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   175篇
  免费   26篇
  国内免费   37篇
  2023年   2篇
  2022年   3篇
  2021年   5篇
  2020年   6篇
  2019年   7篇
  2018年   9篇
  2017年   15篇
  2016年   4篇
  2015年   7篇
  2014年   11篇
  2013年   22篇
  2012年   8篇
  2011年   8篇
  2010年   6篇
  2009年   9篇
  2008年   9篇
  2007年   12篇
  2006年   5篇
  2005年   7篇
  2004年   10篇
  2003年   9篇
  2002年   12篇
  2001年   3篇
  2000年   7篇
  1999年   6篇
  1998年   6篇
  1997年   6篇
  1996年   4篇
  1995年   3篇
  1994年   2篇
  1993年   2篇
  1992年   1篇
  1991年   3篇
  1990年   2篇
  1989年   1篇
  1985年   1篇
  1983年   1篇
  1982年   1篇
  1980年   1篇
  1978年   1篇
  1976年   1篇
排序方式: 共有238条查询结果,搜索用时 16 毫秒
11.
Seed dispersal often limits tropical forest regeneration and animals disperse most rainforest tree seeds. This presents two important questions for restoration ecologists: (1) which animals are common seed dispersers? and (2) which restoration techniques attract them? Fourteen restoration sites were planted with four tree species in three designs, (1) controls (no planting, natural regeneration) (2) islands (trees planted in small patches), and (3) plantations (trees planted continuously over a large patch). We sampled birds in November, February, and April 2007–2008 with mist nets, in February and July 2009 with observations, and in July 2008 with both techniques. We documented 30 seed species from fecal samples of captured birds. All identified seed species were early‐successional forms. Four tanager species, three thrushes, two saltators, two flycatchers, and one finch were categorized as common seed dispersers, based on their high likelihood of dispersing seeds. Common dispersers were generalist species with small gape widths (<15 mm). Common dispersers were captured significantly more often in plantations than controls in most seasons and more often in plantations than islands during one season. Common disperser observations were significantly greater in plantations than controls during two periods and in plantations compared with islands in one period. Results indicate that plantation‐style planting is the conservative strategy to maximize attractiveness to common dispersers in tropical restoration sites. Island planting is an alternative when resources are limited although disperser activity may be lower in some seasons than in plantations. Additional research should investigate how to attract large, forest‐associated dispersers.  相似文献   
12.

Although a total ban on the use of TBT coatings is not expected in the short term, there is a growing need for environmentally safe antifouling systems. To assist in the rapid screening of a large number of potential antifouling substances, a method that is simple, efficient and inexpensive is required. The production of byssus threads by the blue mussel, Mytilus edulis, has often been studied for testing the antifouling efficacy of various compounds. The present study reports a new antifouling assay based on the inhibition of purified M. edulis phenoloxidase activity. The method has the advantage of being specific, reliable, sensitive and rapid.  相似文献   
13.
用电镜和细胞化学技术对毛竹[Phyllostachys edulis(Carr.)H.De Lehaie]节部“韧皮部结”发育过程中Ca^2+-ATP酶进行了超微细胞化学定位研究.结果显示:在“韧皮部结”形成期,仅细胞质膜和细胞核上具有很高的Ca^2+-ATP酶活性;随着“韧皮部结”的发育,发育期细胞质膜上的Ca^2+-ATP酶活性较形成期有所降低,而细胞核上仍保持较高的Ca^2+-ATP酶活性,胞间连丝、运输小泡膜上都具有Ca^2+-ATP酶活性;发育后期,液泡膜及内质网上也开始出现Ca^2+-ATP酶沉积物;成熟期的“韧皮部结”细胞质膜上的Ca^2+-ATP酶活性较发育期有所升高,并且在“韧皮部结”成熟的过程中,细胞核、内质网、胞间连丝、质体膜和细胞质降解物上始终都有较高的Ca^2+-ATP酶活性.实验结果表明“韧皮部结”细胞具有活跃的生理代谢以及频繁的共质体运输和信息交流.  相似文献   
14.
