全文获取类型
收费全文 | 474篇 |
免费 | 15篇 |
专业分类
林业 | 135篇 |
农学 | 12篇 |
103篇 | |
综合类 | 36篇 |
农作物 | 16篇 |
水产渔业 | 37篇 |
畜牧兽医 | 123篇 |
园艺 | 7篇 |
植物保护 | 20篇 |
出版年
2020年 | 7篇 |
2019年 | 6篇 |
2018年 | 8篇 |
2017年 | 6篇 |
2016年 | 10篇 |
2015年 | 8篇 |
2014年 | 12篇 |
2013年 | 11篇 |
2012年 | 18篇 |
2011年 | 30篇 |
2010年 | 10篇 |
2009年 | 15篇 |
2008年 | 28篇 |
2007年 | 20篇 |
2006年 | 22篇 |
2005年 | 17篇 |
2004年 | 19篇 |
2003年 | 22篇 |
2002年 | 12篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1997年 | 4篇 |
1992年 | 4篇 |
1989年 | 4篇 |
1986年 | 3篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1977年 | 4篇 |
1975年 | 3篇 |
1974年 | 5篇 |
1972年 | 6篇 |
1969年 | 3篇 |
1968年 | 3篇 |
1967年 | 5篇 |
1966年 | 3篇 |
1965年 | 4篇 |
1962年 | 3篇 |
1956年 | 4篇 |
1948年 | 7篇 |
1941年 | 3篇 |
1934年 | 3篇 |
1933年 | 3篇 |
1932年 | 12篇 |
1927年 | 7篇 |
1919年 | 6篇 |
1918年 | 5篇 |
1915年 | 4篇 |
1904年 | 5篇 |
1902年 | 3篇 |
排序方式: 共有489条查询结果,搜索用时 15 毫秒
431.
Karin Taus Friedrich Schmoll Ziad El‐Khatib Herbert Auer Heidemarie Holzmann Stephan Aberle Shiva Pekard‐Amenitsch Stefanie Monschein Tatjana Sattler Romana Steinparzer Franz Allerberger Daniela Schmid 《Zoonoses and public health》2019,66(7):842-851
We investigated the prevalence of Hepatitis E Virus (HEV), Leptospira and Ascaris suum (A. suum) seropositivity, and of nasal methicillin‐resistant Staphylococcus aureus (MRSA) colonization among Austrian practising veterinarians, and assessed the association with occupational swine livestock exposure. The 261 participants completed a questionnaire on demographics, intensity of occupational swine livestock contact and glove use during handling animals and their secretions. Participants' blood samples were tested for HEV, Leptospira and A. suum seropositivity and nasal swabs cultured for MRSA. We compared swine veterinarians (defined as >3 swine livestock visits/week) to non‐swine veterinarians (≤3 swine livestock visits/week) with regard to the outcomes through calculating prevalence ratio (PR) and 95% confidence interval (CI). Furthermore, the relationship between occupational swine livestock contact and the study outcomes was examined by age (</≥55 years) and glove usage. The prevalence of nasal MRSA colonization was 13.4% (95% CI: 9.3–17.6), of HEV seropositivity 20.8% (95% CI: 15.8–25.7) and A. suum seropositivity 44% (95% CI: 37.7–50.2). The highest anti‐leptospiral antibodies titres were 1:200 (L. hebdomadis) and 1:100 (L. autumnalis, L. caicola) found in three non‐swine veterinarians. Compared to non‐swine veterinarians, swine veterinarians were 1.9 (95% CI: 1.0–3.4) and 1.5 (95%CI: 1.0–2.3) times more likely HEV seropositive and A. suum seropositive, respectively, and 4.8 (95%CI: 2.5; 9.3) times more likely nasally colonized with MRSA. Among glove‐using veterinarians, occupational swine contact was no longer a determinant for HEV seropositivity (PR 1.6; 95% CI: 0.8–2.9). Similar was found for A. suum seropositivity, which was no longer associated with occupational swine livestock contact in the subgroup of glove using, ≥55‐year‐old veterinarians (PR: 1.07; 95% CI: 0.4–3.3). Our findings indicate that >3 occupational swine livestock visits per week is associated with HEV and A. suum seropositivity and nasal MRSA colonization and that glove use may play a putative preventive role in acquiring HEV and A. suum. Further analytical epidemiological studies have to prove the causality of these associations. 相似文献
432.
Walleye pollock (Gadus chalcogrammus) supports one of the largest commercial fisheries in the world. Juvenile pollock are important forage fish in the eastern Bering Sea (EBS) ecosystem, often representing the largest fraction in the diets of major Bering Sea piscivores. Large variability in the EBS pollock stock biomass in recent years has been attributed primarily to fluctuations in recruitment. It has been hypothesized that predation rates on forage fishes increase when the cold pool (a body of cold water < 2°C) is extensive and covers much of the middle continental shelf, which tends to concentrate larger predatory fishes in the outer shelf and slope regions. In contrast, young pollock appear to tolerate colder temperatures than older fish and can stay in the cold pool, thereby reducing predation. We used a multispecies modeling approach to examine the effects of the cold pool size on predation of juvenile pollock. We found that predation on age‐1 pollock by age‐3+ pollock decreased, and predation on age‐1 and age‐2 pollock by arrowtooth flounder increased with increasing bottom temperature, which was used as a proxy for the cold pool size. These results suggest that the cold pool creates spatial separation between juvenile pollock and arrowtooth flounder, but not between adult and juvenile pollock. The model developed in this study could be used to examine the effects of other covariates on interspecific interactions, help explain observed changes in fish communities, and understand implications of climate change on ecosystems and their productivity. 相似文献
433.
434.
