全文获取类型
收费全文 | 771篇 |
免费 | 68篇 |
专业分类
林业 | 70篇 |
农学 | 27篇 |
基础科学 | 4篇 |
196篇 | |
综合类 | 51篇 |
农作物 | 63篇 |
水产渔业 | 74篇 |
畜牧兽医 | 257篇 |
园艺 | 23篇 |
植物保护 | 74篇 |
出版年
2024年 | 3篇 |
2023年 | 7篇 |
2022年 | 15篇 |
2021年 | 37篇 |
2020年 | 41篇 |
2019年 | 30篇 |
2018年 | 35篇 |
2017年 | 36篇 |
2016年 | 46篇 |
2015年 | 32篇 |
2014年 | 40篇 |
2013年 | 50篇 |
2012年 | 53篇 |
2011年 | 60篇 |
2010年 | 38篇 |
2009年 | 26篇 |
2008年 | 37篇 |
2007年 | 32篇 |
2006年 | 36篇 |
2005年 | 37篇 |
2004年 | 39篇 |
2003年 | 24篇 |
2002年 | 24篇 |
2001年 | 8篇 |
2000年 | 8篇 |
1999年 | 6篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1977年 | 1篇 |
1975年 | 3篇 |
1964年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有839条查询结果,搜索用时 15 毫秒
81.
Mathieu Denoël Gentile Francesco Ficetola Dejan Radovi? Miloš L. Kalezi? Tanja D. Vukov 《Biological conservation》2009,142(3):509-517
Facultative paedomorphosis, a process in which newt larvae can opt for reproduction before or after metamorphosis, is geographically heterogeneous. Despite numerous ecological studies and recent evidence of declines in paedomorphic populations, however, no attempt to model environmental variables that explain the presence of paedomorphs has been made at a multi-scale level. Our aim was to fill this gap in studying three newt species (Lissotriton vulgaris, Mesotriton alpestris, and Triturus macedonicus) of the Montenegrin karst as model species. To this end, we used multivariate analysis on three scales of habitat: the breeding pond, the land use and the climatologic features. Results show that the study area is both an important hotspot for paedomorphosis and where intraspecific diversity is quickly disappearing (20-47% extirpation) because of fish introductions. Other habitat variables (water permanency, pH or the habitat origin) were shown to act on paedomorphosis but not consistently across species, confirming complexity of the evolutionary and ecological processes. This study appeals for more long-term and detailed landscape studies of polyphenisms, a neglected but promising topic, to better understand and protect alternative modes of development. Particularly, measures should be taken to identify hotspots of intraspecific diversity at a global scale and stop fish introductions before we reach a point of no-return. 相似文献
82.
Assessing solid waste compost application as a practical approach for salt-affected soil reclamation
Abdelbasset Lakhdar Chokri Hafsi Ahmed Debez Francesco Montemurro Naceur Jedidi Chedly Abdelly 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(3):284-288
Abstract A short-term pot experiment was made to evaluate the effectiveness of municipal solid waste compost amendment on salt-affected soil. Hordeum maritimum plants were cultivated in pots filled with a clay-loam soil containing 0 or 40 t ha?1 of compost and irrigated with tap water at 0 or 4 g l?1 NaCl. Soil properties and heavy metal (Zn2 +, Pb2 +, Cd2 +) accumulation were investigated. Municipal solid waste compost application significantly increased the soil contents of carbon, nitrogen and potassium under both non-saline and saline conditions. Soil heavy metal concentrations increased substantially too, but the recorded values were below the toxicity limits. Interestingly, plants subjected to the salt–compost interaction were more vigorous, compared with those grown on non-amended soil. Altogether, our data indicate that short-term utilization of municipal solid waste compost at 40 t ha?1 may be of potential interest in the perspective of the rehabilitation of salt-affected soils. Yet, it must be stressed that the present findings are preliminary and need to be further evaluated under field conditions before practical recommendations can be inferred. 相似文献
83.
Francesco Bonomi Stefania Iametti Gianfranco Mamone Pasquale Ferranti 《Cereal Chemistry》2013,90(4):358-366
Substantial progress has been made in breaking down the complex pattern of proteins in wheat, and the constant improvement of “‐omics” approaches has allowed relating the abundance of selected wheat proteins to flour and semolina performance during processing. This strategy has provided some sound molecular basis for the work of geneticists, breeders, and growers. Along with an update on work in this area, this review is meant to highlight that performance‐relevant proteins may need specific structural features to carry out performance‐relevant functions during processing. In this frame, some of the approaches used to investigate structural features of wheat proteins are discussed, with a focus on water‐insoluble gluten proteins and on those approaches that allow minimal disturbance of the protein structure itself. Selected examples of the application of some of these approaches to the study of starting materials and of structural modifications that occur at various processing stages are presented. The effects of process‐induced modifications on the various interactions among macromolecules that govern the physical and sensory features of wheat‐based foods are also briefly discussed. 相似文献
84.
