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   590篇
  免费   31篇
林业   59篇
农学   38篇
  96篇
综合类   89篇
农作物   17篇
水产渔业   68篇
畜牧兽医   226篇
园艺   2篇
植物保护   26篇
  2020年   16篇
  2019年   6篇
  2018年   14篇
  2017年   8篇
  2016年   13篇
  2015年   9篇
  2014年   10篇
  2013年   21篇
  2012年   32篇
  2011年   18篇
  2010年   8篇
  2009年   14篇
  2008年   20篇
  2007年   25篇
  2006年   18篇
  2005年   22篇
  2004年   13篇
  2003年   22篇
  2002年   14篇
  2001年   23篇
  2000年   19篇
  1999年   15篇
  1998年   13篇
  1996年   5篇
  1995年   9篇
  1994年   6篇
  1993年   9篇
  1992年   11篇
  1991年   10篇
  1990年   7篇
  1989年   8篇
  1988年   6篇
  1987年   14篇
  1986年   6篇
  1985年   7篇
  1984年   6篇
  1983年   4篇
  1982年   7篇
  1979年   5篇
  1975年   3篇
  1974年   12篇
  1973年   7篇
  1972年   12篇
  1971年   6篇
  1970年   7篇
  1969年   8篇
  1968年   7篇
  1966年   5篇
  1965年   3篇
  1962年   3篇
排序方式: 共有621条查询结果,搜索用时 15 毫秒
11.
The agar-gel immunodiffusion test was used to evaluated 35 dogs with histopathologically confirmed blastomycosis and 98 dogs without blastomycosis. The test had a sensitivity of 91% and a specificity of 96%. Thirteen of the dogs treated for blastomycosis were tested at 6 to 33 months after treatment with amphotericin B. Ten of 13 dogs became seronegative and 3, though clinically normal, remained seropositive at 19, 20, and 20 months, respectively, after amphotericin treatment.  相似文献   
12.
13.
Summary A review is given about publications of the last 30 years, concerning problems of high nitrate content of feeds. Nearly 10 areas of scientific work can be discerned. The most important of them have to do with: Analysis of nitrate and nitrite; danger of poisoning by feeds and water rich in nitrate; physiological and pathological consequences of high doses of nitrate or nitrite; reduction of nitrate (in the rumen and in the fermentation of plants) to nitrite, hydroxylamine and ammonia; behaviour of nitrate in the process of silage making; adverse effects upon the functions of the thyroid gland by nitrite and the disturbances of the availability of vitamin A and vitamin E by nitrate-nitrite.
Résumé On a donné un rapport sur les travaux scientifiques publiés dans les dernières trente années, concernant les problèmes d'une teneur haute en nitrate dans les fourrages. On peut discerner à peu près dix régions de travail scientifique. Les plus importantes sont: analyses du nitrate et du nitrite; le danger des intoxications par les fourrages et par l'eau, qui sont riches de nitrate; les conséquences physiologiques et pathologiques des doses hautes du nitrate ou du nitrite; la réduction du nitrate (dans le panse des ruminants et dans les fourrages en fermentation) au nitrite, au hydroxylamine et à l'ammonique; les réactions du nitrate pendant la préparation des silages; les influences défavorables aux fonctions de la glande thyroide par le nitrite; et les actions de déranger l'utilisation de la vitamine A et de la vitamine E par nitrate-nitrite.
  相似文献   
14.
ABSTRACT Pseudomonas putida 06909-rif/nal was applied repetitively during the irrigation season in two citrus orchards over 3 years. In a mature (50-yearold) commercial citrus orchard covering 2.02 ha, weekly applications of Pseudomonas putida 06909-rif/nal with an in-field fermentor resulted in soil populations that fluctuated between 2.83 log CFU + 1 per g of soil and 4.35 log CFU + 1 per g of soil. Resulting rhizosphere populations of Phytophthora parasitica were significantly reduced in 1999 but not 1997 or 1998. In a newly planted citrus orchard, yearly applications of Pseudomonas putida 06909-rif/nal at the beginning of the irrigation season resulted in high soil populations of Pseudomonas putida 06909-rif/nal that declined rapidly and never reduced the rhizosphere populations of Phytophthora parasitica. When Pseudomonas putida 06909-rif/nal was applied weekly, soil populations increased throughout the 1997 and 1998 irrigation seasons, reaching a maximum in 1998 and remained high throughout the 1999 irrigation season. Rhizosphere populations of Phytophthora parasitica were significantly reduced in 1998. Yearly applications of the fungicide metalaxyl and the nematicide phenamiphos reduced rhizosphere populations of Phytophthora parasitica in 1997 but not in 1998 or 1999. Pseudomonas putida 06909-rif/nal was uniformly distributed throughout the soil profile to a depth of 75 cm in both yearly and weekly applications. When applied through low-volume minisprinklers, Pseudomonas putida 06909-rif/nal was found in aerosols up to 3 m away.  相似文献   
15.
16.
17.
Summary Wood-destroying insects react to and depend regarding their nutrition on compounds contained in wood or produced by microorganisms in wood. This relation is a complex matter in the biology of the insects and the chemistry of wood and of the metabolism of woodinhabiting microorganisms. Results on the reaction of Coleoptera and Isoptera to attractive or repellent compounds in wood species or substances produced by fungi in wood are reviewed with emphasis to differences among various insect species. Nutrition of wood-destroying insects depends on nitrogen compounds of the wood; the content of nitrogen can be increased by the presence of fungi. Existing results on the relation between microorganisms and insects are also summarized including toxicity or parasitic influence of part of the microorganisms on insects. The survey may stimulate further investigations which are necessary for better knowledge of the complex interrelations.Prepared for the Convention of the International Academy of Wood Science at Raleigh (S.-Carol., USA) in March 1971.  相似文献   
18.
Zusammenfassung Nach einer Mitteilung aus dem Ende des 18. Jahrhunderts sollen sich in Blüte stehende Pflanzen vonVerbascum thapsus als Mittel zur Vertreibung vonMus musculus undRattus norvegicus eignen. Eine Nachprüfung dieser Empfehlung mitV. thapsus, lychnitis undthapsiforme anMus verlief negativ.
Summary At the end of the eighteenth centuryGoeze reports about the action ofVerbascum thapsus as a repellent againstMus musculus andRattus norvegicus. A revision of this information withV. thapsus, lychnitis andthapsiforme andMus musculus as test animals does not confirm his findings.
  相似文献   
19.
Rao  M.R.  Palada  M.C.  Becker  B.N. 《Agroforestry Systems》2004,61(1-3):107-122
Agroforestry Systems - A large number of people in developing countries have traditionally depended on products derived from plants, especially from forests, for curing human and livestock...  相似文献   
20.
Becker P  Gribben RJ  Lim CM 《Tree physiology》2000,20(14):965-967
The model of West, Brown and Enquist showed that total hydraulic resistance in trees can be independent of path length, provided that vascular conduits taper sufficiently. This model assumes that the tree branch network is volume-filling, so that segment lengths increase exponentially from tree top to base. We show that partial buffering of hydraulic resistance from path-length effects can occur even for moderate tapering, and that this effect is stronger when segment lengths are fixed. Still needed are measurements of tracheary size and hydraulic resistance designed to test this model, which shows how hydraulic limitation of tree height growth may be mitigated.  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