Friedrich Franz 《European Journal of Forest Research》1973,92(1):217-225
Ohne Zusammenfassung 相似文献
435.
436.
H. J. Müller E. Hennig J. Syrjämäki V. Schefer-Immel B. Weber R. Mrkva M. Inouye G. F. Bornemissza F. J. Löcher M. Markkula S. Myllymäki K. Meunier H. Bruns M. Nuorteva S. Günther R. Lange J. Franz A. Szmidt W. Stein J. Franz A. Szmidt H. A. Koch E. Schwartz M. Schmidt 《Journal of pest science》1961,34(8):125-128
Ohne Zusammenfassung 相似文献
437.
Cornelia Fürstenau Franz W. Badeck Petra Lasch Manfred J. Lexer Marcus Lindner Peter Mohr Felicitas Suckow 《European Journal of Forest Research》2007,126(2):225-239
In this study, the overall utility of forest management alternatives at the forest management unit level is evaluated with
regard to multi-purpose and multi-user settings by a multi-criteria analysis (MCA) method. The MCA is based on an additive
utility model. The relative importance of partial objectives of forest management (carbon sequestration, ground water recharge,
biodiversity, and timber production) is defined in cooperation with stakeholders. The forest growth model 4C (Forest Ecosystems
in a Changing Environment) is used to simulate the impact of six forest management strategies and climate on forest functions.
Two climate change scenarios represent uncertainties with regard to future climatic conditions. The study is based on actual
forest conditions in the Kleinsee management unit in east Germany, which is dominated by Scots pine (Pinus sylvestris L.) and oak (Quercus robur L. and Quercus petraea Liebl.) stands. First, there is an analysis of the impact of climate and forest management on forest functions. Climate change
increases carbon sequestration and income from timber production due to increased stand productivity. Secondly, the overall
utility of the management strategies is compared under the priority settings of different stakeholder groups. From an ecological
perspective, a conservation strategy would be preferable under all climate scenarios, but the business as usual management
would also fit the expectations under the current climate due to high biodiversity and carbon sequestration in the forest
ecosystem. In contrast, a forest manager in public-owned forests or a private forest owner would prefer a management strategy
with an intermediate thinning intensity and a high share of pine stands to enhance income from timber production while maintaining
the other forest functions. 相似文献
438.
Franz Ludwig Graf Stauffenberg 《European Journal of Forest Research》1989,108(1):327-333
Ohne Zusammenfassung 相似文献
439.
Geue L Köhler H Klawonn W Dräger K Hess RG Conraths FJ 《Berliner und Münchener tier?rztliche Wochenschrift》2007,120(1-2):67-78
Paratuberculosis or Johne's Disease, caused by Mycobacterium avium subspecies paratuberculosis (MAP), is a notifiable disease in Germany which produces enormous economical losses in dairy farms. At present,there is no confirmed data about the actual number of infected livestock herds in Germany. A countrywide monitoring program to evaluate the prevalence in dairy herds would only be economically feasible on the basis of bulk milk testing. In this study, we evaluated two ELISA test kits (SVANOVIR Ptb-ELISA, IDEXX-M.pt. Milk test kit) for the detection of antibodies against MAP in bulk milk. First, the Paratuberculosis-status of the herd derived from the history of the farm was used as a gold standard. Paratuberculosis-negative farms were tested negative with each test, but paratuberculosis-positive or Paratuberculosis-serologically-positive farms were detected only in one case (Svanovir) or three cases (IDEXX), respectively. Even if inconclusive results are counted as positive, 82.9 % (Svanovir) or 80 % (IDEXX) of the paratuberculosis-positive or serologically paratuberculosis positive farms were not detected. Nevertheless, a re-validation of both ELISAs by means of ROC and TG-ROC analyses was attempted by searching for ideal cut-offs, optimised for bulk milk. If a high specificity was selected, no acceptable sensitivity could be reached.The best results were obtained using a sensitivity of 32.3 % at a specificity of 100 % (Svanovir). With a small change of the cut-off value, the sensitivity increased to still 57 %, but this reduced the specificity to 67 %. Similar results were obtained with the IDEXX-ELISA. We then evaluated the Svanovir-ELISA for the detection of bulk milk samples on the basis of the current paratuberculosis prevalence within 69 dairy herds from Rhineland-Palatinate using individual milk samples.When the bulk milk samples were tested in two different laboratories using the same ELISA, considerable differences in the results became evident. Nearly all samples were tested with a higher relative test result in one laboratory, which often led to differences in the classification of the prevalence levels.The estimated within-herd seroprevalences ranged between 0 % and 37 %.There was little agreement between the historical paratuberculosis herd status and the within-herd prevalence in milk serum, as reflected in a kappa-index of 0.146.To determine the sensitivity and specificity of the bulk milk ELISA by ROC and TG-ROC analysis, 116 bulk milk samples were used that had been obtained from the 69 dairy herds participating in the study. The optimal ratio of sensitivity (81 %) and specificity (77 %) relative to a "gold standard" was obtained when the cut-off was set at the 10 % level. These values for sensitivity and specificity were better than those obtained in an evaluation of the same ELISA in which the historical Paratuberculosis herd-status was used as a "gold standard." The results of this study question the suitability of the available ELISAs for bulk milk testing.Taking into account that the Svanovir-ELISA for individual milk samples has a sensitivity of 60 96% relative to the blood serum variant of the test, and that the latter has also a limited sensitivity due to the pathogenesis of paratuberculosis, the available test systems examined in this Study do not seem to be suitable for herd diagnosis by using bulk milk samples. 相似文献
440.
Daniela Klein-J?bstl Tim Arnholdt Franz Sturmlechner Michael Iwersen Marc Drillich 《Acta veterinaria Scandinavica》2015,57(1)