K. Hata  R. Atari  K. Sone 《Mycoscience》2002,43(5):0369-0373
 Endophytic fungi were isolated from leaves of Pasania edulis, one of the most important trees of the warm temperate forests in southern Kyushu, by the surface sterilization method using H2O2 as a sterilizing agent. From a tree in the Experimental Nursery of Kagoshima University, located at the city of Kagoshima, Phyllosticta sp. and Colletotrichum spp. were frequently isolated. From a stand in a laurel forest in Mt. Takakuma, an ascomycetous fungus (Ascomycete sp. 1) and Phomopsis sp. were frequently isolated. Phyllosticta sp. was isolated more frequently from petiole segments and leaf segments with midrib and Phomopsis sp. from petiole segments and leaf-base segments with midrib than other segments. Colletotrichum spp. were isolated less frequently from petioles and Ascomycete sp. 1 from petiole segments and leaf-base segments with midrib than other segments. As possible causes of such biases in within-leaf distributions of the endophytes, differences in infection modes and negative interactions of major endophytes within leaves are suggested. Received: December 13, 2001 / Accepted: June 7, 2002 Acknowledgments The authors thank the staff members of the Experimental Forests of Kagoshima University for enabling the present study. Correspondence to:K. Hata  相似文献   
15.
利用生物信息学方法,于毛竹(Phyllostachys edulis (Carr.) Lehaie)全基因组中鉴定获得18个GRF转录因子,并对其理化特性、保守结构域、系统发育关系、mi R396靶位点以及基因表达模式进行了分析。结果表明,18个Pe GRF蛋白长度为170~551 aa,分子量为18.5~58.8 k D;这些Pe GRF蛋白均具有QLQ和WRC结构域,部分Pe GRF含有FFD和TQL保守结构域。对毛竹、拟南芥(Arabidopsis thaliana (L.) Heynh)和水稻(Oryza sativa L.)的系统进化分析结果显示,毛竹18个GRF可分为3个亚类,且单子叶植物毛竹和水稻的GRF转录因子亲缘关系更近。mi R396靶位点预测分析结果发现,在13个Pe GRF基因序列的编码区存在毛竹mi R396结合位点; Pe GRF基因表达模式分析结果显示,Pe GRF主要在毛竹的竹笋中表达。  相似文献   
16.
两株滇产广义美味牛肝菌的分离培养及其分子鉴定   总被引:1,自引:0,他引:1  
采用组织分离法从广义美味牛肝菌子实体分离获得2株稳定的菌株,初步研究了两菌株的分离和培养条件。用ITS序列分析,对分离菌株进行了分子鉴定。基于ITS序列构建的系统树表明两株菌属于美味牛肝菌复合群,并与夏生牛肝菌Boletus aestivalis(Paul.)Fr.有较近的亲缘关系。  相似文献   
17.
18.
Electrical currents in underwater sea cables could induce magnetic fields. The sea cables lie on or within the sea bottom and this is the living area for many invertebrate and vertebrate species. North Sea prawn Crangon crangon (Crustacea, Decapoda), round crab Rhithropanopeus harrisii (Crustacea, Brachyura), glacial relict isopod Saduria entomon (Crustacea, Isopoda), blue mussel Mytilus edulis (Bivalvia), and young flounder Plathichthys flesus (Pisces) were exposed to a static magnetic field (MF) of 3.7 mT for several weeks. The results showed no differences in survival between experimental and control animals. Mussels M. edulis were kept under static magnetic field conditions for 3 months during their reproductive period in spring. The determination of gonad index and condition index revealed no significant differences to the control group.  相似文献   
19.
20.
Proteomics provide potential in the discovery of new sensitive biomarkers for environmental pollution. To evaluate this potential, we have utilized ProteinChip® technology to analyze the proteomic profile of blue mussels (Mytilus edulis) from polluted marine habitats surrounding the island of Karmøy, Norway. Two different types of contamination, heavy metals and polyaromatic hydrocarbons (PAHs), were compared to a clean reference site. Differentially expressed proteins/peptides were found, which showed a specific induction or a general suppression associated with the field site of origin. By combining sets of protein markers in a tree-building algorithm, we were able to correctly classify samples from these sites with an accuracy of 90%.  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