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   129篇
  免费   3篇
林业   4篇
农学   1篇
基础科学   1篇
  29篇
综合类   2篇
农作物   20篇
水产渔业   21篇
畜牧兽医   31篇
园艺   3篇
植物保护   20篇
  2023年   1篇
  2022年   5篇
  2021年   13篇
  2020年   5篇
  2019年   7篇
  2018年   6篇
  2017年   5篇
  2016年   6篇
  2015年   7篇
  2014年   7篇
  2013年   14篇
  2012年   8篇
  2011年   7篇
  2010年   6篇
  2009年   6篇
  2008年   10篇
  2007年   5篇
  2006年   5篇
  2005年   3篇
  2004年   1篇
  2002年   1篇
  2001年   1篇
  1997年   1篇
  1975年   2篇
排序方式: 共有132条查询结果,搜索用时 31 毫秒
101.
The aim of this study was to assess the effect of high temperature on cadmium (Cd)-induced skeletal deformities in juvenile Mosquitofish, Gambusia affinis. For this purpose, 188 juveniles (1 day old) were equally divided into the control group, which was maintained in Cd-free water at 24°C, and three treated groups exposed either to Cd (0.4 mg/l as Cd Cl2) at 24°C, to high temperature (32°C), or to Cd at 32°C for 30 days. The results showed that Cd exposure at 24°C significantly increased the Cd accumulation (P < 0.0001) in the whole tissues of juveniles as well as the incidence of skeletal deformities (P < 0.01) compared with control animals. Exposure to high temperature also led to a significant increase in the incidence of skeletal deformities (P < 0.01) with respect to the control group. Interestingly, our results showed that the combined exposure to Cd and high temperature led to a more significant increase in Cd accumulation and in the frequency of spinal deformities than exposure to Cd or high temperature alone. These results confirm that temperature increases Cd toxicity and needs to be taken into account for the accurate prediction and assessment of Cd-induced spinal deformities in fish.  相似文献   
102.
The technique of thermometric titrimetry was applied to the study of humic acid and its interaction with metal ions. The nature of the thermometric titration curve of humic acid with sodium hydroxide is consistent with the presence in humic acid of many classes of ionizable groups. La3+ and Cu2+ reacted endothermically with sodium humate and in each case 1 g organic matter reacted with approximately 1.7 mequiv. metal ion. The end point of these titrations was characterized by an abrupt “bump”, attributed to conformational changes in the macromolecular network of the organic matter accompanying precipitation of the metal-humate complexes. The thermometric method is also used to determine chloride in the presence of humic acid or sodium humate.  相似文献   
103.
This study evaluated the genetic variance for survival at harvest of Indian white shrimp (Fenneropenaeus indicus) using a pedigreed synthetic population generated upon collecting broodstock from different fishery grounds in Egypt. The estimated heritabilities (h2 ± SE) of survival from generations G0 to G3 ranged from 0.144 ± 0.026 to 0.008 ± 0.030 using a model that included the common environmental effect (c2). Low heritability (0.014 ± 0.015) was estimated across generations with the inclusion of common environmental effect (c2). However, the h2 of survival from G0 to G1 ranged from 0.569 ± 0.071 to 0.410 ± 0.011 when c2 was not included. The genetic correlation for survival between different ponds from G0 to G3 was moderate to high (0.79 ± 0.042 to 0.83 ± 0.012) but significantly different (P < 0.05). There were low correlation coefficients (?0.237 ± 0.089 to 0.316 ± 0.073) between body weight estimated breeding value (EBV) and survival EBV of families in four generations.  相似文献   
104.
We have investigated the antioxidant activities of eight hydrolysates from cuttlefish by-products obtained by treatment with various gastrointestinal proteases (chymotrypsin, trypsin, and crude alkaline enzyme extracts from cuttlefish and sardinelle) and bacterial proteases (Alcalase and crude enzymes from Bacillus pumilus A1, Bacillus mojavensis A21, and Bacillus cereus BG1). The antioxidant activities of the cuttlefish by-products protein hydrolysates (CPHs) were evaluated using various in vitro antioxidant assays, such as 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity, reducing power, and total antioxidant capacity. All hydrolysates showed different degrees of hydrolysis (DH) and varying degrees of antioxidant activity. Among the different hydrolysates, cuttlefish crude enzyme hydrolysate exhibited the highest antioxidant activity, followed by sardinelle crude enzyme and Alcalase hydrolysates. Further, CPHs with different degrees of hydrolysis were prepared by treatment with proteolytic enzymes from cuttlefish, sardinelle, and B. mojavensis A21. All hydrolysates showed a greater antioxidative activity as indicated by all the methods considered. In addition, antioxidant activity in hydrolysates was positively correlated with the increase of DH. The results of this study indicated that CPHs might be a good candidate for further investigation in developing new antioxidants.  相似文献   
105.
