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   345篇
  免费   21篇
林业   68篇
农学   8篇
  41篇
综合类   19篇
农作物   15篇
水产渔业   35篇
畜牧兽医   123篇
园艺   10篇
植物保护   47篇
  2023年   1篇
  2022年   4篇
  2021年   9篇
  2020年   8篇
  2019年   10篇
  2018年   12篇
  2017年   9篇
  2016年   12篇
  2015年   13篇
  2014年   7篇
  2013年   34篇
  2012年   20篇
  2011年   31篇
  2010年   18篇
  2009年   14篇
  2008年   19篇
  2007年   16篇
  2006年   16篇
  2005年   16篇
  2004年   5篇
  2003年   12篇
  2002年   9篇
  2001年   9篇
  2000年   14篇
  1999年   9篇
  1998年   5篇
  1997年   1篇
  1996年   3篇
  1994年   1篇
  1992年   2篇
  1991年   5篇
  1990年   5篇
  1988年   4篇
  1987年   4篇
  1985年   1篇
  1984年   1篇
  1983年   3篇
  1981年   1篇
  1980年   1篇
  1972年   1篇
  1967年   1篇
排序方式: 共有366条查询结果,搜索用时 15 毫秒
101.
Tolerance to sheep red cells: breakage with thymocytes and horse red cells   总被引:2,自引:0,他引:2  
Mice rendered tolerant to sheep red cells and then given normal thymocytes, made no antibody when immunized with these cells. When immunized with horse red blood cells, however, they made significant amounts of noncross-reacting antibody to sheep red blood cells. This suggests that antibody-making precursor cells (B cells) which are nontolerant but nonactivatable by specific antigen, may exist in tolerant hosts.  相似文献   
102.
The immune response during the onset of coliform mastitis in vaccinated cows was investigated by measuring lactoferrin (LF), interleukin-8 ( IL-8), and interleukin-1β (IL-1β) concentrations and somatic cell counts in 28 milk samples at the onset of acute coliform mastitis (ACM) and 73 milk samples at the onset of peracute coliform mastitis (PCM). Vaccinated ACM, unvaccinated ACM, and vaccinated PCM showed significantly higher values for LF and IL-1β levels than unvaccinated PCM (p < .01). The IL-8 concentration was lower in vaccinated PCM than in unvaccinated PCM (p < .05). There was no significant difference in somatic cell counts for each parameter. There were no significant differences in the parameters between vaccinated and unvaccinated ACM cows, or vaccinated ACM and PCM cows. From the above results, it is suggested that mastitis vaccination improved the early immune response, particularly at the onset of PCM, and played a large role in host defense against the initial infection.  相似文献   
103.
Medium-chain fatty acids (MCFAs) have antialgal, antibacterial, antifungal, antiprotozoan, and antiviral activities. However, antibacterial activities of MCFAs in the hindgut of pigs and cattle are still unknown. We report the effects of the supplementation of MCFAs on fecal bacteria of pigs, lactating cows, and Japanese Black calves. Lactobacillus spp., Bifidobacterium spp., eaeA(+) Escherichia coli, Salmonella spp., Campylobacter jejuni, and Clostridium perfringens in the feces of animals were quantified by real-time PCR assay. There was no significant increase or decrease in Lactobacillus spp. and Bifidobacterium spp. in the three animals. In the pig feces, eaeA(+) E. coli was reduced to less than a third in the treatment group (P < 0.01). C. jejuni in the pig feces was also significantly less in the treatment group compared with the control (P < 0.01). In the lactating cow, eaeA(+) E. coli was reduced to one fifth of that in the control (P < 0.01). Salmonella spp. was halved in calf feces (P < 0.01). Thus, a reduction in Gram-negative pathogenic bacteria was observed. In conclusion, supplementation of a MCFA calcium soap in the diet would be beneficial to growing pigs, lactating cow, and calves by reducing pathogenic bacteria.  相似文献   
104.
Six ruminal-cannulated nonlactating Holstein Friesian cows (mean body weight:660 ± 42.9 kg) were used to investigate the effect of soybean meal (SBM) supplementation on voluntary rice straw (RS) intake, feed particle size reduction, and passage kinetics in the rumen. They were allocated to two dietary treatments: RS alone or RS supplemented with SBM. Voluntary dry matter intake of RS and total tract fiber digestibility was increased by SBM supplementation (p < 0.05). Supplementation with SBM decreased rumination time per dietary dry matter (DM) and neutral detergent fiber (NDFom) intake (p < 0.01). Particle size distribution in the rumen and total ruminal NDFom digesta weights were not affected by SBM supplementation. However, the disappearance rates of total digesta and large and small particles from the rumen were increased by SBM supplementation (p < 0.01). Moreover, SBM supplementation increased the rate of size reduction in ruminal particles (p < 0.05). In situ disappearance of DM and NDFom of RS in the rumen was greater in SBM-supplemented cows than in nonsupplemented cows (p < 0.05). This study clearly showed that increased ruminal RS particle size reduction, passage, and fermentation due to SBM supplementation accelerated the RS particle clearance from the rumen and resulted in increased voluntary RS intake of dairy cows.  相似文献   
105.
