全文获取类型
| 收费全文 | 1129篇 |
| 免费 | 113篇 |
专业分类
| 林业 | 55篇 |
| 农学 | 24篇 |
| 基础科学 | 2篇 |
| 209篇 | |
| 综合类 | 86篇 |
| 农作物 | 53篇 |
| 水产渔业 | 50篇 |
| 畜牧兽医 | 619篇 |
| 园艺 | 32篇 |
| 植物保护 | 112篇 |
出版年
| 2023年 | 12篇 |
| 2022年 | 9篇 |
| 2021年 | 37篇 |
| 2020年 | 28篇 |
| 2019年 | 45篇 |
| 2018年 | 28篇 |
| 2017年 | 30篇 |
| 2016年 | 26篇 |
| 2015年 | 29篇 |
| 2014年 | 41篇 |
| 2013年 | 50篇 |
| 2012年 | 81篇 |
| 2011年 | 89篇 |
| 2010年 | 46篇 |
| 2009年 | 43篇 |
| 2008年 | 85篇 |
| 2007年 | 78篇 |
| 2006年 | 66篇 |
| 2005年 | 57篇 |
| 2004年 | 57篇 |
| 2003年 | 43篇 |
| 2002年 | 51篇 |
| 2001年 | 14篇 |
| 2000年 | 10篇 |
| 1999年 | 10篇 |
| 1998年 | 6篇 |
| 1997年 | 5篇 |
| 1996年 | 7篇 |
| 1995年 | 9篇 |
| 1993年 | 5篇 |
| 1989年 | 7篇 |
| 1988年 | 4篇 |
| 1985年 | 4篇 |
| 1984年 | 5篇 |
| 1983年 | 6篇 |
| 1980年 | 4篇 |
| 1979年 | 3篇 |
| 1978年 | 3篇 |
| 1977年 | 5篇 |
| 1967年 | 6篇 |
| 1966年 | 4篇 |
| 1964年 | 3篇 |
| 1963年 | 4篇 |
| 1962年 | 5篇 |
| 1961年 | 5篇 |
| 1960年 | 8篇 |
| 1959年 | 7篇 |
| 1958年 | 5篇 |
| 1955年 | 8篇 |
| 1932年 | 4篇 |
排序方式： 共有1242条查询结果，搜索用时 109 毫秒
991.
992.
993.
Waxy gene haplotypes: Associations with apparent amylose content and the effect by the environment in an international rice germplasm collection 总被引：1，自引：1，他引：0
Ming-Hsuan Chen Christine Bergman Shannon Pinson Robert Fjellstrom 《Journal of Cereal Science》2008,47(3):536-545
Apparent amylose content (AAC), the key determinant of rice end-use quality attributes, is primarily controlled by the Waxy gene which codes for granule bound starch synthase (GBSS). We examined the combination of sequence variation in the Waxy gene and environmental effects, and their associations with AAC using 171 rice accessions originating from 43 countries. The combination of two single-nucleotide-polymorphism (SNP) markers in the Waxy gene allows for the identification of three marker haplotypes in this gene. The first SNP is at the leader intron splice site (In1 SNP), and the second polymorphism is in exon 6. The haplotypes explained 86.7% of the variation in AAC and discriminated the three market classes of low, intermediate and high AAC rice from each other. The environment affected the AAC of all haplotypes. Higher air temperature during grain development associated with a decrease in AAC of low and intermediate AAC-types, but with an increase in AAC of high AAC-type. The association of AAC with several Waxy RM190 microsatellite-(CTn) alleles in combination with the In1 SNP was also examined. In conclusion, the Waxy haplotypes studied appear to be useful markers for selecting the AAC of breeding lines developed from the world's rice germplasm. 相似文献
994.
Stefan Wessel‐Bothe Stefan Ptzold Christine Klein Gerhard Behre Gerhard Welp 《植物养料与土壤学杂志》2000,163(1):53-56
Sorption of pesticides and DOC on glass and ceramic suction cups Suction cups are widely used for the sampling of soil solution. Due to sorption and desorption processes the concentration of dissolved substances in the samples may vary considerably depending on the material of the suction cups. In order to minimize these losses, a new glass suction cup was developed. In laboratory studies, aqueous solutions of pesticides and DOC were percolated through both types of suction cups; the concentration of pesticides and DOC in the percolates was examined. The pesticides pendimethaline, terbuthylazine, metolachlor and chlortoluron were tested at concentrations of 2, 20, and 200 μg 1−1. The average losses due to sorption by the suction cups were 10% (1.1—31%) for the ceramic cups and 3.1% (0—11%) for the glass cups. Sorption effects increased with increasing hydrophobicity of the pesticides and decreasing pesticide concentrations. Thus, at a concentration of 2 μg 1−1 ceramic cups sorbed 31% of pendimethaline compared with 7.7% in the case of glass cups. Corresponding tests with soilborne DOC solutions yielded comparable results. Ceramic suction cups adsorbed up to 50% of the DOC input concentration, while glass cups retarded 2.4% on average. These results are especially noteworthy because soilborne dissolved organic substances are effective sorbents and carriers for pesticides. The new type of glass suction cups may help to improve the results of pesticide field studies and, in consequence, the assessment and prediction of the leaching behavior of pesticides. 相似文献
995.
