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   20734篇
  免费   934篇
  国内免费   693篇
系统科学   1537篇
丛书文集   537篇
教育与普及   690篇
理论与方法论   331篇
现状及发展   918篇
研究方法   59篇
综合类   18288篇
自然研究   1篇
  2024年   99篇
  2023年   205篇
  2022年   317篇
  2021年   327篇
  2020年   177篇
  2019年   81篇
  2018年   824篇
  2017年   859篇
  2016年   615篇
  2015年   429篇
  2014年   545篇
  2013年   473篇
  2012年   784篇
  2011年   1491篇
  2010年   1375篇
  2009年   1111篇
  2008年   1272篇
  2007年   1432篇
  2006年   546篇
  2005年   604篇
  2004年   535篇
  2003年   569篇
  2002年   528篇
  2001年   433篇
  2000年   502篇
  1999年   801篇
  1998年   678篇
  1997年   738篇
  1996年   620篇
  1995年   591篇
  1994年   569篇
  1993年   445篇
  1992年   401篇
  1991年   355篇
  1990年   326篇
  1989年   280篇
  1988年   213篇
  1987年   105篇
  1986年   71篇
  1985年   26篇
  1984年   4篇
  1983年   1篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1967年   1篇
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
981.
The authors concern robust model predictive control for linear continuous systems with polytopic uncertainties and input constraints. At each sampling time, a piecewise constant control sequence is obtained by solving a set of linear matrix inequalities. The sufficient conditions on the existence of the model predictive control are given, and the robust stability of the closed-loop systems is guaranteed. A simulation example illustrates the efficiency of the proposed method.  相似文献   
982.
This paper deals with the development of scientific policy advice by providing a methodology to foster a social learning process. The methodology, called participatory Sustainability Impact Assessment (pSIA), aims to structure complex problem situations, to clarify interests and basic assumptions, to interpret scientific studies, to develop impact assessment, and to explore sensitivity of uncertainty and lack of information. In pSIA workshops the participants are supposed to build conceptual models with different modelling methods, like System Dynamics, Value Chain Analysis, and Morphological Analysis. A case study is presented that describes a workshop series with political as well as academic actors, applying the pSIA approach to an impact assessment of Economic Partnership Agreements between the European Union and the Eastern and Southern Africa Region.
Manuel GottschickEmail: URL: www.agchange.de
  相似文献   
983.
To identify common variants influencing body mass index (BMI), we analyzed genome-wide association data from 16,876 individuals of European descent. After previously reported variants in FTO, the strongest association signal (rs17782313, P = 2.9 x 10(-6)) mapped 188 kb downstream of MC4R (melanocortin-4 receptor), mutations of which are the leading cause of monogenic severe childhood-onset obesity. We confirmed the BMI association in 60,352 adults (per-allele effect = 0.05 Z-score units; P = 2.8 x 10(-15)) and 5,988 children aged 7-11 (0.13 Z-score units; P = 1.5 x 10(-8)). In case-control analyses (n = 10,583), the odds for severe childhood obesity reached 1.30 (P = 8.0 x 10(-11)). Furthermore, we observed overtransmission of the risk allele to obese offspring in 660 families (P (pedigree disequilibrium test average; PDT-avg) = 2.4 x 10(-4)). The SNP location and patterns of phenotypic associations are consistent with effects mediated through altered MC4R function. Our findings establish that common variants near MC4R influence fat mass, weight and obesity risk at the population level and reinforce the need for large-scale data integration to identify variants influencing continuous biomedical traits.  相似文献   
984.
采用分块编码的小波图像压缩技术   总被引:5,自引:1,他引:4  
研究了基于小波变换的图像压缩技术。在小波分解的基础上,结合人眼视觉系统(HVS)特性,提出了一种分块编码的图像编码算法。该算法利用小波变换系数子带内和子带间的相关性以及小波系数的分布特点,有效地对高频子带数据进行了压缩。该方法实现简单,可达到很好的压缩效果。  相似文献   
985.
Study on the REM Model for Group Decision Making   总被引:1,自引:0,他引:1  
IntroductionAsocialchoicefunctionisamappingwhichassignsanonemptysubsetofthepotentialfeasiblesubsettoeachorderedpairconsistentofapotentialfeasiblesubsetofalternativesandascheduleorprofileofvoters'preferences.Consideranopinionaggregationprobleminwhichagroupofexpertsgivetheirscoresthatexpresstheirpreferencestoasetofalternativesanddesiretocombinetheirscoresintoasingleaggregationpreferenceoverthealternativeset.Theunderlyingideahereisthattheconsensusofnumerousexpertsresultsinasuperiorpreferenceonthe…  相似文献   
986.
二维发汗控制方程的直线解法及其收敛性   总被引:4,自引:0,他引:4  
袁兆鼎 《系统仿真学报》1999,11(6):395-400,425
对二维发汗控制方程建立了直线解法,可用任何解常微分方程组的数值方法求解。对固定边界(非烧蚀)和活动边界(烧蚀)情形分别进行讨论。在某些假定下给出了直线法的收敛性。  相似文献   
987.
市场经济条件下,企业的最大目的就是取得理想的经济效益,公路建设成本控制是关键,控制好影响成本主要因素的材料使用数量是公路施工企业的重要工作之一.  相似文献   
988.
文章针对广珠城际轨道交通工程施工中450 t提运架设备箱梁架设施工方法、工艺及技术保证措施展开论述。  相似文献   
989.
文[2]曾指出L-Fuzzy拓扑学中关于L-Fuzzy子集的几种仿紧性不是一般拓扑学中子集仿紧性的真正推广,即它们不以分明子集仿紧性为特款,进一步修正了几个定义并重新证明了有关的几个定理,在这篇文章中,我们拟对层仿紧性进行修正并重证相关的几个定理。  相似文献   
990.
Atopic disease, including atopic dermatitis (eczema), allergy and asthma, has increased in frequency in recent decades and now affects approximately 20% of the population in the developed world. Twin and family studies have shown that predisposition to atopic disease is highly heritable. Although most genetic studies have focused on immunological mechanisms, a primary epithelial barrier defect has been anticipated. Filaggrin is a key protein that facilitates terminal differentiation of the epidermis and formation of the skin barrier. Here we show that two independent loss-of-function genetic variants (R510X and 2282del4) in the gene encoding filaggrin (FLG) are very strong predisposing factors for atopic dermatitis. These variants are carried by approximately 9% of people of European origin. These variants also show highly significant association with asthma occurring in the context of atopic dermatitis. This work establishes a key role for impaired skin barrier function in the development of atopic disease.  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