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   119篇
  免费   15篇
林业   2篇
农学   1篇
  10篇
综合类   9篇
农作物   3篇
水产渔业   8篇
畜牧兽医   100篇
植物保护   1篇
  2023年   2篇
  2022年   3篇
  2021年   7篇
  2020年   10篇
  2019年   7篇
  2018年   4篇
  2017年   6篇
  2016年   5篇
  2015年   4篇
  2014年   8篇
  2013年   4篇
  2012年   12篇
  2011年   12篇
  2010年   4篇
  2009年   4篇
  2008年   4篇
  2007年   7篇
  2006年   4篇
  2005年   6篇
  2004年   5篇
  2003年   7篇
  2002年   5篇
  2001年   1篇
  2000年   2篇
  1999年   1篇
排序方式: 共有134条查询结果,搜索用时 338 毫秒
91.
92.
A real-time PCR assay based on TaqMan probe chemistry was developed for the detection of Theileria parva DNA in blood samples. It uses a Theileria genus-specific PCR primer set and a T. parva-specific probe to amplify and hybridize with a species-specific part of the 18S rRNA gene of the parasite. The test was evaluated using positive and negative reference blood samples and shown to be specific for T. parva. Analytical sensitivity was determined by testing a dilution series of T. parva positive blood. It was shown to be able to detect parasitaemia as low as 2 × 10(-6)%. The Taqman assay results were also compared with that obtained with the real-time hybridization probe PCR assay, which is currently employed as the official test for the diagnosis of T. parva infections in buffalo and cattle and was shown to be equally sensitive. A panel of 1164 field samples was screened using both assays and 164 samples tested positive in both tests, indicating a good correlation.  相似文献   
93.
  1. Accurately mapping the extent and status of biogenic reefs formed by polychaete worms of the genus Sabellaria is of conservation importance given their protected status across Europe.
  2. Traditionally, side‐scan sonar (SSS) combined with ground‐truthing in the form of seabed photography and videography has been widely accepted as the most suitable approach for mapping these reefs in the subtidal zone. In highly turbid environments visibility at the seabed can be near zero, however, rendering optical‐based ground‐truthing redundant. Consequently, the true distribution and status of Sabellaria reefs in some shallow subtidal areas around the UK remains unclear despite their designation as Annex‐I features of several Special Areas of Conservation (SACs) under the Habitats Directive.
  3. Acoustic camera imagery (ACI) collected using acoustic cameras in two deployment configurations matched well with the backscatter signatures of seabed features in corresponding SSS data. The ACI was of suitable resolution for visualizing Sabellaria colony structures, allowing for their Annex‐I ‘reef’ defining attributes (extent, patchiness, and elevation) to be assessed. Colony formation ‘type’ was also distinguishable in the ACI, although confidence in differentiating between low‐lying Sabellaria formations and surrounding substrates was low, particularly when using a pole‐mounted configuration.
  4. This study provides a proof of concept for using acoustic cameras as tools for ground‐truthing SSS interpretation and assessing the status of Sabellaria bioconstructions in low‐visibility environments. Further development of this approach and incorporating it into statutory monitoring programmes could improve the management of the reef habitats in subtidal areas of the Severn Estuary and other highly turbid environments.
  相似文献   
94.
95.
96.
The ultrasonographic findings in three small breed dogs with intracranial arachnoid cysts are described. Ultrasound images were obtained via the foramen magnum, temporal window and persistent bregmatic fontanelle (when possible). In transverse, dorsal and sagittal transcranial ultrasound images there was marked dilation of the lateral ventricles and a well-defined, oval to triangular-shaped anechoic area between the caudal aspect of the occipital lobes, dorsal to the midbrain, and rostral to the cerebellum. These findings were consistent with a diagnosis of concurrent hydrocephalus and an arachnoid cyst within the quadrigeminal cistern.  相似文献   
97.
98.
For much of the last century, the South was a net loser of blacks and whites to other regions. The end of this “Great Migration” occurred around 1970. Since then, the South is the only U.S. region to gain both blacks and whites through migration in every decade. As recessions often perturb migration systems by restraining rates of movement and altering patterns, this paper explores how the Great Recession of 2007–2009 and its aftermath affected the established migration gains of native‐born blacks and whites within the South. We use data from the 1990 and 2000 censuses and pooled data from American Community Survey to evaluate these changes. While the South continued to add both blacks and whites from migration during the recessionary years, key states bucked this trend. Georgia, for example, experienced a net migration gain of blacks but a net loss of whites. Florida added population in all time periods studied but lost large numbers of educated blacks and whites between 2008–2010. Texas, in contrast, added both blacks and whites from migration no matter their age or education throughout the recent recession. This economic downturn, then, has disturbed long‐term migration patterns in the South. A more nuanced set of interstate movements has emerged, differentiated by age and education within race groups, which we suspect will last for some time.  相似文献   
99.
Following collection of soil, storage prior to analyses is often required where the microbial community is unlikely to remain stable. We assessed the change in microbial community level physiological profiles (CLPP) during cold storage at 4 °C between 3 and 101 days. We hypothesized that the microbial community in soils containing less carbon would be affected more rapidly by storage. In particular we wanted to ascertain whether variability in CLPP through time masked inherent differences between soils derived from different ecosystems. Results illustrated that whilst total CO2 evolution did vary with incubation time, significant differences in microbial community structure were detected between ecosystems for all times. Thus storage time did not mask intrinsic differences in microbial community structure between ecosystems.  相似文献   
100.
Objective  To describe the most common canine breeds affected with cataracts in Rio de Janeiro.
Animals  Three hundred and three dogs were included in this retrospective study. Animal ages ranged from 6 months to 14.8 years.
Material and methods  All records of dogs seen by the Ophthalmology Service of Policlínica Veterinária Botafogo between January 2005 and June 2008 were reviewed. Animals with cataracts were separated, and breed and age were evaluated.
Results  Most of the dogs presented with cataracts were Toy Poodles with a mean age of 8.2 years, followed by Cocker Spaniels and Bichon Frises. The percentage of Toy Poodles affected with cataracts was 13.8% while 33.3% of Bichon Frise was diagnosed with cataracts.
Conclusions  Toy Poodles are a popular breed in Rio de Janeiro. Without regulations on breeding, the prevalence of cataracts may increase rapidly. Furthermore, due to the relatively late onset of cataract formation in the Toy Poodle (mean 8.2 years of age), affected animals may have produced several litters of puppies. This study emphasizes the importance of screening for the presence of inherited ocular abnormalities such as cataracts prior to breeding.  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