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   172篇
  免费   22篇
林业   1篇
  10篇
综合类   25篇
农作物   1篇
水产渔业   1篇
畜牧兽医   149篇
园艺   1篇
植物保护   6篇
  2020年   3篇
  2019年   4篇
  2018年   5篇
  2017年   2篇
  2016年   8篇
  2015年   8篇
  2014年   3篇
  2013年   11篇
  2012年   4篇
  2011年   5篇
  2010年   7篇
  2009年   7篇
  2008年   9篇
  2007年   4篇
  2006年   9篇
  2005年   4篇
  2004年   5篇
  2003年   5篇
  2002年   5篇
  2001年   2篇
  2000年   2篇
  1999年   4篇
  1998年   9篇
  1997年   12篇
  1996年   5篇
  1995年   3篇
  1994年   5篇
  1991年   3篇
  1989年   5篇
  1988年   3篇
  1987年   2篇
  1986年   4篇
  1985年   4篇
  1984年   2篇
  1982年   1篇
  1980年   2篇
  1979年   1篇
  1978年   1篇
  1976年   1篇
  1973年   1篇
  1971年   1篇
  1969年   2篇
  1967年   1篇
  1964年   1篇
  1961年   1篇
  1960年   1篇
  1954年   1篇
  1944年   1篇
  1943年   1篇
  1902年   1篇
排序方式: 共有194条查询结果,搜索用时 178 毫秒
51.
52.
Summary The oil contents of single kernels of corn can be determined by wideline nuclear magnetic resonance spectroscopy. Since this analytical procedure does not alter seed composition or viability, it could accelerate the development of crops having higher oil contents. A highly significant correlation was found between the oil contents of single kernels of corn and their progeny ears. This indicates that single-kernel differences in oil content are heritable. The importance of this development in terms of the increasing world-wide demand for polyunsaturated oils is discussed.
Zusammenfassung Der Öl-Gehalt einzelner Maiskörner kann durch kernmagnetische Resonanz-Spektroskopie festgestellt werden. Da dieses analytische Verfahren weder die Samenzusammensetzung noch die Lebensfähigkeit des Samens ändert, könnte sie dazu benutzt werden, die Entwicklung von Maisbeständen mit höherem Ölgehalt zu beschleunigen. Es wurde eine höchst beachtliche Korrelation zwischen dem Ölgehalt der einzelnen Kerne und dem der daraus entstehenden Kerne gefunden. Dies weist darauf hin, daß Einzel-Kern-Unterschiede im Ölgehalt vererbbar sind. Die Bedeutung dieser Entwicklung in Bezug auf die weltweite Nachfrage nach mehrfach ungesättigten Ölen wird besprochen.

Résumé La quantité d'huile contenue dans les grains de maïs isolés peut être déterminée par la spectroscopie à résonance magnétique nucléaire à grande amplitude. Comme ce procédé ne cause aucune altération de la composition ou de la viabilité de la semence il pourrait accélérer la production de récoltes a rendement d'huile élevé. Une corrélation très étroite a été établie entre la quantité d'huile contenue dans les grains individuels et celle contenue dans leur progéniture. Ceci indique que la difference entre les quantités d'huile contenues dans deux grains individuels peut-être héritée. Cet article traite de l'importance de cette application scientifique en liaison avec la demande croissante d'huiles polyinsaturées dans le monde entier.


with 4 figs.

