全文获取类型
收费全文 | 16513篇 |
免费 | 4篇 |
专业分类
林业 | 3624篇 |
农学 | 1304篇 |
基础科学 | 137篇 |
2755篇 | |
综合类 | 720篇 |
农作物 | 2101篇 |
水产渔业 | 1788篇 |
畜牧兽医 | 1080篇 |
园艺 | 1110篇 |
植物保护 | 1898篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 2746篇 |
2017年 | 2703篇 |
2016年 | 1182篇 |
2015年 | 66篇 |
2014年 | 22篇 |
2013年 | 12篇 |
2012年 | 791篇 |
2011年 | 2132篇 |
2010年 | 2102篇 |
2009年 | 1252篇 |
2008年 | 1321篇 |
2007年 | 1584篇 |
2006年 | 34篇 |
2005年 | 100篇 |
2004年 | 107篇 |
2003年 | 155篇 |
2002年 | 70篇 |
2001年 | 6篇 |
2000年 | 41篇 |
1999年 | 2篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 14篇 |
1992年 | 10篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 6篇 |
1988年 | 12篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1977年 | 4篇 |
1972年 | 2篇 |
1969年 | 1篇 |
1968年 | 4篇 |
1967年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Aki Namba Yuya Shigenobu Masahiro Kobayashi Takanori Kobayashi Ichiro Oohara 《Fisheries Science》2010,76(5):873-878
To construct high-quality 16S rDNA clone libraries for microbial communities associated with Porphyra yezoensis and to minimize the detection of rDNA from leafy gametophytes of P. yezoensis, we designed a new 16S rDNA universal primer (75F). Of the clones prepared using 75F, which was designed to distinguish between
bacteria and P. yezoensis, 95% were classified into four groups, namely, β-proteobacteria, γ-proteobacteria, Lentisphaerae, and Flavobacteria. PCR-based analysis of the 16S rDNA primer constructed in this study can be used to implement 16S rDNA-based methodologies
for the investigation of microbial community composition and diversity related to the Porphyra group. 相似文献
22.
23.
Huimin Yang Murray Unkovich Ann McNeill Xianzhi Wang 《Biology and Fertility of Soils》2011,47(4):377-385
Symbiotic N2 fixation by lucerne (Medicago sativa) has capacity to provide significant inputs of N to agro-ecosystems, and the species has also been shown to scavenge soil
mineral N and thus act as a sink for excess reactive N. The balance between these two N cycle processes was investigated in
an extensive irrigated lucerne growing region where nitrate contamination of groundwater has been reported. We sampled 18
permanent pure lucerne stands under irrigation for standing dry matter, total shoot N, and N2 fixation using 15N natural abundance along with activity of the inducible enzyme nitrate reductase as indicators of use of soil NO3− by lucerne. On average 65% of lucerne N was obtained from symbiotic N2 fixation. Converting standing dry matter estimates to annual N2 fixation amounts we calculated average N2 fixation of 311 kg N/ha, including N in roots and nodules. Uptake of N from soil by lucerne was calculated to be 181 kg N/ha/year.
We were not able to identify the source of this soil mineral N, although nitrate reductase activity of lucerne was higher
than that of non-N2 fixing species examined. 相似文献
24.
25.
26.
27.
28.
29.
30.