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   140434篇
  免费   7874篇
  国内免费   90篇
林业   6124篇
农学   4584篇
基础科学   868篇
  18785篇
综合类   21728篇
农作物   5675篇
水产渔业   7398篇
畜牧兽医   71474篇
园艺   1937篇
植物保护   9825篇
  2020年   1345篇
  2019年   1482篇
  2018年   2360篇
  2017年   2708篇
  2016年   2450篇
  2015年   2006篇
  2014年   2561篇
  2013年   5761篇
  2012年   4697篇
  2011年   5579篇
  2010年   3511篇
  2009年   3643篇
  2008年   5381篇
  2007年   5037篇
  2006年   4628篇
  2005年   4390篇
  2004年   4095篇
  2003年   4196篇
  2002年   3731篇
  2001年   4281篇
  2000年   4373篇
  1999年   3499篇
  1998年   1511篇
  1997年   1411篇
  1996年   1325篇
  1995年   1550篇
  1994年   1376篇
  1993年   1244篇
  1992年   2682篇
  1991年   2790篇
  1990年   2678篇
  1989年   2699篇
  1988年   2467篇
  1987年   2447篇
  1986年   2517篇
  1985年   2423篇
  1984年   1945篇
  1983年   1742篇
  1982年   1185篇
  1979年   1837篇
  1978年   1478篇
  1977年   1221篇
  1976年   1257篇
  1975年   1330篇
  1974年   1581篇
  1973年   1571篇
  1972年   1480篇
  1971年   1380篇
  1970年   1274篇
  1969年   1308篇
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
971.
972.
973.
974.
975.
976.
Summary As a prisoner of war the writer was working for nearly three years in different POW camps, and outside them, along the Burma railway from Thanbyuyzat in southern Burma up to Kanchanabury in Thailand. In the army of the Netherlands-Indian archipelago (KNIL) he had the military rank of reserve horse-doctor. In civilian life he was attached to the Veterinary Institute in Buitenzorg (now Bogor) as a veterinary bacteriologist. His task as a POW became that of meathygienist and supervisor of the living animals in the camps. In this function he diagnosed swine fever in growing pigs which had mainly been fed on the offal of the Japanese kitchen. The acute course and the pathological alterations observed during the post-mortem examinations were identical with those of the Southern-African type of the disease. In slaughter cattle the author diagnosed some cases of lung tuberculosis, one of anthrax, several of rinderpest, some of rhinal granulomatosis and one of foot and mouth disease. In chickens he found NCD (pseudo-fowlpest) and in ducklings a mortal disease which the author then called 'keeling disease' but which he many years later, recognized as virus hepatitis. As assistant bacteriologist and ex-POW he joined the British regimental hospital in Bangkok. Here he had the opportunity to assist the bacteriologist pathologist, Maj. C. R. Peck IMS / IAMC in diagnosing the first case of melioidosis in an ex-POW of the KNIL who died from the sub-acute infection, notwithstanding treatment in the hospital with sulfa-drugs and penicillin.  相似文献   
977.
The cercariae of Eurytrema pancreaticum (Janson, 1889) possess four types of gland cells - proper cystogenic, penetration, ventral and dorsal gland cells. The secretion of ventral and dorsal gland cells is released into the tegument. The proper cystogenic gland cells are the largest and their contents serve for the formation of the cyst wall of metacercariae in the second intermediate host. The secretion of proper cystogenic gland cells contains besides neutral mucosubstances also acid mucosubstances with both carboxyl- and sulphogroups digestible with beta-glucuronidase. The secretion of penetration gland cells contains neutral mucosubstances and proteins with tyrosine, tryptophan and SS groups. The ventral gland cells contain mostly acid mucosubstances with sulphogroups, which are digested with beta-glucuronidase, and proteins with tyrosine, tryptophan and SH groups. The rudimentary dorsal gland cells contain a small amount of acid mucosubstances. The whole tegument of cercariae and the two main collecting canals of the excretory system exhibit a high alkaline phosphatase activity. The nerve ring and the main nerve truncs contain proteins with SH groups and hydrophilic lipids and exhibit a cholinesterase activity. The suckers contain a larger amount of glycogen.  相似文献   
978.
Summary The prevalence of antibodies to various viruses was investigated in a series of serum samples collected from horses in the Netherlands between 1963 and 1966 and from 1972 onwards. Neutralizing antibodies to equine rhinopneumonitis virus, equine arteritis virus and to equine rhinovirus types 1 and 2 were detected in respectively 76%, 14%, 66% and 59% of the equine serum samples tested. The observed incidence of serum samples positive to equine adenovirus in the complement fixation test was 39%. Precipitating antibodies to equine infectious anaemia virus were detected only in serum samples from two horses imported from abroad. Haemagglutination inhibiting antibodies to Myxovirus influenzae A / equi-1, M. Influenzae A / equi-2, and Reovirus types 1, 2, and 3 were present in respectively 82%, 50%, 10%, 33% and 3.6% of the serum samples tested. The most frequently observed incidence of antibodies to the various equine respiratory viruses occurred in the groups of horses having repeatedly contact with other horses.  相似文献   
979.
The tissue reaction to Cysticercus bovis in the lung of cattle with an experimental infection was an inflammatory rim originating in the immediate vicinity of the cysts. The cysts recovered at days 83 and 102 p.i. contained living cysticerci. The rim was composed either of a layer of high histiocytes organized in palisades (at day 83 p.i.), or a lyer of flat histiocytes (at day 102 p.i.). The outer layer of the rim consisted of fibroblasts, reticular cells and a different number of eosinophil- and neutrophil luekocytes. On the periphery, the rim was formed by granulation tissue infiltrated with lymphoplasmocytes. At the border between the layers of the inflammatory rim there were conspicuous foci of a necrotic appearance typical of a tissue reaction to C. bovis.  相似文献   
980.
On the older leaves ofPelargonium zonale chlorotic rings and flecks are common, especially during spring and fall. From such plants an isometric virus can be isolated that causes local lesions on the leaves ofChenopodium quinoa. An attempt was made to produce symptomless plants, reacting negatively onC. quinoa. Meristem tips on a basal medium supplemented with α-naphthalene acetic acid and coconut milk produced abundant callus, but no plantlets. However, on media containing low concentrations of indole acetic acid and kinetin or benzyl adenine, some plants were produced that fulfilled the above requirements. Those selected on horticultural properties, are considered as valuable mother plants. Of twenty-one cultivars such plants were obtained. They may prove an important contribution to the improvement of theP. zonale industry in the Netherlands.  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