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   301篇
  免费   30篇
林业   30篇
农学   8篇
基础科学   2篇
  63篇
综合类   2篇
农作物   9篇
水产渔业   67篇
畜牧兽医   92篇
园艺   14篇
植物保护   44篇
  2024年   2篇
  2023年   11篇
  2022年   6篇
  2021年   10篇
  2020年   9篇
  2019年   13篇
  2018年   13篇
  2017年   17篇
  2016年   16篇
  2015年   13篇
  2014年   11篇
  2013年   50篇
  2012年   25篇
  2011年   22篇
  2010年   21篇
  2009年   6篇
  2008年   10篇
  2007年   4篇
  2006年   12篇
  2005年   9篇
  2004年   4篇
  2003年   5篇
  2002年   7篇
  2001年   5篇
  2000年   1篇
  1998年   2篇
  1997年   1篇
  1996年   4篇
  1995年   2篇
  1993年   2篇
  1990年   1篇
  1989年   1篇
  1987年   1篇
  1985年   2篇
  1984年   5篇
  1983年   3篇
  1982年   1篇
  1979年   1篇
  1977年   1篇
  1968年   1篇
  1958年   1篇
排序方式: 共有331条查询结果,搜索用时 15 毫秒
81.
The purpose of this study was to investigate the influence of soil geochemistry on the concentrations of Ca, K, Mg, P, Co, Ni, Zn, Mn, Cu, and Fe in cabbage (Brassica oleracea L. var. capitata) grown on acid sulfate (AS) soils in Western Finland. A total of 11 topsoil (0–20 cm) and corresponding cabbage samples and three whole‐soil profiles (≈ 0–260 cm) were collected on three agricultural fields. The concentrations of Co and Zn in cabbage were correlated with the NH4Ac‐extractable (easily available) concentrations in the topsoil, indicating that the uptake of these elements in cabbage is largely governed by soil geochemistry. Yet, the concentrations of Co and Zn in cabbage were not in general elevated relative to that of Finnish average values, although some AS soils showed enriched concentrations of these metals in the soil and cabbage. Significant geochemical differences (e.g., oxidation depth, organic‐matter and S content, pH) were observed among the studied AS soils, while, on the other hand, the concentrations of Ca, K, Mg, P, Ni, Mn, Cu, and Fe in cabbage were relatively similar. The hydroxylamine‐extractable concentrations of these elements in the topsoil were not correlated to those in cabbage, suggesting that uptake is not governed by the oxide‐bound fraction of these elements in the soil. Similarly, the easily available concentrations of Ca, P, Ni, Mn, Cu, and Fe in the topsoil were not correlated to those in cabbage, indicating that uptake is independent of the easily available concentrations in the soil. Hence, it is suggested that cabbage can regulate and thus optimize its concentrations of Ca, P, Ni, Mn, Cu, and Fe. Oxidation depth affected neither the easily available concentrations of Co, Ni, Zn, and Mn in the topsoil nor the concentrations in cabbage. However, the subsoil with a lower oxidation depth, which is to a smaller extent affected by leaching, may partly be enriched in these metals. Nevertheless, these showed no increased concentrations in cabbage. Based on these findings, it is suggested that the large amounts of metals mobilized in AS soils are easily lost to drains, subsequently contaminating nearby waterways and estuaries whereas they are only partly enriched in cabbage and other previously studied crops (oat).  相似文献   
82.
Slope length effects on microbial biomass and activity of eroded sediments   总被引:2,自引:0,他引:2  

Purpose  

Due to climatic and topographic conditions, soil erosion is a major problem in Turkey; approximately 86% of the land is suffering from some degree of erosion. This study investigated the relationship between bare soil slope length and the erosion-induced degradation of soil quality and the loss of carbon (C) and nitrogen (N) from the microbial biomass in eroded sediment in the Western Black Sea Region of Turkey.  相似文献   
83.
84.
Ölmez  Selime  Ulusoy  M. Rifat 《Phytoparasitica》2003,31(5):524-528
A list is given of aphid parasitoids found in Diyarbakır Province, Turkey. In the survey, performed between 1998 and 2000, 16 species of aphid parasitoids were found on different hosts in Diyarbakır Province.Monoctonus mali is reported for the first time in the Turkish aphid parasitoids fauna. http://www.phytoparasitica.org posting Oct. 20, 2003.  相似文献   
85.
Phyllonorycter apparella (Herrich-Schäffer, 1855) (Lepidoptera: Gracillariidae) is a new record for the Turkish fauna and a new trembling aspen(Populus tremula L.) pest for Turkey. Its biology, damage and infestation ratio were studied in Sankami?. (Kars), Turkey, during 1996 and 1997.P. apparella has one generation a year. The developmental stages of the pest are described briefly. P.apparella hibernates in the adult stage. At the beginning of June, the adults appear. Females deposit their eggs on both leaf surfaces, generally one by one, 7–10 days after emerging. The early instars (sap-feeding larvae) start to mine mostly from the underside of leaves. Each mine has one larva, and each leaf may have up to 26 mines. The last instar (tissue-feeding larva) begins to pupate in the mine after mid August. The adults emerge from mid September to the beginning of October, and move to the trunks of old pine trees, where they hibernate in bark crevices. The infestation level may be as high as 90% of the leaves on some trees.  相似文献   
86.
