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   99篇
  免费   23篇
农学   4篇
  13篇
综合类   17篇
农作物   6篇
水产渔业   3篇
畜牧兽医   71篇
植物保护   8篇
  2023年   2篇
  2021年   1篇
  2020年   2篇
  2019年   2篇
  2018年   2篇
  2017年   8篇
  2016年   8篇
  2015年   5篇
  2014年   9篇
  2013年   16篇
  2012年   5篇
  2011年   4篇
  2010年   3篇
  2009年   3篇
  2008年   4篇
  2007年   4篇
  2006年   6篇
  2005年   1篇
  2004年   3篇
  2003年   3篇
  2000年   3篇
  1999年   2篇
  1998年   1篇
  1997年   1篇
  1996年   1篇
  1995年   1篇
  1994年   2篇
  1993年   1篇
  1991年   2篇
  1990年   2篇
  1989年   1篇
  1988年   1篇
  1986年   5篇
  1982年   2篇
  1981年   1篇
  1979年   3篇
  1972年   1篇
  1971年   1篇
排序方式: 共有122条查询结果,搜索用时 46 毫秒
1.
2.
Trace minerals feeding had significant effects on sperm production and fertility with better absorption and proper utilization within the body for optimum reproductive function. Several studies have shown that more influenced trace elements in the diets of animals are copper (Cu) and zinc (Zn). Bucks showing deficiency of this mineral might affect the quality of semen production which in turn would affect the fertility. This experiment was thus designed to test the effects of organic Cu and Zn supplementation on antioxidants enzyme activities and sperm functional attributes in fresh semen of bucks. Forty bucks (n = 40, Aged 5 months) were assigned to ten groups of four animals in each group, supplemented (for a period of 8 months) with different levels of organic Zn: 20 mg (T2), 40 mg (T3) and 60 mg (T4), organic Cu: 12.5 mg (T5), 25 mg (T6), 37.5 mg (T7) and combined organic Zn and Cu: 20 + 12.5 mg (T8), 40 + 25 mg (T9), 60 + 37.5 mg (T10), respectively, per kg dry matter and no additional mineral diet (control; T1). One hundred and sixty semen samples were collected through electro‐ejaculator and analysed for sperm quantity, quality, acrosome intactness and plasma membrane integrity and correlated with the catalase, superoxide dismutase, glutathione peroxidase and glutathione reductase enzyme activities in seminal plasma. The results indicated organic Cu and zinc supplemented bucks produced more sperm cells, had higher sperm concentrations, maintained higher (< .01) sperm livability, plasma membrane and acrosome integrities, more motility and velocity. The increased antioxidant enzyme activities, reduced oxidative stress and lowered lipid peroxidation were positively correlated (< .05) with the sperm functional attributes. In conclusion, organic Cu and Zn supplement to male goats showed protective roles against oxidative damage and maintained better fresh semen characteristics.  相似文献   
3.
Weed populations and pathogens   总被引:2,自引:0,他引:2  
Cousens  & Croft 《Weed Research》2000,40(1):63-82
Plant:pathogen systems are complex, highly spatial and fluctuate considerably. The dynamics of their individual populations depends on factors such as their patchiness, shapes and scales of dispersal distributions, genetic polymorphism and their responses to their biotic and abiotic environments. We review knowledge of these population properties in the context of weed management and biological control and discuss their likely influence on the population dynamics of pathogens.  相似文献   
4.
EEGs have been recorded from 207 dogs and cats with presumed intra-cranial space-occupying lesions; twenty-seven cases were confirmed postmortem. The clinical presenting signs of the series are considered, and the abnormal characters of the EEGs are analysed and discussed. The place of the EEG in differential diagnosis and its possible future value in association with brain surgery are discussed.
Résumé. On a enregistré des électroencéphalogrammes de 207 chiens et chats suspects de lésions intracraniennes expansives; ce diagnostic a pu être confirmé par l'examen nécropsique. On décrit les manifestations cliniques majeures dans cette série et on considère les anomalies de l'E.E.G., dont on analyse les particularités et dont on envisage l'importance diagnostique sous Tangle de la chirurgie du cerveau.
Zusammenfassung. Es wurden EEGs von 207 Katzen und Hunden mit vermuteten raumbean-spruchenden Läsionen im Schädelraum aufgenommen; 27 Fälle da von wurden durch Autopsie bestätigt. Die klinischen Erscheinungsbilder der Serie werden betrachtet und der anomale Gharakter der EEGs wird analysiert und besprochen. Der Platz des EEG in der Differentialdioagnose und sein möglicher künftiger Wert in Zusammenhang mit der Gehirnchirurgie wird besprochen.  相似文献   
5.
6.
