全文获取类型
收费全文 | 607篇 |
免费 | 45篇 |
专业分类
林业 | 18篇 |
农学 | 14篇 |
基础科学 | 1篇 |
45篇 | |
综合类 | 116篇 |
农作物 | 8篇 |
水产渔业 | 24篇 |
畜牧兽医 | 393篇 |
园艺 | 14篇 |
植物保护 | 19篇 |
出版年
2021年 | 6篇 |
2019年 | 12篇 |
2018年 | 8篇 |
2017年 | 5篇 |
2016年 | 15篇 |
2015年 | 6篇 |
2014年 | 16篇 |
2013年 | 25篇 |
2012年 | 18篇 |
2011年 | 15篇 |
2010年 | 15篇 |
2009年 | 14篇 |
2008年 | 27篇 |
2007年 | 30篇 |
2006年 | 16篇 |
2005年 | 18篇 |
2004年 | 34篇 |
2003年 | 13篇 |
2002年 | 18篇 |
2001年 | 22篇 |
2000年 | 16篇 |
1999年 | 9篇 |
1998年 | 6篇 |
1997年 | 7篇 |
1994年 | 5篇 |
1992年 | 13篇 |
1991年 | 14篇 |
1990年 | 12篇 |
1989年 | 12篇 |
1988年 | 5篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1985年 | 17篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 12篇 |
1973年 | 11篇 |
1972年 | 5篇 |
1971年 | 7篇 |
1970年 | 6篇 |
1969年 | 4篇 |
1966年 | 4篇 |
1942年 | 4篇 |
1911年 | 4篇 |
排序方式: 共有652条查询结果,搜索用时 18 毫秒
51.
52.
53.
54.
55.
56.
57.
Soil quality and financial performance of biodynamic and conventional farms in new zealand 总被引:3,自引:0,他引:3
Biodynamic farming practices and systems show promise in mitigating some of the detrimental effects of chemical-dependent, conventional agriculture on the environment. The physical, biological, and chemical soil properties and economic profitability of adjacent, commercial biodynamic and conventional farms (16 total) in New Zealand were compared. The biodynamic farms in the study had better soil quality than the neighboring conventional farms and were just as financially viable on a per hectare basis. 相似文献
58.
59.
Curran MA van Ommen TD Morgan VI Phillips KL Palmer AS 《Science (New York, N.Y.)》2003,302(5648):1203-1206
The instrumental record of Antarctic sea ice in recent decades does not reveal a clear signature of warming despite observational evidence from coastal Antarctica. Here we report a significant correlation (P < 0.002) between methanesulphonic acid (MSA) concentrations from a Law Dome ice core and 22 years of satellite-derived sea ice extent (SIE) for the 80 degrees E to 140 degrees E sector. Applying this instrumental calibration to longer term MSA data (1841 to 1995 A.D.) suggests that there has been a 20% decline in SIE since about 1950. The decline is not uniform, showing large cyclical variations, with periods of about 11 years, that confuse trend detection over the relatively short satellite era. 相似文献
60.
Copper porphyrins in deep-sea sediments: a possible indicator of oxidized terrestrial organic matter
Copper porphyrins have been isolated from deep-sea sediments collected during six legs of the Deep Sea Drilling Project-International Program of Ocean Drilling. These pigments are present in depositional areas receiving high inputs of terrestrially derived oxidized organic matter. Such areas include the Black Sea, the Bay of Biscay, the Blake-Bahama Basin, and slumped Miocene deposits off Cape Bojador on the west coast of Africa. 相似文献