Paper presented at 6th International Congress of Nutrition, Edinburgh, August 9–15, 1963.  相似文献   
53.
54.
The aim of this study was to investigate the effect of applying a progesterone‐based oestrous synchronization protocol at 51–57 days postpartum in high‐producing dairy cows. The data analysed were derived from 1345 lactating cows. Cows between 51 and 57 days postpartum were assigned to the groups: control, PRID (receiving a progesterone‐releasing intravaginal device for 9 days, and prostaglandin F 24 h before PRID removal) or GnRH–PRID (the same as the PRID group plus GnRH at PRID insertion). Oestrus was detected by using pedometers and confirmed by examination of the genital tract at AI. Oestrous and conception rates before days 71–77 postpartum, pregnancy loss in early pregnant cows or the cumulative conception rate registered on day 120 postpartum were considered as the dependent variables in four consecutive logistic regression analyses. Based on the odds ratios, the oestrous rate increased by a factor of 1.73 in cows showing oestrus before treatment for each unit increase in the number of previous oestruses; decreased by a factor of 0.44 in the control group with respect to the treatment groups; and by a factor of 0.61 in cows without luteal structures at treatment with respect to cows with corpora lutea. The conception rates of cows inseminated before days 71–77 postpartum remained similar across the groups, whereas the likelihood of pregnancy loss for cows becoming pregnant during this period was 0.11 times lower in the PRID group than in the control. Based on the odds ratio, the likelihood of a higher cumulative conception rate on day 120 postpartum: increased in cows showing oestrus before treatment by a factor of 1.41 for each unit increase in the number of previous oestruses, was reduced 0.56‐fold in control cows compared with treated cows, and was also reduced by a factor of 0.98 for each kilogram of milk production increase recorded at treatment. In conclusion, although oestrous synchronization programmes performed in this study did not improve fertility, cows treated with progesterone could be inseminated earlier than untreated cows, such that the treatments increased the cumulative pregnancy rates determined on day 120 postpartum. In addition, fewer pregnancy losses were observed in early pregnant cows in the PRID group than the GnRH–PRID group.  相似文献   
55.
56.
The presence of the zona pellucida has been perceived as a requirement for the oviductal transfer of cloned embryos at early stages of development while protecting the embryo from an immune system response. We hypothesized that steroid hormone therapy could reduce a potential cellular immune response after the transfer of zona‐free cloned embryos into the oviduct of recipient female goats. In Experiment 1, seven does were used to study the systemic immunosuppressant effect of the methylprednisolone administration (for 3 days) on blood cell counts. Whole blood was collected prior to treatment with methyprednisolone and then on Days 1, 2, 3, 4, 7, 14, 21 and 28 after the first dose of methylprednisolone for the analysis of haematological parameters. Methylprednisolone treatment significantly reduced circulating white blood cells and neutrophils in comparison with pre‐treatment levels, demonstrating a systemic immunosuppressant effect. In Experiment 2, a group of 58 does were used as recipient females to study the effect of administration of methylprednisolone for 3 days on the establishment of pregnancies after the transfer of zona‐free cloned embryos into the oviducts. No effects on pregnancy rates on Day 30 were observed regarding the distinct treatment groups (control vs. methylprednisolone), the source of oocytes (in vivo‐ vs in vitro‐matured) or the presence or absence of the zona pellucida in embryos. In summary, methylprednisolone was effective at inducing a systemic immunosuppressed state in goats, but the treatment prior to embryo transfer did not affect pregnancy rates. Moreover, pregnancy rates were similar between zona‐free and zona‐intact goat cloned embryos.  相似文献   
57.
Chromatographic fractionation of crude extracts (C8 extracts) from the protein-enriched flour of commercial field peas (Pisum sativum L.) has been shown here to yield peptide mixtures related to the pea albumin 1b (PA1b) family of cysteine-rich plant peptides. The mixtures were obtained initially by flash chromatography with silica gel. Following elution of soyasaponins and lysolecithins, the end fractions obtained with the use of two flash chromatographic solvent systems displayed activity in a flour disk antifeedant bioassay with the rice weevil [Sitophilus oryzae (L.)]. Chemical properties of these mixtures were compared by thin-layer chromatography, high-performance liquid chromatography (HPLC), IR, MS, and amino acid analyses. The major peptides of C8 extracts, with average masses of 3752, 3757, and 3805 Da, were isolated by anion exchange chromatography. Samples enriched in the peptide of mass 3752 were isolated by cation exchange chromatography. Reduction plus alkylation experiments in combination with electrospray ionization mass spectrometry showed that C8 extracts contained about 10 peptides and, like PA1b, each peptide possessed six cysteine residues (three disulfide bonds). Disulfide bond reduction with 2-mercaptoethanol destroyed the antifeedant activity. The native peptides of C8 extracts were found to be resolved into nine peaks with XTerra HPLC columns operating at alkaline pH. These columns were employed to assess the distribution of pea peptides in the isolated fractions, with photodiode array and electrospray detection.  相似文献   
58.
59.
SUMMARY: The IgG concentration of plasma from 13 mares was measured by radial immunodiffusion when fresh and after storage at -4°C and thawing by 3 methods. There was no significant (P > 0.05) reduction in the IgG concentration when plasma was thawed over 6 hours at 22°C (1352.9 ± 101.6 mg/dL) (mean ± SEM) compared with the fresh sample (1369.5 ± 88.1 mg/dL). In contrast, there was a significant (P < 0.05) reduction in the IgG concentration of plasma that was rapidly thawed at 57°C over 50 minutes (1142.9 ±66.2 mg/dL), or placed in a microwave oven for 20 to 25 minutes (1093.4 ± 74.4 mg/dL). When plasma is administered to hypo-gammaglobulinaemic newborn foals, a larger volume is required when thawing is rapid than when thawing is slow or when fresh plasma is administered.  相似文献   
60.
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