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   6782篇
  免费   518篇
  2023年   44篇
  2021年   32篇
  2020年   129篇
  2019年   224篇
  2018年   267篇
  2017年   268篇
  2016年   338篇
  2015年   219篇
  2014年   228篇
  2013年   1853篇
  2012年   252篇
  2011年   294篇
  2010年   248篇
  2009年   201篇
  2008年   194篇
  2007年   191篇
  2006年   176篇
  2005年   109篇
  2004年   99篇
  2003年   102篇
  2002年   98篇
  2001年   99篇
  2000年   101篇
  1999年   86篇
  1998年   76篇
  1997年   68篇
  1996年   54篇
  1995年   67篇
  1994年   48篇
  1993年   55篇
  1992年   42篇
  1991年   45篇
  1990年   52篇
  1989年   46篇
  1988年   34篇
  1987年   49篇
  1986年   51篇
  1985年   54篇
  1984年   54篇
  1983年   49篇
  1982年   47篇
  1981年   49篇
  1980年   45篇
  1979年   43篇
  1978年   40篇
  1977年   44篇
  1976年   29篇
  1974年   31篇
  1973年   29篇
  1972年   29篇
排序方式: 共有7300条查询结果,搜索用时 15 毫秒
101.
In the Andes, there are several pre-Hispanic irrigation networks with structures destined for water storage. However, it has not been widely discussed in archaeological research. This is probably due to their being difficult to identify. The aim of this study is to explore the use of diatom assemblage analysis as a methodological tool suitable to help in the identification and characterization of these ancient hydraulic structures. We analyzed two archaeological structures interpreted as water reservoirs from north-western Argentina (EH1 in Antofagasta de la Sierra and U-88R1 in Yocavil) and compared them to current reservoirs. The diatom species composition and the changes in the dominant ecological groups in the studied structures highlight different periods of hydraulic behavior. EH1 contained and stored water, but there were periods of time in which there was a lack of use or abandonment of the structure. However, the U88-R1 structure does not have diatom evidence of containing standing water for a prolonged time but presence of wet soils. Thus, the structure could have been used for other water management strategies. The results show that diatom analysis is a methodological tool with a high potential to study ancestral hydrotechnologies.  相似文献   
102.
Tel Megiddo is a major type-site for the Middle Bronze in the Levant. During this period a new burial custom appeared in which the dead were interred beneath occupied houses. This tradition is well attested in Area K at the site. Area H, near the palatial complex, revealed a monumental masonry-constructed chamber tomb. This article presents the results of residue analysis conducted on ceramic vessels placed in these tombs as burial offerings. Hundreds of intramural Middle Bronze tombs with ceramic offerings were excavated in the Levant, but this is the first time the content of the vessels is revealed.  相似文献   
103.
While food allergy prevalence has been studied at the national level, we know little of food allergy prevalence or perceptions of prevalence/management at the local level. This paper uses Waterloo Region as a case study to 1) document self-reported individual and household food allergy and sensitivity prevalence at the local level; 2) investigate perceptions of food allergy prevalence; and 3) explore perceived confidence in anaphylaxis management. Survey data were collected from January to March 2019. Respondents (n = 500) self-reported individual and household food allergy and sensitivity, estimated the percentage of Canadians with food allergy, and were queried about their knowledge of food allergy management. Prevalence estimates were weighted to the structure of the 2016 Canadian Census, and univariate and bivariate analysis were conducted. Prevalence of self-reported food allergy was 12.1% (95%CI, 8.8%-15.3%), and prevalence of self-reported food sensitivity was 26.3% (95%CI, 21.9%-30.7%). When asked to estimate the percentage of Canadians with food allergy, the mean perceived percentage was 35.1% (SD = 22.96). Self-reported prevalence of food allergy appears higher in Waterloo Region, and the estimated percentage of Canadians with food allergy is inflated. Understanding prevalence and perceptions at the local level is important for targeted allocation of public health resources to ensure safe spaces for individuals with food allergy.  相似文献   
104.
105.
106.
107.
Recent research in central Europe is changing our understanding of the role of centers in economic and social systems of late prehistoric times. Increased attention to smaller, more typical settlements shows that they engaged in economic activities similar to those at the large, fortified complexes. Abundant new evidence pertaining to ritual activity indicates that ritual was often integrated into daily life at settlements. The evidence from the exceptionally rich data on late prehistoric central Europe can be of substantial value for developing models applicable to contexts in other parts of the world.  相似文献   
108.
109.
"The spread of HIV-1 in the United Kingdom is simulated by a model which integrates behavioural and epidemiological processes within a multi-regional population projection framework and represents the spatial heterogeneities in the distribution of HIV which have significant effects on transmission patterns. Analyses determine the significance of different parameters in contributing to prediction uncertainty and highlight the importance of behavioural change and international population movements."  相似文献   
110.
A multidisciplinary programme of research on Islamic pottery has been focused on questions of the dating, provenance and technology of Islamic pottery. One particular question has been the development of stonepaste, a material made primarily of crushed quartz with added frit-glass and clay. The combination of the different approaches of this study has revealed early foundations for the technology in ninth-century AD Iraq, apparently originating in the clay ceramic rather than the ‘Egyptian faience’ tradition. Subsequent and final practice developed in tenth- and eleventh-century AD Egypt. This technology becomes the primary body for all fine Islamic ceramics.  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