996.
Lisa A. McCauley Christine A. Ribic Lars Y. Pomara Benjamin Zuckerberg 《Landscape Ecology》2017,32(4):807-821
Context
Temperate grasslands and their dependent species are exposed to high variability in weather and climate due to the lack of natural buffers such as forests. Grassland birds are particularly vulnerable to this variability, yet have failed to shift poleward in response to recent climate change like other bird species in North America. However, there have been few studies examining the effect of weather on grassland bird demography and consequent influence of climate change on population persistence and distributional shifts.Objectives
The goal of this study was to estimate the vulnerability of Henslow’s Sparrow (Ammodramus henslowii), an obligate grassland bird that has been declining throughout much of its range, to past and future climatic variability.Methods
We conducted a demographic meta-analysis from published studies and quantified the relationship between nest success rates and variability in breeding season climate. We projected the climate-demography relationships spatially, throughout the breeding range, and temporally, from 1981 to 2050. These projections were used to evaluate population dynamics by implementing a spatially explicit population model.Results
We uncovered a climate-demography linkage for Henslow’s Sparrow with summer precipitation, and to a lesser degree, temperature positively affecting nest success. We found that future climatic conditions—primarily changes in precipitation—will likely contribute to reduced population persistence and a southwestward range contraction.Conclusions
Future distributional shifts in response to climate change may not always be poleward and assessing projected changes in precipitation is critical for grassland bird conservation and climate change adaptation.997.
998.
Isolates of the reported mycoparasites Pythium oligandrum, P. acanthicum and P. periplocum markedly reduced growth and cellulolysis by Botryotrichum piluliferum, grew rapidly across agar plates precolonized by Phialophora radicicola var radicicola (sensu Deacon) and, where tested (not P. periplocum), were non-pathogenic towards higher plants. Isolates of P. echinulatum, P. mamillatum. P. megalacanthum, P. spinosum, P. ultimum and one isolate of P. acanthicum behaved differently from the mycoparasites and could, themselves, be placed in two groupings in these tests. It is suggested that the ability or otherwise to grow on Phialophora-precolonized agar plates may help to distinguish broad biological groupings within the genus Pythium, but these groupings may cut across conventional taxonomic ones.One isolate of P. acanthicum was tested for its effects on a range of cellulolytic fungi: it reduced their growth to different extents, as did P. oligandrum.Plates of potato-dextrose agar precolonized by Phialophora radicicola were used to isolate selectively P. oligandrum and similar fungi from soils, but the use of hemp seed baits in conjunction with precolonized plates was less selective for these fungi.Straw pieces precolonized by P. oligandrum and buried in soil decomposed at the same rate as virgin straws or those precolonized by P. ultimum or Mucor hiemalis. Subsequently, Stachyholrys atra appeared to colonize straws more frequently from soil, and Fusarium spp. less so, in the presence of P. oligandrum than in its absence. In the laboratory, P. oligandrum was antagonized by Slachyholrys, whereas Fusarium spp. were frequently overgrown by the Pythium. 相似文献
999.
Maya Rima Jeanne Trognon Laure Latapie Asma Chbani Christine Roques Fatima El Garah 《Marine drugs》2022,20(2)
The organization of bacteria in biofilms is one of the adaptive resistance mechanisms providing increased protection against conventional treatments. Thus, the search for new antibiofilm agents for medical purposes, especially of natural origin, is currently the object of much attention. The objective of the study presented here was to explore the potential of extracts derived from three seaweeds: the green Ulva lactuca, the brown Stypocaulon scoparium, and the red Pterocladiella capillacea, in terms of their antibiofilm activity against P. aeruginosa. After preparation of extracts by successive maceration in various solvents, their antibiofilm activity was evaluated on biofilm formation and on mature biofilms. Their inhibition and eradication abilities were determined using two complementary methods: crystal violet staining and quantification of adherent bacteria. The effect of active extracts on biofilm morphology was also investigated by epifluorescence microscopy. Results revealed a promising antibiofilm activity of two extracts (cyclohexane and ethyl acetate) derived from the green alga by exhibiting a distinct mechanism of action, which was supported by microscopic analyses. The ethyl acetate extract was further explored for its interaction with tobramycin and colistin. Interestingly, this extract showed a promising synergistic effect with tobramycin. First analyses of the chemical composition of extracts by GC–MS allowed for the identification of several molecules. Their implication in the interesting antibiofilm activity is discussed. These findings suggest the ability of the green alga U. lactuca to offer a promising source of bioactive candidates that could have both a preventive and a curative effect in the treatment of biofilms. 相似文献
1000.