全文获取类型
收费全文 | 1956篇 |
免费 | 105篇 |
国内免费 | 83篇 |
专业分类
林业 | 798篇 |
农学 | 81篇 |
基础科学 | 23篇 |
32篇 | |
综合类 | 721篇 |
农作物 | 89篇 |
水产渔业 | 54篇 |
畜牧兽医 | 202篇 |
园艺 | 114篇 |
植物保护 | 30篇 |
出版年
2024年 | 1篇 |
2023年 | 13篇 |
2022年 | 31篇 |
2021年 | 36篇 |
2020年 | 38篇 |
2019年 | 10篇 |
2018年 | 12篇 |
2017年 | 42篇 |
2016年 | 54篇 |
2015年 | 51篇 |
2014年 | 96篇 |
2013年 | 79篇 |
2012年 | 160篇 |
2011年 | 156篇 |
2010年 | 152篇 |
2009年 | 103篇 |
2008年 | 97篇 |
2007年 | 133篇 |
2006年 | 137篇 |
2005年 | 101篇 |
2004年 | 109篇 |
2003年 | 94篇 |
2002年 | 64篇 |
2001年 | 49篇 |
2000年 | 57篇 |
1999年 | 42篇 |
1998年 | 29篇 |
1997年 | 31篇 |
1996年 | 27篇 |
1995年 | 37篇 |
1994年 | 25篇 |
1993年 | 20篇 |
1992年 | 18篇 |
1991年 | 18篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1985年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有2144条查询结果,搜索用时 15 毫秒
1.
通过引进不同品种羽扇豆,进行茶园套种,观察并测定羽扇豆的成活率、株高、冠幅、开花率、结果率。结果表明,羽扇豆的成活率为83%,羽扇豆平均株高为45.8厘米,最高达78.5厘米,最低仅38厘米。羽扇豆平均冠幅为32厘米×22厘米,冠幅最高达38厘米×36厘米,最低仅22厘米×18厘米。开花率96%,结果率82%。说明,羽扇豆在安庆市桐城市西部黄甲镇能够成活并生长,羽扇豆可在大别山低海拔区域进行露地栽培。 相似文献
2.
青岛地区竹种质资源异地保存及生长监测 总被引:2,自引:2,他引:0
中国竹种质资源大多分布在长江以南地区,在黄河流域中原地区分布的为数不多的竹种资源就显得弥足珍贵,因而加快中原地区竹种质资源的收集保存工作迫在眉睫。文章选择在中原地区(河南省博爱县)生长较好的16个竹种,将其引种至青岛市即墨区集中保存。结果表明:16个竹种在引种地总体生长效果较好,新生竹平均胸径和新竹数量总体呈增长趋势;散生竹和铺地竹的抗寒性较丛生竹好;极寒气候对竹子地上部分秆叶的影响远大于对地下部分竹鞭的影响。此次引种取得的经验可为下一步更多竹种的异地保存提供借鉴。 相似文献
3.
猕猴桃果实风味独特,富含维生素C,享有“水果之王”的美称,近年来发展迅速。江苏省气候适合猕猴桃的生长,栽培面积逐年增加,本文对四个猕猴桃优良品种‘青皮红香’、‘早鲜’、‘翠香’和‘晚红’在南京地区的引种栽培表现进行了观测。四个猕猴桃品种果实各具特点,且与其他地区的表现有所差异,‘青皮红香’果皮无毛,红肉,但在南京果肉为绿色,其他果皮品质也不佳;‘早鲜’成熟早,在南京8月中旬即可成熟,耐贮藏,果实重量达到91.03 g,且维生素C含量较高,为82.13 mg/100g,但口味偏酸;‘翠香’果皮易剥落,果肉翠绿,可溶性糖含量(9.56%)和糖酸比(8.25)较高,口味佳;‘晚红’果肉绿,果心周围具红色,可溶性固形物含量高达19.11,但果实较小,为62.92 g。 相似文献
4.
5.
6.
