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   364篇
  免费   30篇
林业   23篇
农学   18篇
基础科学   2篇
  41篇
综合类   22篇
农作物   32篇
水产渔业   26篇
畜牧兽医   197篇
园艺   7篇
植物保护   26篇
  2024年   1篇
  2023年   1篇
  2022年   6篇
  2021年   11篇
  2020年   21篇
  2019年   20篇
  2018年   27篇
  2017年   23篇
  2016年   16篇
  2015年   21篇
  2014年   18篇
  2013年   31篇
  2012年   18篇
  2011年   20篇
  2010年   12篇
  2009年   19篇
  2008年   8篇
  2007年   5篇
  2006年   6篇
  2005年   7篇
  2004年   6篇
  2003年   5篇
  2002年   2篇
  2001年   5篇
  2000年   4篇
  1999年   5篇
  1998年   6篇
  1997年   7篇
  1996年   6篇
  1995年   2篇
  1994年   5篇
  1993年   7篇
  1992年   6篇
  1991年   5篇
  1990年   5篇
  1989年   9篇
  1988年   3篇
  1987年   3篇
  1986年   3篇
  1985年   2篇
  1984年   5篇
  1983年   1篇
  1982年   1篇
排序方式: 共有394条查询结果,搜索用时 0 毫秒
41.
Under the umbrella of WTO, the reduction in trade barriers has forced the policy makers to focus on the export competitiveness. Rice is an important source for foreign exchange earnings for the economy of Pakistan, keeping in mind of this fact, the competitiveness of Pakistan’s rice with other major exporters was examined by applying revealed competitive advantage. The domestic consumption trends of rice among the major rice exporting countries were also analyzed in the current study. The results revealed that as compare to other major exporters of rice in the world, Pakistan had high competitive and comparative advantage in the production of rice. The comparison of the movements in comparative advantage indices for Pakistan with the major world rice competitors/exporters showed that Pakistan possessed relatively high comparative and competitive advantages in rice production. The declining domestic per capita consumption of rice and increasing trends in competitiveness for Pakistan clearly revealed the expected potential of higher growth which meant that rice exports from Pakistan could continue to play an important role for the earnings of foreign exchange. In order to exploit the potential benefits of rice exports, we need to strengthen the competitiveness in rice sector of Pakistan.  相似文献   
42.
43.
Disease of geese caused by a new herpesvirus   总被引:3,自引:0,他引:3  
A goose flock farmed outdoors in south-eastern Queensland suffered an outbreak of peracute disease with high death rate (97%). Small button ulcers and large plaques overlying lymphocyte aggregates were present on the mucosa of the small intestine of affected birds. Small white foci of necrosis and focal haemorrhages were seen in the livers. Numerous intranuclear inclusion bodies were observed microscopically in hepatocytes and a herpesvirus which grew rapidly in chicken kidney cells was isolated from tissues. Duck virus enteritis (DVE) was suspected but DVE antiserums failed to neutralise the virus. Further serological studies with a limited range of known avian herpesviruses have failed to identify the virus. Experimental transmission resulted in high mortality in geese (100%), lower mortality in ducklings and nil mortality in chickens. Surveillance studies showed no evidence of infection in domestic and wild birds beyond the original farm and the infection appears not to have been established in the area. Wild ducks, which were frequent visitors to the farm dam, were considered the most likely source of the infection.  相似文献   
44.
Forty-seven pregnant uteri were collected from an abattoir at eight chronological stages of gestation. Assessments were made of placentome number, weight, length shape and ratio of foetal to maternal tissue by weight. The study showed that there was a great variation in number, size, weight and shape of placentomes. There was no significant change in the total number of placentomes during gestation. Both mean weight and length increased significantly during gestation, but there was a significant change in the relationship between the two as gestation progressed. There was no correlation between the number of placentomes and the mean weight or length of the placentomes. The development of the placenta in the non-pregnant horn was significantly different from that of the pregnant horn, with fewer, smaller, lighter placentomes. However, there was no evidence that placentome development in the non-pregnant horn was affected by placentome development in the pregnant horn. The proportion of the placentome that was maternal tissue increased during gestation, but there was no significant effect of placentome number, or individual placentome weight or length on this proportion. Two placentome shapes were identified, but no effect on foeto-maternal proportion or relationship between shape and total placentome number or weight was identified.  相似文献   
45.
The housing, management and internal parasite control practices used in piggeries in Western Australia was surveyed by interviewing the owner/manager of 100 randomly selected piggeries. At the time of the interview 20 faecal samples were collected from pigs and examined for evidence of internal parasites. Most herds (80%) in which anthelmintics were used, had evidence of nematode infection. Some pig producers were using an anthelmintic that was ineffective against nematode species present while some herds had nematodes that should have been controlled by the anthelmintic being used. Prevalence of nematode infection was higher in pigs run in paddocks than in pigs housed intensively. Washing sows prior to farrowing was associated with a lower prevalence of nematode infection. The findings suggested that pig producers should ensure that the anthelmintic used is effective against the nematodes present in their pigs. It was concluded that administering anthelmintics as a single dose in the feed may not be the most effective method of deworming pigs.  相似文献   
46.
The effects of beta-glucanase expressed by transformed Lactobacillus strains on growth performance, apparent digestibilities of dry matter and crude protein, and apparent metabolisable energy were studied. Two hundred and forty 1-d-old chicks (Avian-43) were randomly divided into three dietary treatment groups and fed with the following diets: (i) basal diet (control) (BD); (ii) basal diet with parental Lactobacillus strains (BDP) and (iii) basal diet with transformed Lactobacillus strains (BDT). At 21 d of age, the body weight, body weight gain and feed conversion ratio of the BDT-fed chickens were significantly improved. At 14 and 21 d of age, the proportions of dry matter in the duodenum, jejunum, ileum, caeca and excreta of chickens given the BDT diet were significantly higher than those of chickens given the BD and BDP diets. Apparent metabolisable energy, digestibilities of crude protein and dry matter were also significantly improved (by 3.5, 5.6 and 3.5%, respectively) by the BDT diet. These results showed that the transformed Lactobacillus strains improved digestibility as well as enhanced the growth performance of chickens.  相似文献   
47.
48.
SUMMARY The polymerase chain reaction was used to detect the presence of blue-tongue virus (BTV) in a number of clinical and insect samples collected in the Northern Territory of Australia. Sequence analyses of the amplified BTV genes differentiated endemic Australian and exotic viruses. Two potential exotic BTV were detected as a result of PCR analyses of blood from sentinel animals and of the insect vector, Culicoides wadai. The detection of BTV in C wadai was the first direct demonstration of the presence of BTV in this potential vector. This new technology can significantly reduce the time taken for a diagnosis from a clinical sample and increase the amount of useful information obtained on a BTV isolate by using rapid sequencing techniques. Sequence data were used to differentiate between BTV20 isolated in 1975 and two isolates of the same serotype, isolated in 1992, and indicated that the latter were probably a recent incursion into Australia from Indonesia due to their greater VP3 sequence homology to the BTV9 (Java) than to Australian BTV isolates.  相似文献   
49.
Veterinary Research Communications - Avian polyomavirus (APV) infection, also called as budgerigar fledgling disease (BFD) causes various health problems in many psittacine species which may cause...  相似文献   
50.
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