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   108篇
  免费   3篇
林业   4篇
农学   4篇
基础科学   10篇
  26篇
综合类   7篇
农作物   4篇
水产渔业   6篇
畜牧兽医   36篇
园艺   6篇
植物保护   8篇
  2023年   3篇
  2022年   4篇
  2021年   5篇
  2020年   2篇
  2019年   4篇
  2018年   4篇
  2017年   5篇
  2016年   4篇
  2015年   1篇
  2013年   11篇
  2012年   4篇
  2011年   4篇
  2010年   5篇
  2009年   8篇
  2008年   5篇
  2007年   8篇
  2006年   6篇
  2005年   6篇
  2004年   6篇
  2003年   2篇
  2002年   3篇
  2001年   4篇
  2000年   2篇
  1997年   1篇
  1993年   1篇
  1991年   1篇
  1990年   1篇
  1984年   1篇
排序方式: 共有111条查询结果,搜索用时 15 毫秒
21.
The prolonged irrigation with marginal quality water can cause secondary salinization of soils, which necessitates for better understanding of water management alternatives. Relative performance of sulfuric acid and gypsum is still controversial to counter sodium hazards in soil/water system. As an alternative, sulfurous acid generators (SAG) are also being marketed. But up-till-now, there is not even a single field study published in scientific journals about their efficiency and economical viability for the treatment of saline-sodic water. Therefore, a field study was carried out to compare the effectiveness of SAG and alternate amendments applied on an equivalent basis to grow rice crop. SAG treatment of saline-sodic tube well water decreased only residual sodium carbonate (RSC) from 5.4 to 3.6 mmolc l−1, and had no beneficial effect on its sodium adsorption ratio (SAR) or electrical conductivity (EC). All the treatments kept soil EC and SAR around their respective threshold levels. For paddy yield, SAG, sulfuric acid, and gypsum treatments depicted nonsignificant differences. SAG and sulfuric acid treatments of water were about six times expensive than that of gypsum. It was concluded that soil-applied gypsum, to counter sodic hazards of irrigation water, is economical to sustain irrigated rice in dry regions.  相似文献   
22.
Membrane filtration is a cost‐effective alternative to heat pasteurization of corn steep water. Trials were done in an operating ethanol plant with commercial spiral‐wound modules. Flux increased with transmembrane pressure and became independent of pressure at >10 psi (69 kPa) with flux being higher at higher cross‐flow velocities. Average flux at 4× concentration factor over 24‐hr operating cycles was 34 L/m2/hr under optimum conditions. Capital cost of the membrane system is expected to be lower because it eliminates the heat pasteurizer and centrifuge and reduces cooling requirements. Operating cost of the microfilter are about one‐third of a heat pasteurization system and provides the opportunity to recover insoluble protein and starch for use in corn gluten feed. Microfiltered steep water could improve ethanol fermentation efficiency and reduce fouling of heat exchangers in the fermenters, beer still, and steep evaporators.  相似文献   
23.
ABSTRACT

Treated wastewater was compared with tap water for irrigation of croton (Codiaeum variegatum Blume cv. ‘Petra’) in substrates consisting of 1 peat moss: 1 perlite (PP) or 1 soil: 1 sand (SS), alone or supplemented with zeolitic tuff at a ratio of 3:1 (PPZ and SSZ). Substrates were allowed to reach 80% of available water before the plants were irrigated with wastewater or tap water. Results indicated that neither water quality nor substrate affected plant width, leaf area, shoot fresh weight, or root length or weight. Wastewater increased stem diameter; node and leaf number; tissue nitrogen (N); sodium (Na); and chloride (Cl); substrate electrical conductivity (EC); phosphorus (P); Na, Cl, and leachate EC; and concentrations of Na, Cl, NO3 ?, and NH4 +. Root count, tissue Na, substrate potassium (K) and Na, and leachate pH were higher for zeolite-containing substrates. Shoot dry weight and tissue contents of N and P were the highest for wastewater-irrigated PP and PPZ. Wastewater-irrigated plants in PP and tap water-irrigated plants in PPZ exhibited the highest K content. The highest level of tissue Cl was recorded for SS. Tap water-irrigated PPZ had the highest pH and K concentration. Wastewater-irrigated PP, PPZ, and SS exhibited the highest contents of N, Na, and Cl, respectively. Based on the results, amendment of the substrate with zeolitic tuff is recommended to offset the adverse effect of salinity associated with wastewater.  相似文献   
24.
Durum wheat landrace genotypes are disappearing from the main wheat areas in Jordan, because of spreading of new uniform cultivars and the serious reduction in wheat cultivation. This study was conducted to evaluate genetic diversity in durum wheat landraces from Jordan and to identify desirable agronomic traits. Landraces were collected from two target areas: Ajloun and Karak. The collected material was grown under rainfed conditions using an augmented design with five blocks and four repeated check cultivars. Data were collected for 14 morphological and agronomic traits. Phenotypic diversity index (H′) was estimated, and the relationships among accessions were measured using cluster analysis and dendrogram similarity matrix. The results revealed the presence of a wide range of variability among landraces., which possess high levels of variability for biological yield, fertile tillers, number of seeds per spike, seed weight per spike and weight of 1000 seeds. These landraces must be considered as a reservoir of genes that plant breeders need in their wheat improvement programs and should be conserved both ex situ and in situ.  相似文献   
25.
为了找到安全有效的防控香蕉枯萎病的生防菌株,采用组织分离法从香蕉叶片中分离出内生细菌菌株YX-11.采用形态学、生物化学和16 S rDNA基因序列分析,该菌株被鉴定为贝莱斯芽孢杆菌Bacillus velezensis.YX-11具有溶磷、解钾和固氮的能力,还可以促进香蕉的生长,能抑制10种植物病原菌,其中对香蕉枯萎...  相似文献   
26.
