全文获取类型
收费全文 | 663篇 |
免费 | 34篇 |
国内免费 | 3篇 |
专业分类
林业 | 61篇 |
农学 | 35篇 |
基础科学 | 4篇 |
119篇 | |
综合类 | 109篇 |
农作物 | 27篇 |
水产渔业 | 46篇 |
畜牧兽医 | 236篇 |
园艺 | 8篇 |
植物保护 | 55篇 |
出版年
2023年 | 7篇 |
2022年 | 3篇 |
2021年 | 14篇 |
2020年 | 8篇 |
2019年 | 16篇 |
2018年 | 17篇 |
2017年 | 26篇 |
2016年 | 24篇 |
2015年 | 12篇 |
2014年 | 12篇 |
2013年 | 25篇 |
2012年 | 46篇 |
2011年 | 43篇 |
2010年 | 27篇 |
2009年 | 28篇 |
2008年 | 50篇 |
2007年 | 42篇 |
2006年 | 22篇 |
2005年 | 26篇 |
2004年 | 26篇 |
2003年 | 31篇 |
2002年 | 24篇 |
2001年 | 7篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 10篇 |
1988年 | 4篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 6篇 |
1972年 | 3篇 |
1971年 | 3篇 |
1969年 | 6篇 |
1967年 | 4篇 |
1964年 | 3篇 |
1939年 | 2篇 |
排序方式: 共有700条查询结果,搜索用时 15 毫秒
1.
Ecology of Salmonids in Estuaries around the World: Adaptations,Habitats and Conservation Colin D. Levings University of British Columbia Press 2016. Vancouver, 388 pp,ISBN‐13: 978‐0774831734, CDN 75; USD 83; GBP 71 (hardcover).
下载免费PDF全文
Lia Chalifour Morgan J. Black Kieran Cox Sarah Schroeder Francis Juanes 《Fish and Fisheries》2017,18(4):790-791
2.
Adriano Francis Dorigan Silvino Intra Moreira Sarah da Silva Costa Guimarães Valter Cruz-Magalhães Eduardo Alves 《Pest management science》2023,79(12):4731-4753
Fungicides are indispensable for high-quality crops, but the rapid emergence and evolution of fungicide resistance have become the most important issues in modern agriculture. Hence, the sustainability and profitability of agricultural production have been challenged due to the limited number of fungicide chemical classes. Resistance to site-specific fungicides has principally been linked to target and non-target site mechanisms. These mechanisms change the structure or expression level, affecting fungicide efficacy and resulting in different and varying resistance levels. This review provides background information about fungicide resistance mechanisms and their implications for developing anti-resistance strategies in plant pathogens. Here, our purpose was to review changes at the target and non-target sites of quinone outside inhibitor (QoI) fungicides, methyl-benzimidazole carbamate (MBC) fungicides, demethylation inhibitor (DMI) fungicides, and succinate dehydrogenase inhibitor (SDHI) fungicides and to evaluate if they may also be associated with a fitness cost on crop pathogen populations. The current knowledge suggests that understanding fungicide resistance mechanisms can facilitate resistance monitoring and assist in developing anti-resistance strategies and new fungicide molecules to help solve this issue. © 2023 Society of Chemical Industry. 相似文献
3.
Genevieve Patrick Andrea M. Tarnecki Nicole Rhody Ryan Schloesser Kevan Main Roy Yanong Ruth Francis‐Floyd 《Aquaculture Research》2019,50(12):3793-3801
Almaco jack (Seriola rivoliana Valenciennes) is an excellent candidate for aquaculture due to its fast growth rate and high market value. While S. rivoliana have adapted well to captivity, survival at early life stages can be improved to increase profitability during production. A wide range of variables cause larval mortalities but high bacterial loads in rearing tanks are often correlated with these losses. The aim of this study was to investigate the effect of egg disinfection on bacterial load and hatch rate of S. rivoliana. Disinfectants tested included formalin (F100 and F200; 100 and 200 mg/L, respectively, for 60 min), hydrogen peroxide (HPO; 300 mg/L for 10 min) and peracetic acid/hydrogen peroxide (PAA/HPO; 15.7 mg/L/39.6 mg/L for 1 min). Concentrations and contact times were determined based on current use in marine aquaculture and preliminary trials. Eggs treated with HPO and F100 had significantly higher hatch rates than the untreated control group. All treatments significantly decreased total Vibrio counts compared to untreated eggs; however, total bacterial counts were only decreased following treatments with PAA/HPO and F200. To prevent egg mortality due to bacterial overgrowth, consideration should be given to the use of surface disinfection using HPO or F100. Future studies should investigate the use of peracetic‐based products at lower doses. 相似文献
4.