Six flavone C-glycosides were isolated from young leaves of barley. One of the C-glucosides has a new type of nucleus, a 2',4',5,5', 7-penta-OH-substituted flavone bearing a 6-C-beta-D-glucoside, which has apparently never been isolated before. One mono- and two di-C-glycosyl flavones were isolated for the first time from barley and identified as isoscoparin 7-O-beta-D-glucoside, carlinoside, and shaftoside, respectively. Other flavones were 7-O-beta-D-glucosides of isoorientin and isovitexin. The known problematic NMR structure elucidation of C-glycosyl flavonoids has been solved by using both a temperature close to the freezing point of the solvent (22.5 degrees C in DMSO-d(6)) and a high temperature (70, 90 degrees C) for comparison during NMR measurements. Structural determination of all the compounds was achieved by employing 1D and 2D NMR techniques.  相似文献   
106.
An entire, female, mixed-breed cat of unknown age was presented with a 6-week history of lethargy, anorexia and vomiting. There was an increase in the number of white blood cells in the blood, including neutrophils and eosinophils; moderate anaemia; ascites; and possible mesenteric peritonitis. Exploratory laparotomy revealed firm, multifocal small nodules in the mesentery. As the nodules were surgically unresectable, they were biopsied. Histologically, the nodules were composed of thin trabeculae of dense collagen fibres mixed with plump fibroblasts and numerous eosinophils, consistent with feline gastrointestinal eosinophilic sclerosing fibroplasia. Bacteria were not detected on histological examination of the nodules and cytology of the ascites. Remission of disease occurred following treatment with prednisolone and ciclosporin A for 22 days and antibiotics for 40 days. After remission, ciclosporin A was administered for 236 days and then discontinued. Eosinophilia also resolved after treatment with ciclosporin A. The cat is still alive and in good condition on day 689. This report describes what may be an atypical case of feline gastrointestinal eosinophilic sclerosing fibroplasia, lacking involvement of the gastrointestinal tract, and was apparently cured by treatment that involved ciclosporin A.  相似文献   
107.
A cDNA fragment encoding goldfish Hsp27 was amplified by polymerase chain reaction and its nucleotide sequence was determined. The deduced amino-acid sequence of goldfish Hsp27 showed 58–62% identity to Hsp27 from other vertebrates. Three serine residues reported to be phosphorylated in human Hsp27 were conserved in goldfish Hsp27. The Hsp27 gene was transcribed in goldfish culture cells after temperature shift from 20°C to 40°C, but not from 20°C to 35°C. Recombinant goldfish Hsp27 was examined for its in vitro chaperone activity and compared to those of Hsp30 from the same fish and human recombinant Hsp27. Goldfish Hsp27 and Hsp30 showed a similar activity at 10 μM, which was significantly lower than that of human Hsp27. At 1 and 5 μM concentrations, however, goldfish Hsp27 showed slightly lower activity than goldfish Hsp30, but the activities of both goldfish proteins still remained significantly lower than that of human Hsp27. Meanwhile, goldfish Hsp27 formed oligomer, which was slightly smaller than that of Hsp30. These results suggest that goldfish Hsp27 contributes as a molecular chaperone in association with Hsp30 to compensate for stress resulting from rapid temperature fluctuations. The nucleotide sequence reported in this paper has been registered into the DDBJ/EMBL/GenBank databases with accession number AB239443 for goldfish Hsp27.  相似文献   
108.
109.
In the course to find a new whitening agent, we evaluated the methanol extract from bud of clove (Syzygium aromaticum) on melanin formation in B16 melanoma cells. Eugenol and eugenol acetate were isolated as the active compounds and showed melanin inhibition of 60% and 40% in B16 melanoma cell with less cytotoxicity at the concentration of 100 and 200 μg/mL, respectively. Furthermore, an essential oil prepared from the bud of clove, which contain eugenol and eugenol acetate as dominant components, showed melanin inhibition of 50% and 80% in B16 melanoma cells at the concentration of 100 and 200 μg/mL, respectively.  相似文献   
110.
Endosulfan, an organochlorine insecticide, and its metabolite endosulfan sulfate are persistent in environments and are considered toxic. We investigate the possible nontoxic bioremediation of endosulfan. An endosulfandegrading fungus that does not produce endosulfan sulfate was selected from eight species of white-rot fungi. High degradation of endosulfan and low accumulation of endosulfan sulfate were found in cultures of Trametes hirsuta. A degradation experiment using endosulfan sulfate as the substrate revealed that T. hirsuta is able to further degrade endosulfan sulfate following the oxidative conversion of endosulfan to endosulfan sulfate. Endosulfan and endosulfan sulfate were converted to several metabolites via hydrolytic pathways. In addition, endosulfan dimethylene, previously reported as a metabolite of the soil bacterium Arthrobacter sp., was detected in T. hirsuta culture containing endosulfan sulfate. Our results suggest that T. hirsuta has multiple pathways for the degradation of endosulfan and endosulfan sulfate and thus has great potential for use as a biocatalyst in endosulfan bioremediation.  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