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   165篇
  免费   8篇
林业   5篇
农学   6篇
基础科学   4篇
  46篇
综合类   12篇
农作物   9篇
水产渔业   18篇
畜牧兽医   43篇
园艺   14篇
植物保护   16篇
  2023年   2篇
  2022年   6篇
  2021年   7篇
  2020年   2篇
  2019年   4篇
  2018年   13篇
  2017年   5篇
  2016年   10篇
  2015年   5篇
  2014年   6篇
  2013年   13篇
  2012年   6篇
  2011年   11篇
  2010年   15篇
  2009年   7篇
  2008年   12篇
  2007年   9篇
  2006年   8篇
  2005年   8篇
  2004年   6篇
  2003年   8篇
  2002年   2篇
  2000年   2篇
  1999年   2篇
  1998年   1篇
  1988年   1篇
  1985年   1篇
  1983年   1篇
排序方式: 共有173条查询结果,搜索用时 15 毫秒
41.
The present work was carried out to study genetic diversity among 17 populations of wild emmer wheat sampled from South-eastern Turkey, considered to be an important region for domestication of wheat. Eleven RFLP clones and 4 restriction enzymes combinations were used to probe the genomic DNA. A total of 151 polymorphic loci were obtained from the enzyme-probe combinations. The Genetic Distance (GD) values were from 0.019 (Gaziantep-3 and Sanliurfa-4) to 0.200 (Gaziantep-1 and K. Maras). Cluster analysis results showed that populations formed 2 clades within the dendrogram. Population Gaziantep-1 was unique and genetically most diverse from the remaining 16 populations. The results of average genetic distance (GD) among populations suggested that narrow genetic variability exist among 17 populations in the present study.  相似文献   
42.
Four different‐sized (390±3, 140±2, 40±2, 16±1 g) Nile tilapia, Oreochromis niloticus (L.), stocked at the same biomass in timed pulse feeding chambers were provided 27–29°C water dominated by Microcystis (82%) and Scenedesmus (18%) to determine the effect of fish size on filtration rates. The number of Microcystis and Scenedesmus units filtered from the water decreased significantly with increasing tilapia size. The shaping constants and maximum filtration rates for Ivlev's feeding model used to describe the relation between filtration rates and the suspended particulate organic carbon (POC) concentrations were significantly different among the four sizes. Filtration rates of 763, 671, 512 and 300 mg C kg?1 h?1, which correspond to 70%, 82%, 86% and 90% saturation levels, were achieved at POC levels of 30, 32, 32 and 33 mg C L?1 for 16, 40, 140 and 390 g Nile tilapia respectively. Smaller tilapia achieved these rates at lower POC concentrations than larger tilapia.  相似文献   
43.
Regulatory approval of ozone has increased commercial interest in the development of applications to ensure produce quality and safety. However, ozone sometimes fails to inactivate microorganisms on packaged produce and this may be a consequence of poor diffusion into packages. Gaseous ozone (900 ± 12 μL/L) was applied to several common plastic films with a range of ventilation areas and diffusion through them determined. A semi-quantitative method using the reaction of ozone with indigo trisulfonate or with indigo carmine dye solutions was used. Dye de-colorization occurred relatively rapidly (in less than 1 h) after exposure to ozone, indicating that it diffused through all tested materials. Although the extent of ozone diffusion followed the sequence of high-density polyethylene > polypropylene > low density polyethylene, differences among them were small and not significant (P > 0.05). Ozone diffusion was also determined through a low density polyethylene film with ventilation areas of 1.3, 5.2, and 10.4% created by circular holes 6.5 mm in diameter. Gradual but modest increases in ozone diffusion occurred as the ventilation area increased.  相似文献   
44.