Changaram Venugopal Nithya Mariappan Earnestine Holmes Catherine Koch Joseph Francis Susan Eades 《Journal of Equine Veterinary Science》2011,31(12):732-737
Endothelin-1 (ET-1), a physiological as well as an inflammatory mediator, causes contraction of airway smooth muscles by binding to endothelin-A (ETA) and endothelin-B (ETB) receptors. We investigated the interaction between endothelin receptors on contractions and oxidative stress of bronchial rings of clinically healthy horses. Rings for response studies were set in tissue chambers containing oxygenated Tyrode’s solution. Concentration-response relationships were determined for ET-1 on control rings, rings incubated with ETA antagonist (BQ123), rings incubated with ETB antagonists (IRL 1038 and BQ788), and rings incubated with all antagonists combined. For oxidative stress studies, rings were incubated for 30 minutes separately with ET-1, ETA antagonist + ET-1, ETB antagonists + ET-1, and all three antagonists + ET-1. The control rings were not treated with any agents. Electron paramagnetic resonance (EPR) method was used to measure total reactive oxygen species (ROS), superoxide, and peroxynitrite. Results showed that ET-1 caused dose-dependent contractions which were increased by ETA blockade and decreased by ETB blockade. Combined blockade significantly inhibited the response to ET-1. Regarding the oxidative stress, ET-1 and its antagonists significantly reduced the total ROS. Superoxide production was significantly decreased by ETA antagonist and completely abolished when ETA and ETB antagonists were combined. Peroxynitrite production was not changed significantly. The study suggested that an interaction between ET receptors exists in the expression of contractile responses and oxidative stress. ET-1 attenuated oxidative stress by decreasing total ROS. ETA receptors may be primarily responsible for superoxide production. It appears that ET-1 does not affect peroxynitrite production in normal equine tissues. 相似文献
5.
Marron N Dreyer E Boudouresque E Delay D Petit JM Delmotte FM Brignolas F 《Tree physiology》2003,23(18):1225-1235
Responses to successive drought and re-watering cycles (1-3 cycles) were compared in greenhouse-grown cuttings of Populus x canadensis (Moench) clones, 'Luisa_ Avanzo' and 'Dorskamp.' Total leaf number increment rate, duration of leaf expansion, total and individual leaf area expansion rates and stomatal conductance were recorded periodically during the experiment. Soil water content (SWC) and predawn leaf water potential (Psi(WP)) were measured four times during each drought cycle. In parallel, relative leaf water content (RWC) and specific leaf area (SLA) were estimated on leaves collected from the top to bottom of each cutting. Under well-watered conditions, 'Luisa_Avanzo' and 'Dorskamp' differed in their patterns of leaf area expansion. Although duration of leaf expansion was similar between clones, 'Luisa_ Avanzo' exhibited higher total leaf number increment rates and individual leaf area increases than 'Dorskamp.' As a result, 'Luisa_Avanzo' cuttings reached larger individual and total leaf areas than 'Dorskamp.' 'Dorskamp' leaves had lower SLA than 'Luisa_Avanzo' leaves. In response to successive drought cycles, both clones underwent decreases in total leaf number increment rates and in total leaf area expansion rates, but both whole-plant and individual leaf areas were drastically reduced only in 'Luisa_Avanzo.' 'Dorskamp' maintained a constant leaf area as a result of an increase in the duration of leaf expansion during drought and a significant stimulation of individual leaf area expansion rate and total leaf number increment rate in response to re-watering. Drought caused a greater decrease in SLA in 'Luisa_Avanzo' than in 'Dorskamp.' Expanded leaves of 'Dorskamp' were constitutively dense or thick, or both, whereas leaves of 'Luisa_Avanzo' became dense or thick, or both, only in response to drought. In both clones, re-watering caused partial recovery of SLA to control values. Our data confirm previous field and greenhouse observations that 'Dorskamp' is more tolerant to successive drought and re-watering cycles than 'Luisa_Avanzo.' We conclude that this difference is mainly attributable to the plasticity of 'Dorskamp' after re-watering, rather than to clonal differences in drought responses. 相似文献
6.
We followed the establishment and growth response of 13 commercial tree species to canopy opening, above-ground biomass removal, and experimental burns of low and high intensities in a lowland dry forest in Bolivia. Three patterns of response to treatments were observed among the most abundant commercial tree species. (1) Shade-intolerant species regenerated mostly from seed and had the highest survival and growth rates following high-intensity burns. (2) Shade-tolerant species were abundant in gap control and plant removal treatments. Treatments had little effect on the height growth of these species. (3) Individuals of root sprouting species were most abundant following plant removal and low-intensity burn treatments. Treatments had little effect on the height growth of these species. The wide variation in species responses to gap treatments found in this study not only reinforces the concept that species are distributed along a continuum of shade-tolerance levels, but that other aspects of species biology, such as seed dispersal type or sprouting behavior, further differentiate regeneration strategies. The variety of regeneration strategies found among the species at this forest site will require a flexible management scheme that mixes more intensive silvicultural treatments such as prescribed burning with less intensive treatments. 相似文献
7.
