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   84173篇
  免费   4641篇
  国内免费   317篇
林业   4005篇
农学   2822篇
基础科学   520篇
  10712篇
综合类   15024篇
农作物   3285篇
水产渔业   3883篇
畜牧兽医   42435篇
园艺   970篇
植物保护   5475篇
  2019年   857篇
  2018年   1409篇
  2017年   1499篇
  2016年   1343篇
  2015年   1170篇
  2014年   1444篇
  2013年   3373篇
  2012年   2586篇
  2011年   2976篇
  2010年   1994篇
  2009年   2097篇
  2008年   2907篇
  2007年   2781篇
  2006年   2604篇
  2005年   2360篇
  2004年   2257篇
  2003年   2239篇
  2002年   2052篇
  2001年   2585篇
  2000年   2533篇
  1999年   2012篇
  1998年   802篇
  1997年   844篇
  1996年   778篇
  1995年   861篇
  1994年   776篇
  1993年   735篇
  1992年   1490篇
  1991年   1621篇
  1990年   1503篇
  1989年   1542篇
  1988年   1439篇
  1987年   1434篇
  1986年   1463篇
  1985年   1410篇
  1984年   1123篇
  1983年   1014篇
  1979年   1145篇
  1978年   920篇
  1977年   789篇
  1976年   785篇
  1975年   857篇
  1974年   1099篇
  1973年   1032篇
  1972年   1065篇
  1971年   961篇
  1970年   931篇
  1969年   942篇
  1968年   773篇
  1967年   828篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
152.
153.
The effect of a novel lairage environment on the ability of sheep to recover from 16 h of transport was investigated. Sheep were transported from grass paddocks to either novel outside paddocks or inside pens, and housed groups were transported to either familiar or novel inside pens. During transport, sheep from outside paddocks lay down less than those from inside pens. In sheep transported to inside pens, those from outside paddocks spent more time lying and spent less time eating; hay and water intakes during the first 12 h post-transport were lower than those previously kept inside. There was no obvious effect of a novel environment post-transport on blood biochemistry, suggesting that the lower post-transport feed and water intakes in a novel environment did not have a significant effect on the ability of the sheep to recover from the feed and water deprivation associated with transport.  相似文献   
154.
155.
156.
The objective of this study was to investigate epidemiological risk factors for porcine non-specific colitis (NSC). Forty-seven Scottish pig farms, with and without a clinical history of diarrhoea during the growing period (15-40 kg), were selected. The study included farm visits, clinical inspection of pigs, completion of farm management questionnaires, pathological tests into the cause of the diarrhoea and analysis of the non-starch polysaccharide (NSP) content of feeds. The results from 17 farms designated as NSC and 10 control farms suggest dietary associations with NSC. Farms with NSC fed diets with significantly higher levels of NSPs, especially containing the sugars glucose, arabinose and xylose. Few management factors were identified, although the high prevalence of infectious colitis reduced the power of the study.  相似文献   
157.
Sequential leaching experiments were performed to evaluate the effects of humic acid (HA) and pH on SO4 retention and release in a Swedish podzolic B-horizon. Results showed that the presence of HA reduced SO4 retention and that HA was released when SO4 was retained. Increasing HA concentration increased the rate of SO4 release. The ability of HA to compete with SO4 increased with pH. More than 40% of total sorbed SO4 was irreversibly retained.  相似文献   
158.
Equine proliferative enteropathy (EPE) is a disease of foals caused by the obligate intracellular organism Lawsonia intracellularis. This emerging disease affects mainly weanling foals and causes fever, lethargy, peripheral oedema, diarrhoea, colic and weight loss. The diagnosis of EPE may be challenging and relies on the presence of hypoproteinaemia, thickening of segments of the small intestinal wall observed upon abdominal ultrasonography, positive serology and molecular detection of L. intracellularis in faeces. Although the clinical entity, diagnostic approach and treatment of EPE are well established and described, the epidemiology for this disease has remained largely unaddressed. This article focuses on new developments in the field of EPE, including epidemiology, pathophysiology, clinical signs, diagnosis, treatment and prevention. The Summary is available in Chinese – see Supporting information.  相似文献   
159.
160.
Veterinary pharmacovigilance, as it operates in the European Union (EU), covers a very broad remit, including adverse effects in treated animals, exposed humans and the environment, and in addition, it extends to cover the violation of maximum residue limits. The mainstay of veterinary pharmacovigilance is the spontaneous reporting scheme working along side other systems such as those reporting on residues surveillance. One of the most well established schemes in the EU is that operating in the UK and this paper examines the evolution of that scheme and some of its findings, data from other countries, and information available from the literature. It also tentatively examines the ways that pharmacovigilance can be used for regulatory purposes, and the contribution from pharmacoepidemiology.  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