首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   52篇
  免费   6篇
农学   3篇
  5篇
综合类   4篇
水产渔业   5篇
畜牧兽医   36篇
园艺   2篇
植物保护   3篇
  2023年   1篇
  2021年   1篇
  2020年   6篇
  2019年   7篇
  2018年   3篇
  2017年   3篇
  2016年   2篇
  2015年   3篇
  2014年   1篇
  2012年   3篇
  2011年   6篇
  2010年   6篇
  2009年   2篇
  2008年   2篇
  2007年   3篇
  2006年   2篇
  2005年   1篇
  2004年   1篇
  2003年   2篇
  2001年   2篇
  1992年   1篇
排序方式: 共有58条查询结果,搜索用时 140 毫秒
11.
Methylcyclopentadienyl manganese tricarbonyl (MMT) was used between 1990 and 2003 as an antiknock agent and as an octane booster in Canadian unleaded gasoline. Its combustion leads to Mn emissions. The objective of this research was to examine the variations in atmospheric Mn in Montreal (Canada) from 2001 to 2007, covering the period prior (2001?C2003) to and following (2005?C2007) MMT use. Three sampling stations were selected because of their proximity to roads with widely differing and well-known traffic patterns. Filters from 2001 to 2007 were obtained from the Montreal Urban Community. The first sample of each month was selected, and Mn analysis was performed by neutron activation analysis. Total suspended particulates (TSP) was calculated by weighing the filters before and after dust collection. Results show a significant decrease of Mn over time at each station, whereas TSP decreased significantly in two stations. Comparing atmospheric Mn during and after the period of use of MMT 2001?C2003 vs 2005?C2007 showed a significant decrease at all stations. For TSP, only one station showed borderline significant decline between these two periods. Overall, between the two periods, Mn and TSP decreased by 39% and 17%, respectively. These data suggest that the combustion of MMT led to an increase of airborne Mn of approximately 22%. These findings should help in decision-making processes concerning the use of MMT in gasoline in other countries.  相似文献   
12.
13.
14.
The present work aimed to investigate the presence of T. vivax DNA in the semen of experimentally infected goats. Twelve male goats native to the Brazilian Northeast, adults, were randomly assigned to two experimental groups: the infected group consisting of six goats infected intravenously with 0.5 mL of blood containing approximately 1.25?×?105 trypomastigotes of T. vivax, and a control group composed of six uninfected goats. After the infection, clinical examinations aiming to evaluate rectal temperature, parasitemia and hematocrit were performed. Semen samples were collected from goats by electroejaculation on the 7th, 14th and 21st days post-infection (dpi). The recombinant DNA-encoding gene encoding the L-like-specific gene for T. vivax. The infection was characterized by increased rectal temperature, high parasitemia and significant reduction of hematocrit values. Results for T. vivax DNA detection using TviCatL-PCR were positive in all semen samples from the infected group collected on 7th, 14th and 21st dpi. The presence of T. vivax DNA in 7th dpi suggests the early invasion of the parasite in the reproductive organs. Also, the finding of T. vivax DNA in all periods analyzed may suggest the continued elimination of the parasite in the semen, which may increase the chances of sexual transmission. Thus, T. vivax DNA is recorded for the first time in the semen of infected goats. Thus, these data are of great importance, since the detection of the T. vivax genetic material in the semen may point to the possibility that the parasite may be transmitted through the sexual pathway.  相似文献   
15.
The crossing of host species barriers, through the spreading populations of introduced pet animals that become established in the wild, sets the stage for zoonotic pathogen (re)emergence. A literature review on pathogens that are hosted by the ring-necked parakeet (Psittacula krameri), a worldwide introduced pet, highlighted local infections of captive birds by chlamydial agents with high sanitary risk for human health in its introduced range. We searched for these pathogens through cloacal swabs collected from 85 individuals in an invasive population established in the suburban areas of Paris (Ile-de-France) from 5 localities during the winter seasons between 2011 and 2014. Based on quantitative PCR analysis, Chlamydiaceae shedding was detected at too low levels for species identification in 5 birds, but 1 parakeet (found dead) was positive for Chlamydiaceae typed as Chlamydia avium. The only known hosts recorded for C. avium in Europe are feral pigeons (Columba livia) and captive psittacines. This result raises the question of the sanitary risks associated with new pathogen transmission from exotic pets released in the wild, which could locally affect birds and potentially people who feed birds.  相似文献   
16.
