全文获取类型
收费全文 | 285篇 |
免费 | 4篇 |
专业分类
林业 | 93篇 |
农学 | 6篇 |
96篇 | |
综合类 | 22篇 |
农作物 | 8篇 |
水产渔业 | 2篇 |
畜牧兽医 | 36篇 |
园艺 | 4篇 |
植物保护 | 22篇 |
出版年
2020年 | 3篇 |
2014年 | 3篇 |
2013年 | 15篇 |
2012年 | 11篇 |
2011年 | 14篇 |
2010年 | 3篇 |
2009年 | 9篇 |
2008年 | 15篇 |
2007年 | 13篇 |
2006年 | 8篇 |
2005年 | 8篇 |
2004年 | 10篇 |
2003年 | 13篇 |
2002年 | 8篇 |
2001年 | 3篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1981年 | 4篇 |
1976年 | 2篇 |
1973年 | 2篇 |
1968年 | 2篇 |
1967年 | 3篇 |
1965年 | 2篇 |
1959年 | 3篇 |
1958年 | 2篇 |
1957年 | 2篇 |
1956年 | 2篇 |
1955年 | 2篇 |
1954年 | 2篇 |
1942年 | 2篇 |
1938年 | 8篇 |
1936年 | 6篇 |
1935年 | 4篇 |
1931年 | 5篇 |
1930年 | 6篇 |
1929年 | 5篇 |
1928年 | 5篇 |
1927年 | 5篇 |
1926年 | 10篇 |
1925年 | 4篇 |
1907年 | 2篇 |
1895年 | 4篇 |
排序方式: 共有289条查询结果,搜索用时 15 毫秒
61.
Breijo M Isnardi F Brauer M Schenker R Ferrari M Ferreira AM 《Veterinary parasitology》2011,181(2-4):341-344
The aim of this work was to evaluate the potential of lufenuron, a benzylphenylurea with ability to interfere with the formation of insect exoskeleton, as a therapeutic drug for larval echinococcosis (hydatid disease). For this purpose lufenuron, alone or in combination with albendazole, was administered to CD1 mice bearing Echinococcus granulosus hydatid cysts in the peritoneal cavity. Neither of the drugs alone was able to exert parasiticidal effects. However, in combination with albendazole, lufenuron reduced the growth of cysts (30-40% in cyst diameter respect to control, p<0.05). This effect was associated with ultrastructural alterations of the hydatid cyst wall and a reduction of the content of myo-inositol-hexakisphosphate, the major component of the electron dense granules of the laminated layer. Overall, this work provides evidence that lufenuron could represent a useful compound for the use in chemotherapy against larval echinococcosis, by enhancing albendazole parasiticidal activity. 相似文献
62.
Bourguinat C Keller K Blagburn B Schenker R Geary TG Prichard RK 《Veterinary parasitology》2011,176(4):374-381
Macrocyclic lactone (ML) molecules have been used for heartworm control for more than 25 years. However, in recent years, there have been reports of loss of efficacy of ML heartworm preventatives against Dirofilaria immitis in some locations in the United States. Macrocyclic lactone resistance is a common problem in nematode parasites of livestock, and more recently, evidence of ivermectin resistance has been reported in the human filarial nematode Onchocerca volvulus. In this study, four D. immitis sample groups from the United States with different treatment histories were investigated for evidence of ML-driven genetic selection. DNA from individual adult worms and microfilariae was amplified by polymerase chain reaction to investigate a gene encoding a P-glycoprotein, a protein class known to be involved in ML pharmacology. A significant correlation of a GG-GG genotype with ivermectin response phenotype was found. Moreover, a significant loss of heterozygosity was found in a low responder group; loss of heterozygosity is commonly seen in loci when a population has been under selection. Further studies are required to confirm ML resistance in heartworm populations. However, the genetic changes observed in this study may be useful as a marker to monitor for ML resistance in D. immitis. 相似文献
63.