A sensitive, specific polymerase chain reaction-based assay was developed for the detection of the causal agent of ratoon stunting disease of sugarcane, Clavibacter xyli subsp. xyli . This assay uses oligonucleotide primers derived from the internal transcribed spacer region between the 16S and 23S rRNA genes of the bacterial rRNA operon. The assay is specific for C. xyli subsp. xyli and does not produce an amplification product from the template of the closely related bacterium C. xyli subsp. cynodontis , nor from other bacterial species. The assay was successfully applied to the detection of C. xyli subsp. xyli in fibrovascular fluid extracted from sugarcane and was sensitive to approximately 22 cells per PCR assay. A multiplex PCR test was also developed which identified and differentiated C. xyli subsp. xyli and C. xyli subsp. cynodontis in a single PCR assay.  相似文献   
7.
Morphological changes were observed in the blood forms of Trypanosoma vivax strain Y486 in mice on Days 12-13 of infection, following the peak parasitaemia. During this period elongate trypomastigotes, 25-40 micron long, were observed, most showing an anterior movement of the kinetoplast towards the nucleus and some having a blunt posterior end. In a few parasites a complete transformation to the epimastigote form, 40-42 micron long, was observed. Small sphaeromastigotes were also present, especially in the fine capillaries of various organs. Smears and electron microscopy suggested the presence of extra-vascular forms in the spleen.  相似文献   
8.
This study was conducted to identify and analyse the expression of gametogenesis‐associated genes and proteins in foetal and adult buffalo gonads of both the sexes. Relative quantification of the genes was determined by qPCR and Western blotting. Immunohistochemistry was also performed for various gametogenesis‐associated proteins in foetal and adult gonads of both the sexes. We observed significantly (p < 0.05) increased expression of primordial germ cell‐specific, meiotic as well as genes associated with oocyte maturation and development in foetal ovaries as compared to the adult ones. However, significantly (p < 0.05) increased expression of proteins associated with oocyte maturation like GDF9 and ZP4 was found in adult ovaries, indicating temporal regulation of mRNA translation during oogenesis. Meiotic genes showed significantly (p < 0.05) increased expression in adult testes as compared to foetal testes and ovaries, indicating onset of meiosis at a later stage in spermatogenesis. In general, the expression of primordial germ cell‐associated as well as meiotic genes was higher in adult testes, indicating the increased biological activity in the organ. Immunohistochemistry revealed localized expression of gametogenesis‐associated proteins in ovarian follicles and seminiferous tubules of testes, while the surrounding somatic tissues were devoid of these proteins. The study gives an understanding of the sequential and temporal events of gene expression as well as mRNA translation during male and female gametogenesis. It could also be concluded that follicles and seminiferous tubules are the functional units of the female and male gonads, respectively, and their function could be enhanced by appropriate chemical and genetic intervention of the somatic tissue immediately surrounding them. This assumes importance in the context that buffalo attains sexual maturity at an older age of 2–3 years and have smaller ovaries with lesser number of primordial follicles in comparison with cattle, which is suggested to be the main reason of their poor breeding performance.  相似文献   
9.
10.
The objective of this study was to explore the possibility of producing wild buffalo embryos by interspecies somatic cell nuclear transfer (iSCNT) through handmade cloning using wild buffalo somatic cells and domestic buffalo (Bubalus bubalis) oocytes. Somatic cells derived from the ear skin of wild buffalo were found to express vimentin but not keratin and cytokeratin‐18, indicating that they were of fibroblast origin. The population doubling time of skin fibroblasts from wild buffalo was significantly (p < 0.05) higher, and the cell proliferation rate was significantly (p < 0.05) lower compared with that of skin fibroblasts from domestic buffalo. Neither the cleavage (92.6 ± 2.0% vs 92.8 ± 2.0%) nor the blastocyst rate (42.4 ± 2.4% vs 38.7 ± 2.8%) was significantly different between the intraspecies cloned embryos produced using skin fibroblasts from domestic buffalo and interspecies cloned embryos produced using skin fibroblasts from wild buffalo. However, the total cell number (TCN) was significantly (p < 0.05) lower (192.0 ± 25.6 vs 345.7 ± 42.2), and the apoptotic index was significantly (p < 0.05) higher (15.1 ± 3.1 vs 8.0 ± 1.4) for interspecies than that for intraspecies cloned embryos. Following vitrification in open‐pulled straws (OPS) and warming, although the cryosurvival rate of both types of cloned embryos, as indicated by their re‐expansion rate, was not significantly different (34.8 ± 1.5% vs 47.8 ± 7.8), the apoptotic index was significantly (p < 0.05) higher for vitrified–warmed interspecies than that for corresponding intraspecies cloned embryos (48.9 ± 7.2 vs 23.9 ± 2.8). The global level of H3K18ac was significantly (p < 0.05) lower in interspecies cloned embryos than that in intraspecies cloned embryos. The expression level of HDAC1, DNMT3a and CASPASE3 was significantly (p < 0.05) higher, that of P53 was significantly (p < 0.05) lower in interspecies than in intraspecies embryos, whereas that of DNMT1 was similar between the two types of embryos. In conclusion, these results demonstrate that wild buffalo embryos can be produced by iSCNT.  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