Passi S Ricci R Cataudella S Ferrante I De Simone F Rastrelli L 《Journal of agricultural and food chemistry》2004,52(9):2587-2592
The levels of hydrophilic, lipophilic, and enzymatic antioxidants, the oxidative damage to lipids and proteins, and the fatty acid patterns of triglyceride and phospholipid fractions were assayed in fresh muscle tissue of rainbow trouts (Oncorhynchus mykiss) and sea basses (Dicentrarchus labrax) during aging, to investigate the correlation between oxidative stress and aging processes in fish. The present studies suggests that lipid peroxidation and accumulation of oxidized proteins during in vivo aging are most likely to be linked with an age-dependent decline of lipophilic antioxidants (CoQH(2), CoQ, and vitamin E) and vitamin C contents in muscle tissue, whereas fish aging is not linked to a decline in antioxidant enzymes and reduced glutathione levels. Lipophilic antioxidant and vitamin C levels represent a reliable marker of oxidative stress during aging, and their determination might be useful for the assessment of fish age. 相似文献
85.
86.
87.
Ten years of bovine virus diarrhoea virus (BVDV) control in Norway: a cost-benefit analysis 总被引:1,自引:0,他引:1
Valle PS Skjerve E Martin SW Larssen RB Østerås O Nyberg O 《Preventive veterinary medicine》2005,72(1-2):189-207; discussion 215-9
A retrospective cost-benefit analysis was carried out on the Norwegian bovine virus diarrhoea (BVD) control and eradication strategy, for the years 1993-2003. Information regarding the control cost input parameters was gathered from the cattle industry (TINE Norwegian Dairies, GENO Breeding and AI association, and GILDE Norwegian Meat), The National Animal Health Authorities and The Veterinary Institute. We accounted for variable costs (both direct costs associated with the control, and those costs carried by the farmers as a consequence of the control program). The benefit was estimated as the difference between the assumed losses without control - represented overall as 10% increase of the observed 1993 BVD virus infection level - and the observed losses during the control period. An estimate of the financial losses associated with the BVD virus (BVDV) infection was based on studies of the herd level effects on health, reproduction, and production in dairy herds with evidence of recent BVDV infection. We used a stochastic simulation model to account for the total uncertainty in both the control cost and financial loss estimates. The annual net benefits over the 10 years of BVD control were discounted to a 1993 net present value (NPV). The median NPV of the BVD control, nationally, was estimated at 130 million NOK with a distribution of the NPV ranging from +51 to +201 million NOK (5th and 95th percentiles, respectively). Out of the total control costs the farmers and the farmer-owned industries (the co-operatives) had carried about 62% of these costs; however, the farmers were also the main beneficiaries. The Norwegian experience shows a robust cost-efficiency for a BVDV eradication strategy; this stands in sharp contrast to earlier studies where the results were not supportive. Even though every cattle population and country is unique, the Norwegian findings and experiences should have wider implications. 相似文献
88.
Alessandro Acquavita Sergio Predonzani Giorgio Mattassi Pietro Rossin Francesco Tamberlich Jari Falomo Iztok Valic 《Water, air, and soil pollution》2010,211(1-4):95-111
A set of ten heavy metals (Al, As, Cd, Cr, Cu, Hg, Ni, Pb, V, and Zn) was investigated in surface sediments (0–5 cm) collected in 21 sites of the Gulf of Trieste, Northern Adriatic Sea (Italy). The aim of this work was to obtain a preliminary assessment about the levels and spatial distribution of these selected elements. Ancillary parameters such as grain size, total organic carbon, and total nitrogen were also determined. The enrichment factor was calculated to discriminate if a natural condition or a status of anthropogenic contamination occurs. In addition, a set of sediment quality guidelines, mean effect low range and effect medium range quotients, was also applied in order to predict the probability of adverse biological effects on the benthic community. 相似文献
89.
Bertola F 《Science (New York, N.Y.)》2002,295(5553):283-284
90.
Christian Maltecca Matteo Bergamaschi Francesco Tiezzi 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2020,137(1):4-13
The existence of genetic control over the abundance of particular taxa and the link of these to energy balance and growth has been documented in model organisms and humans as well as several livestock species. Preliminary evidence of the same mechanisms is currently under investigation in pigs. Future research should expand these results and elicit the extent of genetic control of the gut microbiome population in swine and its relationship with growth efficiency. The quest for a more efficient pig at the interface between the host and its metagenome rests on the central hypothesis that the gut microbiome is an essential component of the variability of growth in all living organisms. Swine do not escape this general rule, and the identification of the significance of the interaction between host and its gut microbiota in the growth process could be a game-changer in the achievement of sustainable and efficient lean meat production. Standard sampling protocols, sequencing techniques, bioinformatic pipelines and methods of analysis will be paramount for the portability of results across experiments and populations. Likewise, characterizing and accounting for temporal and spatial variability will be a necessary step if microbiome is to be utilized routinely as an aid to selection. 相似文献