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   127篇
  免费   2篇
  国内免费   2篇
林业   15篇
农学   8篇
  9篇
综合类   31篇
农作物   5篇
水产渔业   1篇
畜牧兽医   50篇
园艺   2篇
植物保护   10篇
  2023年   1篇
  2020年   1篇
  2018年   1篇
  2015年   3篇
  2014年   4篇
  2013年   4篇
  2012年   8篇
  2011年   5篇
  2010年   5篇
  2008年   8篇
  2007年   6篇
  2006年   3篇
  2005年   1篇
  2004年   4篇
  2003年   3篇
  2002年   4篇
  2001年   11篇
  2000年   7篇
  1999年   1篇
  1998年   1篇
  1997年   1篇
  1995年   2篇
  1994年   1篇
  1992年   3篇
  1991年   1篇
  1990年   1篇
  1989年   2篇
  1987年   2篇
  1986年   1篇
  1985年   2篇
  1984年   3篇
  1982年   1篇
  1980年   1篇
  1979年   1篇
  1976年   1篇
  1975年   2篇
  1974年   2篇
  1973年   2篇
  1972年   2篇
  1971年   3篇
  1970年   2篇
  1969年   3篇
  1968年   1篇
  1967年   2篇
  1965年   1篇
  1951年   1篇
  1915年   1篇
  1913年   2篇
  1909年   2篇
  1881年   1篇
排序方式: 共有131条查询结果,搜索用时 31 毫秒
41.
This article represents only a brief glimpse into one of the fascinating aspects of the chemistry of electronically excited molecules. More exhaustive coverage of synthetic applications of photochemical reactions may be found in texts and reviews. We summarize here by noting that classification of reliable photoreactions is possible, but that the most effective application of the classification scheme requires a familiarity with some of the special features of the chemistry of electronically excited states. Thus, knowledge of the properties of singlet and triplet states, the factors which determine photochemical efficiency and reactivity, and the special technical aspects of photochemical procedures such as selective direct and phtosensitized excitation and photoexcitation at low temperatures or solid matrices make photochemistry a useful tool for the construction of organic molecules. It is our hope that the material and flavor of this article will whet the intellectual and experimental appetites of researchers who are concerned with various aspects of the synthesis of oganic molecules.  相似文献   
42.
Three rhesus monkeys Macaca mulatta, formerly dependent on morphine, had increased sensitivity to nalorphine's effect of suppressing operant responding for food, as compared with two monkeys with no history of morphine exposure. Within the dose range employed, nalorphine injections produced emesis, salivation, and hyperirritability in formerly morphine-dependent monkeys but not in controls.  相似文献   
43.
The purpose of this work was to identifymicrosatellite markers linked to a gene forresistance to Heterodera glycinesIchinohe (Soybean Cyst Nematode – SCN) insoybean cultivar Hartwig. ABC1F2 mapping population derivedfrom a cross between Hartwig (resistant)and the Brazilian soybean line Y23(susceptible) was used. About 200microsatellite or simple sequence repeat(SSR) primer pairs were tested in a bulkedsegregant analysis (BSA). Those thatshowed clear polymorphisms were amplifiedin the BC1F2 population, whichhad been previously inoculated andevaluated for resistance/susceptibility toSCN Race 3. Three SSR markers linked toSCN resistance were detected in thepopulation. Two of them, Satt 038 and Satt163, flanking a dominant resistant gene(d/a = –0.90), explained 37% of thephenotypic variance. This gene was mappedat the edge of molecular linkage group G. Broad and narrow sense heritabilities wereestimated to be 50.54% and 37.73%,respectively. A selection efficiency of91.18% was obtained with the simultaneoususe of the two markers. The identified SSRmarkers will be useful tools for assistingthe selection of homozygous genotypes andfor expediting the introgression of the SCNresistance locus from cv. Hartwig tosoybean elite cultivars.  相似文献   
44.
45.
46.
47.
48.
Resistance of Fasciola hepatica to triclabendazole   总被引:1,自引:0,他引:1  
  相似文献   
49.
A possibility was shown, how to quantify the water content of nitrogen and COD (Chemical Oxygen Demand) from intensive fish production, independent of flow rate and feeding time. The nitrogen excretion could be reduced 50% by feeding a protein reduced fish feed (A: 38.4% XP) compared with an fish feed B contending 47.9% protein (XP). The excretion-compartments were evaluated with the waste water parameter COD. Doing this, it could be shown that the COD input by feed A is reduced 20% in opposite to feed B. Further more the separation of fish faeces would achieve an COD reduction from about 50% to 70%.  相似文献   
50.
Hormonal dependency of canine mammary tumours (CMT) has been studied over the last few decades. However, studies assessing the prognostic and predictive potential of serum and/or tissue steroid hormone levels are still scarce in CMT. To the best of our knowledge, this is the first report relating serum and tissue levels of steroid hormones and prognosis in dogs. Serum and tumour tissue from 45 female dogs with spontaneous CMT were included in the study. Moreover, serum and normal mammary tissue from 13 healthy female dogs were also included as controls. Steroid hormones were determined by competitive enzyme immunoassay. Overall, levels of steroid hormones in serum and tissue homogenates were significantly different between malignant and benign mammary tumours (p < 0.01), except for progesterone (P4) serum levels that revealed no statistical differences between groups. In malignant tumours, oestrone sulphate (SO4E1), dehydroepiandrosterone (DHEA), androstenedione (A4), testosterone (T) and P4 elevated tissue concentrations were significantly associated with tumour relapse and/or distant metastasis during follow‐up. A significant association was found between elevated tissue SO4E1 (p = 0.003), 17β‐oestradiol (E2) (p = 0.036), DHEA (p = 0.022), A4 (p = 0.001) and P4 (p = 0.013) concentrations and shorter disease‐free survival and overall survival in female dogs with malignant mammary tumours. The high levels of tissue steroids found in cases of poor prognosis open the possibility of additional new therapeutic approaches. Future clinical trials will be needed to clarify the usefulness of targeting steroid hormones in the treatment of this neoplastic disease.  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