The essential oils of aerial parts of Achillea gypsicola Hub.-Mor., Hypericum scabrum L., Satureja hortensis L., and Origanum acutidens (Hand.-Mazz.) Letswaart were analyzed in this study by GC and GC–MS and their oils were tested for toxicity against broadbean weevil (Bruchus dentipes). A. gypsicola oil contained camphor (40.17%), 1,8-cineole (22.01%), piperitone (11.29%), borneol (9.50%) and α-terpineol (1.56%) as major components. A total of 74 components were identified by GC–MS in H. scabrum oil, including α-pinene (9.26%), terpinen-4-ol (5.12%), camphor (5.94%), δ-cadinene (4.52%), pulegone (4.45%), γ-muurolene (4.12%), pinocarvone (3.97%) and β-caryophyllene (3.42%) as predominant components. The essential oils of O. acutidens and S. hortensis were characterized by high contents of carvacrol (86.99% and 55.74%), γ-terpinene (0.71% and 20.94%), p-cymene (1.95% and 12.30%), α-terpinene (0.13% and 2.04%) and β-caryophyllene (1.30% and 1.08%). All of the essential oils were toxic to adults of B. dentipes and insect mortality increased with increasing concentration of each oil. The oils (20 μl dose) brought about 100% mortality in 36 h. Although desirable insecticidal activities against the pest were achieved with the oils from all four plant species, S. hortensis and O. acutidens oils were more effective, particularly after 6 h of treatment. The current results concluded that the essential oils, in particular O. acutidens and S. hortensis oils, may be used as potential botanical insecticides against B. dentipes.  相似文献   
45.
The proximate properties, the fatty acid and mineral contents of different almond kernel varieties were determined. The crude protein contents of kernels ranged between 12.7% (guara) and 16.3% (cristomorto). The oil yields from these kernels were established between 48.8% (cristomorto) and 55.7% (ferragnes). The acidity value of oils were found between 1.389 and 3.559%. In addition, peroxide values were established between 7.586 (nonpareil) and 15.590 mequiv./kg (cristomorto). The major fatty acids of almond kernel oils were oleic (72.5–79.9%), linoleic (13.5–19.8%) and palmitic acids (5.9–6.7%). The predominant mineral in most kernel was potassium (13.1–15.1 mg/100 g). The mineral contents of the kernels were established as 7.94–9.38 mg/100 g potassium, 2.9–4.0 mg/100 g magnesium and 1.84–2.94 mg/100 g calcium. From the results of the present study, it can be concluded that the kernels of almond varieties are being potential sources of valuable oil which might be used for edible and other industrial applications.  相似文献   
46.
BACKGROUND: Bovine viral diarrhea virus (BVDV) infection is one of the causes of hemorrhagic diathesis in cattle but there have been limited field studies about that condition. HYPOTHESIS: To identify the cause of hemorrhagic diathesis in calves and describe its clinical findings. ANIMALS: Five calves from a farm with 150 dairy cows. METHODS: Clinical examination of the calves was performed. After blood samples were obtained from 2 calves, whole blood, sera, and leukocyte samples were used for hematologic and hemostatic examinations, neutralization tests, virus isolation, and viral genome sequencing. RESULTS: The calves had moderate pyrexia, dullness, serous or mucous nasal discharge, and petechial and ecchymotic hemorrhages on mucosal surfaces. Severe thrombocytopenia and anemia were identified on hematologic examinations. All calves died within 10 days of the onset of clinical signs. Virologic examinations identified BVDV as the causative agent of the disease. CONCLUSIONS AND CLINICAL IMPORTANCE: This paper identifies a hemorrhagic syndrome-like disease in calves with bovine viral diarrhea and mucosal disease complex in Turkey.  相似文献   
47.
1. The aim of the present study is to describe, immunohistochemically, the expression and cell type localisation of growth factor receptors and some of their ligands in the oropharyngeal organs of the Chukar partridge.

