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   93752篇
  免费   5602篇
  国内免费   2147篇
林业   4140篇
农学   3985篇
基础科学   1741篇
  11545篇
综合类   20637篇
农作物   3636篇
水产渔业   4195篇
畜牧兽医   44222篇
园艺   1743篇
植物保护   5657篇
  2022年   941篇
  2021年   1332篇
  2020年   1338篇
  2019年   1504篇
  2018年   1696篇
  2017年   2089篇
  2016年   1856篇
  2015年   1888篇
  2014年   2120篇
  2013年   3591篇
  2012年   3740篇
  2011年   4352篇
  2010年   3081篇
  2009年   2866篇
  2008年   3740篇
  2007年   3529篇
  2006年   3177篇
  2005年   2999篇
  2004年   2525篇
  2003年   2567篇
  2002年   2466篇
  2001年   2719篇
  2000年   2756篇
  1999年   2126篇
  1998年   946篇
  1997年   827篇
  1996年   767篇
  1995年   851篇
  1994年   786篇
  1993年   760篇
  1992年   1621篇
  1991年   1785篇
  1990年   1721篇
  1989年   1649篇
  1988年   1512篇
  1987年   1549篇
  1986年   1589篇
  1985年   1400篇
  1984年   1192篇
  1983年   1016篇
  1979年   1059篇
  1978年   829篇
  1976年   711篇
  1975年   746篇
  1974年   1003篇
  1973年   984篇
  1972年   951篇
  1971年   878篇
  1970年   852篇
  1969年   804篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Three dogs with multilobular osteochondrosarcoma of the skull were evaluated using magnetic resonance (MR) imaging. Spin echo T1, T2, proton weighted and post contrast T1W images were obtained with a 1.5 Tesla magnet. The MR imaging findings were similar in all three dogs with mixed signal intensities in the T1W, T2W and proton weighted images and fairly large areas of contrast enhancement in the post contrast T1W images. The extent of brain and soft tissue involvement were well delineated and provided useful information concerning surgical planning. MR imaging provided a useful method of evaluating dogs with skull tumors.  相似文献   
102.
Humoral immune responses of black-footed penguins (Spheniscus demersus) to DNA-mediated immunization with a beta-galactosidase reporter gene expression plasmid were evaluated. Six male and 6 female adult penguins received either test plasmid, pCMV-beta, containing the beta-galactosidase gene or control plasmid, pCI, lacking a gene for expression. Three birds from each group were used previously in a diluent control group and given one injection of sterile saline. All samples were screened for anti-beta-galactosidase antibodies by indirect enzyme-linked immunosorbent assay with anti-chicken immunoglobulin G as secondary antibody. Antibodies to beta-galactosidase were detected in the sera of pCMV-beta-inoculated penguins, with a peak response on day 21. Antibody titers of the test plasmid group versus both control groups on days 21, 28, and 42 differed significantly. These results demonstrate that black-footed penguins can be safely transfected with the gene encoding beta-galactosidase and will mount a humoral response against the in vivo-expressed protein. Knowledge from this initial study can be applied to the development of DNA-mediated vaccines against specific infectious diseases of penguins.  相似文献   
103.
104.
The clinical documentation of enteropathogenic bacteria causing diarrhea in dogs is clouded by the presence of many of these organisms existing as normal constituents of the indigenous intestinal flora. The diagnosis of a putative bacterial enteropathogen(s) in dogs should be made based on a combination of parameters, including signalment and predisposing factors, clinical signs, serologic assays for toxins, fecal culture, and PCR. Relying on results of fecal culture alone is problematic, because C perfringens, C difficile, Campylobacter spp, and pathogenic and non-pathogenic E coli are commonly isolated from apparently healthy dogs [10,13,33]. Nevertheless, culture may be useful in procuring isolates for the application of molecular techniques, such as PCR, for detection of specific toxin genes or molecular typing of isolated strains to establish clonality in suspected outbreaks. The oversimplistic attempt to characterize bacterially associated diarrhea by anatomic localization of clinical signs should be discouraged, because most of the previously mentioned bacteria have been associated with small and large intestinal diarrhea. Accurate diagnosis of infections may require diagnostic laboratories to incorporate PCR-based assays using genus- and species-specific primers to facilitate detection of toxin genes and differentiation of species that appear phenotypically and biochemically similar. There has been tremendous interest in the application of microarray technology for the simultaneous detection of thousands of genes or target DNA sequences on one glass slide. This powerful tool could be used for detection of specific pathogenic bacterial strains in fecal specimens obtained from dogs in the future.  相似文献   
105.
鸭疫里氏杆菌各血清型在我国的分布   总被引:3,自引:1,他引:2  
鸭疫里氏杆菌病(Riemerella anatipestifersis,RA)是家鸭、火鸡、鹅和多种其它鸟类的一种接触性传染病,能引起1~8周龄的鸭发生浆膜炎、心包炎、气囊炎和肝周炎等为特征的急性败血性传染病。我国近年来对该病病原的分离及其血清型的鉴定等方面进行了较多的研究,目前已证实我国有1、2、3、4、5、6、7、8、10、11、13、14、15、17等14种血清型的RA,另新发现4种新血清型(22、23、24、25型),多种血清型的存在是造成该病防制困难的重要原因。本文介绍了我国对RA血清型的研究,及各血清型在我国的分布,以期对综合防制该病有一定的启发和指导。  相似文献   
106.
107.
In summary, peritonitis in the horse is a potentially life-threatening disease that must be treated promptly and aggressively. Therapy should be aimed at reducing systemic shock and hypovolemia, correction of the primary cause, antibiotic and anti-inflammatory therapy, and abdominal drainage and lavage. The prognosis depends on the ability to diagnose and treat the underlying cause and prevent the development of complications. Mortality rates can be as high as 59.7%, with horses developing postoperative peritonitis having a 56% mortality rate. Long-term complications like adhesion formation or internal abscesses may further reduce the survival rate. The prognosis is best determined by an early and quick response to aggressive treatment.  相似文献   
108.
109.
110.
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