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   451篇
  免费   18篇
林业   31篇
农学   1篇
基础科学   14篇
  17篇
综合类   69篇
农作物   9篇
水产渔业   29篇
畜牧兽医   271篇
园艺   5篇
植物保护   23篇
  2020年   6篇
  2019年   6篇
  2018年   11篇
  2017年   7篇
  2016年   6篇
  2015年   3篇
  2014年   3篇
  2013年   18篇
  2012年   11篇
  2011年   21篇
  2010年   9篇
  2009年   10篇
  2008年   15篇
  2007年   19篇
  2006年   21篇
  2005年   23篇
  2004年   10篇
  2003年   17篇
  2002年   24篇
  2001年   11篇
  2000年   15篇
  1999年   24篇
  1998年   13篇
  1997年   7篇
  1996年   5篇
  1995年   6篇
  1993年   2篇
  1992年   13篇
  1991年   5篇
  1990年   11篇
  1989年   11篇
  1988年   9篇
  1987年   5篇
  1986年   5篇
  1985年   7篇
  1984年   11篇
  1983年   9篇
  1982年   7篇
  1981年   4篇
  1980年   3篇
  1979年   5篇
  1978年   3篇
  1977年   2篇
  1976年   3篇
  1973年   4篇
  1972年   3篇
  1970年   3篇
  1969年   2篇
  1965年   2篇
  1943年   2篇
排序方式: 共有469条查询结果,搜索用时 109 毫秒
141.
Every year, the Student Debates Subcommittee (SDS) of the Student Affairs Committee (SAC) for the annual Entomological Society of America (ESA) meeting organizes the Student Debates. This year, the SAC selected topics based on their synergistic effect or ability to ignite exponential positive change when addressed as a whole. For the 2019 Student Debates, the SAC SDS identified these topic areas for teams to debate and unbiased introduction speakers to address: 1) how to better communicate science to engage the public, particularly in the area of integrated pest management (IPM), 2) the influential impacts of climate change on agriculturally and medically relevant insect pests, and 3) sustainable agriculture techniques that promote the use of IPM to promote food security. Three unbiased introduction speakers gave a foundation for our audience to understand each debate topic, while each of six debate teams provided a strong case to support their stance or perspective on a topic. Debate teams submitted for a competitive spot for the annual ESA Student Debates and trained for the better part of a year to showcase their talents in presenting logical arguments for a particular topic. Both the debate teams and unbiased introduction speakers provided their insight toward a better understanding of the complexities of each topic and established a foundation to delve further into the topics of science advocacy and communication, climate change, and the many facets of integrated pest management.  相似文献   
142.
The genome sequence of Drosophila melanogaster   总被引:2,自引:0,他引:2  
The fly Drosophila melanogaster is one of the most intensively studied organisms in biology and serves as a model system for the investigation of many developmental and cellular processes common to higher eukaryotes, including humans. We have determined the nucleotide sequence of nearly all of the approximately 120-megabase euchromatic portion of the Drosophila genome using a whole-genome shotgun sequencing strategy supported by extensive clone-based sequence and a high-quality bacterial artificial chromosome physical map. Efforts are under way to close the remaining gaps; however, the sequence is of sufficient accuracy and contiguity to be declared substantially complete and to support an initial analysis of genome structure and preliminary gene annotation and interpretation. The genome encodes approximately 13,600 genes, somewhat fewer than the smaller Caenorhabditis elegans genome, but with comparable functional diversity.  相似文献   
143.
Stimulatory effect of avian influenza virus on chicken lymphocytes   总被引:1,自引:0,他引:1  
A study was conducted to examine the effect of avian influenza virus (AIV) on chicken lymphocyte activation. Unprimed or Brucella abortus antigen (Ag)-primed lymphocytes were incubated with various doses of the T-cell mitogen concanavalin A (Con A) or Ag, respectively, plus serial dilutions of inactivated AIV for 72 hr, and cell proliferation was measured via uptake of tritiated thymidine. AIV enhanced the proliferative response to Con A or Ag by 150% or better, and the enhancement decreased in a viral dose-dependent manner. The effects were more readily observed in cells that had not been maximally activated by the Con A or Ag. The enhanced response was observed in lymphocytes from both white rock and white leghorn breeds of chicken and in mature peripheral blood lymphocytes or immature thymocytes. The viral activity could be abrogated by pre-treatment of the viral preparation with AIV-specific antisera or prior adsorption of the AIV with chicken erythrocytes. These results indicate that AIV can interact with and modify the in vitro activity of chicken lymphocytes and may exert modulatory effects on the avian immune system.  相似文献   
144.
R K Gast  P S Holt 《Avian diseases》2001,45(2):425-431
Detecting infected laying flocks is a vital part of many efforts to control egg-associated transmission of Salmonella enteritidis to humans. The relationship between the development of a specific antibody response in infected hens and the deposition of S. enteritidis in eggs is important for establishing the epidemiologic relevance of serologic testing methods. In two trials, laying hens were infected with large oral doses of phage types 13a and 14b isolates of S. enteritidis. Approximately 38% of all infected hens produced at least one contaminated egg, at an overall incidence of 5.2%, between 3 and 23 days postinoculation. As determined by enzyme-linked immunosorbent assay with an S. enteritidis flagellar antigen, 91.7% of inoculated hens produced specific serum antibodies. Although hens with very high antibody titers were associated with a significantly elevated frequency of egg contamination, a consistently direct relationship was not evident between the magnitude of the antibody responses of individual hens and the frequency at which they laid contaminated eggs. Accordingly, although serologic tests can be valuable screening tools for preliminary detection of S. enteritidis infections in poultry, the magnitude of the antibody responses detected in individual hens may not predict the overall risk of egg contamination associated with particular laying flocks.  相似文献   
145.
The management of quality in the distribution of produce which exhibits significant and inevitable deterioration with time and event is a neglected but essential component of physical distribution management. This paper concentrates on horticultural produce and, in particular, on apples.Horticultural distribution is described as a system and systems thinking is employed to develop a ‘hard systems’ methodology for the management of quality. A management system is defined in terms of quality-price, quality-cost and quality-happening relations. An example from apple distribution demonstrates the methodology and is used to emphasize the central importance of quantitative models of price, cost, quality and of their interactions with time and happening.  相似文献   
146.
147.
A survey was carried out at Kano abattoir in order to estimate the incidence of hydatidosis and cysticercosis in slaughtered livestock. Of the animal species examined, hydatid disease was found in sheep (11.4 per cent), goats (26.5 per cent), cattle (14.7 per cent) and camels (55.5 per cent). Cysticercus tenuicollis was found to be most prevalent in goats (34.2 per cent), followed by sheep (21.4 per cent) and cattle (0.1 per cent). Out of 4844 cattle examined, less than 2 per cent haboured Cysticercus bovis cysts; while Cysticercus ovis cysts were found in sheep (1 per cent) and goats (0.8 per cent).  相似文献   
148.
Although relatively uncommon in small animal orthopaedics, tarsal collateral ligament injuries may present problems to the veterinary surgeon dealing with trauma cases. The author's method of approach to the condition and the management of thirteen cases are described and discussed.  相似文献   
149.
150.
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