全文获取类型
收费全文 | 2860篇 |
免费 | 119篇 |
国内免费 | 187篇 |
专业分类
林业 | 410篇 |
农学 | 243篇 |
基础科学 | 313篇 |
220篇 | |
综合类 | 1260篇 |
农作物 | 184篇 |
水产渔业 | 118篇 |
畜牧兽医 | 252篇 |
园艺 | 70篇 |
植物保护 | 96篇 |
出版年
2024年 | 20篇 |
2023年 | 55篇 |
2022年 | 70篇 |
2021年 | 107篇 |
2020年 | 97篇 |
2019年 | 122篇 |
2018年 | 52篇 |
2017年 | 80篇 |
2016年 | 117篇 |
2015年 | 100篇 |
2014年 | 169篇 |
2013年 | 162篇 |
2012年 | 269篇 |
2011年 | 200篇 |
2010年 | 201篇 |
2009年 | 185篇 |
2008年 | 153篇 |
2007年 | 166篇 |
2006年 | 147篇 |
2005年 | 148篇 |
2004年 | 116篇 |
2003年 | 78篇 |
2002年 | 57篇 |
2001年 | 55篇 |
2000年 | 35篇 |
1999年 | 18篇 |
1998年 | 28篇 |
1997年 | 19篇 |
1996年 | 24篇 |
1995年 | 20篇 |
1994年 | 20篇 |
1993年 | 19篇 |
1992年 | 11篇 |
1991年 | 4篇 |
1990年 | 12篇 |
1989年 | 7篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1955年 | 2篇 |
排序方式: 共有3166条查询结果,搜索用时 15 毫秒
151.
152.
深水网箱发展现状与水流影响初探 总被引:5,自引:0,他引:5
描述了国内外深水网箱的发展现状,对深水网箱进行了新的分类,介绍了国外水流对网箱影响的研究成果,最后提出了深水网箱的发展方向。 相似文献
153.
Tiziana La Rosa Simone Mirto Antonio Mazzola Teresa Luciana Maugeri 《Aquaculture (Amsterdam, Netherlands)》2004,230(1-4):153-167
We studied the impact of organic loads due to the biodeposition of a fish farm in a non-impacted coastal area of the Tyrrhenian Sea (Western Mediterranean). Sediment chemistry and benthic microbial community were investigated from July 1997 to February 1998 on monthly basis at two stations: one was located under the fish farm, while the second was about 1 km away, and served as a reference site. The presence of the cage induced rapid changes in the benthic conditions: the sediments were rapidly (after 6 weeks) reduced. A significant accumulation of biopolymeric carbon was observed beneath the cage both 2 weeks after the initial cage deployment, on non-impacted sediments, and 5–7 months after, and appeared to be related to the fish farm production cycle. The density of microbial communities beneath the fish farm increased only during the first month of farming activity (July) and partially 7 months after cage disposal (i.e. in January), when there was a significant sediment organic enrichment. Additional evidence of rapid impact of the fish farm on the benthic bacterial communities is provided by the increase in the numbers of autofluorescent microbial cells. The photosynthetic eukaryotic cells displayed a highly reduced contribution to total autofluorescent microbial density, indicating that their decrease is related with biopolymeric carbon accumulation, and probably was due also to “shadow effect” induced by suspended material, coming from the fish farm, on the environment below. We propose here, to apply the ratio of culturable heterotrophic bacteria to microbial direct counts (CFU/MDC) to detect fish farm impact. In cage sediments, organic enrichment and the consequent modification of the characteristics of the benthic environment, determined an increase in aerobic heterotrophic bacteria and vibrio density indicating that they are efficient colonizers of organic-rich sediments. Densities of Escherichia coli and Enterococci were not significantly higher than in the reference site, and are likely of terrestrial origin. Thus they cannot be used as specific indicators of fish farm impact. 相似文献
154.
Isabelle Ruhnke John V. DeBiasio Jan S. Suchodolski Shelley Newman Mark W. Musch J?rg M. Steiner 《Journal of veterinary science (Suw?n-si, Korea)》2014,15(2):297-307
This study was conducted to evaluate an adapter-modified Ussing chamber for assessment of transport physiology in endoscopically obtained duodenal biopsies from healthy cats and dogs, as well as dogs with chronic enteropathies. 17 duodenal biopsies from five cats and 51 duodenal biopsies from 13 dogs were obtained. Samples were transferred into an adapter-modified Ussing chamber and sequentially exposed to various absorbagogues and secretagogues. Overall, 78.6% of duodenal samples obtained from cats responded to at least one compound. In duodenal biopsies obtained from dogs, the rate of overall response ranged from 87.5% (healthy individuals; n = 8), to 63.6% (animals exhibiting clinical signs of gastrointestinal disease and histopathological unremarkable duodenum; n = 15), and 32.1% (animals exhibiting clinical signs of gastrointestinal diseases and moderate to severe histopathological lesions; n = 28). Detailed information regarding the magnitude and duration of the response are provided. The adapter-modified Ussing chamber enables investigation of the absorptive and secretory capacity of endoscopically obtained duodenal biopsies from cats and dogs and has the potential to become a valuable research tool. The response of samples was correlated with histopathological findings. 相似文献
155.
试验采用直接骨髓法制备林芝藏鸡染色体,通过显微自动成像系统观察藏鸡细胞有丝分裂全过程,包括间期、早前期、前期、中期、后期和末期,并分析了藏鸡有丝分裂过程染色体的形态变化规律。通过比较有丝分裂各期的形态,结果发现藏鸡有丝分裂的前期染色体伸展最长,碱基暴露最多,适合于做基因定位工作。同时进行了藏鸡染色体的核型分析,数据统计结果发现林芝地区藏鸡染色体数目2n=78,其中前5对染色体和性染色体中有3对中央着丝粒(m)染色体、1对近中着丝粒(sm)染色体、2对端着丝粒(t)染色体。与前人试验结果进行了比较,结果显示存在一定差异,原因仍需进一步试验验证。 相似文献
156.
Fatih Basaran Huseyin Ozbilgin & Yeliz Doganyilmaz Ozbilgin 《Aquaculture Research》2007,38(5):452-456
Farmed gilthead sea bream, Sparus aurata, frequently escape from the sea cages and interact with wild populations. The impact of these interactions on the wild populations will depend, in part, on differences in performance of the bream. This study compared the swimming performance of the wild and farmed fish in a current channel. The absolute critical swimming speed (Ucrit) increased with increasing size while the relative Ucrit decreased. Even at the same length there were noticeable performance differences between the individuals. The wild sea bream have significantly higher (P<0.05) absolute Ucrit performance (0.86±0.01 m s−1) than the farmed fish (0.79±0.01 m s−1) and significantly higher (P<0.05) relative Ucrit performance (4.52±0.05 BL s−1) than the farmed fish (4.21±0.05 BL s−1). The present study suggests that cultured sea bream may not have the ability to compete with wild sea bream in native seawaters. 相似文献
157.
159.
160.
以信阳市和谐动物医院在20122013年间接诊的112个细菌病例为研究对象,选取18种常见的抗菌素药敏片,运用纸片扩散法来分析直接药敏试验在临床上的应用效果。结果表明:从112个细菌病例中选出92个病例做研究,36个病例可筛选出3种以上的高敏药物,28个病例可筛选出2种以上的高敏药物,39个病例只能筛选出1种高敏药物,16个病例只能筛选出中敏药物,4个病例对常规的18种药物全部耐药。 相似文献