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   15884篇
  免费   795篇
  国内免费   21篇
  2023年   106篇
  2022年   241篇
  2021年   421篇
  2020年   252篇
  2019年   256篇
  2018年   398篇
  2017年   430篇
  2016年   495篇
  2015年   672篇
  2014年   742篇
  2013年   1037篇
  2012年   1141篇
  2011年   1039篇
  2010年   625篇
  2009年   571篇
  2008年   656篇
  2007年   648篇
  2006年   563篇
  2005年   475篇
  2004年   448篇
  2003年   378篇
  2002年   345篇
  2001年   334篇
  2000年   305篇
  1999年   244篇
  1998年   125篇
  1997年   106篇
  1996年   96篇
  1995年   112篇
  1994年   101篇
  1993年   95篇
  1992年   221篇
  1991年   206篇
  1990年   200篇
  1989年   193篇
  1988年   168篇
  1987年   164篇
  1986年   148篇
  1985年   174篇
  1984年   167篇
  1983年   115篇
  1982年   112篇
  1981年   99篇
  1980年   92篇
  1979年   147篇
  1978年   109篇
  1977年   95篇
  1974年   118篇
  1973年   91篇
  1972年   100篇
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
801.
Capsule: Global Positioning System (GPS)-tagged adult Golden Eagles Aquila chrysaetos breeding in forests in northern Sweden selected clear-cuts, coniferous forests with lichens and steep slopes during the breeding season but avoided wetlands and mixed forest.

Aims: To investigate the habitat selection patterns of tree-nesting Golden Eagles, and identify how potential conflicts with wind farm development could be minimized.

Methods: The study is based on GPS tracking data from 22 adult eagles. We estimated home range sizes using a biased random bridge approach and habitat selection patterns using resource selection functions following a use-availability design.

Results: Core home range size among adults was variable during the breeding season (5–30?km2). Individual movement extents were variable, but sexes did not significantly differ in their scale of movement. At the landscape scale, individuals selected for clear-cuts and coniferous forest with ground lichens, whereas wetland, water bodies and mixed forest were avoided. Steeper and south facing slopes were selected for, whereas, north facing slopes were avoided.

Conclusions: Potential conflicts between eagles and wind energy establishment can be reduced if wind farms are placed away from steep slopes, minimizing areas that are clear-cut during construction, and locating turbines within dense, young and other less favoured forest habitats.  相似文献   

802.
Among hydrocarbon pollutants, diesel oil is a complex mixture of alkanes and aromatic compounds which are often encountered as soil contaminants leaking from storage tanks and pipelines or as result of accidental spillage. One of the best ecofriendly approaches is to restore contaminated soil by using microorganisms able to degrade those toxic compounds in a bioremediation process. In the present study, nineteen bacteria were isolated by enrichment culture technique from diesel spilled soil collected from electric generator shed of NBAIM, Mau. All the isolates were subjected to screening for lipase production and twelve isolates were found to be positive for lipase. When the isolates were screened for biosurfactant production using CTAB-methylene blue agar plates, only one isolate viz. 2NBDSH3 was found positive which was found to be phylogenetically closely related with Bacillus flexus. Despite having low emulsification index, the bacterium could degrade 88.6% of diesel oil in soil. Biosurfactant from the isolate was extracted and characterized through infra-red spectroscopy which indicated its possible lipopeptide nature which was further supported by strong absorption in UV range in the UV-Vis spectrum. The results of the present study indicated that the isolate either does not produce any bioemulsifier or produces very low amount of emulsifier rather it produces a lipopeptide biosurfactant which helps in degradation of diesel oil by lowering the surface tension. The bacterium thus isolated and characterized can serve as a promising solution for ecofriendly remediation of bacterium diesel contaminated soils.  相似文献   
803.
Pandey  Shiv S.  Singh  Sucheta  Babu  C. S. Vivek  Shanker  Karuna  Srivastava  N. K.  Kalra  Alok 《Planta》2016,243(5):1097-1114
Planta - Endophytes reside in different parts of the poppy plant and perform the tissue-specific functions. Most leaf endophytes modulate photosynthetic efficiency, plant growth, and productivity...  相似文献   
804.
805.
806.
807.
808.
809.
810.
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