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   70篇
  免费   0篇
系统科学   1篇
现状及发展   5篇
研究方法   8篇
综合类   27篇
自然研究   29篇
  2021年   1篇
  2016年   1篇
  2013年   1篇
  2012年   1篇
  2011年   35篇
  2010年   3篇
  2008年   4篇
  2007年   6篇
  2006年   1篇
  2005年   4篇
  2004年   3篇
  2003年   5篇
  2002年   1篇
  1994年   1篇
  1990年   1篇
  1982年   1篇
  1973年   1篇
排序方式: 共有70条查询结果,搜索用时 140 毫秒
1.
 从“十四五”保护与发展的生态关系角度,探讨了生态保护与绿色发展的十大生态关系,阐述了生态保护和绿色发展中的一系列有关生态关系的生态智慧及生态技术,并对长江、黄河等流域的生态保护和修复提出了相关建议。  相似文献   
2.
An artifact constructed from a bison ( Bison bison ) hornsheath was recovered from the surface of a sandstone shelter also containing skeletal remains of bison and bighorn ( Ovis Canadensis ). Radiocarbon dating of bison, bighorn, and the artifact indicate that all co-occurred on the central Colorado Plateau, southeastern Utah, either between A. D. 1405 and A. D. 1420, or between A. D. 1535 and A. D. 1605. Skeletal remains of the bison imply that the animal was of the local faunal community during the transition between Protohistoric and Historic time.  相似文献   
3.
4.
5.
Diatoms epiphytic on Phragmites australis (Cav.) Trin. ex Steaded stems were collected from a single clone at the southern end of Provo Bay, Utah Lake, Utah. Diatom populations from both living and dead stem sections were analyzed. Species diversity in each sample was high, indicating that the stems provide a relatively stable habitat for diatom epiphytes. Of the 23 genera found, only Gomphonema and Navicula showed significant trends toward stem preference. The diatoms in this study support the current view that Utah Lake is a slightly saline, eutrophic system.  相似文献   
6.
Late Quaternary-age arthropods were recovered from dry cave deposits and packrat middens located in the Grand Canyon, Canyonlands, and Glen Canyon region of the Colorado Plateau. This Quaternary data resource has not been analyzed before from the Colorado Plateau national parks. Radiocarbon dates on the various deposits containing arthropods range from 1510 to 30,660 yr B.P. The fossil assemblages yielded 57 identified taxa of insects, arachnids, and millipedes, including 15 taxa taken to the species level. The information from the fossil insect record of the Colorado Plateau is not yet sufficiently detailed to permit precise paleoenvironmental reconstructions. However, preliminary conclusions suggest a cooler, moister climatic regime during the late Wisconsin glacial and a mosaic of vegetation types, such as grassland and shrubby communities, unlike the present vegetation at the localities.  相似文献   
7.
Lichens are common components of microbiotic soil crusts. A total of 34 species from 17 genera are reported from soil crust communities throughout the Intermountain Area. Distribution of terricolous lichens is determined by various physical and biological factors: physical and chemical characteristics of the soil, moisture regimes, temperature, insolation, and development and composition of the vascular plant community. Some species demonstrate a broad ecological amplitude while others have a more restricted distribution. All growth forms are represented; however, the vast majority of soil crust lichens are squamulose (minutely foliose). Fruticose species are least abundant. In exposed, middle-elevation sites vagrant (detached) species are common. This paper describes and discusses terricolous lichen communities of desert habitats of the intermountain western United States. Effects of various human-related activities including grazing, wildfire, air pollution, and recreation vehicles on soil crust lichens are discussed. Gypsoplaca macrophylla (Zahlbr.) Timdal, a rare squamulose lichen which occurs on gypsifersous soils, was recently collected in Emery County, Utah, and is reported as new to the state.  相似文献   
8.
陆生植物的菌根已被广泛研究,对湿生植物菌根的研究却很少.本研究的目的是检测在水淹、潮湿和干旱条件下水生植物L.salicaria的菌根合成状况及其对植物生长的影响.在三种水份条件下,L.salicaria与来源于不同地点(干旱和水淹)的两种接种物(F2和F1)均可形成菌根,水份条件和接种物种类都显著地影响菌根的合成水平(P《0.05).F1和F2接种物与植物合成菌根的水平均在水淹处理中最低. F1接种物与L.salicaria合成菌根的水平在潮湿和干旱处理中显著地高于水淹处理(P《0.05),并且趋势是:潮湿》干旱》水淹处理.F2接种物与L.salicaria合成菌根的水平在三种水份处理中没有显著区别,但仍然可观察到一个趋势:干旱》潮湿》水淹处理.在水淹和干旱处理中,菌根对植物地上部分的生长和根的生物量积累没有影响.在潮湿处理中被F1接种的植株与被F2接种的植株与对照植株相比,地上部分干重、根鲜重显著地低;地上部分鲜/干重比、地上部分/根鲜重比显著地高.水份条件显著地影响植物的生长行为.  相似文献   
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