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   1281篇
  免费   62篇
  国内免费   15篇
林业   143篇
农学   34篇
基础科学   4篇
  202篇
综合类   237篇
农作物   50篇
水产渔业   65篇
畜牧兽医   549篇
园艺   14篇
植物保护   60篇
  2023年   12篇
  2021年   21篇
  2020年   21篇
  2019年   18篇
  2018年   19篇
  2017年   27篇
  2016年   33篇
  2015年   24篇
  2014年   25篇
  2013年   48篇
  2012年   51篇
  2011年   51篇
  2010年   49篇
  2009年   41篇
  2008年   56篇
  2007年   49篇
  2006年   43篇
  2005年   44篇
  2004年   43篇
  2003年   45篇
  2002年   20篇
  2001年   19篇
  2000年   22篇
  1999年   24篇
  1998年   18篇
  1997年   9篇
  1996年   16篇
  1994年   16篇
  1992年   21篇
  1991年   32篇
  1990年   18篇
  1989年   31篇
  1988年   12篇
  1987年   21篇
  1986年   22篇
  1985年   22篇
  1984年   12篇
  1982年   9篇
  1980年   9篇
  1979年   16篇
  1978年   15篇
  1976年   9篇
  1974年   15篇
  1973年   11篇
  1972年   14篇
  1970年   20篇
  1969年   11篇
  1968年   14篇
  1967年   21篇
  1966年   9篇
排序方式: 共有1358条查询结果,搜索用时 15 毫秒
61.
    
Ohne Zusammenfassung  相似文献   
62.
Summary Wood storage has a great influence on the efficiency of a pulpmill. Great problems arise when using outside chip storage, especially in processing hardwoods, in that hardwood chips discolorate after a few days, which is not the case with spruce chips. The causes of such a different behavior of beech and spruce were investigated. It could be shown that a sufficient amount of active peroxidase, malate dehydrogenase and oxygen are prerequisites for the formation of phenoxy radicals within the beech lignin. This causes formation of new chromophores that discolorize the wood. Sufficient amounts of such enzymes are present in beech wood after harvesting.  相似文献   
63.
Six‐week‐old seedlings of slash pine (Pinus elliottii) were inoculated with sporidia of Cronartium strobilinum, which is the cause of southern cone rust disease, by wounding the apical tips of the seedlings. Pycnial sori developed abundantly within 1 month of inoculation on the epicotyl and primary needles. The progress of the pathogen was confirmed histologically within the cells of the stem and haustoria were observed near the nucleus of the cells. In the needles, pycnial pustules developed and the fungus was abundant in the mesophyll.  相似文献   
64.
达明珠 《木材工业》2005,19(1):33-34,39
介绍了原木蒸煮废水的处理方法,提出氧化塘法是小型木材加工厂处理该废水的最佳选择,并用实例简单介绍了氧化塘的设计选型问题.  相似文献   
65.
For testing the prompt and long-term effectiveness of a THURICIDE-dust containingBacillus thuringiensis var.kurstaki, serotype 3a, 3b with a viable spore count of 6 to 10 million per mg and an insecticidal activity of 3,2×103 international units (IU) per mg, the biopreparation was applied to rye on which larvae of the Indian Meal Moth (Plodia interpunctella Hbn.) were fed. A concentration of 20 mg (64×103 IU) of dust in 100 g of grain caused in 82% mortality, and a six-fold higher concentration (120 mg, 384 × 103 IU respectively) resulted in 99,0% mortality. The efficiency of the preparation was not reduced by storage for as long as 5 months in any five tests, which were at temperatures from 12°C to 28°C with 75% r.h. The larval stage of the surviving was prolonged by 3 to 4 weeks. Surviving moths, whose larvae were reared on grain to which the preparation was applied, were fertile and did not infest the following generation.  相似文献   
66.
67.
68.
Packaging foils made of cellulose actetate, cellophane, polyethylene, polypropylene, polystyrene, polyester, polyvinyl chloride, attacked byRhizopertha dominica F.,Stegobium paniceum L.,Tribolium castaneum Hbst. and larvae ofPlodia interpunctella Hbn. were examined with the scanning electron microscope (SEM). Because of the destruction marks made by the insects, it is possible to determine with the SEM the side of packaging material which has been attacked by the pests. Due to the shape and position of the mouthparts of the insects the gnawing marks are rather typical for the different species. By means of a standard of comparison it might be possible to determine the family and perhaps the genus or species of the insects involved. The influence of shape and size of the mouthparts as well as the position of the mandibles in relation to the anatomy and to the axis of the body on the gnawing ability of stored-product pests is discussed. The reasons for the insect resistance of packaging materials are discussed (smoothness of the surface, rigidity, thickness).  相似文献   
69.
70.
Zusammenfassung Es wird über das Auftreten von 25 Vorratsschädlingen, darunter 17 Käfer- und 3 Mottenarten, in den Lägern der Bevorratungsabteilung des Senators für Wirtschaft und Arbeit, der sonstigen Großlagerhaltung sowie in den Vorräten privater Haushalte berichtet. Die häufigsten Schädlinge in der Großlagerei waren Brotkäfer (Stegobium paniceum L.) und Speichermotten (Ephestia elutella Hbn.). Für den Vorratsschutz interessante Fälle und besondere Arten werden ausführlicher behandelt. Außerdem wird ein Überblick über die Entwesungs- und Entseuchungsarbeiten gegeben, bei denen neben den Begasungsmitteln mit den Wirkstoffen Methylbromid, Phosphorwasserstoff und Blausäure auch Vorratsschutzmittel auf der Grundlage von Dichlorvos, Pyrethrum und Piperonylbutoxid in verschiedenen Anteilen eingesetzt werden.
Stored products protection activities of the Plant Protection Office Berlin. Pests of foodstuffs and pest-control in warehouses from 1980 to 1986
It is reported about the appearance of 25 stored-product pests, within 17 species of beetles and 2 species of moths in warehouses of the Bevorratungsabteilung des Senators für Wirtschaft und Arbeit as well as in the other warehouses and private households. The drugstore bettle (Stegobium paniceum L.) and the warehouse moth (Ephestia elutella Hbn.) were the most common pests. Cases of special interest and particular species are described in detail. Also is given a survey about the pest-controlling measures carried out with poisongas as methylbromide, phosphine and hydrocyanic acid and with insecticides on basis of dichlorvos, pyrethrum and piperonylbutoxide.


Mit einer Abbildung und 3 Tabellen  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