Francis O. C. Nwonwu 《Agroforestry Systems》1987,5(4):455-462
The costs and benefits of the use of three labour alternatives: direct permanent, direct casual and taungya labour in Gmelina arborea pulpwood plantation establishment in Nigeria were investigated. Results show that cost per hectare is lowest with taungya labour and highest with permanent labour with savings in cost of as much as 30% and 47% by taungya labour over casual and permanent labour respectively. The net present value per hectare of investment is highest when taungya labour is used and lowest and negative with permanent labour. Also, the internal rate of return of investment is highest with taungya labour and lowest with permanent labour. The net present values and internal rates of return for Gmelina plantations calculated for the three pulp and paper mills in Nigeria show the same trend in favour of taungya labour. 相似文献
8.
Francis Zvomuya Francis J. Larney Walter D. Willms Ryan K. Beck Andrew F. Olson 《Strength and Conditioning Journal》2011,64(4):375-383
Landspraying while drilling (LWD) is an approved disposal method for water-based drilling mud (WBM) systems in western Canada. The mud is applied either on cultivated land, where it is incorporated by cultivation, or on vegetated land where it is not incorporated. This study examined the effects of summer WBM application (0, 15, 20, 40, and 80 m3 · ha?1) on native vegetation properties. Our results indicated that LWD increased bare ground but decreased lichen cover at the 80 m3 · ha?1 rate relative to the untreated control. Nitrogen (N), sulfur (S), and magnesium (Mg) concentrations in aboveground plant tissue increased with increasing LWD rate in samples taken 45 d after WBM application, but these differences disappeared 1 yr after treatment. Increase in tissue concentration of phosphorus (P) with LWD rate, however, was only detected 3 yr after LWD. Nonetheless, these changes in tissue chemistry were not associated with significant changes in biomass yield or species composition. Overall, our results suggest that single WBM applications at rates (≤ 20 m3 · ha?1) commonly used in western Canada, if properly managed, are unlikely to adversely affect native prairie vegetation. 相似文献
9.
Stipanovic AJ Hennessy PJ Webster FX Takahashi Y 《Journal of agricultural and food chemistry》2004,52(8):2301-2308
The potential utility of micrometer-sized particles as controlled-release devices for the volatilization of insect pheromones for mating disruption applications is evaluated in this study for two pheromone/model compound systems (codlemone/1-dodecanol and disparlure/1,2-epoxyoctadecane). To expedite the measurement of release rates from these particle devices, two techniques based on thermogravimetric analysis (TGA) have been exploited: isothermal TGA (I-TGA) at elevated temperatures (40-80 degrees C) with N(2) convection and volatilization temperature (VT) by dynamic TGA. A correlation between these two methods has been established. Samples that exhibit a higher VT provide a lower release rate from a particle substrate. Using these techniques, it has been demonstrated that chemical interactions between adsorbed liquids and particle surfaces may play a small role in defining release characteristics under conditions of low surface area, whereas parameters associated with total surface area and micropore structure appear to be much more significant in retarding evaporation for uncoated particles containing an adsorbed liquid. Additional regulation of release rates was achieved by coating the particle systems with water-soluble or water-dispersible polymers. By careful selection of particle porosity and coating composition, it is envisioned that the evaporation rate of pheromones can be tailored to specific insect control applications. 相似文献
10.
Berry fruit supplementation and the aging brain 总被引:1,自引:0,他引:1
The onset of age-related neurodegenerative diseases such as Alzheimer's or Parkinson's disease, superimposed on a declining nervous system, could exacerbate the motor and cognitive behavioral deficits that normally occur in senescence. In cases of severe deficits in memory or motor function, hospitalization and/or custodial care would be a likely outcome. This means that unless some way is found to reduce these age-related decrements in neuronal function, health-care costs will continue to rise exponentially. Thus, it is extremely important to explore methods to retard or reverse age-related neuronal deficits, as well as their subsequent behavioral manifestations, to increase healthy aging. In this regard, consumption of diets rich in antioxidants and anti-inflammatory polyphenolics, such as those found in fruits and vegetables, may lower the risk of developing age-related neurodegenerative diseases. Research suggests that the polyphenolic compounds found in berry fruits, such as blueberries and strawberries, may exert their beneficial effects either through their ability to lower oxidative stress and inflammation or directly by altering the signaling involved in neuronal communication, calcium buffering ability, neuroprotective stress shock proteins, plasticity, and stress signaling pathways. These interventions, in turn, may exert protection against age-related deficits in cognitive and motor function. The purpose of this paper is to discuss the benefits of these interventions in rodent models and to describe the putative molecular mechanisms involved in their benefits. 相似文献