全文获取类型
收费全文 | 180篇 |
免费 | 4篇 |
专业分类
林业 | 8篇 |
农学 | 4篇 |
47篇 | |
综合类 | 19篇 |
农作物 | 7篇 |
水产渔业 | 6篇 |
畜牧兽医 | 58篇 |
园艺 | 11篇 |
植物保护 | 24篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 5篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 4篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 4篇 |
2014年 | 5篇 |
2013年 | 5篇 |
2012年 | 15篇 |
2011年 | 14篇 |
2010年 | 8篇 |
2009年 | 7篇 |
2008年 | 15篇 |
2007年 | 15篇 |
2006年 | 10篇 |
2005年 | 10篇 |
2004年 | 15篇 |
2003年 | 10篇 |
2002年 | 4篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有184条查询结果,搜索用时 326 毫秒
61.
It has been assumed that high winter N2O emissions from soils are the result of increased amounts of microbially available organic C liberated during freezing and metabolized during subsequent thawing. In a laboratory experiment, we attempted to simulate freeze‐thaw events by adding dissolved organic C (DOC) to sieved soil of high water content (95% water‐filled pore space). In a full factorial design, CO2 and N2O emissions of a) soil samples provided with DOC extracted from frozen soil and b) soil samples frozen for 46 days and thawed were compared. Additionally, NO , DOC and microbial ATP contents of all treatments were repeatedly analyzed during the experiment. The addition of DOC to unfrozen soil (–F+C) resulted in a substantial (22‐fold) increase in N2O emissions as compared to the control (–F–C). However, following thawing, the increase in N2O emissions was much larger (828‐fold in +F–C and 1243‐fold in +F+C). Freezing, but not the addition of DOC led to increased CO2 emissions. Neither treatment affected microbial adenylate content. By adding 15N‐labeled nitrate to the soil samples, the main process leading to elevated N2O flux rates after both DOC addition and freeze‐thaw treatment was identified as denitrification. We conclude that the availability of C substrate plays an important role for freeze‐thaw‐related N2O emissions. However, the fact that the simulated treatment and the freeze‐thaw treatment yielded significantly different amounts of N2O suggests that both quantity and quality of available C differed between the treatments. The localization of the liberated substrate, i.e., the availability in situ, seems to be of major importance for the amount of N2O produced. 相似文献
62.
63.
Karin Müller Susanne Eder Ulrike Jakop Jürgen Schiller Peter Müller Mohammad Bashawat 《Reproduction in domestic animals》2020,55(Z2):55-60
Cryobanking of gametes in combination with artificial insemination is an essential option to support conservation programmes for endangered and threatened species. About two-thirds of the felid species are classified as ‘near threatened’, ‘vulnerable’ or ‘endangered’ ( www.cites.org ), and mostly, epididymal sperm are collected from euthanized or castrated male felids and cryopreserved. However, epididymal compared with ejaculated and cryopreserved compared with fresh sperm have a limited potential to fertilize if vaginal non-surgical insemination is applied in feline species. Missing or highly diluted seminal fluid in epididymal and cryopreserved sperm, as well as a potential interference of extender ingredients with the natural interactive properties of sperm in the female genital tract is discussed as potential drawback which hampers a proper sperm transit and fertilization besides the limited longevity of cryopreserved feline sperm. Individual components in seminal fluid as well as cryoextenders may adversely alter sperm properties and have a different impact on fertility and preservation success. The identification and investigation of beneficial as well as detrimental components is a precondition to deduce options for improving the process of cryopreservation in felids, particularly, if only epididymal sperm are available. 相似文献
64.
Systematical status and soil development of the Tschernosem des Oberrheintales and the Smonica of Rheinhessen (W-Germany) The Tschernosem des Oberrheintales and the Smonica of Rheinhessen are discussed respectively to their position in the soil system of the Federal Republik of Germany, as well as in the FAO/Unesco classification and USDA Soil Taxonomy. Both soils are subrelictic, and the recent behavior of the Smonica does not allow it to be placed among the Vertisols. The history of these soils is described as investigated by field work, palynology and micromorphology. Some connecting profiles between the exposed ones have been outlined. 相似文献
65.
66.
Schröer U Kaspar H Wallmann J 《Berliner und Münchener tier?rztliche Wochenschrift》2007,120(9-10):431-441
National Resistance Monitoring of the Federal Office of Consumer Protection and Food Safety (BVL), which was put into service in 2001, has made it possible to implement a valid and representative database on the basis of which the resistance situation, development and spread in animal pathogens can be evaluated. Escherichia coil (E. coli) strains originating from calves and pigs suffering from enteritis were first included in the investigations in the 2004/2005 study. A total of 258 bovine and 492 porcine E. coli strains were tested using the broth microdilution method to determine the in vitro susceptibility (minimum inhibitory concentration) to 23 (fattening pigs) and 28 (calves, piglets, weaners) different antimicrobial substances. Considerable prevalences of resistance were found for some antimicrobials. The strains originating from both animal species displayed high prevalences of resistance for tetracycline, trimethoprim, trimethoprim/sulfamethoxazole, doxycycline and ampicillin. Reduced susceptibility was detected particularly in the E. coli strains from calves. The data reveal that the resistance level of E. coli strains isolated from cases of enteric disease in calves and pigs is altogether higher than has so far been reported in pathogens causing different diseases and in other food-producing animal species. Based on the results presented, it is possible to assess the current resistance situation for E. coli strains in calves and pigs in Germany. This in turn helps to deduce the necessary management measures that can be taken in order to minimise resistance to antibiotics. Furthermore, the data help to decide on adequate therapy of E. coli infections of the intestinal tract in calves and pigs and encourage the responsible use of antibiotics in the interests of animal health and consumer protection. 相似文献
67.
