全文获取类型
收费全文 | 230篇 |
免费 | 41篇 |
国内免费 | 31篇 |
专业分类
林业 | 6篇 |
农学 | 9篇 |
基础科学 | 1篇 |
9篇 | |
综合类 | 58篇 |
农作物 | 7篇 |
水产渔业 | 102篇 |
畜牧兽医 | 82篇 |
园艺 | 24篇 |
植物保护 | 4篇 |
出版年
2023年 | 14篇 |
2022年 | 7篇 |
2021年 | 7篇 |
2020年 | 17篇 |
2019年 | 19篇 |
2018年 | 13篇 |
2017年 | 19篇 |
2016年 | 25篇 |
2015年 | 10篇 |
2014年 | 14篇 |
2013年 | 19篇 |
2012年 | 16篇 |
2011年 | 17篇 |
2010年 | 16篇 |
2009年 | 7篇 |
2008年 | 8篇 |
2007年 | 5篇 |
2006年 | 13篇 |
2005年 | 12篇 |
2004年 | 6篇 |
2003年 | 7篇 |
2002年 | 2篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1987年 | 2篇 |
排序方式: 共有302条查询结果,搜索用时 15 毫秒
1.
Frederick Feyrer Matthew Young Oliver Patton David Ayers 《Ecology of Freshwater Fish》2020,29(2):188-196
Clear Lake Hitch is an imperilled minnow endemic to Clear Lake, Lake County, California, United States listed as threatened under the California Endangered Species Act (ESA) and a candidate for listing under the United States ESA. It exhibits a potamodromous life cycle whereby adults, which reach up to 6 + years in age and over 350 mm in length, migrate into Clear Lake's ephemeral tributaries briefly during spring to spawn. Conservation and management of Clear Lake Hitch is inhibited, in part, by a lack of information on the lacustrine habitat of nonbreeding individuals within Clear Lake. To address this problem, we sampled Clear Lake Hitch with gill nets in a stratified random sampling design to determine the distribution and habitat associations in early summer 2017 and 2018. We identified abundance-habitat relationships for juveniles and adults using Bayesian zero-inflated negative binomial generalised linear mixed modelling. Results indicated that dissolved oxygen concentration was the most important habitat feature measured; juveniles and adults were substantially more abundant in normoxic (≥2 mg/l) than in hypoxic (<2 mg/l) habitat. Both also exhibited weak positive relationships with chlorophyll fluorescence, suggesting relatively productive habitats may support higher numbers of Clear Lake Hitch. Spatially, juveniles were most abundant in nearshore habitats while adults were ubiquitous, indicating an ontogenetic habitat expansion that may be associated with a resource availability-predation risk trade-off. Management actions undertaken to improve hypoxia problems in Clear Lake would also improve Clear Lake Hitch habitat. 相似文献
2.
Appetite,metabolism and growth regulation in Atlantic salmon (Salmo salar L.) exposed to hypoxia at elevated seawater temperature 下载免费PDF全文
High temperature combined with low dissolved oxygen (DO) is one of the most challenging environmental conditions farmed fish experience; thus, understanding their impact on growth regulation is of relevance to cultured and wild populations. This study examines appetite‐ and growth‐regulating mechanisms in Atlantic salmon postsmolt exposed to either high (HO) or low oxygen (LO) at a suboptimally high temperature (17°C). Additionally, the effects of high (HE) and low (LE) dietary energy (DE) were examined. After a month of treatment, analyses of hormones, regulating appetite (ghrelin) and growth (growth hormone receptor ghr1 and insulin‐like growth factor IGF‐1), and free amino acids (FAA) were measured pre‐ and postprandially at ?4, ?2, 0, 2, 4 and 6 h. No preprandial ghrelin peaks were detected despite a significant reduction in feed intake and growth under hypoxia compared to normoxia. LO treatment also had an overall negative effect on survival compared to HO, while nutrient retention efficiency, FCR and plasma FAA concentrations were unaffected (P > 0.05). Feeding HE diet resulted in increased growth (+17%) and improved FCR (?14%) and energy retention efficiency (+26%) independent of DO. Plasma FAA concentrations were unaffected by LO treatment and DE (P > 0.05). Growth regulatory gene expressions possibly reflect an overall lower growth at a high temperature overriding the impacts of DO and DE. This study also indicates that optimal adaptation time to environmental conditions and feeding regime is crucial for establishing a regular hormonal appetite signalling that reflects real feeding anticipation in salmon. 相似文献
3.
