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   16714篇
  免费   17篇
林业   3699篇
农学   1299篇
基础科学   138篇
  2777篇
综合类   719篇
农作物   2104篇
水产渔业   1788篇
畜牧兽医   1172篇
园艺   1111篇
植物保护   1924篇
  2022年   2篇
  2020年   11篇
  2019年   6篇
  2018年   2749篇
  2017年   2712篇
  2016年   1189篇
  2015年   72篇
  2014年   31篇
  2013年   23篇
  2012年   811篇
  2011年   2144篇
  2010年   2109篇
  2009年   1262篇
  2008年   1331篇
  2007年   1596篇
  2006年   50篇
  2005年   108篇
  2004年   120篇
  2003年   165篇
  2002年   71篇
  2001年   9篇
  2000年   47篇
  1999年   5篇
  1998年   2篇
  1996年   4篇
  1995年   8篇
  1994年   2篇
  1993年   14篇
  1992年   10篇
  1990年   3篇
  1989年   5篇
  1988年   11篇
  1987年   2篇
  1986年   2篇
  1978年   3篇
  1977年   5篇
  1974年   2篇
  1972年   3篇
  1971年   1篇
  1970年   2篇
  1969年   4篇
  1968年   7篇
  1967年   2篇
  1964年   1篇
  1962年   3篇
  1961年   1篇
  1960年   1篇
  1958年   1篇
  1943年   1篇
  1938年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Umma Tamima 《林业研究》2016,27(4):853-861
The objective was to evaluate the performance of the co-management of Nishorgo Support Project at Chunati Wildlife Sanctuary in Bangladesh. I adopted the Focus Groups Discussion method for opinion survey and applied the SWOTAHP technique for data analysis. Local people did not participate in the decision-making process of forest management and they perceived co-management as a threat to their livelihoods. Moreover, mistrust and misunderstanding among different stakeholders, political and ethical conflicts, lack of property rights of tribal communities, and lack of accountability and transparency were identified as the drawbacks of co-management.  相似文献   
42.
43.
44.
45.
Fish associations with different types of littoral habitats were studied in four canyon‐shaped reservoirs in the Czech Republic in years 2010 and 2011 by gillnets. Two to three habitats per reservoir–beaches (former meadows), stump fields (former forest) and rubble slopes–were defined and sampled along the longitudinal axis of reservoirs. Effects of reservoir, habitat and locality (position along longitudinal axis) on fish biomass, abundance and species structure were tested for juvenile and adult fish separately. Hierarchical analysis of variance revealed that habitats differed significantly in fish biomass and abundance. Redundancy analysis showed that analysed environmental variables had significant influence on fish community structure. Most variability in community structure was explained by reservoir and then by combination of habitat and slope steepness. Locality position had the smallest influence on community structure. For both adult and juvenile fish total abundance and biomass, the most inhabited habitat was beaches; rubble slopes were the least inhabited. Habitat associations differed among species. Among adults, bream Abramis brama, white bream Blicca bjoerkna and roach Rutilus rutilus were associated with beaches and stump fields, whereas perch Perca fluviatilis, ruffe Gymnocephalus cernuus, asp Aspius aspius and pike Esox lucius were associated with rubble slopes. Bream, white bream, bleak Alburnus alburnus, roach, ruffe and pikeperch Sander lucioperca were associated with beaches among juveniles, whereas the only juvenile associated with rubble slopes was perch. We showed that most common species are associated with distinct habitats and also that utilisation of various littoral habitats differs in general.  相似文献   
46.
47.
A new functional porous carbons (PC-WF) is prepared by activation-pyrolysis method use waste cotton fabrics (WF) as an abundant, cheap and available precursor for removal of Brilliant Crocein (BC-GR) and Cationic Red 2GL (CR-GL) from aqueous phase. The PC-WF was characterized by BET, FTIR, SEM, and XRD techniques, the surface area, total pore volume, average pore diameter was found as 1463.5 m2 g-1, 0.783 cm3 g-1 and 2.14 nm, respectively. The influences on BC-GR and CR-GL adsorption of various experimental factors such as initial concentration and temperature were investigated. Adsorption kinetics was found to be best represented by the pseudo-second order model. The adsorption capacity was 319.8 mg g-1 for BC-GR and 842.5 mg g-1 for CR-GL at 30 °C, respectively. The results indicate that for waste cotton fabrics in particular, the practical application of this process to the production of porous carbon would be possible.  相似文献   
48.
49.
50.
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