Environment Institute of Geology Geophysics Chinese Academy of Sciences Beijing China Graduate University of Chinese Academy of Sciences Beijing 《科学通报(英文版)》2011,56(32):3451-3456
Phytoliths are noncrystalline minerals that form inside cells and cell walls of different parts of plants. Organic carbon in living cells can be occluded in phytoliths during plant growth. It has been documented that the occluded carbon within phytoliths is an important long-term terrestrial carbon reservoir that has a major role in the global carbon cycle. Common millet and foxtail millet have become typical dry-farming crops in China since the Neolithic Age. The study of carbon conservation within phytoliths in these crops could provide insights into anthropogenic influences on the carbon cycle. In this study, we analyzed the carbon content in phytoliths of common millet and foxtail millet. The results indicated that (1) common millet and foxtail millet contained 0.136% ± 0.070% and 0.129% ± 0.085% phytolith-occluded carbon (PhytOC) on a dry mass basis, respectively; (2) based on the mean annual production of common millet and foxtail millet in the last 10 years, the phytolith occluded carbon accumulation rate of common millet and foxtail millet was approximately 0.023 ± 0.015 and 0.020 ± 0.010 t CO 2 ha 1 a 1 , respectively; (3) assuming a similar phytolith occluded carbon accumulation rate as for common millet (the highest accumulation rate was 0.038 t CO 2 ha 1 a 1 ), this could result in the sequestration of 2.37 × 10 6 t CO 2 per year for the 62.4 × 10 6 ha dry-farming crops in China. Although there was a decline in the annual production rate and planting area of foxtail millet during 1949 to 2008, the total phytolith carbon sequestration rate was 7×10 6 t CO 2 within the 60-year period. However, phytolith occluded carbon has not yet been fully considered as a global carbon sink. Also, this carbon fraction is probably one of the best candidates for the missing carbon sink. 相似文献