In the current study, the performance of three endophytic actinomycetes identified as Actinoplanes campanulatus, Micromonospora chalcea and Streptomyces spiralis previously shown to reduce seedling damping-off, and root and crown rots of mature cucumber (Cucumis sativus) caused by Pythium aphanidermatum in pots under greenhouse conditions were further evaluated to determine their potential as biological control agents and as plant growth promoters in the field under the conditions of commercial production of cucumbers in the United Arab Emirates (UAE). When applied individually or in combination to cucumber seedlings, the three isolates significantly promoted plant growth and yield and reduced seedling damping-off and root and crown rots of mature cucumber plants. Individually the performance level of S. spiralis was relatively the best followed by A. campanulatus and then by M. chalcea. The three isolates (which were not inhibitory to each other) performed better, both as biological control agents as well as plant growth promoters, when applied together than when they were inoculated individually. The ability of these three isolates to colonize the internal tissues of roots, stems and leaves under field conditions, and to persist up to 8 weeks after seedling inoculation, showed that they can easily adapt to an endophytic habit systemically within healthy cucumber plants. As the three endophytic actinomycete isolates also colonized the rhizosphere and showed outstanding rhizosphere competency it is clear that they are facultative and not obligate endophytes. The success with the three inoculants indicated that they could well be used in place of the fungicide metalaxyl which is currently recommended for the management of Pythium diseases in the UAE. This is the first successful field use of endophytic actinomycetes as promising plant growth promoters and biological control agents against Pythium diseases of cucumber.  相似文献   
106.
Nowadays, people’s exposure to pesticides such as 2,4-dichlorophenoxyacetic acid (2,4-D) is increasing continuously. This compound is suspected to produce in excess free radicals which have adverse effects on human health causing several cell alterations in the organism. The present study investigated oxidative stress in the bone and erythrocytes of suckling rats whose mothers were treated with 2,4-D. Experiments were carried out on adult Wistar rats given 600 mg/L of 2,4-D in their drinking water from the 14th day of pregnancy until day 14 after delivery. Exposing dams to 2,4-D caused disorders in the bone of their progeny. Indeed, it induced changes in bone mineralization, especially calcium and phosphorus levels. Moreover, total tartrate-resistant acid phosphatase, which reflected bone resorption, was enhanced while total alkaline phosphatase, which reflected bone formation, was reduced suggesting that this herbicide accelerated bone resorption. The impairment of bone function corresponded histologically.Rats exposed to 2,4-D showed in both bone and erythrocytes an increase in malondialdehyde, advanced oxidation protein products and protein carbonyl levels and a decrease in non-enzymatic (glutathione, non-protein thiol, and vitamin C) and enzymatic (superoxide dismutase, catalase, and glutathione peroxidase) antioxidant system.  相似文献   
107.
Anthocyanins in wild blueberries of Quebec: extraction and identification   总被引:4,自引:0,他引:4  
Anthocyanins were extracted from a mixture of berries of Vaccinium angustifolium and Vaccinium myrtillo?des at 7.7 degrees C, 26 degrees C, and 79 degrees C using ethanol alone or ethanol acidified with hydrochloric, citric, tartaric, lactic, or phosphoric acids at a solvent to solid ratio of 10. The effect of these parameters on extracted anthocyanins stability was investigated. The pH-differential and HPLC-DAD methods were used to determine anthocyanin contents. Extracted anthocyanins were purified on a C-18 solid-phase extraction cartridge and characterized by HPLC/electrospray ionization/mass spectrometry (HPLC-ESI-MS/MS). Anthocyanins were identified according to their HPLC retention times, elution order, and MS fragmentation pattern and by comparison with standards and published data. Anthocyanin extractions gave different yields depending on the type of added acid and the extraction temperature. High yields of monomeric and total anthocyanins (26.3 and 28.9 mg/g of dry matter) were obtained at 79 degrees C using phosphoric acid. Extraction using tartaric acid at 79 degrees C provided the lowest degradation index (1.05). Anthocyanins were stable and browning by polyphenol oxidase was inhibited under these conditions. Of the six common anthocyanindins, five were identified in the extracts, namely, delpinidin, cyanidin, peonidin, petunidin, and malvidin; pelargonidin was not found. In addition to well-known major anthocyanins, new anthocyanins were identified for the first time in extracts of wild blueberries from Quebec.  相似文献   
108.
