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   888篇
  免费   52篇
  2023年   8篇
  2022年   10篇
  2021年   41篇
  2020年   20篇
  2019年   26篇
  2018年   34篇
  2017年   25篇
  2016年   48篇
  2015年   45篇
  2014年   52篇
  2013年   43篇
  2012年   70篇
  2011年   74篇
  2010年   45篇
  2009年   33篇
  2008年   47篇
  2007年   52篇
  2006年   42篇
  2005年   35篇
  2004年   22篇
  2003年   20篇
  2002年   27篇
  2001年   13篇
  2000年   2篇
  1999年   6篇
  1998年   6篇
  1997年   4篇
  1995年   6篇
  1994年   6篇
  1993年   3篇
  1992年   3篇
  1991年   4篇
  1990年   9篇
  1989年   2篇
  1988年   9篇
  1987年   5篇
  1986年   3篇
  1985年   2篇
  1984年   3篇
  1983年   2篇
  1982年   2篇
  1981年   8篇
  1980年   3篇
  1979年   3篇
  1976年   2篇
  1974年   3篇
  1973年   2篇
  1965年   1篇
  1964年   1篇
  1953年   3篇
排序方式: 共有940条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
The extrinsic determinants hypothesis emphasizes the essential role of environmental heterogeneity in species’ colonization. Consequently, high resident species diversity can increase community susceptibility to colonizations because good habitats may support more species that are functionally similar to colonizers. On the other hand, colonization success is also likely to depend on species traits. We tested the relative importance of environmental characteristics and species traits in determining colonization success using census data of 587 vascular plant species collected about 70 yr apart from 471 islands in the archipelago of SW Finland. More specifically, we explored potential new colonization as a function of island properties (e.g. location, area, habitat diversity, number of resident species per unit area), species traits (e.g. plant height, life-form, dispersal vector, Ellenberg indicator values, association with human impact), and species’ historical distributions (number of inhabited islands, nearest occurrence). Island properties and species’ historical distributions were more effective than plant traits in explaining colonization outcomes. Contrary to the extrinsic determinants hypothesis, colonization success was neither associated with resident species diversity nor habitat diversity per se, although colonization was lowest on sparsely vegetated islands. Our findings lead us to propose that while plant traits related to dispersal and establishment may enhance colonization, predictions of plant colonizations primarily require understanding of habitat properties and species’ historical distributions.  相似文献   
5.
6.
Graphical virtual environments are currently far from accessible to blind users as their content is mostly visual. This is especially unfortunate as these environments hold great potential for this population for purposes such as safe orientation, education, and entertainment. Previous tools have increased accessibility but there is still a long way to go. Visual-to-audio Sensory-Substitution-Devices (SSDs) can increase accessibility generically by sonifying on-screen content regardless of the specific environment and offer increased accessibility without the use of expensive dedicated peripherals like electrode/vibrator arrays. Using SSDs virtually utilizes similar skills as when using them in the real world, enabling both training on the device and training on environments virtually before real-world visits. This could enable more complex, standardized and autonomous SSD training and new insights into multisensory interaction and the visually-deprived brain. However, whether congenitally blind users, who have never experienced virtual environments, will be able to use this information for successful perception and interaction within them is currently unclear.We tested this using the EyeMusic SSD, which conveys whole-scene visual information, to perform virtual tasks otherwise impossible without vision. Congenitally blind users had to navigate virtual environments and find doors, differentiate between them based on their features (Experiment1:task1) and surroundings (Experiment1:task2) and walk through them; these tasks were accomplished with a 95% and 97% success rate, respectively. We further explored the reactions of congenitally blind users during their first interaction with a more complex virtual environment than in the previous tasks–walking down a virtual street, recognizing different features of houses and trees, navigating to cross-walks, etc. Users reacted enthusiastically and reported feeling immersed within the environment. They highlighted the potential usefulness of such environments for understanding what visual scenes are supposed to look like and their potential for complex training and suggested many future environments they wished to experience.  相似文献   
7.
Cystic echinococcosis (CE) caused by Echinococcus granulosus is a major public health problem worldwide, including Turkey. The aim of the current study was to identify the strains and to estimate the potential risk factors of E. granulosus in operated pediatric cases in eastern Turkey. Ten pediatric patients (7 boys and 3 girls) living in rural areas, with ages ranging from 3 to 15 years old and various clinical histories, were included in this study. Eight patients had only liver hydatid cyst, while 1 patient had liver and lung hydatid cyst and the other liver, lung, and spleen, together. There were 2 ruptured liver cysts. After surgery, during follow-up, no increase was observed in hemagglutination levels, there were no mortalities, and there was no evidence of recurrence at 2 years post operation in all patients. Molecular analysis was performed on hydatid cyst samples obtained from the 10 pediatric cases. According to mt-12S rRNA PCR results, all cases were found to be G1/G3 cluster of E. granulosus sensu stricto.  相似文献   
8.
9.
10.
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