Relation between soil organic matter and yield levels of nonlegume crops in organic and conventional farming systems 总被引:2,自引:0,他引:2
Christopher Brock Andreas Fließbach Hans‐Rudolf Oberholzer Franz Schulz Klaus Wiesinger Frank Reinicke Wernfried Koch Bernhard Pallutt Bärbel Dittman Jörg Zimmer Kurt‐Jürgen Hülsbergen Günter Leithold 《植物养料与土壤学杂志》2011,174(4):568-575
The aim of this study was to evaluate the interaction between yield levels of nonleguminous crops and soil organic matter (SOM) under the specific conditions of organic and conventional farming, respectively, and to identify implications for SOM management in arable farming considering the farming system (organic vs. conventional). For that purpose, correlations between yield levels of nonlegume crops and actual SOM level (Corg, Nt, Chwe, Nhwe) as well as SOM‐level development were examined including primary data from selected treatments of seven long‐term field experiments in Germany and Switzerland. Yield levels of nonlegume crops were positively correlated with SOM levels, but the correlation was significant only under conditions of organic farming, and not with conventional farming treatments. While absolute SOM levels had a positive impact on yield levels of nonlegumes, the yield levels of nonlegumes and SOM‐level development over time correlated negatively. Due to an increased demand of N from SOM mineralization, higher yield levels of nonlegumes obviously indicate an increased demand for OM supply to maintain SOM levels. Since this observation is highly significant for farming without mineral‐N fertilization but not for farming with such fertilization, we conclude that the demand of SOM‐level maintenance or enhancement and thus adequate SOM management is highly relevant for crop production in organic farming both from an agronomical and ecological point of view. Under conventional management, the agronomic relevance of SOM with regard to nutrient supply is much lower than under organic management. However, it has to be considered that we excluded other possible benefits of SOM in our survey that may be highly relevant for conventional farming as well. 相似文献
64.
Elżbieta Suchowilska Marian Wiwart Zbigniew Borejszo Danuta Packa Wolfgang Kandler Rudolf Krska 《Journal of Cereal Science》2009
This study analyses the variability of key yield components, the content of protein and crude fat in grain and the fatty acid composition of 50 spring accessions of Triticum monococcum, Triticum dicoccum and Triticum spelta of various origins. The average protein content of the grain of T. monococcum was 20.8%, of T. dicoccum 19.7%, and of spelt 17.0%. The crude fat content of T. monococcum grain (2.7%) was significantly higher compared with T. spelta (2.4%) and T. dicoccum (2.3%). In crude fat, fatty acids C18:2, C18:1 and C16 predominated. T. spelta was characterised by the highest concentrations of C18:2 and C16 (55.89% and 18.77% respectively), while T. monococcum had the highest content of C18:1 (26.35%). The structure of analysed fatty acids proved to be highly desirable in this species. A discriminant analysis performed separately for five variables: protein and fat content and three biometrical characters and separately for fatty acid composition enabled three Triticum species to be distinguished. These species also differed significantly with respect to the C18:1/C16 ratio which was equal to 1.78, 1.06, 1.47 and 0.99 in T. monococcum, T. dicoccum, T. spelta and Triticum aestivum respectively. 相似文献
65.
66.
The control of pollen transfer is important for determining the components of yield performance of lupins. By tearing off the first, second and third petals and leaving the fourth and fifth untouched, key signals of the flower are removed and pollen vectors are prevented from visiting the flower. Although this partial removal of petals alters the biomechanics of the flower selfing remains unimpaired. The technique allows autogamy in to be obtained lupins under natural conditions and with little expense. 相似文献
67.
Rudolf Geiger Fabricius A. Howard Grön und Ernst 《Forstwissenschaftliches Centralblatt》1928,50(4):124-135
Ohne Zusammenfassung 相似文献
68.
Lukinger Reinhold Backmund Rudolf Geiger und Schüpfer 《Forstwissenschaftliches Centralblatt》1930,52(1):27-32
Ohne Zusammenfassung 相似文献
69.
70.
Rudolf Geiger Fabricius A. Howard Grön Ernst 《European Journal of Forest Research》1928,50(4):124-135