Assessing vulnerability of New Zealand lakes to loss of conservation value from invasive fish impacts 下载免费PDF全文
- Predictions of invasion risk for seven non‐indigenous fish species, ecological impact scores for individual species, and lake conservation rankings were linked to develop Invasion Risk Impact (IRI) and Lake Vulnerability (LV) indices that help identify New Zealand lakes most at risk of loss of conservation value from potential multi‐species invasions.
- Species‐specific IRI scores (the product of predicted invasion risk and species impact) highlighted Eurasian perch (Perca fluviatilis) and the brown bullhead (Ameiurus nebulosus), as the species most likely to spread and cause ecological harm in lakes. For 3431 lakes >1 ha throughout New Zealand, total IRI tended to be highest for lowland riverine and dune lakes most of which are already colonized by multiple invasive fish species.
- The LV index indicated that lakes most at risk of loss of conservation value from invasive fish impacts were predominantly (i) in the northern half of the North Island where several uncommon lake types occur, and (ii) along the west coast of the South Island where conservation value is often greater, largely because of low catchment modification.
- The IRI and LV indices can be used to assist with setting priorities for surveillance monitoring, advocacy, and response planning targeted at preventing the establishment of invasive fish in moderate‐to‐high value lakes most susceptible to ecological impacts. Both indices can be adapted to accommodate alternative impact and conservation scoring systems, providing a flexible tool for local‐ and national‐scale assessments of lake vulnerability to fish invasion impacts.
7.
- Few reports exist that describe marine non‐native species in the Southern Ocean and near‐shore waters around the Antarctic continent. Nevertheless, Antarctica's isolated marine communities, which show high levels of endemism, may be vulnerable to invasion by anthropogenically introduced species from outside Antarctica via vessel hull biofouling.
- Hull surveys of the British Antarctic Survey's RRS James Clark Ross were undertaken between 2007 and 2014 at Rothera Research Station on the Antarctic Peninsula (Lat. 67°34'S; Long. 68°07'W) to investigate levels of biofouling. In each case, following transit through scouring sea‐ice, over 99% of the vessel hull was free of macroscopic fouling communities. However, in some surveys microbial/algal biofilms, balanomorph barnacles and live individuals of the cosmopolitan pelagic barnacle, Conchoderma auritum were found in the vicinity of intake ports, demonstrating the potential for non‐native species to be transported to Antarctica on vessel hulls.
- Increasing ship traffic volumes and declining duration of sea ice in waters to the north and west of the Antarctic Peninsula mean the region may be at increased risk of non‐native species introductions. Locations at particular risk may include the waters around popular visitor sites, such as Goudier Island, Neko Harbour, Whalers Bay, Cuverville Island and Half Moon Island, and around northern peninsula research stations.
- Simple and cost‐effective mitigation measures, such as intentionally moving transiting ships briefly through available offshore sea ice to scour off accessible biofouling communities, may substantially reduce hull‐borne propagule pressure to the region. Better quantification of the risk of marine non‐native species introductions posed by vessel hulls to both Arctic and Antarctic environments, as sea ice patterns and shipping traffic volumes change, will inform the development of appropriate regional and international management responses.
8.
灰色系统理论在木薯引种评价上的应用 总被引:3,自引:0,他引:3
以期为江西红壤旱地木薯良种选择提供依据。应用灰色系统理论的关联度方法,对2010年和2011年新引进的38个木薯品种的主要性状进行了分析。结果表明,38个木薯品种中以H867、H628、H989、H632、H680、SC205、GR024-2、ZM99229、SC8和H1312与参考品种的关联度较高(大于0.619),在江西红壤旱地的综合表现较好,而‘瑞士P11’、‘桂热3号’、G37、F100和‘瑞士88’与参考品种的关联度较低(小于0.506),综合表现较差。可见,灰色系统理论可作为木薯引种适应性的评价方法。H867、H628、H989、H632、H680、SC205、GR024-2、ZM99229、SC8和H1312等品种适宜在江西种植,并获得高产。 相似文献
10.