Survival and respiration of marbled rabbitfish (Siganus rivulatus) fingerlings at various oxygen tensions 下载免费PDF全文
Jessica Babikian Nivin Nasser Samer Monzer Imad Patrick Saoud 《Aquaculture Research》2017,48(8):4219-4227
Marbled rabbitfish, Siganus rivulatus, is an economically valuable herbivorous fish and a potential candidate for warmwater aquaculture. This study was carried out to: (1) assess the effect of various oxygen concentrations on survival and behaviour of S. rivulatus fingerlings and (2) investigate the response of S. rivulatus to hypoxia and determine its critical oxygen tension (Pcrit). In the first experiment, groups of rabbitfish (15 fish per group) were maintained for 1 h in waters of various oxygen concentrations. They were then transferred to well‐aerated tanks and observed for 72 h. Survival was recorded, fish behaviour at low oxygen concentrations observed, and LC50 after 1‐h hypoxia and 72‐h recovery evaluated. In the second experiment, a series of stop‐flow respirometry experiments were performed during which dissolved oxygen was allowed to drop to 0.5 mg L?1 and respiration rate recorded at various oxygen concentrations. In the first experiment, all fish survived for 1 h at oxygen concentration of 1.44 mg L?1 and greater, but started dying at oxygen concentrations below 0.65 mg L?1 (16% survival). The LC50 of S. rivulatus fingerlings was 0.6 mg L?1. Results of the second experiment showed that S. rivulatus is an oxyregulator until Pcrit (1.7 mg L?1 O2) is reached, becoming an oxyconformer below this concentration. Findings allow for a better understanding of environmental oxygen tolerances and minimum acceptable oxygen concentration in rabbitfish aquaculture. 相似文献
4.
低氧胁迫对河川沙塘鳢抗氧化酶及ATP酶活性的影响 总被引:1,自引:0,他引:1
研究了在急性低氧1.5 h、5 h和慢性低氧3 d下,河川沙塘鳢(Odontobutis potamophila)5种组织(心、脑、肝、鳃和肾)的超氧化物歧化酶(SOD)、过氧化氢酶(CAT)及谷胱甘肽过氧化物酶(GPX)3种抗氧化酶和ATP酶活性的变化规律。结果显示:在急性低氧暴露1.5 h时,河川沙塘鳢SOD和GPX的活力在各组织中与对照组相比均无显著差异,CAT活力在心、鳃和肝3种组织呈现显著升高(P0.05),ATP酶活力在心和肝组织极显著升高(P0.01);在急性低氧暴露5 h时,除肝组织SOD酶活性显著降低外(P0.05),其它4种组织的CAT、GPX和ATP酶均不同程度显著升高(P0.05);在慢性低氧处理3 d时,心、脑组织的抗氧化酶已基本恢复至与对照组无显著差异的水平,但鳃、肝和肾中酶活力仍较高(P0.05)。研究表明,河川沙塘鳢能通过自身调节抗氧化酶及ATP酶活性,改变代谢底物,提高机体适应低氧环境的能力。 相似文献
5.
6.
Devadoss Thulasi Moturi Muralidhar Ramamoorthy Saraswathy 《Aquaculture Research》2020,51(6):2389-2399
Sulphide is one of the known environmental stressors, which potentially binds to cytochrome C oxidase (COX), a key enzyme in the electron transport chain, thereby blocking oxygen transport and ATP production. To ascertain the toxic effects of sulphide on Pacific white shrimp, Penaeus vannamei, two distinct exposure experiments were carried out with varying concentration of sulphide (0–1 mg/L), dissolved oxygen (normoxia and hypoxia) and pH values (8.2, 6 and 5). The activity of enzymes viz COX, superoxide dismutase (SOD), phenoloxidase and lactate accumulation was investigated. Outer membrane integrity and COX monomer separation were also done with the isolated crude mitochondrial preparations. Results indicated a significant reduction (p ≤ .05) in COX enzyme activity in sulphide exposed treatments when compared to control. The reduction was more intense when pH levels were reduced under hypoxia condition. Lactate accumulation as a result of anaerobic metabolism was found to be higher in hypoxic treatments. No significant difference (p ≥ .05) was observed in superoxide dismutase activity between the treatments, whereas phenoloxidase activity significantly decreased at higher concentration sulphide. Separation of mitochondrial proteins resulted in the identification of ~205 kDa of COX monomer, and significant damage was found in outer membrane integrity under hypoxia and pH treatments. From this study, it is evident that at a given concentration, sulphide is toxic to P. vannamei, and in association with hypoxia and low pH, they further intensify sulphide toxicity. Our results indicated that sulphide toxicity should not be considered as a single factor, rather it should be a considered as combination of factors. 相似文献
7.
