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   596篇
  免费   35篇
  国内免费   142篇
  2024年   2篇
  2023年   6篇
  2022年   12篇
  2021年   16篇
  2020年   13篇
  2019年   24篇
  2018年   13篇
  2017年   25篇
  2016年   20篇
  2015年   24篇
  2014年   36篇
  2013年   26篇
  2012年   25篇
  2011年   34篇
  2010年   25篇
  2009年   34篇
  2008年   21篇
  2007年   28篇
  2006年   31篇
  2005年   32篇
  2004年   30篇
  2003年   26篇
  2002年   30篇
  2001年   18篇
  2000年   30篇
  1999年   10篇
  1998年   11篇
  1997年   14篇
  1996年   10篇
  1995年   11篇
  1994年   15篇
  1993年   12篇
  1992年   15篇
  1991年   8篇
  1990年   11篇
  1989年   8篇
  1988年   8篇
  1987年   8篇
  1986年   7篇
  1985年   5篇
  1984年   7篇
  1983年   5篇
  1982年   8篇
  1981年   1篇
  1980年   5篇
  1978年   7篇
  1977年   1篇
  1976年   4篇
  1973年   1篇
排序方式: 共有773条查询结果,搜索用时 359 毫秒
91.
Kielhorn  K. -H.  Keplin  B.  Hüttl  R. F. 《Plant and Soil》1999,213(1-2):117-125
On a study site in the Lusatian lignite mining region (Germany), sandy mine spoil was ameliorated with either sewage sludge, compost or mineral fertilizer. Plots were sown with the grass Secale multicaule and planted with pine seedlings except for a control that was not meliorated and not revegetated. Pitfall catches of ground beetles in 1996/97 yielded high numbers of species and individuals directly after revegetation. The dominant beetles were xerophilic species, known to prefer open sandy sites. Catches in different plots were positively correlated with the amount of vegetation cover and declined as follows: amelioration with sewage sludge > compost > mineral fertilizer > untreated control. Even beetles characteristic of open sandy sites showed a distinct preference for plots with high vegetation cover treated with organic waste. For the dominant species, an attraction to shelter and a more balanced, humid microclimate is assumed. A year-to-year comparison showed an increase in beetles typical of dry grasslands and ruderal sites in the second year, while characteristic species of open sandy sites decreased. Application of organic waste combined with revegetation led to an immediate increase in beetle numbers. In the long term, revegetation would be expected to reduce suitable habitats for endangered ground beetles which prefer open sites with poor sandy soils. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   
92.
四种红树林植物的淡水驯化试验   总被引:3,自引:0,他引:3  
贺建  陈桂珠  罗航 《生态科学》1999,18(3):12-15
选择秋茄、木榄、桐花树、无瓣海桑4 种红树林植物的幼苗, 在中山大学附属中学校园内进行了8 个月的池塘和陆地的淡水驯化试验。对之分别计算了成活率、茎高增加量、基茎增加量、生物量的增量和凋落物量, 并定期对其成活状况、生长状况进行观察和记录。发现各树种在淡水池塘中均能较好生长, 木榄和桐花树对陆地也有较强的适应性。  相似文献   
93.
在污水处理领域,藻菌共生有同步脱氮、除磷效率高、排放温室气体量低、生物质可资源化回收等优势,近年来受到学者的重视.目前鲜有综述污水处理中藻类与细菌、真菌及混合藻菌间互作机制的文章.本文从藻类-细菌、藻类-真菌、混合藻-混合菌3个方面介绍藻菌共生处理污水的研究进展,重点阐述藻菌间营养物质交换、信号传导及生物絮凝3种不同互...  相似文献   
94.
95.
In order to explore the responses of the bacterioplankton community to different types of aquaculture environments, three mariculture ponds comprised of groupers (Epinephelus diacanthus, ED), prawns (Penaeus vannamei, PV), and abalone (Haliotis diversicolor supertexta, HDS) in southeast, coastal China were investigated. The free-living bacterial diversity was analyzed through the construction of 16S rDNA clone library. A total of 203 16S rDNA sequences from three clone libraries were classified into 118 operational taxonomic units (OTUs), of which 51, 31, and 42 OTUs were distributed in the ED, PV, and HDS pond, respectively, with Bacteroidetes (30.6%), Actinobacteria (55.2%), and Cyanobacteria (32.8%) as the dominant division in the respective ponds. Meanwhile, each pond occupied some unique OTUs that were affiliated with uncommon (sub-)phyla, such as candidate OP11 division, Acidobacteria, Deltaproteobacteria, Planctomycetes, and Verrucomicrobia. Bacterial diversity in the ED pond was the richest, followed by the HDS and the PV pond. OTUs of 61.9% and 94.9% have less than 90% and 97% similarity to their nearest neighbors in public databases, respectively. All OTUs were grouped into 67 clusters, covering 11 (sub-)phyla. The OTUs only from single pond distributed in 53 clusters (79.1%), the OTUs shared by two ponds were affiliated with 14 clusters (20.9%), and none of clusters was formed by the OTUs which commonly originated from the three pond libraries, suggesting that the composition of bacterial populations in these ponds were significantly different. These results indicate that the aquatic environment created by different mariculture animals may foster very special and complex bacterial communities. Handling editor: David Philip Hamilton  相似文献   
96.
