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   2407篇
  免费   137篇
  国内免费   10篇
  2023年   16篇
  2022年   37篇
  2021年   72篇
  2020年   35篇
  2019年   43篇
  2018年   57篇
  2017年   68篇
  2016年   76篇
  2015年   130篇
  2014年   158篇
  2013年   180篇
  2012年   188篇
  2011年   177篇
  2010年   131篇
  2009年   100篇
  2008年   146篇
  2007年   124篇
  2006年   97篇
  2005年   113篇
  2004年   89篇
  2003年   85篇
  2002年   71篇
  2001年   26篇
  2000年   23篇
  1999年   25篇
  1998年   18篇
  1997年   9篇
  1996年   9篇
  1995年   11篇
  1994年   10篇
  1993年   13篇
  1992年   19篇
  1991年   18篇
  1990年   13篇
  1989年   8篇
  1988年   6篇
  1987年   6篇
  1986年   11篇
  1985年   10篇
  1984年   5篇
  1983年   6篇
  1982年   10篇
  1980年   10篇
  1976年   6篇
  1974年   13篇
  1973年   11篇
  1972年   5篇
  1971年   5篇
  1970年   10篇
  1969年   5篇
排序方式: 共有2554条查询结果,搜索用时 15 毫秒
91.
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   
92.
93.
94.
95.
96.
97.
Crows (Corvus splendens) and white herons (Ardea alba) inhabit the agricultural landscapes nearby human habitats which represent dynamic ecosystem and show seasonal crop patterns. We studied the movement pattern in these birds at dawn and dusk, during solstices (December and June) and equinoxes (March and September). The movement directions were changed from uniform at dawn to a concentrated distribution at dusk all along the season suggesting that morning movements are more exploratory than evening with seasonal differences. Differential use of directions in December than June could be the effect of temperature, food availability or wind direction and speed. During breeding, less number of directions used suggests that birds might be moving towards the directions having high probability of food availability. It is likely that avian dispersal in space and time is dependent on the food availability however, further studies are required to be carried out.  相似文献   
98.
A field experiment was conducted to observe the effect of TS amendments on soil enzymes and phytoremediation potential of two economically important cultivars of geranium. Different doses of TS were applied in soil to examine threshold limit of HMs where geranium cultivars can be grown successfully in contaminated sites. Treatment variation significantly affected pH, EC, OC, N, P, K and HM content in soil after 50 days of incubation. After harvest, both cultivars were examined to assess the impact of various treatments on their fresh herb, dry matter, essential oil yield and HM accumulation. C/G ratio close to 1 was observed at 50 tha?1 sludge treatment in both cultivars. Urease and β-glucosidase activities in soil were maximum at 50 tha?1 whereas dehydrogenase and phosphatase activities were maximum at 100 tha?1 in both cultivars. β-glucosidase, acid and alkaline phosphatase, urease and dehydrogenase activities were relatively high after 85 days over 45 days in both cultivars. Maximum metal uptake was found in roots of cv. Bourbon followed by leaves. Geranium was observed to be a good candidate for phytoremediation as it mitigates metal toxicity by root absorption and cv. Bourbon is better candidate for the same.  相似文献   
99.
Mercury (Hg), arsenic (As), cadmium (Cd), and lead (Pb) are the major toxic metals released by coal mining activities in the surrounding environment. These metals get accumulated in the soils. The plants grown on the contaminated soil uptake these toxic metals in their roots and aerial parts. This study monitored the bioaccumulation of Hg and other three toxic metals in coal mine soil. The pot study of Hg accumulation in Brassica juncea showed that the extent of Hg uptake by roots and shoots of the plants grown on was high in the mature plant and Hg content in root was higher than the shoot. In the soil of unreclaimed overburden (OB) dump, the toxic metal content was higher than that of reclaimed OB dump which posed high ecological risk in the soil of unreclaimed OB dump. Bioaccumulation coefficient (BAC) value showed that Hg was not accumulated in the leaves of Dalbergia sissoo L., Gmelina arborea, Peltaphorum inerme L., Cassia seamea L, and Acacia mangium L grown on coal mine soil.  相似文献   
100.
Gulf of Mannar (GoM) in the southeast coast of India is known for its coral reefs and reef-associated biodiversity. Corals in GoM were affected to a significant extent by climate change-driven coral bleaching in 2016, and are currently recovering. After the bleaching mortality that corals suffered, the competition for space between corals and sponges is obvious in GoM. Rhabdastrella globostellata is a common marine sponge found overgrowing live coral colonies of the patch reefs in GoM at Pattinamaruthoor in March 2019. Underwater assessment of the reef revealed that 60.06% live coral cover was dominated by Acropora corals (81.91%). Among the acroporans 8.23% of colonies were found overgrown by R. globostellata. During the night dives the tiger cowrie Cypraea tigris was observed to feed on R. globostellata. From this observation the present study infers that C. tigris helps the corals fight these sponges, and concludes that tiger cowries should be protected and promoted to tackle climate change implications.  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