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   185篇
  免费   7篇
  国内免费   1篇
林业   5篇
农学   21篇
  60篇
综合类   8篇
农作物   10篇
水产渔业   5篇
畜牧兽医   56篇
园艺   1篇
植物保护   27篇
  2023年   6篇
  2022年   10篇
  2021年   12篇
  2020年   8篇
  2019年   10篇
  2018年   8篇
  2017年   10篇
  2016年   12篇
  2015年   6篇
  2014年   8篇
  2013年   7篇
  2012年   12篇
  2011年   9篇
  2010年   9篇
  2009年   2篇
  2008年   7篇
  2007年   4篇
  2006年   4篇
  2005年   3篇
  2004年   2篇
  2003年   1篇
  1998年   1篇
  1997年   5篇
  1996年   2篇
  1995年   1篇
  1993年   4篇
  1992年   3篇
  1990年   3篇
  1988年   1篇
  1987年   2篇
  1986年   1篇
  1985年   1篇
  1984年   2篇
  1983年   1篇
  1982年   3篇
  1979年   2篇
  1977年   2篇
  1976年   1篇
  1973年   1篇
  1969年   1篇
  1965年   1篇
  1956年   2篇
  1954年   1篇
  1953年   1篇
  1947年   1篇
排序方式: 共有193条查询结果,搜索用时 17 毫秒
41.
Exposure to mercuric chloride (HgCl2; 5 mg kg?1 body weight; i.p.) induced oxidative stress in mice and substantially increased lipid peroxidation (LPO) and oxidized glutathione (GSSG) levels, decreased the level of reduced glutathione (GSH) and various antioxidant enzymes in liver and also increased the activities of liver marker enzymes in serum. Therapy with propolis extract, a resinous wax‐like beehive product (200 mg kg?1 orally, after mercury administration), for 3 days inhibited LPO and the formation of GSSG and increased the level of GSH in the liver. Release of serum transaminases, alkaline phosphatase, lactate dehydrogenase and γ‐glutamyl transpeptidase were significantly restored after propolis treatment. The activities of antioxidant enzymes, that is, superoxide dismutase, catalase, glutathione‐S‐transferase and glucose‐6‐phosphate dehydrogenase, were also concomitantly restored towards normal levels after propolis administration. These observations clearly demonstrate that propolis treatment augments antioxidant defense against mercury‐induced toxicity and provide evidence that propolis has therapeutic potential as a hepatoprotective agent.  相似文献   
42.
Adipose tissue-derived stromal vascular fraction (AdSVF) comprises a heterogeneous cell population, including the multipotent mesenchymal stem cells, hematopoietic stem cells, immune cells, endothelial cells, fibroblasts, and pericytes. As such, multipotent adipose tissue-derived mesenchymal stem cells (AdMSCs), are one of the important components of AdSVF. Commonly used techniques to harvest AdSVF involve enzymatic or non-enzymatic methods. The enzymatic method is considered to be the gold standard technique due to its higher yield. The cellular components of AdSVF can be resuspended in normal saline, platelet-rich plasma, or phosphate-buffered saline to produce a ready-to-use solution. Freshly isolated AdSVF has exhibited promising osteogenic and vasculogenic capacity. AdSVF has already been proven to possess therapeutic potential for osteoarthritis management. It is also an attractive therapeutic option for enhancing wound healing. In addition, the combined use of AdSVF and platelet-rich plasma has an additive stimulatory effect in accelerating wound healing and can be considered an alternative to AdMSC treatment. It is also widely used for managing various orthopaedic conditions in clinical settings and has the potential for regenerating bone, cartilage, and tendons. Autologous AdSVF cells are used along with bone substitutes and other biological factors as an alternative to conventional bone grafting techniques owing to their promising osteogenic and vasculogenic capacity. It can also be used for treating osteonecrosis, meniscus tear, chondromalacia, and tendon injuries in veterinary practice. It has several advantages over in vitro expanded AdMSC, including precluding the need for culturing, reduced risk of cell contamination, and cost-effectiveness, making it ideal for clinical use.  相似文献   
43.
