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   176篇
  免费   7篇
林业   18篇
农学   11篇
基础科学   1篇
  20篇
综合类   11篇
农作物   9篇
水产渔业   17篇
畜牧兽医   85篇
园艺   2篇
植物保护   9篇
  2023年   2篇
  2022年   2篇
  2021年   4篇
  2020年   3篇
  2019年   2篇
  2018年   5篇
  2017年   1篇
  2016年   9篇
  2015年   8篇
  2014年   3篇
  2013年   10篇
  2012年   11篇
  2011年   18篇
  2010年   2篇
  2009年   9篇
  2008年   7篇
  2007年   11篇
  2006年   8篇
  2005年   12篇
  2004年   10篇
  2003年   10篇
  2002年   4篇
  2001年   4篇
  2000年   4篇
  1999年   4篇
  1998年   6篇
  1996年   1篇
  1990年   2篇
  1988年   1篇
  1987年   2篇
  1985年   4篇
  1984年   1篇
  1983年   2篇
  1975年   1篇
排序方式: 共有183条查询结果,搜索用时 328 毫秒
141.
A rare lymphoma that developed in the cecum of a domestic pet rabbit (6 years old, male, crossbred) was examined pathologically. The tumor consisted of proliferating neoplastic lymphoid cells, which were strongly stained with anti-CD79alpha monoclonal antibody. Electron microscopy revealed the tumor cells were composed of rough endoplasmic reticula and/or dilated rough endoplasmic reticula filled with moderately electron-dense material. These findings indicated the present case was rare digestive tract lymphoma originated from B-lymphocytic lineage in the cecum.  相似文献   
142.
Cyclophilin A (CyPA) was originally discovered in bovine thymocytes as a cytosolic binding protein of the immunosuppressive drug cyclosporine A. Recent studies have revealed that in mice and humans, CyPA is secreted from cells in injured or infected tissues and plays a role in recruiting inflammatory cells in those tissues. Here we found that in cattle abundant level of extracellular CyPA was observed in tissues with inflammation. To aid in investigating the role of extracellular CyPA in cattle, we generated recombinant bovine CyPA (rbCyPA) and tested its biological activity as an inflammatory mediator. When bovine peripheral blood cells were treated with rbCyPA in vitro, we observed that rbCyPA reacts with the membranous surface of granulocytes, monocytes and lymphocytes. Chemotaxis analysis showed that the granulocytes migrate toward rbCyPA and the migration is inhibited by pre-treatment with an anti-bovine CyPA antibody. These results indicate that, as for mice and humans, extracellular CyPA possesses chemotactic activity to recruit inflammatory cells (e.g., granulocytes) in cattle, and could thus be a potential therapeutic target for the treatment of inflammation.  相似文献   
143.
The objective of this study was to develop an in‐straw dilution method suitable for direct transfer of vitrified bovine sexed embryos. Embryo sexing was performed by molecular diagnosis. Several sexed and vitrified‐warmed embryos were transferred after evaluation of morphologically embryonic survival at warming and in‐straw dilution (Evaluation group). The other embryos were immediately directly transferred to recipients without first being expelled from the straws after in‐straw dilution (Non‐evaluation group). The pregnancy rates of vitrified sexed embryos were 38.7% and 34.8% in the Evaluation group and Non‐evaluation group, respectively, which were not significantly different. The viability of lower quality embryos before vitrification tended to be lower (P = 0.087) than that of the higher quality embryos regardless of evaluating embryos after warming and in‐straw dilution. The abortion rates were similar, and there was no difference between the two groups (13.9% and 12.5%, respectively). These results demonstrate that vitrified bovine sexed embryos can be vitrified and diluted by the in‐straw method and that the vitrified and warmed sexed embryos can develop to term.  相似文献   
144.
145.
Nitrogen (N) inputs are recognised to maximise herbage mass (HM) in tropical perennial grasses, whereas less is clear on their impact on HM distribution and the effects on leaf mass (LM) and leaf area index (LAI) in the upper stratum. This 2 year study, carried out in Pirassununga, Brazil, assessed the HM distribution in the upper (>20 cm) and lower (<20 cm) strata in Urochloa hybrid ‘Mavuno’ grass maintained under similar pre- and post-cutting canopy heights with contrasting N fertilisation rates applied after each cutting (no-nitrogen, 15, 30, and 45 kg N ha−1). The relevance of specific leaf area (SLA), leaf N concentration (NLeaf), tiller weight (TW) and population density to the LM and LAI of the upper stratum were also examined. Mavuno grass expressed a stable HM < 20 cm (59%–71% during Year I and 66%–80% for Year II), and apparent N fertilisation impacts on HM > 20 cm were verified at specific regrowth cycles during Year II. Mavuno grass pastures expressed plasticity for adjustments on leaf, tiller and population attributes, which were modulated by both climatic conditions and N fertilisation. Under favourable growth conditions during Year I, fertilised pastures were able to sustain higher NLeaf and SLA but associated with lower TW, resulting in maximisation of LAI but not in LM in the upper stratum. During Year II, fertilised pastures expressed higher NLeaf, SLA, number of basal tillers, despite the lowest TW, which resulted in higher LAI and LM in the upper stratum compared with non-fertilised pastures. Our results highlighted that adjustments on leaf and population attributes within the canopy were driven to maximise the upper stratum LAI, being positively affected by N fertilisation.  相似文献   
146.