2. The tissue samples from 10 healthy adult partridges were dissected under ether anaesthesia and then embedded in paraffin following routine histological procedures. The immunoreaction for receptors and ligands of the epidermal growth factor receptor (EGFR)/ligand system was localised in the cell membrane, nucleus and cytoplasm of the luminal and glandular epithelial cells, stromal and striated muscle cells, and vascular endothelial and smooth muscle cells.

3. Variations were observed in the avian oropharyngeal organs. The immunostaining for the erbB1/HER1 (human epidermal growth factor receptor 1) and the EGF (epidermal growth factor) and AREG (Amphiregulin) ligands in the luminal epithelial cells was higher than in the glandular epithelial, stromal and striated muscle cells. However, the immunostaining for erbB3/HER3 (human epidermal growth factor receptor 3) and erbB4/HER4 (human epidermal growth factor receptor 4) were similar in the luminal epithelium, stromal and striated muscle cells.

4. Growth factor receptors and some of their ligands were localised in different cell types in the oropharyngeal organs. We suggest that erbB/HERs (human epidermal growth factor receptors) and their ligands play an important role in proliferation, differentiation, growth, survival and migration of the cells.  相似文献   

48.
Comparisons were made between yield measurements with an impact based yield sensor and an electronic scale in adjacent harvest strips and on the same grain stream within a combine. Yield measurements in adjacent strip comparisons were more prone to errors as the segment lengths decreased. Grain yield difference between the yield sensor and electronic scale ranged from 5 to 14%, 4 to 13%, 3 to 12%, and 2 to 11% for 15, 30, 60, and 300 m long segments. The yield differences between neighboring segments might have been caused by yield variability to a degree; however, a consistent decrease in yield differences with increasing segment lengths implied that better accuracies could be obtained in longer management areas. The combine responses to grain yield changes and the effect of varying ground speed on accuracy were also evaluated by creating artificial yield patterns in harvest strips. Grain diffusion within the combine was more obvious when abrupt yield changes were introduced at known locations. Grain mixing and redistribution inside the combine may dictate the selection of segment sizes in the site-specific decision making process. Constant ground speed provided more stable grain flow values than varying ground speed. The average error in yield estimate was 3.4% and 5.2% at constant ground speed and varying speed, respectively. Careful calibration and constant combine speed were important to achieve better accuracy with the grain yield monitor.  相似文献   
49.
The aim of the present study was to assess the genetic variation in several Israeli and Turkish populations of wild emmer wheat, Triticum turgidum ssp. dicoccoides, the progenitor of most domesticated wheat. Single spikes were collected in 2002 from 60 plants that grew in six different habitats in Ammiad, northeastern Israel (8–12 plants from each habitat), and in 1998 from 56 plants that grew in seven different habitats in Diyarbakir, southeastern Turkey (8 plants from each habitat). Seeds were planted in a nursery and DNA was extracted from every plant and analyzed by the fluorescent-based amplified fragment length polymorphism (AFLP) method. Seven primer combinations produced 788 discernible loci of which 48.6% were polymorphic in Israel and 40.5% in Turkey. The genetic diversity estimates P (frequency of polymorphic loci) and He (gene diversity) were higher in Ammiad than in Diyarbakir (means of P = 0.34 and He = 0.13 in Ammiad vs. P = 0.20 and He = 0.08 in Diyarbakir). Ammiad populations contained more unique alleles than Diyarbakir populations. The relative genetic diversity estimates (θ) values were 0.188 in Ammiad and 0.407 in Diyarbakir, suggesting better differentiation of the populations in Turkey. Genetic distance was larger between Israeli and Turkish populations than between populations of each country. The data indicate that the Israeli and Turkish populations are considerably diverged and that the Israeli populations are more polymorphic than the Turkish ones, having a larger within-populations genetic variation than among-populations one. The significance of the results in relation to the differentiation pattern of wild emmer in the Near East is discussed.  相似文献   
50.
Sonmez  Fatih  Gunesli  Zuhal  Demir  Taki  Cıkrıkcı  Kubra  Ergun  Adem  Gencer  Nahit  Arslan  Oktay 《Erwerbs-Obstbau》2022,64(2):145-153

Total anthocyanins were extracted from eleven sweet cherry cultivars grown in Sakarya, Turkey. In vitro inhibition effects of extracted total anthocyanins on purified carbonic anhydrase I and II were investigated by using CO2 as a substrate. The results showed that all extracted total anthocyanins inhibited the hCA I and hCA II enzyme activities. Among all cultivars, ‘Merton Premier’ was found to be the most active one against both hCA I (IC50?=?0.83?µg/mL) and hCA II (IC50?=?1.16?µg/mL). Additionally, the DPPH activities of the extracts were investigated as antioxidant properties. The results exhibited that ‘Churchill’ and ‘Merton Premier’ have high antioxidant activity with 74.102% and 73.503% DPPH activity, 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