The prediction of the oxidation rate of elemental sulfur (S0) is a critical step in sulfur (S) fertilizer strategy to supply plant-available sulfur. An incubation experiment was conducted to determine the rate and amount of S0 oxidation in relation to the contribution of Thiobacillus spp. and aerobic heterotrophic S-oxidizing bacteria. After 84 days, 16.3% and 22.4% of the total S0 applied to the soil were oxidized at 20 and 30 ℃, respectively. The oxidation of S0 proved to be a two-step process with a rapid oxidation during the first 28 days and a slow oxidation from then on. The highest oxidation rate of 12.8 μg S cm-2 d-1 was measured during the first two weeks at 30 ℃. At 20 ℃ the highest oxidation rate of 10.2 μg S cm-2 d-1 was obtained from two to four weeks after start of the experiment. On an average the soil pH declined by 3.6 and 4.0 units after two weeks of experiment. At the same time the electric conductivity increased nine times. With the oxidation of S0 the population of Thiobacillus spp. and aerobic heterotrophic S-oxidizing bacteria increased. The corresponding values for Thiobacillus spp. and aerobic heterotrophic S-oxidizing bacteria increased from 2.9 × 105 and 1.4 × 105 g-1 soil at the start of the experiment to 4 × 108 and 5.6 × 108 g-1 soil 14 days after S0 application, respectively. No Thiobacillus spp. was present eight weeks after S0 application. The results suggested that oxidation of residual S0 completely relied on aerobic heterotrophic S-oxidizing bacteria.  相似文献   
44.
Prawn shell waste collected from shrimp‐processing plants in Cochin, India, was subjected to fermentation using 20 chitinoclastic and proteolytic/non‐proteolytic bacterial strains. The products generated were analysed for protein, lipid, total sugars, N‐acetyl glucosamine, free amino acids and ash. Shrimp diets were prepared using these 20 fermented products and a control diet using raw prawn shell waste. Feeding experiment was conducted with postlarvae (PL21) of Indian white prawn, Fenneropenaeus indicus for a period of 21 days. Biogrowth parameters such as mean weight gain, feed conversion ratio, specific growth rate and protein efficiency ratio were estimated and the animals were challenged with white spot virus orally via diet. Enhanced growth could be observed in prawns fed F134 and F124, incorporated with the fermentation products generated using Bacillus spp., C134 and C124 respectively. The percentage survival of prawns after 7 days of challenge was found to be highest for groups fed diet F111 incorporated with fermentation product generated using Bacillus sp. These products of bacterial fermentation hold promise as growth enhancers and immunostimulants in aquaculture.  相似文献   
45.
The present study describes detection of picobirnavirus (PBV) in faecal samples from bovine and buffalo calves employing the polyacrylamide gel electrophoresis (PAGE). A total of 136 faecal samples from buffalo (n = 122) and cow calves (n = 14) exhibiting clinical signs of diarrhoea and from healthy calves were collected during 2007–2010 from subtropical (central India) and tarai area of western temperate Himalayan foothills (Uttarakhand). The dsRNA nature of the virus was confirmed by nuclease treatment (RNase A, RNaseT1 and DNase 1). PAGE results confirmed 3.67% (5/136) positivity for PBV, showing a typical genomic migration pattern with two discrete bands with size of approximately 2.4 and 1.7 kbps for the larger and smaller segments, respectively. Among the five PBV samples identified, three were from buffalo calves and one from cow calf exhibiting clinical signs of acute diarrhoea, while one sample from non-diarrhoeic buffalo calf also showed the presence of PBV. None of the samples showed dual infection of rotavirus and PBV. The preliminary findings indicate sporadic incidences of PBV in bovine calves and emphasize the need for the development of better diagnostics for early detection and genetic characterization of these emerging isolates of farm animals of economic significance.  相似文献   
46.
High-throughput deep-sequencing technology and bioinformatics analysis of the small RNA(sRNA) population isolated from plants allows universal virus detection and complete virome reconstruction for a given sample. In the present sRNA deep-sequencing analysis of virus-infected wheat samples in the Czech Republic, samples were firstly tested for barley yellow dwarf viruses(BYDVs), wheat streak mosaic virus(WSMV) and wheat dwarf virus(WDV) using ELISA, RT-PCR and PCR. Subsequent sRNA sequencing of these samples yielded more than ~60 million single-end 50-bp reads with high confidence for nine field samples of wheat. Overall, 16.5% of reads were virus-specific and 83.5% were mapped to the host. More 21-nt reads(~7.7 E+06 reads) were found than 24-nt(~6.20 E+06 reads) or 22-nt(~4.30 E+06 reads) reads. De novo assembly of the high-quality contigs revealed the presence of three earlier reported viruses in the Czech Republic: BYDVs(31.48%), WSMV(24.23%) and WDV(26.66%). We also showed the presence of cereal yellow dwarf virus(14.33%; two species CYDV-RPS and CYDV-RPV(family Luteoviridae/Polerovirus) and wheat yellow dwarf virus(WYDV, 3.30%; Luteoviridae). Phylogenetic analysis showed CYDV and WYDV grouped separately from BYDVs. Furthermore, several recombination breakpoints were found among the groups of yellow dwarf viruses(BYDVs, CYDV, and WYDV). Using RNA deep sequencing, we confirmed the presence of the three known viruses(BYDVs, WSMV, and WDV) and the first record of two species of CYDV and WYDV in wheat in the Czech Republic.  相似文献   
47.