Wallmann J Schröer U Kaspar H 《Berliner und Münchener tier?rztliche Wochenschrift》2007,120(9-10):452-463
In the study 2004/2005, the current quantitative resistance level of Escherichia coli, Pasteurella multocida, Pseudomonas aeruginosa, Salmonella sp. and Staphylococcus aureus from chickens and turkeys was determined for the first time within the framework of the National Resistance Monitoring of the Federal Office of Consumer Protection and Food Safety (BVL).The objective was to implement a valid database on the basis of which the development and spread of resistance can be evaluated and monitored. During the investigation period from January 2004 to February 2005,927 strains were collected and 857 (92%) bacteria strains which corresponded to the specifications of the study protocol were tested with the broth microdilution method to determine the in vitro susceptibility (minimum inhibitory concentration) to 22 to 28 antimicrobial agents or antibiotic combinations. The results document a prevalence of resistance that exceeds that of bacterial pathogens of other animal species, especially in the case of tetracycline. Apart for S. aureus, clinical resistance to fluoroquinolones can still be considered low in poultry pathogens (E. coli approx. 2%). By applying the MICG of 4 mg/L for enrofloxacin, a susceptibility of approximately 78 % was calculated for S. aureus. A comparison of the prevalence of resistance between chickens and turkeys, showed that a slightly higher prevalence of resistance can be expected in turkeys. Differences between the susceptibility data of chicks and adult animals could only be found in turkeys. In the case of E. coli, the prevalence of resistance of strains isolated from adult turkeys was up to 10% higher than those isolated from chicks for the corresponding antimicrobial agents. It must be pointed out that the number of E. coli strains from adult turkeys was much higher (n = 194) than the number from turkey chicks (n = 21). The results indicate clearly that in a resistance monitoring system it is necessary to categorise poultry by animal species (chicken, turkey) as well as by production stage and type (broiler, laying hen), so that the epidemiology of resistance can be correctly represented and evaluated. This information is the basis for the development of long-term management options for minimizing antibiotic resistance. Furthermore, the knowledge of prevailing resistance levels in Germany is a valuable tool for veterinary practitioners when determining an empirical therapy.The data collected by the BVL make an important contribution to the optimisation of the safety of food from animals, and thus to improving consumer protection. 相似文献
68.
Kiening M Niessner R Drs E Baumgartner S Krska R Bremer M Tomkies V Reece P Danks C Immer U Weller MG 《Journal of agricultural and food chemistry》2005,53(9):3321-3327
People suffering from food allergies are dependent on accurate food labeling, as an avoidance diet is the only effective countermeasure. Even a small amount of allergenic protein can trigger severe reactions in highly sensitized patients. Therefore, sensitive and reliable tests are needed to detect potential cross-contamination. In this paper two fast sandwich immunoassays are described for the determination of peanut (Arachis hypogaea) and hazelnut (Corylus avellana) traces in complex food matrices. Mouse monoclonal antibodies were used as capture antibodies, and labeled rabbit polyclonal antibodies were used as detection antibodies in both assays. The assay time was 30 min in total, and cross-reactivities against a variety of fruits and seeds were found to be in the low 10(-4)% (ppm) level or in some cases not detectable. The recoveries in all tested food matrices ranged from 86 to 127%, and the limits of detection were in the range of 0.2-1.2 mg/kg (ppm) in food for both peanut and hazelnut, respectively. 相似文献
69.
Horst Käding Jürgen Augustin Ulrike Münchmeyer Wolfgang Leipnitz 《Archives of Agronomy and Soil Science》2013,59(6):557-572
Aus vorliegenden Versuchsergebnissen werden Aussagen zum N‐Kreislauf auf Niedermoorgrünland bei gestaffelter Stickstoffdüngung gemacht. N‐Düngung und Torfmineralisation sind entscheidende Inputgrößen. Die Outputseite wird wesentlich durch Stickstoffentzüge der Pflanzen bestimmt. Die N‐Zufuhr durch Knöllchenbakterien, freilebende N‐bindende Bakterien und Niederschläge ist anteilmäßig gering. Auch sind die N‐Verluste auf Niedermoorstandorten durch Auswaschung und gasförmige Emissionen niedrig. Die Rohproteinerträge auf nicht mit Stickstoff gedüngtem, aber ausreichend mit Makronährstoffen versorgtem Niedermoor sind Anhaltsgrößen für die Mineralisationsrate des Standortes. Nach Stickstoffdüngung kann, bei einer Ausnutzungsrate von 48%, ebenfalls auf die Netto‐N‐Mineralisationsrate geschlossen werden. 相似文献
70.
Ulrike Hoffmann Aaron Yair Harald Hikel Nikolaus J. Kuhn 《Journal of Soils and Sediments》2012,12(6):811-825