Between 2000 and 2008, 95 rabbits with suspected encephalitozoonosis and neurological symptoms were treated at the Clinic of Small Animal Medicine, Ludwig Maximilian University Munich. Standard treatment consisted of oxytetracycline (from 2000 to 2003; n=50) or fenbendazole and oxytetracycline (from 2004 to 2008; n=45), and the rabbits were randomly assigned to treatment groups with or without dexamethasone. Each therapeutic regime was given for 10 days, with fluids, B vitamins and nutritional support added as needed. Therapeutic success was evaluated by assessing the survival rate on day 10, the neurological score of the surviving rabbits and Kaplan-Meier curves for long-term survival past 10 days. Inclusion of fenbendazole in the treatment protocol was associated with increased survival rates on day 10 (p=0.043), better neurological scores (p=0.008), and improved long-term survival (p=0.025) based on the results of univariate analyses. Treatment with dexamethasone showed no effect on neurological score or on short- or long-term survival. The study did not provide any evidence that dexamethasone is an effective component of the treatment scheme.  相似文献   
17.
18.
Anaplasma marginale infection in Europe has been limited to the Mediterranean and eastern countries, to Austria and to very sporadic cases in Switzerland. There are no reports of its occurrence in the countries north of Switzerland. A severe outbreak of anaplasmosis in August 2002 in a cattle farm in the canton Grisons, Switzerland, north of the Alps, with more than 300 cattle that had to be culled, came unexpected and gave reason to hypothesize presence of an increased yet undetected prevalence of A. marginale in Switzerland. Randomly selected bovine serum samples collected in 1998 and 2003 were tested using a competitive inhibitory ELISA (cELISA) to test the hypothesis. Our validation of the diagnostic sensitivity and specificity of this test, done in the outbreak herd, yielded 99.2 and 83.3%, respectively, probably underestimating the true specificity. The true seroprevalence of anaplasmosis in Swiss cattle determined by cELISA was likely to be zero with upper 95% confidence limits of 2.49% in the canton Grisons and 1.17% in the rest of Switzerland, respectively, in 1998. For 2003, these estimates were even lower. There was no significant difference in apparent prevalences between 1998 and 2003. In search of a possible reservoir, three chamoises out of 46 free ranging wild ruminants from the Swiss National Park, Grisons, tested positive in the cELISA. This reaction is in accordance with A. marginale or a cross reacting agent such as Anaplasma ovis. From our results we conclude that the hypothesis of an increased prevalence of anaplasmosis in cattle in Switzerland must be rejected.  相似文献   
19.
Tree protection legislation in European cities   总被引:1,自引:0,他引:1  
In this study, a survey on regulations and legal requirements concerning tree protection in European cities has been elaborated. It is designed as an information source for decision support in legal development, city planning and nature conservation. The survey is based on questionnaires on the one hand and on laws, ordinances and regulations on the other. Out of the 34 cities which were contacted or for which legal documents were found on the Internet, 25 (74%) have laws protecting trees in public and/or private areas. Against the background of rising ecological awareness, most of the laws were adopted from the 1970s onward.In most cases the protection of a tree is regulated by means of the circumference or the diameter of the stem, while sometimes the height of the tree is the criterion on which protection depends. In other cases, protection is granted if a tree is growing in a protected area or if the tree is submitted to a “Tree Preservation Order”. In all 25 cities the felling of protected trees is subjected to an official authorisation. In many laws interdictions concerning trees are listed. Most frequently, it is prohibited to cut down, to remove, to fell, to damage, to destroy, to modify, and to prune protected trees, and to enhance their decay.A law concerning tree protection seems to make sense, if it can be implemented in a non-bureaucratic, professional and efficient way, respecting the protection and conservation of nature. It should be structured simply and equitably, and its administration and implementation should be simple and efficient.  相似文献   
20.
OBJECTIVE: To measure nitric oxide (NO) concentrations in serum, urine, and synovial fluid (SF) of dogs with naturally occurring cranial cruciate ligament (CCL) rupture and normal dogs, and to compare these with clinical and histologic changes of osteoarthritis (OA). STUDY DESIGN: Prospective clinical study including 2 groups of animals selected from the hospital population. ANIMALS: Forty-three dogs (CCL group) with OA secondary to CCL rupture; 30 healthy dogs (control group) without CCL rupture. METHODS: Serum, urine, and SF were collected before and during surgery in the CCL group or immediately after euthanasia in the control group. Articular cartilage and synovial membrane tissue specimens were prepared for routine histologic examination. The stable end products of NO, total nitrite and nitrate (NOt) activity, were measured in body fluids and compared with macroscopic and histologic degrees of OA. Urinary NOt concentration was compared with urinary creatinine concentration and stated as urinary NOt:creatinine ratio (UNCR). RESULTS-SF NOt concentrations were not significantly different between the 2 groups. Serum NOt concentrations (45.6 vs 28.9 micromol/L; P =.042) and the UNCR (0.007 vs 0.004; P =.035) were significantly higher in dogs of the CCL group compared with the control population. An association between UNCR and histologic and macroscopical OA grades could be demonstrated. CONCLUSION: UNCR might be a useful indicator of nitrite and nitrate production and, therefore, osteoarthritic changes in joints. CLINICAL RELEVANCE: UNCR could be used as a tool to evaluate the NOt production by joint tissues over time and might therefore provide a method of evaluating the effects of drugs in the control of osteoarthritis.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号