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   199篇
  免费   7篇
林业   16篇
农学   14篇
  37篇
综合类   9篇
农作物   1篇
水产渔业   40篇
畜牧兽医   86篇
园艺   1篇
植物保护   2篇
  2023年   3篇
  2022年   7篇
  2021年   5篇
  2020年   3篇
  2019年   1篇
  2018年   7篇
  2017年   7篇
  2016年   6篇
  2015年   12篇
  2014年   15篇
  2013年   31篇
  2012年   20篇
  2011年   14篇
  2010年   7篇
  2009年   2篇
  2008年   11篇
  2007年   9篇
  2006年   15篇
  2005年   7篇
  2004年   3篇
  2003年   3篇
  2002年   5篇
  2001年   3篇
  2000年   1篇
  1999年   4篇
  1998年   1篇
  1992年   1篇
  1990年   2篇
  1988年   1篇
排序方式: 共有206条查询结果,搜索用时 15 毫秒
131.
The main difficulty of large equine embryo cryopreservation is the replacement of blastocoel fluid with cryoprotectant solution. The objective of this study was to improve the cryopreservation of large equine embryos with PMAP and/or LAP. Embryos were collected via the non-surgical transcervical procedure and divided into three groups based on their size (A ≤ 300 µm, 300 µm<B < 700 µm and C ≥ 700 µm). Six embryos 233–1360 µm in diameter were punctured via piezo manipulator and/or laser pulse before cryopreservation. All embryos were cryopreserved on a Cryotop®. Frozen-thawed embryos were cultured for 3h and transferred to the recipient mares. After one week, pregnancy was diagnosed by ultrasonography. Two of six embryos resulted in a positive pregnancy, the result of pregnancy in group A and B was positive, but in group C was negative, and further investigation is necessary for ≥700 µm embryos. The results showed laser-assisted puncture could be helpful to extract blastocoel fluid and replace it with cryoprotectant. This is the first positive pregnancy report in laser puncture-assisted frozen-thawed equine embryo (>300 µm). However, more research is required to find the best method for embryos ≥700 µm.  相似文献   
132.
Male Sprague-Dawley rats, 4 weeks of age, were fed purified diets either with or without 0.2% soy isoflavones rich powder for 5 weeks to elucidate their direct functions such as antioxidative action and regulation of lipid metabolism. Dietary soy isoflavones decreased serum lipid peroxide level in rats. Levels of liver and serum alpha-tocopherol were higher in the rats fed isoflavone than in those fed isoflavones-free diet. Thus, dietary soy isoflavones exhibited mild antioxidative function in this animal experiment. Isoflavone metabolites from diet may act as scavengers of reactive oxygen species. Dietary soy isoflavones lowered hepatic 3-hydroxy-3-methylglutaryl CoA reductase activity, although liver cholesterol level was not modulated. However, the levels of serum cholesterol and triglyceride decreased by consumption of soy isoflavones. Therefore, dietary soy isoflavones may exhibit hypocholesterolemic and hypolipidemic functions. Moreover, dietary soy isoflavones lowered hepatic Delta6 desaturase activity. Reflecting this observation, Delta6 desaturation indices ((18:2(n = 6) + 18:3(n = 6))/20:4(n = 6)) of tissue lipids tended to be lower in rats fed isoflavones than in those fed isoflavones-free diet. This action may contribute to the prevention of inflammatory response by imbalance of eicosanoids. These observations suggest that the positive intake of soy isoflavones may reduce the risk of some cardiovasucular diseases through their radical scavenging function and hypocholesterolemic action.  相似文献   
133.
The solubilization of organic nitrogen (Norg) in soil was examined by using organic acids often present in root exudates. The organic acids tested were classified into two groups depending on their solubilizing ability for Norg in a soil sample. Oxalate, malonate, tartarate, citrate and malate could dissolve Norg by increasing their concentrations, while succinate and glutarate could not dissolve Norg even when their concentrations were increased. The amount of organic N extracted with oxalate, malonate, tartarate, citrate and malate showed a strong correlation with the sum of the amounts of Al and Fe in the extracts. Therefore, it was assumed that the solubilizing ability may be attributed to the structure of these organic acids that can form stable chelate compounds with Al and Fe (oxalate, malonate, tartarate, citrate and malate). Furthermore, the amount of 20 mM cit-rate-extractable Norg (CEON), which was the highest among the organic acids tested, showed a strong correlation with both that of 67 mM phosphate buffer, which is now being widely used as an index for estimating soil N availability in Japan, and N mineralized using an incubation method in 46 soil samples belonging to different soil types. These results suggested that CEON might be an important constituent of mineralizable Norg in soil. Therefore, organic acids secreted by crops play a role in the solubilization of available Norg surrounding the crop rhizosphere.  相似文献   
134.
