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   140069篇
  免费   8110篇
  国内免费   800篇
林业   5894篇
农学   4475篇
基础科学   1053篇
  16805篇
综合类   26165篇
农作物   5344篇
水产渔业   6536篇
畜牧兽医   71914篇
园艺   1834篇
植物保护   8959篇
  2019年   1400篇
  2018年   2047篇
  2017年   2330篇
  2016年   2105篇
  2015年   1953篇
  2014年   2272篇
  2013年   5117篇
  2012年   4268篇
  2011年   5137篇
  2010年   3447篇
  2009年   3343篇
  2008年   4834篇
  2007年   4632篇
  2006年   4203篇
  2005年   4017篇
  2004年   3688篇
  2003年   3867篇
  2002年   3604篇
  2001年   4112篇
  2000年   4134篇
  1999年   3232篇
  1998年   1381篇
  1997年   1356篇
  1995年   1448篇
  1994年   1284篇
  1993年   1266篇
  1992年   2658篇
  1991年   2971篇
  1990年   2886篇
  1989年   2839篇
  1988年   2666篇
  1987年   2672篇
  1986年   2772篇
  1985年   2535篇
  1984年   2214篇
  1983年   1880篇
  1982年   1325篇
  1979年   2005篇
  1978年   1565篇
  1977年   1402篇
  1976年   1383篇
  1975年   1437篇
  1974年   1854篇
  1973年   1858篇
  1972年   1789篇
  1971年   1669篇
  1970年   1634篇
  1969年   1553篇
  1968年   1274篇
  1967年   1412篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Samples of rapeseed from three Italian growing environments (Bologna, Perugia and Palermo) were analysed for glucose content and dry weight of 1000 seeds every three or four days starting from the end of flowering until complete ripening. In addition, the content of oil, soluble and total proteins, glucosinolates and myrosinase activity was determined in samples of mature seeds. The cultivars used were jet Neuf and Lingot (type 0) and Tandem, Jade and Santana (type 00). From the results it emerged that the point of intersection of the two branches of the linear regression plots for different glucose-consumption kinetics found during seed filling, in addition to being strongly affected by the climate of the test environment, is correlated with quantitative and qualitative production, independently of the genotype.  相似文献   
62.
山羊脑灰质软化症 (POLIOEN CEPHALOMALACIA)和李氏杆菌病 (LIS TERIOSIS)是症状相似治疗方法截然不同的两种疾病。山羊饲养者和兽医工作者必须从两种疾病的细微差别中进行鉴别 ,以便正确治疗和处理病羊。多数情况下 ,这两种疾病出现在饲养条件比较好、但饲养方法不当的地方。特别是在快速育肥时。精饲料喂量过多 ,而含粗纤维的饲料喂量过少是诱发两种疾病的重要因素。突然更换饲料常常导致此病突然发作。脑灰质软化症 (通常又称为大脑皮层坏死症 )是缺乏硫胺 (即维生素B1)而造成的一种代谢性疾病。瘤胃环…  相似文献   
63.
64.
65.
66.
67.
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   
68.
1118 Friesian cows and 101 Friesian heifers were investigated in internal pelvic measurements and their relationships to external measurements. The mean of the pelvic vertical and the medium diagonally diameter of the pelvis are 19.8 cm and 18.3 cm. 363.9 square centimetres and 76.3 centimetres were found for the pelvic surface and pelvic circumference. The difference between the biggest and smallest pelvis was 295.0 square centimetres. Medium to high coefficiences of correlation were detected between the internal pelvic measurements but relationships between internal and external pelvic measurements were low. From determined external pelvic measurements only the hip breadth provides usefull informations of the pelvic shape.  相似文献   
69.
A 2-year-old female Japanese domestic cat weighing 3.6 kg was presented due to marked abdominal distention and was diagnosed as hepatic cyst. The bile acid concentration of the hepatic cyst was as low as the serum bile acid concentration. The membrane of the cysts was excised from the edge of the compressed hepatic tissue and no other surgical manipulation was performed. This surgical procedure is simple and quick compared to hepatic lobectomy, however, it is necessary to evaluate the fluid of the cyst before performing this procedure.  相似文献   
70.
Mixed cropping of leguminous underseed species and cereal crops may increase productivity and serve some additional purposes. Two leguminous weed species which are widely distributed in annual crops of the Ethiopian highlands have been studied with varying coverage in greenhouse trials in Ethiopia with regard to their suitability as underseeds and with wheat ( Triticum turgidum [L.] Thell. var. durum [Desf.] MacKey) as a main crop. The competitive effects of Scorpiurus muricatus L. on the grain yield of wheat were smaller than those of Medicago polymorpha L. (-14.1 % and -23.6 % respectively, compared with the underseed free control) which is mainly ascribed to differences in their speed of development and shoot height. The residual effects of the underseed's root masses on the grain yield of the successive teff crop (Eragrostis tef [Zucc] Trotter) were significantly higher with Scorpiurus muricatus (+99.3 %) than with Medicago polymorpha (+63.6 %). The results are discussed with regard to the specific site conditions in the cereal-dominated cropping systems of the Ethiopian highlands.  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