全文获取类型
| 收费全文 | 832篇 |
| 免费 | 71篇 |
| 国内免费 | 55篇 |
专业分类
| 林业 | 164篇 |
| 农学 | 96篇 |
| 基础科学 | 50篇 |
| 53篇 | |
| 综合类 | 327篇 |
| 农作物 | 12篇 |
| 水产渔业 | 87篇 |
| 畜牧兽医 | 137篇 |
| 园艺 | 15篇 |
| 植物保护 | 17篇 |
出版年
| 2024年 | 4篇 |
| 2023年 | 19篇 |
| 2022年 | 16篇 |
| 2021年 | 26篇 |
| 2020年 | 23篇 |
| 2019年 | 22篇 |
| 2018年 | 24篇 |
| 2017年 | 35篇 |
| 2016年 | 39篇 |
| 2015年 | 40篇 |
| 2014年 | 52篇 |
| 2013年 | 58篇 |
| 2012年 | 61篇 |
| 2011年 | 61篇 |
| 2010年 | 54篇 |
| 2009年 | 39篇 |
| 2008年 | 53篇 |
| 2007年 | 38篇 |
| 2006年 | 50篇 |
| 2005年 | 30篇 |
| 2004年 | 27篇 |
| 2003年 | 24篇 |
| 2002年 | 18篇 |
| 2001年 | 37篇 |
| 2000年 | 19篇 |
| 1999年 | 15篇 |
| 1998年 | 12篇 |
| 1997年 | 16篇 |
| 1996年 | 6篇 |
| 1995年 | 5篇 |
| 1994年 | 3篇 |
| 1993年 | 10篇 |
| 1992年 | 3篇 |
| 1991年 | 6篇 |
| 1990年 | 4篇 |
| 1989年 | 4篇 |
| 1988年 | 3篇 |
| 1987年 | 1篇 |
| 1978年 | 1篇 |
排序方式： 共有958条查询结果，搜索用时 390 毫秒
11.
Josiane C. Panisson Nathália C. Oliveira Cristina M. Sá-Fortes Adsos A. Passos Claudia C. da Silva Wagner A. G. Araújo Idael M. G. Lopes Gleison M. S. Costa Iara Q. Ataíde Bruno A. N. Silva 《Animal Science Journal》2021,92(1):e13592
Improvements in sow productivity have raised questions regarding dietary vitamin D recommendations. The present study aimed to evaluate the effects of the housing system with access to sunlight exposure and supplementation of 25-hydroxicholecalciferol on performance and serum levels of 25(OH)D3 in sows during gestation and lactation. Sows were distributed in an experimental design with two housing systems: gestation crates or gestation free-range system with external area for sunlight exposure; and two diets: 0 or 50 μg of 25-hydroxicholecalciferol kg−1. The use of 25-hydroxicholecalciferol tended (P = 0.052) to improve total born and influenced (P = 0.046) on number of born alive. Litter weight at birth was also increased (P = 0.01) by 25-hydroxicholecalciferol supplementation; 25-hydroxicholecalciferol supplementation and housing system (free-range with sunlight exposure) tended to increase weaning weight (P = 0.07) and litter daily gain (P = 0.051) during lactation. Exposure to sunlight and 25-hydroxicholecalciferol supplementation increased 25(OH)D3 serum levels when compared with control treatment during gestation (136.95 vs. 113.92 ng mL−1; P = 0.035) and lactation (120.29 vs. 88.93 ng mL−1; P = 0.026). In conclusion, the association of 25-hydroxicholecalciferol supplementation with exposure to sunlight during gestation improved significantly 25(OH)D3 serum levels and consequently performance traits in gestation and lactation. 相似文献
12.
Housing industry is a prop industry with great potential, but it is restricted by shortage of funds. So it is necessary to probe the financing system of housing industrialization in China. This paper puts forward a financing plan for the international cooperative project in industrialized housing in Chongqing. Furthermore, it investigates the concrete financing system of the whole housing industry. 相似文献
13.
FU Hong yuan 《保鲜与加工》2001,(3):67-71
This article studies the opportunities and challenges in housing industry in China and proposes its development tendency. 相似文献
15.
With the strengthening of constitutional protection that legal private property is not to be encroached upon and the land usufructs paid regime are further clear, the regime of urban housing dismantling and moving is facing a vigorous test. This paper analyzes three problems: the justice of the withdrawal of land use right, the legality of the alteration of the land use right and the rationality of the compensation of the land use right during the urban housing dismantling and moving. Finally, this paper tries to find some effective measures to solve the chain problems. 相似文献
16.
17.
Based on the Modigliani's Life-Cycle Hypothesis of consumption,and relevant data,the paper empirically studies stock market and real estate market wealth effect in China by using the method of unit root test and cointegrating regression.The results show that,regardless of short-run effect and long-run effect,the stock market wealth has significantly negative effect on civil' consumption level,but real estate market wealth or housing market wealth has significantly positive effect on civil' consumption level. 相似文献
18.
我国畜禽舍机械式降温系统的研究与发展现状 总被引：2，自引：0，他引：2
论述了我国畜禽舍机械式降温系统的研究与应用现状;比较分析了各种降温系统的优缺点与应用条件;考虑到设备投资与应用成本,认为采用正压送风的湿帘冷风机具有较大的应用潜力,集中式雾化降温系统和喷雾冷风机具有一定的优势;同时,指出了喷雾降温系统的研究重点是开发低成本的设备和完善适用于低压喷雾的集中式雾化降温系统的水雾分离装置. 相似文献
19.
基于有限元方法的载货汽车驱动桥壳分析 总被引：3，自引：0，他引：3
对载货汽车驱动桥壳进行了强度计算和有限元模拟分析,得出了零件的应力和变形分布,验证了设计的合理性,为汽车驱动桥的强度评价及疲劳寿命估算提供了相关数据。 相似文献
20.
准确提取单木树冠边界是获取森林数量参数的重要基础,是高分辨率遥感图像林业应用的技术难题。基于DOM航空影像数据源,采用面向对象的方法对研究区内的2个树种的林分进行了单木树冠边界提取研究。首先利用桉树和杉木的空间分布矢量数据对DOM航空影像进行掩膜处理,在掩膜区域内进行多层次多尺度图像分割得到初步树冠分割结果,并剔除非树冠信息;再以树冠信息种子对象为基础,使用区域增长算法对树冠信息种子对象增长得到单木树冠范围;最后使用形态学滤波的方法优化单木树冠边界,完成林区内桉树和杉木两类树种的单木树冠边界提取。结果表明,由于不同树种的树冠存在尺度和形态差异,进行单木树冠分割时需要设置不同的参数才能到达较好的分割效果。本研究中桉树和杉木的单木树冠提取总体精度分别为86.75%与89.21%,可满足林业部门获取森林单木树冠的精度需求。 相似文献