Slit, a secreted protein, functions as a chemorepellent factor in axon guidance and neuronal migration and as an inhibitor in leukocyte chemotaxis. In humans, slit2 protein attracts endothelial cells and promotes tube formation in the tumor angiogenic mechanism. In this study, we cloned a part of the canine slit subfamily and examined the expression of slit subfamily mRNAs in 3 normal canine mammary glands and 11 mammary tumor samples by RT-PCR. The cloned part of the slit gene sequences showed high similarity to those of the human, mouse, and rat. The mRNAs were expressed at low levels in the normal mammary gland. The expression levels of slit1 mRNA were low in both the normal and tumor tissues. In contrast, the expression of slit2 mRNA increased in most of the malignant mammary tumors, and an increase in slit3 mRNA expression was observed in 2 of the malignant mixed tumors. These results suggest that the expression of slit2 plays an important role in tumor angiogenesis in canine mammary gland tumors and that slit2 can be a putative marker for malignancy diagnosis of these tumors.  相似文献   
135.
136.
137.
138.
Phosphate buffer-extractable organic nitrogen (PEON), which can be extracted from soil with a 67-mM neutral phosphate buffer solution, is considered to be a major source of mineralizable nitrogen (N) that is ubiquitous in soil. We have developed a Western blot analysis and enzyme-linked immune sorbent assay (ELISA) method for determining PEON. First, anti-PEON antibody (IgG) from a rabbit was produced using purified PEON from a volcanic ash soil. PEON was detected as a ladder-like staining pattern in the high-molecular-weight region and as a single band under 14 kDa in Western blot analysis using the anti-PEON IgG. In the ELISA assay, the anti-PEON IgG could specifically react with PEON irrespective of soil type and management. Furthermore, the absorbance at 450 nm in ELISA was highly correlated to the concentration of organic N (Norg) in phosphate extracts of different soils. We propose the immune assay using the anti-PEON IgG as a possible novel method for evaluating available N in soil.  相似文献   
139.
This study examined the relationship between postpartum metritis, reactive oxygen species (ROS) generation, and plasma lipopolysaccharide (LPS) concentration in peripartum dairy cows. Blood was collected twice weekly from 2 weeks prepartum through 6 weeks postpartum. Whole blood chemiluminescence (WBCL) was measured using the luminol‐enhanced zymosan‐stimulated chemiluminescence assay. Cows were examined for uterine health disorders and classified into two groups, healthy (n = 11) and metritis (n = 5). Metritis had a significant effect on WBCL, with cows with metritis having a higher WBCL. Plasma LPS concentrations in cows with metritis were significantly higher than in healthy cows. To examine the effect of LPS on WBCL, blood was sampled in healthy peripartum cows (1 to 2 weeks prepartum, n = 8; 0 to 3 weeks postpartum, n = 11; and 4 to 8 weeks postpartum, n = 8) and incubated with LPS. At 1 endotoxin units/mL of LPS, similar to the plasma LPS concentration in cows with metritis, the WBCL increased in cows at 0 to 3 weeks postpartum. Results indicate that the increase in ROS generation and plasma LPS concentration are associated with metritis, and LPS may be responsible for enhanced ROS generation in early postpartum dairy cows.  相似文献   
140.
In this study, effects of grazing‐experienced heifer presence on foraging behavior development at the feeding station (FS) scale for first‐grazing season calves were determined. A group of four calves grazing alone (C), and another comprising four calves (Wc) and three grazing‐experienced heifers (Wh), were alternately stocked every day for 2 h on the same pasture for 26 days. The foraging time budget for Wc was significantly longer than that for C (P < 0.05) on day 7, and was similar to that for Wh on all days. Bite rate per FS was significantly higher for Wc (15.5 bite/min) than for C (13.2 bite/min) from day 1 to 14 (33.4 vs. 29.0 bite/min, respectively; P < 0.01) and significantly lower than that for Wh on all days. The number of steps taken between adjacent FSs by Wc (4.7) was significantly lower than that for C (7.2) on days 1 and 14 (2.1 vs. 2.9 steps, respectively; P < 0.01) and was similar to Wh on all days. This suggests that grazing‐experienced heifers have positive effects on the foraging behavior development of new‐season grazing calves through 14 days after the start of stocking.  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