全文获取类型
收费全文 | 4215篇 |
免费 | 242篇 |
国内免费 | 428篇 |
专业分类
林业 | 784篇 |
农学 | 290篇 |
基础科学 | 403篇 |
755篇 | |
综合类 | 1937篇 |
农作物 | 84篇 |
水产渔业 | 62篇 |
畜牧兽医 | 196篇 |
园艺 | 252篇 |
植物保护 | 122篇 |
出版年
2024年 | 57篇 |
2023年 | 202篇 |
2022年 | 215篇 |
2021年 | 164篇 |
2020年 | 179篇 |
2019年 | 180篇 |
2018年 | 119篇 |
2017年 | 185篇 |
2016年 | 202篇 |
2015年 | 168篇 |
2014年 | 247篇 |
2013年 | 227篇 |
2012年 | 349篇 |
2011年 | 328篇 |
2010年 | 295篇 |
2009年 | 283篇 |
2008年 | 224篇 |
2007年 | 236篇 |
2006年 | 196篇 |
2005年 | 129篇 |
2004年 | 129篇 |
2003年 | 79篇 |
2002年 | 79篇 |
2001年 | 60篇 |
2000年 | 50篇 |
1999年 | 41篇 |
1998年 | 34篇 |
1997年 | 31篇 |
1996年 | 26篇 |
1995年 | 26篇 |
1994年 | 26篇 |
1993年 | 17篇 |
1992年 | 20篇 |
1991年 | 19篇 |
1990年 | 21篇 |
1989年 | 23篇 |
1988年 | 12篇 |
1987年 | 5篇 |
1986年 | 2篇 |
排序方式: 共有4885条查询结果,搜索用时 62 毫秒
1.
The objective of this study was to determinate grain unique protein inherent molecular structure that are related physiochemical and nutrient profiles in CDC developed oat varieties [CDC Nasser (Feed Type) and CDC Seabiscuit (Milling Type)] grown in cool climate condition in western Canada in comparison with conventional barley variety of CDC Meredith as a control using advanced molecular spectroscopy. Multivariate analyses, including an agglomerative hierarchical cluster analysis (CLA) and principal component analysis (PCA), were performed to identify protein molecular structural differences among the grains. The results revealed that CDC Seabiscuit contained greater (P < 0.05) protein structural Amide I and II than CDC Nasser and CDC Meredith, while the greater (P < 0.005) structural Amide I to II area and height ratios was detected in CDC Meredith. New oat grains had greater (P < 0.05) β-sheet height than barley grains, however, there was no difference in α-helix to β-sheet ratio values among the varieties. In conclusion, CDC Nasser and CDC Meredith had no difference in protein molecular structural features, while CDC Seabiscuit contains different protein structural characteristics as compared to CDC Meredith grain. The molecular structure features are highly associated with physiochemical and nutrient profiles in grains, which indicate that it also affect nutrient utilization and availability. 相似文献
2.
Fa-chao SUN Min TAN Yuan-chao ZHANG Yu-chao WANG Sheng-liang CAO Guo-fei DING Fang-yuan CONG Li-hong GUO Si-dang LIU Yi-hong XIAO 《农业科学学报》2019,18(7):1436-1442
To investigate the epizootic of swine influenza virus(SIV), 60 nasal swabs were collected from a clinical cases of pig farm in Tai'an City, Shandong Province of China in April 2017. SIV was isolated by inoculating into 10-day-old Special Pathogen Free embryonated eggs and the whole genome was sequenced. An H1N1 subtype SIV was isolated and designated as A/swine/Shandong/TA04/2017(H1N1). Phylogenetic analysis showed that apart from the polymerase A(PA) fragment belonging to the 2009 pandemic H1N1 branch, seven genome segments belonged to avian-like H1N1 influenza virus lineage. The cleavage site sequence of the hemagglutinin(HA) protein was PSIQSR↓G, which is a typical molecular biological characteristic. Five potential N-glycosylation sites(N14, N26, N277, N484 and N543) were found in the HA gene. To further investigate the epidemiology of SIV in this farm, the 995 serum samples were assessed with EAH1N1 2009 pandemic H1N1 and H3 N2 antigens. The results showed that the total positive rate was 65.43%. The positive rates of single virus infection detected by EAH1N1, 2009 pdmH1N1 and H3 N2 for serum HI(Hemagglutination inhibition) were 48.35, 30.85 and 7.47%, respectively. The results showed that SIV in Shandong Province has been reassorted in some segments and the SIV-positive rate was high on the SIV outbreak farm. These data provide evidence of an epizootic of SIV. 相似文献
3.
4.
针对矩阵函数求导时产生的情形,提出立体矩阵这一概念,建立起立体矩阵的初步理论知识体系,并总结了立体矩阵的运算的一系列基本性质,构造了实矩阵域,而后考虑了立体矩阵在实数域和矩阵线性空间。 相似文献
5.
张桂 《湖南农业大学学报(自然科学版)》1996,23(5)
讨论了一类与区域分解算法有关的空间分解问题,将二阶问题的已有的空间分解结果推广到四阶问题的相应空间中。还证明了一致重迭性条件与Badea条件的等价性。 相似文献
6.
7.
8.
9.
本文介绍了开发城市地下空间的必然趋势及前景,阐明开发利用城市地下空间,对节省城市用地、节约能源、改善城市交通、减轻城市污染等都有着重要作用。 相似文献
10.
臧浩刚 《河北农业大学学报》1994,17(1):74-78
本文探讨了用计算机计算含未知量元素行列式的方法与途径,提出了“保值回跳”的思想。并提供了以该思想为基础而编制的空间桁架结构位移响应关于截面设计变量显式表达式程序计算的若干算例。 相似文献