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   81463篇
  免费   4359篇
  国内免费   96篇
林业   3358篇
农学   2121篇
基础科学   479篇
  9069篇
综合类   15796篇
农作物   3265篇
水产渔业   3666篇
畜牧兽医   42639篇
园艺   925篇
植物保护   4600篇
  2019年   773篇
  2018年   1148篇
  2017年   1265篇
  2016年   1117篇
  2015年   943篇
  2014年   1261篇
  2013年   2722篇
  2012年   2234篇
  2011年   2763篇
  2010年   1710篇
  2009年   1806篇
  2008年   2738篇
  2007年   2563篇
  2006年   2458篇
  2005年   2278篇
  2004年   2228篇
  2003年   2282篇
  2002年   2066篇
  2001年   2415篇
  2000年   2469篇
  1999年   1898篇
  1998年   757篇
  1997年   746篇
  1996年   742篇
  1995年   834篇
  1993年   761篇
  1992年   1580篇
  1991年   1771篇
  1990年   1654篇
  1989年   1667篇
  1988年   1485篇
  1987年   1552篇
  1986年   1608篇
  1985年   1566篇
  1984年   1199篇
  1983年   1078篇
  1982年   716篇
  1979年   1157篇
  1978年   910篇
  1977年   765篇
  1975年   787篇
  1974年   1039篇
  1973年   1030篇
  1972年   1046篇
  1971年   995篇
  1970年   990篇
  1969年   906篇
  1968年   813篇
  1967年   807篇
  1966年   739篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
971.
972.
973.
974.
975.
976.
977.
Two field trials were conducted to evaluate the efficacy of a Moraxella bovis bacterin in the control of infectious bovine keratoconjunctivitis. The bacterin did not affect the incidence of infectious bovine keratoconjunctivitis in either trial but did appear to reduce the severity of lesions, treatments required and withdrawals from pasture required in one trial. Possible reasons for the apparently contradictory results are offered. It is suggested that the bacterin may be of some value when used in conjunction with other preventive measures.  相似文献   
978.
Fourteen instances of meningocele-encephalocele in an experimental herd were recorded over a 5-year period. Thirteen of these affected animals were subjected to extensive pedigree analyses. Familial associations were strong, and clearly the meningocele-encephalocele in this herd was under genetic influence. However, additional studies are needed to clarify the mode of inheritance and, perhaps, to identify other factors that might be involved.  相似文献   
979.
Poxvirus infections are common in domestic birds in Germany, but they are rare in birds of prey. Only species of falconidae imported from Arabian or Asian countries have so far tested positive for poxvirus, and, among these, only raptors kept for falconry. As part of a reintroduction programme in the northern county of Mecklenburg-Western Pomerania, which is adjacent to the Baltic Sea, 21 young peregrine falcons were released into the wild; six of them died and one was examined postmortem, its tissues being examined by light and electron microscopy. In addition, an ELISA for fowlpox, pigeonpox and canarypox was applied. No virus could be isolated and propagation in culture failed, but virus particles were detected by electron microscopy in lesions from its skin and tongue.  相似文献   
980.
Young adult heterozygous (carrier) female dogs with X-linked hereditary nephropathy (XLHN) have glomerular proteinuria but are otherwise healthy. Because data regarding dietary influences on the magnitude of proteinuria in dogs with spontaneous glomerular disease are not available, 12 such dogs were studied in a double crossover experiment intended to determine effects of altering dietary protein intake for up to 6 weeks. Dogs were blocked by urine protein : creatinine ratio (UPC) and randomly assigned to receive 2 diets: high protein (34.6% dry matter [DM], HP) or low protein (14.1% DM, LP) fed in HP-LP-HP or LP-HP-LP sequence. Food intake was measured daily, body weight (BW) was measured twice weekly, and UPC, plasma creatinine, blood urea nitrogen, phosphorus, albumin, and protein concentrations were measured at 2-week intervals. Nutrient digestibility was measured during the third treatment period. Diet had a significant effect (P < .0001) on all measured variables except plasma phosphorus (P > .5), but unintended differences in digestibility of protein and energy (P < or = .01) prevented assignment of the diet effect exclusively to protein. Proteinuria was greater (UPC 4.7 +/- 2.2 versus 1.8 +/- 1.1, P < .0001) when the HP diet was fed, but the LP diet did not maintain starting BW or plasma albumin concentration within the normal reference range. Diet greatly affects the magnitude of proteinuria in XLHN carrier females. Dietary protein restriction can reduce proteinuria in dogs with glomerular disease, but BW and blood protein concentrations may not be maintained if the restriction is too severe.  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