48.
Iron oxides from 39 soils derived from various parent materials in south-western Australia have been studied using a variety of techniques. Goethite and hematite were the only two Fe oxides present. The goethite/(goethite+hematite) ratio ranged from 0.18 to 1.0, and was highest in soils on acidic igneous rocks, decreasing for soils on alluvial and mafic parent materials. In a few soils derived from acid rocks only goethite was present. The redness rating of soils increased linearly with increasing amount of hematite. Al substitution in goethite ranged from 13 to 35 mol%, with higher values for soils on acid igneous rocks (median value = 26 mol%) than for soils on mafic (19 mol%) and alluvial (17 mol%) parent materials. Substitution of A1 in hematite ranged from 4 to 23 mol%, and was greatest in soils on mafic parent materials (median value = 12 mol% A1). A1 substitution in hematite was about half of that in associated goethite. The dehydroxylation temperature for goethite increased linearly with increasing A1 substitution. Goethite and hematite had similar crystal sizes (c. 20 nm), and both were in the form of irregular plates. Dissolution with 1 M HCl of iron oxides concentrated from the soils by 5 M NaOH digestion could be described both by the Cube Root Law and by Kabai's equation. Only one straight line was obtained for the dissolution data using Kabai's equation for samples containing both goethite and hematite, in contrast to the results of other workers. Major proportions of the Co, Cr, Cu, Mn, Ni and Zn in the soils were concentrated with the iron oxides, and the dissolution kinetics of these elements indicate that some may be present in the structure of the iron oxides.  相似文献   
49.
盐条件下产胞外多糖植物促生细菌研究   总被引:3,自引:0,他引:3  
Salt-tolerant plant growth-promoting rhizobacteria (PGPR) can play an important role in alleviating soil salinity stress during plant growth and bacterial exopolysaccharide (EPS) can also help to mitigate salinity stress by reducing the content of Na + available for plant uptake.In this study,native bacterial strains of wheat rhizosphere in soils of Varanasi,India,were screened to identify the EPS-producing salt-tolerant rhizobacteria with plant growth-promoting traits.The various rhizobacteria strains were isolated and identified using 16S rDNA sequencing.The plant growth-promoting effect of inoculation of seedlings with these bacterial strains was evaluated under soil salinity conditions in a pot experiment.Eleven bacterial strains which initially showed tolerance up to 80 g L -1 NaCl also exhibited an EPS-producing potential.The results suggested that the isolated bacterial strains demonstrated some of the plant growth-promoting traits such as phosphate solubilizing ability and production of auxin,proline,reducing sugars,and total soluble sugars.Furthermore,the inoculated wheat plants had an increased biomass compared to the un-inoculated plants.  相似文献   
50.
The effects of fly ash at different concentrations (0, 10, 20, 30 … 100% vol./vol. in soil) on plant growth and yield were investigated in tomato plants infected or noninfected with root-knot nematode, Meloidogyne incognita (2000 juveniles per plant) in clay pots. An increase in fly ash concentration in the soil correspondingly increased the availability of carbonates, bicarbonates, sulphate, chlorides, B, P, K, Ca, Mg, Mn, Cu and Zn in the soil. The porosity, water-holding capacity, pH, conductivity and cation exchange capacity also increased progressively in the fly ash amended soil. Ash application enhanced plant growth, leaf pigment concentrations, fruit production, weight of fruit/plant and mean fruit weight of both nematode-infected and noninfected tomato plants, being maximum in the soil containing 50 or 60% fly ash. The yield enhancements were 93.6 (infected plants) and 84% (noninfected plants) at 50 and 60% fly ash levels, respectively. Fly ash treatments adversely affected root invasion by juveniles, disease intensity and reproduction of the nematodes. A gradual increase in the ash concentration in soil caused a corresponding decrease in the numbers of invading juveniles, galls and egg masses per root system and eggs/egg mass, being lowest at 100% fly ash i.e. 52, 16, 10 and 81 against 289, 137, 131 and 238 (control), respectively. Linear regression suggested 40% fly ash as the most economic level, enhancing yield of infected plants by 96% and suppressing the nematode disease and reproduction by 63 and 76%, 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