全文获取类型
收费全文 | 136822篇 |
免费 | 7142篇 |
国内免费 | 81篇 |
专业分类
林业 | 6337篇 |
农学 | 4316篇 |
基础科学 | 784篇 |
15378篇 | |
综合类 | 25424篇 |
农作物 | 5334篇 |
水产渔业 | 6367篇 |
畜牧兽医 | 69760篇 |
园艺 | 1613篇 |
植物保护 | 8732篇 |
出版年
2018年 | 1650篇 |
2017年 | 1806篇 |
2016年 | 1708篇 |
2015年 | 1484篇 |
2014年 | 1820篇 |
2013年 | 4830篇 |
2012年 | 3272篇 |
2011年 | 3947篇 |
2010年 | 2649篇 |
2009年 | 2604篇 |
2008年 | 3963篇 |
2007年 | 3903篇 |
2006年 | 3600篇 |
2005年 | 3450篇 |
2004年 | 3289篇 |
2003年 | 3442篇 |
2002年 | 3185篇 |
2001年 | 3997篇 |
2000年 | 3981篇 |
1999年 | 3243篇 |
1998年 | 1318篇 |
1997年 | 1338篇 |
1995年 | 1514篇 |
1994年 | 1260篇 |
1993年 | 1306篇 |
1992年 | 2711篇 |
1991年 | 2879篇 |
1990年 | 2962篇 |
1989年 | 2947篇 |
1988年 | 2714篇 |
1987年 | 2658篇 |
1986年 | 2767篇 |
1985年 | 2670篇 |
1984年 | 2292篇 |
1983年 | 2023篇 |
1982年 | 1390篇 |
1979年 | 2191篇 |
1978年 | 1705篇 |
1977年 | 1543篇 |
1976年 | 1482篇 |
1975年 | 1609篇 |
1974年 | 2027篇 |
1973年 | 2070篇 |
1972年 | 2069篇 |
1971年 | 1923篇 |
1970年 | 1858篇 |
1969年 | 1750篇 |
1968年 | 1499篇 |
1967年 | 1605篇 |
1966年 | 1403篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
R. Iori O. Leoni L. Lazzeri G. Mosca S. Palmieri 《Journal of Agronomy and Crop Science》1991,167(2):91-95
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
92.
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
93.
AM Mwanza A Madej H Kindahl N Lundeheim & S Einarsson 《Reproduction in domestic animals》2001,36(3-4):157-161
The effects of lipopolysaccharide ( Escherichia coli , O55:B5), administered 18 h after ovulation in the second oestrus after weaning on the hormonal profiles in 14 Swedish cross-bred (Landrace × Yorkshire) multiparous sows were studied. The endotoxin group (E-group) sows were administered with 300 ng/kg of lipopolysaccharide (LPS) whereas the control group (C-group) sows were administered 5 ml of saline intravenously via an indwelling jugular cannula. Blood samples for hormonal analyses were collected from all sows until slaughter. In the E-group, progesterone, cortisol and prostaglandin F2α metabolite levels increased significantly (p < 0.05) following LPS compared with the C-group. It can be concluded from this study that apart from elevating cortisol and prostaglandin F2α metabolite, LPS also elevates progesterone levels. 相似文献
94.
95.
96.
97.
98.
99.
100.
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