The effect of soil amended with stalks of sunflower (Helianthus annuus L.), alfalfa (Medicago sativa L.) and Hungarian vetch (Vicia pannonica Crantz) on onion bulb rot caused byFusarium oxysporum Schlecht. f.sp.cepae (Hanz.) Snyder Hansen andAspergillus niger v. Tieghem was tested in a soil naturally infested with the pathogens under field conditions. All treatments significantly reduced bulb rot incidence. The fungal and antibacterial populations varied among all of the amended tested soils. Heterotrophic fungal populations were more effective than heterotrophic bacterial populations in the suppression of disease. The highest population of fungal microflora was found in plots amended with sunflower stalks. The carbon-to-nitrogen ratio and available moisture content of amended soils have an indirect suppressive role on disease, by increasing the heterotrophic fungal population. http://www.phytoparasitica.org posting June 18, 2002.  相似文献   
87.
Data are presented on the occurrence of 43 species of the family Apionidae and two species of the family Nanophyidae in Turkey based on the material obtained mainly by beating stone-fruit trees in NE Turkey. The identity and information about the three species of Apionidae —Squamapion sp.cf.bifarium (Balfour-Browne),Protapion sp.cf.ruficrus (Germar),Catapion sp.cf.seniculus (Kirby) — must be revised. The faunistic data in the present paper on almost all species add to prior knowledge on their distribution in Turkey.Hypophyes aphyllae (Peyerímhoff),Ceratapion kasbekianum (Gerstaecker),Squamapion ottonis (Wagner),S. samarense (Faust),S. phocopus (Eppelsheim),Taeniapion rufulum (Wencker),Pseudoprotapion astragali (Paykull),P. ergenense (Becker),Stenopterapion intermedium (Eppelsheim) andOxystoma fausti (Desbrochers) are reported for the first time in the Turkish fauna. http://www.phytoparasitica.org posting Nov. 8, 2001.  相似文献   
88.
The impacts of fermentation process with acid and lactic acid bacteria strains (Lactobacillus plantarum, Lactobacillus brevis, Pediococcus acidilactici, Enterococcus gallinarum, and Streptococcus spp.) on the biogenic amine formation of wet and spray-dried fish silage obtained from whole gibel carp (Carassius gibelio, freshwater discard), whole ponyfish (Equulites klunzingeri, seawater discard), and processing by-products of seabass (Dicentrarchus labrax) were investigated. The results showed that among biogenic amines, cadaverine, putrescine, spermidine, spermine, serotonin, dopamine, and agmatine were predominant in all groups. Significant differences (p < 0.05) in biogenic amine concentrations of wet and spray-dried fish silage were observed. Raw fish and wet silages contained histamine level lower than the allowable limit of 50mg/kg, indicating the use of raw fish material with low microbial counts. In addition, no histamine was detected in spray-dried fish silage, except for seabass by-products with a trace quantity of histamine (<0.04mg/100g). The starter culture used for silage preparation did not effectively retard formation of biogenic amines compared to acid silage. It can be concluded that there is potential use of fermented fish silage as a protein source and possibly as a probiotic ingredient for animal feed in both wet and dry form.  相似文献   
89.
Measurement of serum biochemical parameters in response to metal exposures can be especially useful to help identify target organs of toxicity as well as the general health status of animals. Oreochromis niloticus were exposed to 5.0 mg/L Zn, 1.0 mg/L Cd, and 5.0 mg/L Zn + 1.0 mg/L Cd mixture for 7 and 28 days, and alterations in serum enzyme activities and ion levels were measured. Significant changes in all the biochemical parameters were found to be time dependent. Following metal exposure, alkaline phosphatase activity was elevated at both exposure periods. No changes in activities of lactate dehydrogenase and lipase were observed in response to single or combined Zn and Cd exposure at 7 days while they increased at 28 days. Fish exposed to metals showed a decrease in cholinesterase activity at 7 days followed by a return to control levels at the end of the exposure period. The individual and combined effects of metals caused a decline in levels of Na+, Cl, and Ca2+, especially at 28 days. K+ level increased at 7 days but it returned to control levels with increasing duration of exposure. This study indicated that the alterations in serum parameters may be a result of the target tissue (i.e., liver, gill, and kidney) damage and dysfunction induced by the metals and that these parameters can thus be used to assess the effects of metals on organisms.  相似文献   
90.
Journal of Plant Diseases and Protection - The brown marmorated stink bug, Halyomorpha halys (Stål), is a pest of many annual and perennial agricultural products. The species is native to...  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