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   511篇
  免费   26篇
  国内免费   2篇
林业   35篇
农学   16篇
基础科学   1篇
  64篇
综合类   32篇
农作物   18篇
水产渔业   84篇
畜牧兽医   251篇
园艺   3篇
植物保护   35篇
  2022年   4篇
  2021年   13篇
  2020年   8篇
  2019年   9篇
  2018年   6篇
  2017年   10篇
  2016年   19篇
  2015年   12篇
  2014年   24篇
  2013年   41篇
  2012年   30篇
  2011年   37篇
  2010年   14篇
  2009年   9篇
  2008年   36篇
  2007年   38篇
  2006年   31篇
  2005年   33篇
  2004年   34篇
  2003年   36篇
  2002年   20篇
  2001年   18篇
  2000年   16篇
  1999年   3篇
  1998年   2篇
  1996年   4篇
  1995年   1篇
  1994年   1篇
  1992年   4篇
  1991年   3篇
  1990年   4篇
  1989年   5篇
  1988年   2篇
  1987年   1篇
  1986年   2篇
  1985年   4篇
  1984年   1篇
  1981年   3篇
  1972年   1篇
排序方式: 共有539条查询结果,搜索用时 609 毫秒
1.
2.
Eleven feline immunodeficiency virus (FIV) infected asymptomatic carrier (AC) cats were observed for 2 years for development of acquired immunodeficiency syndrome (AIDS). Four of the 11 (36.4%) showed progression of the clinical stage. Persistent generalized lymphadenopathy was noted in three cats as the first sign of illness after the AC phase, while the other showed lymphadenopathy with signs of AIDS-related complex. In all four cats the AIDS-related complex stage lasted for 10 months or longer, and two showed progression of the disease into AIDS. The two cats showing AIDS illnesses died within approximately 1 year after they had developed persistent generalized lymphadenopathy. Pathology confirmed the diagnosis of AIDS characterized by the presence of depletion lesions in the lymphoid organs, and of severe infections of an opportunistic nature. The overall mortality of FIV infected AC cats during a 2 year period was two out of 11 (18.2%). These cats showed decreased concanavalin A mitogen response of peripheral blood mononuclear cells as the disease progressed.  相似文献   
3.
Using target and reference fattened steer populations, the performance of genotype imputation using lower‐density marker panels in Japanese Black cattle was evaluated. Population imputation was performed using BEAGLE software. Genotype information for approximately 40 000 single nucleotide polymorphism (SNP) markers by Illumina BovineSNP50 BeadChip was available, and imputation accuracy was assessed based on the average concordance rates of the genotypes, varying equally spaced SNP densities, and the number of individuals in the reference population. Two additional statistics were also calculated as indicators of imputation performance. The concordance rates tended to be lower for SNPs with greater minor allele frequencies, or those located near the ends of the chromosomes. Longer autosomes yielded greater imputation accuracies than shorter ones. When SNPs were selected based on linkage disequilibrium information, relative imputation accuracy was slightly improved. When 3000 and 10 000 equally spaced SNPs were used, the imputation accuracies were greater than 90% and approximately 97%, respectively. These results indicate that combining genotyping using a lower‐density SNP chip with genotype imputation based on a population of individuals genotyped using a higher‐density SNP chip is a cost‐effective and valid approach for genomic prediction.  相似文献   
4.
The New World monkey Aotus spp. (night monkeys) are expected for use of valuable experimental animal with the close species of Saimiri spp. (squirrel monkeys). Saimiri is known to show spontaneous hypercortisolemia, although few reports in Aotus. We compared basic states of blood steroid hormones and histological structure of the adrenal glands in two monkeys. Serum cortisol and ACTH levels were statistically lower in Aotus than Saimiri. Conversely, Aotus adrenocortical area showed significant enlargement, especially at the zona fasciculata. Electron microscopic observation at Aotus fasciculata cells revealed notable accumulation of large lipid droplets and irregular shapes of the mitochondrial cristae. These results suggest potential differences in cellular activities for steroidogenesis between Aotus and Saimiri and experimental usefulness in adrenocortical physiology and pathological models.  相似文献   
5.
Androgen induces production of male effect pheromone in female goats   总被引:1,自引:0,他引:1  
Previously we showed that the primer pheromone responsible for the "male effect" was produced in specific skin regions of castrated male goats by androgen treatments. In the present study, we examined whether androgen can also induce production of the male effect pheromone in female goats. Capsules containing dihydrotestosterone (DHT) or testosterone (T) were subcutaneously implanted into six ovariectomized (OVX) goats for 28 days. Small skin samples were collected from the head and rump regions, and the pheromone activity of their ether extracts was examined using a bioassay that monitors the electrophysiological manifestation of the hypothalamic gonadotropin-releasing hormone pulse generator as multiple-unit activity. Behaviors of OVX goats towards ovary-intact estrous goats were also examined before and at the end of DHT or T treatment. Before androgen treatment, neither the head nor rump skin samples in OVX goats showed pheromone activity. DHT treatment induced pheromone activity in the head skin sample of six OVX goats and in the rump skin sample of two OVX goats. Similar results were obtained by T treatment. In addition, OVX goats treated with T showed masculine-type sexual behaviors such as courtship and mounting behaviors towards the estrous goats. These results demonstrate that androgen is capable of inducing primer pheromone activity in the female and suggest that the synthesis pathway of the male effect pheromone exists in both sexes in the goat.  相似文献   
6.
7.
Lipid extracted from the ovary of skipjack tuna by the method that we developed is rich in phospholipid-type docosahexaenoic acid. The ovary lipid of skipjack tuna (OLS) was studied for its anti-stress activity in male Wistar rats, focusing on stress-related blood components: recovery from stress was examined after application of water immersion restraint stress. As a result, serum corticosterone (CORT) secretion was inhibited and decreased rapidly after stress application in rats given OLS compared with control rats. As CORT acts as a glucocorticoid, non-esterified fatty acid (NEFA) is expected to increase by stress application. However, the concentration tended to be lower in rats given OLS than in control rats. With respect to OLS concentration, OLS increased serum dehydroepiandrosterone, secretion concentration-dependently. In addition, as with the recovery study, it tended to inhibit the increase in NEFA. These results indicate that OLS may have an anti-stress activity against acute stress.  相似文献   
8.
Management reforms are considered one of the best alternatives in increasing efficiency of the irrigation systems. Transfer of day-to-day operation and maintenance to farmers is not a new concept. However due to lags, even now it is a hot issue in developing countries and Nepal is not an exception. In this context of growing argument about the transfer of management of public irrigation systems to the Water Users' Group, this paper examines the comparative performance of farmer-managed and agency-managed irrigation systems. Khageri Irrigation System in the Chitwan district of Nepal was taken as the study site where complete management transfer has been done in 1996. The situations before and after complete transfer were compared. Intensive case studies of the selected farmers showed that equity in distribution of water and leakage had significantly improved after management transfer. Logit analysis revealed that age and education level of the household head, distance from main canal, leakage of the canal and equity in distribution are significantly related to the satisfaction level of the beneficiary farmers from FMIS compared to AMIS. However, landholding size of the respondent farmer has no significant effect. Similarly results from t-test revealed that rice productivity and overall profits from agriculture has also increased significantly due to irrigation management transfer.  相似文献   
9.
10.
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