The morphological and phylogenetic diversity of the microscopic eukaryotes of the Lake Koronia water column was investigated during a mass kill of birds and fish in August–September 2004. The dominant morphospecies corresponded to the known toxin-producing species Prymnesium parvum , followed by Amoebidium sp., a taxon belonging to the group of parasitic Mesomycetozoea , and the common chlorophyte Pediastrum boryanum. Prymnesium exhibited heteromorphic life-cycle stages (flagellate and nonmotile coccoid cells). Phylogenetic analysis with 18S rRNA gene suggested that these heteromorphic stages belonged to the Platychrysis – Prymnesium monophyletic group. The most abundant phylotype was almost identical to P. boryanum . The fungal phylotypes were related to the Chytridiomycota , and the ciliate-like ones were closely related to Enchelys polynucleata and Pattersoniella vitiphila . Two phylotypes representing novel members belonging to the Jakobida and the Apicomplexa were also found. The microscopic eukaryotes of Lake Koronia include several organisms that are related to parasitic life modes.  相似文献   
97.
Aim:  Previous analysis of tet39 suggests it may be present in other bacterial species. Hence, we investigated the host range of tet39 among bacterial from a poultry waste polluted river in Southwestern Nigeria.
Methods and Results:  Thirteen resistant bacterial isolated from the water and sediment of the polluted river was investigated for the presence of tetracycline resistance genes tetA , tetB , tetC , tet39 and the transposon integrase gene of the Tn916/1545 family by PCR. While tetA , tetB , tetC and integrase genes cannot be detected in any of the organisms, tet39 was detected in eight of the tested organisms including three Gram-positive species. Sequence analysis showed the genes have high sequence identities (≥99%) with tet39 of Acinetobacter sp. LUH5605, the first and only bacterial genus from which the gene has been reported to date. This is a novel observation.
Conclusions:  This study shows that apart from Acinetobacter , tet39 is present in other bacterial species tested in this study.
Significance and Impact of the Study:  This study adds to available information on the occurrence and distribution of tet39 among environmental bacteria and suggests that the gene has a broader host range than previously reported.  相似文献   
98.
Water levels were recorded weekly from six natural vernal pools and 10 created vernal pools at two forested wetland complexes in central Ohio. Vernal pool median water depth and duration of inundation were significantly greater at the created vernal pools than at the natural vernal pools (α = 0.05, P < 0.05). The average period of inundation for created pools was 309 ± 32 days, compared with 250 ± 16 days for natural pools. The created pools produced a range of inundation times, from 163 to 365 days in length, with three pools permanently inundated.  相似文献   
99.
Biological kinetic (bio-kinetic) study of the anaerobic stabilization pond treatment of palm oil mill effluent (POME) was carried out in a laboratory anaerobic bench scale reactor (ABSR). The reactor was operated at different feed flow-rates of 0.63, 0.76, 0.95, 1.27, 1.9 and 3.8 l of raw POME for a day. Chemical oxygen demand (COD) as influent substrates was selected for bio-kinetic study. The investigation showed that the growth yield (YG), specific biomass decay (b), maximum specific biomass growth rate (μmax), saturation constant (Ks) and critical retention time (Θc) were in the range of 0.990 g VSS/g CODremoved day, 0.024 day−1, 0.524 day−1, 203.433 g COD l−1 and 1.908 day, respectively.  相似文献   
100.
Physical and biological removal of diesel oil from contaminated soil was studied in a baffled roller bioreactor. Initially, the effects of four factors (soil loading, temperature, pH, and surfactant) on physical removal of diesel oil were investigated. Only the presence of a surfactant (sodium dodecyl sulfate [SDS]) demonstrated a significant effect on diesel oil removal. Diesel oil removal efficiency was increased from 32.0% to 63.9% in the presence of 100 mg/L SDS. Using a microbial culture enriched from contaminated soil, biological treatment of diesel oil polluted soil under different soil loadings (15% to 50%), different diesel oil concentrations (1 to 50 g/L), and different types of soil (sand, silt, and clay) was then investigated in the baffled roller bioreactor. Biodegradation consisted of both fast and slow stages for degradation of light and heavy compounds, respectively. All biodegradation experiments demonstrated significant decreases in diesel oil concentrations (88.3% in 14 days for initial diesel oil concentrations of 1000 mg/L and a wide range of soil loadings). The presence of silty or sandy soils enhanced the biodegradation rate compared to the control bioreactor (without soil). The sandy soil loading had no effect on the biodegradation results. Using the enriched culture, the baffled roller bioreactor was able to biodegrade high diesel concentrations (up to 50 g/L) with biodegradation rates of 112.2 and 39.3 mg/L· h during fast and slow stages, respectively.  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