Satoshi KAMBAYASHI Masaya IGASE Kosuke KOBAYASHI Ayana KIMURA Takako SHIMOKAWA MIYAMA Kenji BABA Shunsuke NOGUCHI Takuya MIZUNO Masaru OKUDA 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2015,77(11):1405-1412
Hypoxic conditions in various cancers are believed to relate with their
malignancy, and hypoxia inducible factor-1α (HIF-1α) has been shown to be a major
regulator of the response to low oxygen. In this study, we examined HIF-1α expression in
canine lymphoma using cell lines and clinical samples and found that these cells expressed
HIF-1α. Moreover, the HIF-1α inhibitors, echinomycin, YC-1 and 2-methoxyestradiol,
suppressed the proliferation of canine lymphoma cell lines. In a xenograft model using
NOD/scid mice, echinomycin treatment resulted in a dose-dependent regression of the tumor.
Our results suggest that HIF-1α contributes to the proliferation and/or survival of canine
lymphoma cells. Therefore, HIF-1α inhibitors may be potential agents to treat canine
lymphoma. 相似文献
8.
9.
Tiago Edu Kaspary Luan Cutti Rafael Schwalm Rafaeli Carla Andrea Delatorre Aldo Merotto Jr 《Weed Research》2020,60(6):435-449
Evolution of flooding tolerance in weedy rice has occurred in several rice-growing regions, but the genes related to this process and the environmental effects are unknown. The objective of this study was to analyse the expression of genes related to flooding tolerance in response to temperature and flooding during the initial establishment of weedy rice. The experiments were carried out with rice cultivars IRGA 417 and Nipponbare, which are sensitive to flooding, and weedy rice ITJ03 and AV04 genotypes that have high and intermediate tolerance to flooding, respectively. The expression of genes related to reserve mobilisation, anaerobic respiration, escape and quiescence strategies was analysed at periods up to 24 days after sowing. The flooding tolerance of weedy rice genotype ITJ03 was associated with the expression of RAmy3D and OsTPP7 , which are involved in the mobilisation of carbohydrate reserves, ADH1 and ADH2, which participate in anaerobic respiration, and SNRKL1 that triggers rapid elongation of the coleoptile and emergence. Although the genes PDC1, SUS3 and SUB1 are important for flooding tolerance in cultivated rice, their expression was not directly related to flooding tolerance in weedy rice. A temperature of 20°C reduced levels of expression of the RAmy3D, ADH2 and SNRKL1 genes and low temperature had a negative effect on the establishment of weedy rice. Breeding of rice genotypes with tolerance of low temperatures and anaerobic conditions may be a viable strategy to improve the control of weedy rice in paddy fields. 相似文献
10.
In this study,hypoxia inducible factor-1α(HIF-1α) gene was cloned from yak spleen by RT-PCR,and it was divided into two sections for amplification.The sequence and protein structure were analyzed using related bioinformatics tools.The length of the coding region was 2 472 bp,which encoded 823 amino acids.Its molecule mass was 92.13 ku,and PI was 5.09.It displayed as a hydrophilic protein,whose secondary structure was mainly composed of random coil and α-helix.It had 69 phosphorylation sites and 4 N-glycosylation sites.Phylogenetic tree displayed that Maiwa yak,Bos grunniens,Bos mutus and Bos taurus gathered into one cluster.Maiwa yak HIF-1α gene was successfully cloned in this study,it provided a viable reference for further study of genetic characteristics of HIF-1α. 相似文献