Apple is a fruit crop of significant economic importance, and breeders world wide continue to develop novel cultivars with improved characteristics. The lengthy juvenile period and the large field space required to grow apple populations have imposed major limitations on breeding. Various molecular biological techniques have been employed to make apple breeding easier. Transgenic technology has facilitated the development of apples with resistance to fungal or bacterial diseases, improved fruit quality, or root stocks with better rooting or dwarfing ability. DNA markers for disease resistance (scab, powdery mildew, fire-blight, Alternaria blotch) and fruit skin color have also been developed, and marker-assisted selection (MAS) has been employed in breeding programs. In the last decade, genomic sequences and chromosome maps of various cultivars have become available, allowing the development of large SNP arrays, enabling efficient QTL mapping and genomic selection (GS). In recent years, new technologies for genetic improvement, such as trans-grafting, virus vectors, and genome-editing, have emerged. Using these techniques, no foreign genes are present in the final product, and some of them show considerable promise for application to apple breeding.  相似文献   
147.
A 90-day oral toxicity test in rats was performed to evaluate the toxicity of 2-tetradecylcyclobutanone (2-tDCB), a unique radiolytic product of stearic acid. Six-week-old male and female F344 rats (n=15/group) were given 2-tDCB at concentrations of 0, 12, 60 and 300 ppm in a powder diet for 13 weeks. Slight dose-dependent increases in serum total protein and albumin in male rats were found, but these changes were not considered to be a toxic effect. The fasting, but not non-fasting, blood glucose levels of the male rats in the 300 ppm group and female rats in the 60 and 300 ppm groups were lower than those of the controls. Gas chromatography-mass spectrometry analysis showed dose-dependent accumulation of 2-tDCB in adipose tissue, notably in males. Next, we performed an azoxymethane (AOM)-induced two-stage carcinogenesis study. After injection of 6-week-old male F344 rats (n=30/group) once a week for 3 weeks, the animals received 2-tDCB at concentrations of 0, 10, 50 and 250 ppm in a powder diet for 25 weeks. The incidences of colon tumors for the 2-tDCB dosages were 34%, 45%, 40% and 37%, respectively, and were not statistically significant. These data suggest that 2-tDCB shows no toxic or tumor-modifying effects under the present conditions, and that the no-observed-adverse-effect level for 2-tDCB is 300 ppm in both sexes, equivalent to 15.5 mg/kg b.w./day in males and 16.5 mg/kg b.w./day in females.  相似文献   
148.
Neosporosis and toxoplasmosis are two important infections in young and adult sheep, leading to low production and abortion. This study aimed to determine the frequency of antibodies to Toxoplasma gondii and Neospora caninum in sheep from the eastern region of S?o Paulo State, Brazil. Serum samples (382) were collected from the sheep and assayed for T. gondii through modified agglutination test (MAT) and indirect fluorescent antibody test (IFAT), and for N. caninum antibodies, through IFAT, with cut-off titers equal to 16 (T. gondii) and 25 (N. caninum). All frozen samples were sent to the Center for Zoonoses Research (NUPEZO), Department of Veterinary Hygiene and Public Health (DHSVP), FMVZ, UNESP, for serological tests. A total of 71/382 (18.6%) samples reacted to T. gondii, especially at titers 16 (28; 39.4%), 64 (15; 21.1%), 256 (21; 29.6%) and 1024 (6; 8.5%) by MAT, and 16 (34; 47.9%), 64 (18; 25.4%), 256 (14; 19.7%) and 1024 (5; 7%) by IFAT. As regards N. caninum, 49/382 (12.8%) samples reacted at titers 25 (17; 34.7%), 50 (11; 22.5%), 100 (11; 22.5%), and ≥ 200 (10; 20.4%). These animals presented infection but no clinical signs. Six and ten animals had high titers for toxoplasmosis and neosporosis. No significant association was observed between antibodies for both parasites (P=0.535) according to Fisher's exact test, and no correlation was found between T. gondii (MAT) and N. caninum antibody titers (r=-0.0068; P=0.895), T. gondii (IFAT) and N. caninum antibody titers (r=-0.0025; P=0.961). Thus, T. gondii and N. caninum infections were observed in farms located in S?o Paulo State, where sheep play an important economical role for the national and regional business.  相似文献   
149.
150.
The aim in this study is to elucidate the laterality of chicken spinocerebellar (SC) neurons that originate from the caudal cervical to caudal lumbosacral spinal cord. SC neurons in the spinal segment (SS) 17-20 consisted of a mixture of crossed and uncrossed axons. SC neurons in the more cranial and caudal SS than SS 17-20 (transitional zone) were generally uncrossed and crossed, respectively. In the transitional zone, SC neurons in spinal border cells and ventral border cells of the ventral horn changed dramatically from an uncrossed to a crossed type between SS 17 and SS 18. Chicken SC neurons are markedly different in laterality from mammalian SC neurons.  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