全文获取类型
收费全文 | 1108篇 |
免费 | 109篇 |
专业分类
林业 | 55篇 |
农学 | 24篇 |
基础科学 | 1篇 |
207篇 | |
综合类 | 86篇 |
农作物 | 54篇 |
水产渔业 | 50篇 |
畜牧兽医 | 598篇 |
园艺 | 32篇 |
植物保护 | 110篇 |
出版年
2023年 | 12篇 |
2022年 | 10篇 |
2021年 | 37篇 |
2020年 | 27篇 |
2019年 | 45篇 |
2018年 | 28篇 |
2017年 | 30篇 |
2016年 | 24篇 |
2015年 | 26篇 |
2014年 | 41篇 |
2013年 | 49篇 |
2012年 | 79篇 |
2011年 | 88篇 |
2010年 | 44篇 |
2009年 | 43篇 |
2008年 | 84篇 |
2007年 | 76篇 |
2006年 | 62篇 |
2005年 | 56篇 |
2004年 | 56篇 |
2003年 | 43篇 |
2002年 | 50篇 |
2001年 | 15篇 |
2000年 | 7篇 |
1999年 | 9篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1996年 | 7篇 |
1995年 | 9篇 |
1993年 | 5篇 |
1989年 | 6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1217条查询结果,搜索用时 15 毫秒
991.
Variability of total flavonoids in Crataegus--factor evaluation for the monitored production of industrial starting material 总被引:1,自引:0,他引:1
European Hawthorn species (Crataegus spp.) are traditionally used for their demonstrated cardioprotective benefits. Most products are based on the compendial leaf and flower drug (LFD), which is standardised on the total flavonoid content (TF). In order to reduce variability associated with the wild plant origin and to ease product standardisation, we set out to develop a sustainable source of high quality raw material. Firstly, the LFD of wild trees in Germany was screened in terms of TF content (spectrophotometric analysis, calculated as hyperoside) according to the current pharmacopoeia requirements. Secondly, eleven high value provenances were selected, propagated, cultivated and the grafted clones were reanalysed. Thirdly, major environmental and sourcing influences were assessed: the year of harvest, the growing location, exposure to sunlight, the harvest time and the portion of leaf, flower and wood within the LFD. We found the TF in LFD of 150 wild grown Crataegus ranged between 0.28% and 1.92% (average 1.15%). Pure single styled Crataegus monogyna and hybrid trees represented the major portion (57%) of all screened trees. The hybrids with mainly two-styled flowers (pure Crataegus laevigata and hybrids) showed slightly higher TF values. The selected clones proved to maintain a high TF profile in cultivation, although superiority was attenuated when not only O-glycosides, but also C-glycosides were covered by the assay. Environmental influence surpassed in part the genetic variation of the selection in this study. In conclusion, cultivated high performance trees under central European conditions produced LFD exceeding the Pharmacopoeia standards. Careful monitoring of production - particularly in terms of the harvest time and actual LFD location and composition - has decisive impact to guarantee consistent high TF values. 相似文献
992.
993.
An avoidance test using the soil springtail Folsomia candida was used to assess changes in contamination levels at low doses of PAHs following incubation with indigenous microflora. A soil from a former coke site was diluted to 1% in an unpolluted soil from the same site, which was used as a control, then both substrates were remoistened to 80% field capacity. The diluted soil was previously shown to be strongly repellent to F. candida, although not toxic. After 2-month incubation at 20 °C, the mixture lost its repellence capacity and became attractive to the test animal, while the global 16 PAHs content had decreased to a great extent (50%). PAH disappearance was linked to the occurrence of indigenous microbiota able to degrade hydrocarbons. 相似文献
994.
Vanessa Crespy Christine Morand Catherine Besson Claudine Manach Christian Demigne Christian Remesy 《Journal of agricultural and food chemistry》2002,50(3):618-621
Absorption and metabolism of quercetin, isoquercitrin (quercetin 3-O-glucose), and rutin (quercetin 3-O-glucose-rhamnose) were investigated in rats after in situ gastric administration (15 micromol/L) for 30 min. At the end of the experiment, 38% of the initial dose of quercetin had disappeared. Quercetin was rapidly absorbed by the stomach, and was recovered in the bile 20 min after infusion (4.07 +/- 0.10 micromol/L). The administration of rutin and isoquercitrin indicated that these glycosides were not hydrolyzed nor absorbed by this tissue. In conclusion, when flavonols are present in the diet as aglycons, they could be partly absorbed in the stomach, in contrast to their glycosidic forms which are not absorbed. 相似文献
995.
996.
997.
Lantana camara is a recognized weed of worldwide significance due to its extensive distribution and its impacts on primary industries and
nature conservation. However, quantitative data on the impact of the weed on soil ecosystem properties are scanty, especially
in SE Australia, despite the pervasive presence of the weed along its coastal and inland regions. Consequently, mineral soils
for physicochemical analyses were collected beneath and away from L. camara infestations in four sites west of Brisbane, SE Australia. These sites (hoop pine plantation, cattle farm, and two eucalyptus
forests with occasional grazing and a fire regime, respectively) vary in landscape and land-use types. Significant site effect
was more frequently observed than effect due to invasion status. Nonetheless, after controlling for site differences, ~50%
of the 23 soil traits examined differed significantly between infested and non-infested soils. Moisture, pH, Ca, total and
organic C, and total N (but not exchangeable N in form of NO3-) were significantly elevated, while sodium, chloride, copper, iron, sulfur, and manganese, many of which can be toxic to
plant growth if present in excess levels, were present at lower levels in soils supporting L. camara compared to soils lacking the weed. These results indicate that L. camara can improve soil fertility and influence nutrient cycling, making the substratum ideal for its own growth and might explain
the ability of the weed to outcompete other species, especially native ones. 相似文献
998.
999.
Siembieda JL Miller WA Byrne BA Ziccardi MH Anderson N Chouicha N Sandrock CE Johnson CK 《Journal of the American Veterinary Medical Association》2011,239(6):773-783
During 2010, 48 states and Puerto Rico reported 6,154 rabid animals and 2 human rabies cases to the CDC, representing an 8% decrease from the 6,690 rabid animals and 4 human cases reported in 2009. Hawaii and Mississippi did not report any laboratory-confirmed rabid animals during 2010. Approximately 92% of reported rabid animals were wildlife. Relative contributions by the major animal groups were as follows: 2,246 raccoons (36.5%), 1,448 skunks (23.5%), 1,430 bats (23.2%), 429 foxes (6.9%), 303 cats (4.9%), 71 cattle (1.1 %), and 69 dogs (1.1 %). Compared with 2009, number of reported rabid animals decreased across all animal types with the exception of a 1 % increase in the number of reported rabid cats. Two cases of rabies involving humans were reported from Louisiana and Wisconsin in 2010. Louisiana reported an imported human rabies case involving a 19-year-old male migrant farm worker who had a history of a vampire bat (Desmodus rotundus) bite received while in Mexico. This represents the first human rabies case reported in the United States confirmed to have been caused by a vampire bat rabies virus variant. Wisconsin reported a human rabies case involving a 70-year-old male that was confirmed to have been caused by a rabies virus variant associated with tri-colored bats (Perimyotis subflavus). 相似文献
1000.