全文获取类型
收费全文 | 16062篇 |
免费 | 4004篇 |
国内免费 | 802篇 |
专业分类
林业 | 859篇 |
农学 | 1255篇 |
基础科学 | 488篇 |
2642篇 | |
综合类 | 3718篇 |
农作物 | 875篇 |
水产渔业 | 3034篇 |
畜牧兽医 | 5855篇 |
园艺 | 480篇 |
植物保护 | 1662篇 |
出版年
2024年 | 43篇 |
2023年 | 114篇 |
2022年 | 327篇 |
2021年 | 492篇 |
2020年 | 781篇 |
2019年 | 1331篇 |
2018年 | 1151篇 |
2017年 | 1280篇 |
2016年 | 1234篇 |
2015年 | 1225篇 |
2014年 | 1226篇 |
2013年 | 1548篇 |
2012年 | 1169篇 |
2011年 | 1203篇 |
2010年 | 1238篇 |
2009年 | 851篇 |
2008年 | 834篇 |
2007年 | 653篇 |
2006年 | 578篇 |
2005年 | 495篇 |
2004年 | 404篇 |
2003年 | 346篇 |
2002年 | 413篇 |
2001年 | 316篇 |
2000年 | 330篇 |
1999年 | 143篇 |
1998年 | 82篇 |
1997年 | 97篇 |
1996年 | 73篇 |
1995年 | 66篇 |
1994年 | 56篇 |
1993年 | 52篇 |
1992年 | 52篇 |
1991年 | 51篇 |
1990年 | 54篇 |
1989年 | 44篇 |
1988年 | 30篇 |
1987年 | 32篇 |
1986年 | 35篇 |
1985年 | 31篇 |
1984年 | 23篇 |
1983年 | 23篇 |
1979年 | 22篇 |
1978年 | 17篇 |
1977年 | 24篇 |
1974年 | 19篇 |
1973年 | 25篇 |
1972年 | 18篇 |
1970年 | 22篇 |
1969年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Compatibility of root growth and tuber production of potato cultivars with dynamic and static water‐saving irrigation managements 下载免费PDF全文
S. H. Ahmadi M. Agharezaee A. A. Kamgar‐Haghighi A. R. Sepaskhah 《Soil Use and Management》2017,33(1):106-119
The important root characteristics of root length density (RLD) and root mass density (RMD) generally differ among irrigation managements and potato cultivars. The objective of this study was to investigate the RLD and RMD variations and their functional relationships with gross potato tuber yield for two commercial potato cultivars, Agria and Sante, under different irrigation strategies. Full irrigation and water‐saving irrigation strategies, deficit and partial root drying irrigations, were applied statically (S) and dynamically (D) based on daily crop evapotranspiration. Results showed that SPRD had significantly greater RLD (3.64 cm/cm3) and RMD (132.7 μg/cm3) than other irrigation treatments. Between the potato cultivars, Agria had significantly larger values of RLD (3.50 cm/cm3) and RMD (138.7 μg/cm3) than Sante. The functional relationship between the root growth characteristics and tuber yield showed that under water‐saving irrigations, Agria increased root mass at the expense of gross tuber yield but Sante increased root mass to maintain larger gross tuber yields. However, Agria produced more roots and gross tuber yield than Sante, and it is concluded that Agria is a more drought‐tolerant potato cultivar, which is recommended for tuber production in regions where water might be scarce. It was shown that larger root production in potatoes was associated with improved tolerance to water stress. 相似文献
3.
云南怒江傈僳族自治州古树名木资源现状调查 总被引:1,自引:0,他引:1
对怒江傈僳族自治州人为活动区域古树名木资源现状进行调查。结果表明:共记录到古树名木496株,涉及36科54属76种,其中有8种国家重点保护野生植物,分别为澜沧黄杉、秃杉、南方红豆杉、云南榧树、千果榄仁、红椿、光叶珙桐和香果树;怒江州古树名木主要分布在乡村街道及远郊野外,占总数的98.8%,63.6%的古树生长在海拔1500~1999 m;古树名木的生长环境及长势总体较好,但保护力度相对薄弱,应采取相关措施加强保护和管理。 相似文献
4.
The prognosis of liver cancer was inferior among tumors. New medicine treatments are urgently needed. In this study, a novel exopolysaccharide EPS364 was purified from Vibrio alginolyticus 364, which was isolated from a deep-sea cold seep of the South China Sea. Further research showed that EPS364 consisted of mannose, glucosamine, gluconic acid, galactosamine and arabinose with a molar ratio of 5:9:3.4:0.5:0.8. The relative molecular weight of EPS364 was 14.8 kDa. Our results further revealed that EPS364 was a β-linked and phosphorylated polysaccharide. Notably, EPS364 exhibited a significant antitumor activity, with inducing apoptosis, dissipation of the mitochondrial membrane potential (MMP) and generation of reactive oxygen species (ROS) in Huh7.5 liver cancer cells. Proteomic and quantitative real-time PCR analyses indicated that EPS364 inhibited cancer cell growth and adhesion via targeting the FGF19-FGFR4 signaling pathway. These findings suggest that EPS364 is a promising antitumor agent for pharmacotherapy. 相似文献
5.
Kim Birnie‐Gauvin Lasse Birch Hjrup Theis Kragh Lene Jacobsen Kim Aarestrup 《Ecology of Freshwater Fish》2019,28(3):376-384
Pike (Esox lucius) occupy coastal streams and rivers of the Baltic Sea, where they attain large sizes (>5 kg). These large sizes are perhaps due to the fact that they can tolerate relatively high salinities and can thus forage in the nearby more productive brackish environments. In an attempt to quantify the extent to which pike utilise brackish environments, and to provide some insight into the underlying causes for brackish water migrations, we tagged 30 pike from a western Baltic river with acoustic transmitters and were able to track 21 individuals for 1 year. Based on experienced from local anglers, this population was assumed to be brackish in nature, where individuals underwent freshwater migrations to spawn. Our findings however suggest that the smallest and most active individuals make short exits into brackish waters and do so on rare occasions. Our results further indicate that neither sex nor size is related to activity level. We suggest that these patterns reflect two distinct behaviours—active and passive—and that large pike can be supported by the food availability in the river, without the need to venture into coastal zones, thus defying the conventional view that Baltic pike are all brackish in nature. 相似文献
6.
7.
8.
水霉属菌(Saprolegnia)分离培养技术研究 总被引:1,自引:0,他引:1
对水霉(Saprolegnia)的分离培养技术进行了探索,筛选出大麻籽、油菜籽、红花籽、苍蝇、蚜虫、小麦粒、玉米片、茶叶、葵花仁9种材料作为诱发水霉菌的诱饵。其中油菜籽能防止腐霉菌(Pythium)污染,是初步纯化菌种、排除杂菌的适宜饵料。同时发现控制温度能使水霉在最短时间内分别产生无性或有性繁殖。在水培条件下,25℃左右适合菌丝及无性器官的发育,有性器官却不能产生,而只有在15~17℃条件下才能使水霉很快进入有性生殖阶段;在加入200mg/L链霉素的CMA培养基上促发有性阶段则需要在25℃左右的温度下进行,方能缩短培养时间。 相似文献
9.
10.