Polyphenols were determined by HPLC in the juice and oil of packed table olives. The phenolic compositions of the two phases were very different, hydroxytyrosol and tyrosol being the main polyphenols in olive juice and tyrosol acetate, hydroxtyrosol acetate, hydroxytyrosol, tyrosol, and lignans (1-acetoxypinoresinol and pinoresinol) in oil. The type of processing had a marked influence on the concentration of polyphenols in olive juice and little on the content in oil. The analyses carried out on 48 samples showed that turning color olives in brine had the highest concentration in polyphenols ( approximately 1200 mg/kg), whereas oxidized olives had the lowest ( approximately 200 mg/kg). Among olive cultivars, Manzanilla had a higher concentration than Hojiblanca and Gordal. The type of olive presentation also influenced the concentration of polyphenols in olives, decreasing in the order plain > pitted > stuffed. The results obtained in this work indicate that table olives can be considered a good source of phenolic antioxidants, although their concentration depends on olive cultivar and processing method.  相似文献   
109.
Cysts of Sarcocystis capracanis obtained from infected goats were examined to clarify the effect of the parasite on the host. Muscle tissues from fresh oesophagus, tongue, diaphragm and skeletal muscles of 680 goats were slaughtered in the main abattoir of Cairo, Egypt and they were examined microscopically for Sarcocystis infection for the first time in Egypt. 540 out of 680 (79.4%) of examined goats were found to be infected with Sarcocystis sp. The infection was recorded firstly by light microscopy as spindle shaped cysts embedded in the muscle tissues. The validity of this species as S. capracanis was confirmed by means of ultrastructural characteristics of the primary cyst wall which revealed the presence of thick-radially striated wall with finger like projections, underlined by a thick layer of ground substance enclosing the developing metrocytes and merozoites that usually contain nearly all the structures of the apical complex and fill the interior cavity of the cyst. The cyst cavity is divided by many septa extending from the ground substance and producing large number of chambers. An experimental infection using the highly infected muscles was carried out to determine the final host, which is dog. Smears of intestinal epithelium were taken to examine the endogenous stages (gamogony and sporogony) by means of light microscopy. These stages were mainly observed as to infect the lamina propria of the posterior third of the small intestine. Gamogony and zygote formation (fertilization) occurred 2-8 days post infection, while sporulation took place within the final host 13-15 days and sporocysts were passed within faeces of the infected puppies at that time. The prepatent period of S. capracanis was 12-15 days, while the patent period was extended to 37 days. In goats, infection with S. capracanis led to the loss of weight, anaemia, abortion and even death in cases of heavy infection. While bleeding, watery faeces filled with mucous on 5th and 8th day p.i. as well as intestinal lesions are the pathogenic effects occurred in puppies after experimental infection.  相似文献   
110.
During the period between February, 2004 and December, 2006, a cross-sectional study was performed to investigate some epidemiological aspects related to camel brucellosis in Jordan. Four hundred twelve camel sera from 37 herds were randomly collected and analyzed using Rose Bengal plate test and complement fixation test. A structured pre-tested questionnaire was administered to collect information on camel herd health and management. A multivariable logistic regression model was constructed to investigate risk factors associated with seropositivity to Brucella antigens. Moreover, the incidence of Brucella-specific abortion was investigated in 7 camel herds located in different locations in Southern Jordan. The true prevalence of Brucella-seropositive in camels was 12.1%. Thirteen (35.1%) herds had at least one positive camel. The seroprevalence of brucellosis in camels was significantly higher in the southern part of Jordan than that in central or northern Jordan. The multivariable logistic regression model on both individual and herd levels revealed large herds and contact with small ruminants as risk factors for Brucella seropositivity. On the other hand, using disinfectants was identified as a protective factor (OR = 0.8; 95% CI: 0.1, 0.9) only on the camel herd level. The incidence of Brucella-caused abortion was 1.9%. Brucella melitensis biotype 3 was isolated from 4 aborted camel fetuses.  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