This study evaluated oxalic acid accumulation and bioremediation of chromated copper arsenate (CCA)-treated wood by three brown-rot fungi Fomitopsis palustris, Coniophora puteana, and Laetiporus sulphureus. The fungi were first cultivated in a fermentation broth to accumulate oxalic acid. Bioremediation of CCA-treated wood was then carried out by leaching of heavy metals with oxalic acid over a 10-day fermentation period. Higher amounts of oxalic acid were produced by F. palustris and L. sulphureus compared with C. puteana. After 10-day fermentation, oxalic acid accumulation reached 4.2 g/l and 3.2 g/l for these fungi, respectively. Fomitopsis palustris and L. sulphureus exposed to CCA-treated sawdust for 10 days showed a decrease in arsenic of 100% and 85%, respectively; however, C. puteana remediation removed only 18% arsenic from CCA-treated sawdust. Likewise, chromium removal in F. palustris and L. sulphureus remediation processes was higher than those for C. puteana. This was attributed to low oxalic acid accumulation. These results suggest that F. palustris and L. sulphureus remediation processes can remove inorganic metal compounds via oxalic acid production by increasing the acidity of the substrate and increasing the solubility of the metals.An erratum to this article can be found at  相似文献   
27.
The present investigation deals with purification and thermal characterization of an acid invertase produced by Fusarium solani in submerged culture. The maximum enzyme activity (9.90 U mL(-1)) was achieved after 96 h of cultivation at pH 5.0 and 30 degrees C in a basal medium containing molasses (2%) as the carbon and energy source supplemented with 1% peptone. Invertase was purified by ammonium sulfate fractionation and column chromatography on DEAE-cellulose and Sephadex G-200. The purified enzyme was proven to be homogeneous by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The molecular mass of the enzyme was 65 kDa. The optimum pH and temperature for activity were 2.6 and 50 degrees C, respectively. The Km value for sucrose was 3.57 mM with an activation energy of 4.056 kJ mol(-1). Enthalpies of activation (DeltaH) were decreased while entropies (DeltaS) of activation increased at higher temperatures. The effects of alpha-chymotrypsin and 4 M urea were tetraphasic with periodic gain and loss of enzyme activity. A possible explanation for the thermal inactivation of invertase at higher temperatures is also discussed.  相似文献   
28.
A survey of Theileria parasites in cattle in eastern Turkey was carried out using specific polymerase chain reaction. A total of 252 blood samples were collected from clinically healthy cattle between June and July 2004. Of 252 blood samples examined, 41 (16%) were positive for piroplasms by microscopy, whereas 114 (45%) were positive for the presence of at least one species of Theileria by PCR. The percentages of positive animals for Theileria annulata and benign Theileria species (Theileria sergenti/buffeli/orientalis) were 39% (99/252) and 7% (18/252), respectively. By allele-specific PCR examination of 18 field isolates which were positive for benign Theileria parasites, 8 samples were only amplified by B-type specific primers and 10 samples were amplified by both of the B and C-type specific primers, indicating a mixed infection with B and C-type of the parasite. None of the field isolates was amplified by I-type specific primers. Three samples were co-infected with T. annulata and benign Theileria parasites. Two of them which were infected with B-type parasite were also infected with T. annulata, the other sample which was infected both of B and C-type parasites was also infected with T. annulata. A total of 724 ixodid ticks were collected from the cattle. Hyalomma anatolicum anatolicum was the dominant species with 32% (230/724) in the region. H. a. excavatum, Boophylus annulatus and Rhipicephalus bursa represented 25% (183/724), 19% (140/724) and 15% (112/724) of the total number of ticks, respectively. R. sanguineus was the minor species and represented 8% (59/724) of the tick population.  相似文献   
29.
Since 2006, the members of the molecular epidemiological working group of the European "EPIZONE" network of excellence have been generating sequence data on avian influenza and avian paramyxoviruses from both European and African sources in an attempt to more fully understand the circulation and impact of these viruses. This review presents a timely update on the epidemiological situation of these viruses based on sequence data generated during the lifetime of this project in addition to data produced by other groups during the same period. Based on this information and putting it all into a European context, recommendations for continued surveillance of these important viruses within Europe are presented.  相似文献   
30.
Larvae of Metapenaeus monoceros (Fabricius) at protozoea 1 (PZ1) stage were stocked in 2‐L glass flasks to investigate the effects of various salinities (25, 30, 35, 40, 45, 50 and 55 ppt) on growth and survival until the post‐larval (PL) stages. The PZ larvae were not able to tolerate a sudden salinity drop of over 10 ppt. Yet, an abrupt salinity increase of over 10 or even 15 ppt did not cause mortality. The PZ larvae were successfully acclimated to different test salinities at a rate of 4 ppt h?1. The larvae displayed better tolerance to high rather than low salinities. The lowest and highest critical salinities appeared to be 22 and 55 ppt respectively. Taking into account survival, growth and development results, the optimal salinity for the larval culture of M. monoceros inhabiting the Eastern Mediterranean was 40 ppt. At this salinity, the PZ1 larvae were successfully cultured until PL1 stage within 11 days with 68% survival on a feeding regime of Tetraselmis chuii Kylin (Butcher) (20 cells μ L?1), Chaetoceros calcitrans Paulsen (50 cells μ L?1), Isochrysis galbana Parke (30 cells μL?1) and five newly hatched Artemia nauplii mL?1 from M1 onwards at 28 °C.  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