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   148064篇
  免费   8383篇
  国内免费   132篇
林业   5705篇
农学   4347篇
基础科学   901篇
  16870篇
综合类   28555篇
农作物   5971篇
水产渔业   6919篇
畜牧兽医   76497篇
园艺   1784篇
植物保护   9030篇
  2019年   1359篇
  2018年   1993篇
  2017年   2282篇
  2016年   2039篇
  2015年   1792篇
  2014年   2247篇
  2013年   5449篇
  2012年   4086篇
  2011年   4961篇
  2010年   3205篇
  2009年   3270篇
  2008年   4843篇
  2007年   4607篇
  2006年   4407篇
  2005年   4109篇
  2004年   3948篇
  2003年   4010篇
  2002年   3749篇
  2001年   4567篇
  2000年   4540篇
  1999年   3636篇
  1998年   1499篇
  1997年   1441篇
  1996年   1350篇
  1995年   1570篇
  1994年   1407篇
  1993年   1440篇
  1992年   2974篇
  1991年   3162篇
  1990年   3025篇
  1989年   3061篇
  1988年   2704篇
  1987年   2835篇
  1986年   2942篇
  1985年   2850篇
  1984年   2247篇
  1983年   2031篇
  1982年   1431篇
  1979年   2070篇
  1978年   1639篇
  1977年   1407篇
  1975年   1437篇
  1974年   1832篇
  1973年   1862篇
  1972年   1843篇
  1971年   1767篇
  1970年   1700篇
  1969年   1552篇
  1968年   1299篇
  1967年   1348篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
982.
1. The amino acid composition of the whole body protein of 28‐ and 56‐d‐old turkeys is reported.

2. There were some differences between the two ages; these could largely be reconciled by considering the likely differences in the proportion of feather protein.

3. The results were compared with similar values for the chicken and goose; overall there is a striking similarity, both in absolute concentrations and relative proportions of amino acids.  相似文献   

983.
Book reviews     
Research and Development in Relation to Farm Animal Welfare, contributions by B. A. Baldwin, J. R. Bareham, I. J. H. Duncan, R. Ewbank, D. C. Hardwick and K. Vestergaard, Animal Management, 11, Series Edited by D. W. Fölsch. Birkhauser Verlag, Basel, 1981. ISBN‐3–7643–1241–6.

First European Symposium on Poultry Welfare. Edited by L. Yding S0RENSEN. Published by the Danish Branch of World's Poultry Science Association. 1981. 238pp. D.Kr.90. ISBN 87–88162–00–1.  相似文献   

984.
1. The relationship between plasma triglyceride concentrations and body fat content was examined in three groups of male and one of female broiler chickens fed ad libitum on a normal growing diet.

2. Phenotypic correlations between total plasma triglyceride concentration and fat content were + 0.50, + 0.37 and + 0.39 for the three groups of male broilers and +0.33 for the group of females. Triglyceride content of plasma very low density lipoprotein (VLDL) plus low density lipoprotein (LDL) showed similar correlations with fat content.

3. Selection of birds from a flock of 550 male broilers on the basis of high or low plasma VLDL plus LDL triglyceride concentrations produced groups with significant differences in body fat content but little difference in body weight.

4. The results suggest that measurements of plasma triglyceride concentration could be used as an indirect means of selecting for decreased body fat content in broiler breeding programmes.  相似文献   

985.
Light microscope observations on oat cells in the ovine pneumonia-pleurisy complex are presented. This study is based on the experimental production of the disease by viruses and Pasteurella haemolytica. Oat cells appeared only in necrotic lesions associated with large numbers of P. haemolytica in the pneumonic lung. It is suggested that oat cells originate from blood monocytes, which transform into the oat shape when developing in the necrotic, hypoxic environment created by P. haemolytica. They were not, however, observed to be phagocytic. Oat cells are characteristic of pneumonic pasteurellosis but are not pathognomonic because they can also be found in extrapulmonary locations and in other pathological conditions of the lungs.  相似文献   
986.
987.
An 18-month old Friesian heifer which had lost condition and had diarrhoea for several weeks was diagnosed by haematological and pathological examinations as having lymphocytic leukaemia. True lymphatic leukaemia has not previously been described in cattle and does not readily fit into presently accepted classifications of bovine leukosis.  相似文献   
988.
An examination was made of the relationship in Romney sheep between selenium deficiency and (i) the state of the liver drug metabolising enzyme system, (ii) subclinical liver damage, (iii) susceptibility to facial eczema, and (iv) susceptibility to ryegrasss staggers. The microsomal electron transport detoxifying enzymes based on cytochrome P-450 were unaffected by Se deficiency, suggesting that these enzymes are uninduced on ryegrass/clover pastures. Selenium deficiency had no effect on sporidesmin-induced liver damage, which makes it unlikely that peroxidative events countered by Se-dependent glutathione peroxidase (E.C.1.11.10) have a major role in the mechanism of sporidesmin toxicity. Selenium deficiency did appear to suppress the development of photosensitisation. There was no major effect on ryegrass staggers and no deficiency-induced subclinical liver damage.  相似文献   
989.
Subsequent to a cross-sectional serological survey of Manawatu dairy farm workers, a case-control study was carried out to investigate the correlation between titres to leptospiral serovars in workers and those in cattle in their herds. A total of 52 herds was investigated, 25 of which were high risk where milkers had titres of 1:96 or greater, and 27 were case-controls where milkers had no detectable agglutinin titres at a minimum serum dilution of 1:24. The serological prevalence of titres to hardjo in cattle on high risk farms (76.5%) was significantly higher (P<0.05) than on the case-control farms (60.0%). The geometric mean titres of seropositive cattle on high risk farms were also significantly higher (P<0.01) than in the cattle from the case-control farms, especially in the younger cohorts. These findings suggest that there was active endemic hardjo infection in the two- to three-year-old cattle on the high risk farms. Titres to pomona were demonstrated in only 5.2% of the cattle from both types of farm. Workers with titres to pomona tended to be from farms on which stock, especially calves, were bought-in and pigs were kept. Conventional measures for protecting milkers from contact with infected urine appeared to be ineffective and it is concluded that prevention of leptospirosis in dairy farm workers can only be achieved by elimination of infection in the herd by vaccination of cattle.  相似文献   
990.
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