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   26篇
  免费   3篇
林业   1篇
  4篇
综合类   6篇
畜牧兽医   13篇
植物保护   5篇
  2019年   1篇
  2017年   4篇
  2016年   1篇
  2015年   1篇
  2013年   1篇
  2012年   1篇
  2010年   2篇
  2008年   3篇
  2006年   1篇
  2003年   3篇
  2000年   2篇
  1998年   4篇
  1997年   1篇
  1996年   2篇
  1984年   1篇
  1966年   1篇
排序方式: 共有29条查询结果,搜索用时 31 毫秒
1.
2.
REASONS FOR PERFORMING STUDY: It has long been recognised that the production of abnormal respiratory sounds by horses during exercise is frequently associated with upper airway obstructions. Respiratory acoustic measurements have shown promise in investigation of upper airway disorders in man and, more recently, in horses with experimentally-induced obstructions. OBJECTIVES: To evaluate sounds from exercising horses with naturally occurring dynamic obstructions of the upper respiratory tract and to compare these with those from normal horses in order to determine whether different obstructions produce characteristic spectral patterns. METHODS: The audio signal, airflow and videoendoscopic images were recorded simultaneously during an incremental exercise test on a high-speed treadmill. RESULTS: Spectral analysis of the audio signal showed marked differences between control and clinically afflicted horses. Dorsal displacement of the soft palate was characterised by a narrow low frequency (20-80 Hz) peak during expiration. Horses with dynamic laryngeal collapse produced inspiratory sounds characterised by a broad band high frequency spectral component in the range 1.1-2.7 kHz. CONCLUSIONS AND POTENTIAL RELEVANCE: Spectral analysis of respiratory sounds in horses has potential as a diagnostic technique for field use especially when facilities for high-speed treadmill assessment are not practicable.  相似文献   
3.
Inhibitors of cyclin‐dependent kinases, as roscovitine, have been used to prevent the spontaneous resumption of meiosis in vitro and to improve the oocyte developmental competence. In this study, the interference of oil overlay on the reversible arrest capacity of roscovitine in sheep oocytes as well as its effects on cumulus expansion was evaluated. For this, cumulus‐oocyte complexes (COCs) were cultured for 20 h in TCM 199 with 10% foetal bovine serum (Control) containing 75 μm roscovitine (Rosco). Subsequently, they were in vitro matured (IVM) for further 18 h in inhibitor‐free medium with LH and FSH. The culture was performed in Petri dishes under mineral oil (+) or in 96 well plates without oil overlay (?) at 38.5°C and 5% CO2. At 20 and 38 h, the cumulus expansion and nuclear maturation were evaluated under stereomicroscope and by Hoechst 33342 staining, respectively. No group presented cumulus expansion at 20 h. After additional culture with gonadotrophins, a significant rate of COCs from both Control groups (+/?) exhibited total expansion while in both Rosco groups (+/?) the partial expansion prevailed. Among the oocytes treated with roscovitine, 65.2% were kept at GV in the absence of oil overlay while 40.6% of them reached MII under oil cover (p < 0.05). This meiotic arrest was reversible, and proper meiosis progression also occurred in the Control groups (+/?). So, the culture system without oil overlay improved the meiotic inhibition promoted by roscovitine without affecting the cumulus expansion rate or the subsequent meiosis progression.  相似文献   
4.
Malm  O  Guimarães  JRD  Castro  MB  Bastos  WR  Viana  JP  Branches  FJP  Silveira  EG  Pfeiffer  WC 《Water, air, and soil pollution》1997,97(1-2):45-51
Informal economy of gold mining has contaminated some important river basins in Amazon. Follow-up studies on critical compartments showed some areas with high Hg levels in fish as well as in human hair samples. Average Hg in piscivorous fish in the Madeira river itself was 846 ppb (N=284) with a maximum of 3921 ppb. Mercury in fish from non polluted areas in this basin shows high variability, even for single species. A seasonal variation in Hg content was observed, with higher values at the end of the dry season. In the upper Tapajós basin comparable values were found for fish but with a definite decreasing trend downstream. Average value for piscivorous fish in the whole Tapajós basin is 482 ppb (N=122) with a maximum value of 3770 ppb. Hair Hg was higher in fishing villages in the Tapajós (average: 17 ppm; with N=432 and maximum value of 176 ppm) than in the Madeira (average: 9 ppm; N=169; maximum 71 ppm), and data from some areas of the Tapajós suggest a decrease with time. Mercury was much higher in urine of goldshop workers in Santarém (low Tapajós) than in Alta Floresta (high Tapajbs) and show a decreasing trend in both cases, probably related to the significant decline in gold mining activities during the study period (1986–1994).  相似文献   
5.
6.
Global maps of thermal and fast neutron fluxes from the moon suggest three end-member compositional units. A high thermal and low fast neutron flux unit correlates with the lunar highlands and is consistent with feldspathic rocks. The South Pole-Aitken basin and a strip that surrounds the nearside maria have intermediate thermal and fast neutron flux levels, consistent with more mafic rocks. There appears to be a smooth transition between the most mafic and feldspathic compositions, which correspond to low and high surface altitudes, respectively. The maria show low thermal and high fast neutron fluxes, consistent with basaltic rocks.  相似文献   
7.
The Lunar Prospector neutron spectrometer data correlate well with iron and titanium abundances obtained through analysis of Clementine spectral reflectance data. With the iron and titanium dependence removed, the neutron spectrometer data also reveal regions with enhanced amounts of gadolinium and samarium, incompatible rare earth elements that are enriched in the final phases of magma crystallization. These regions are found mainly around the ramparts of the Imbrium impact basin but not around the other basins, including the much larger and deeper South Pole-Aitken basin. This result confirms the compositional uniqueness of the surface and interior of the Imbrium region.  相似文献   
8.
Numerous examples exist of successful mammalian invasive alien species (IAS) eradications from small islands (<10 km2), but few from more extensive areas. We review 15 large‐scale removals (mean area 2627 km2) from Northern Europe since 1900, including edible dormouse, muskrat, coypu, Himalayan porcupine, Pallas' and grey squirrels and American mink, each primarily based on daily checking of static traps. Objectives included true eradication or complete removal to a buffer zone, as distinct from other programmes that involved local control to limit damage or spread. Twelve eradication/removal programmes (80%) were successful. Cost increased with and was best predicted by area, while the cost per unit area decreased; the number of individual animals removed did not add significantly to the model. Doubling the area controlled reduced cost per unit area by 10%, but there was no evidence that cost effectiveness had increased through time. Compared with small islands, larger‐scale programmes followed similar patterns of effort in relation to area. However, they brought challenges when defining boundaries and consequent uncertainties around costs, the definition of their objectives, confirmation of success and different considerations for managing recolonisation. Novel technologies or increased use of volunteers may reduce costs. Rapid response to new incursions is recommended as best practice rather than large‐scale control to reduce the environmental, financial and welfare costs. © 2016 Crown copyright. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.  相似文献   
9.
The objective of this study was to define the patterns of organogenesis and foetal haemodynamics during the normal gestation of healthy agoutis (Dasyprocta prymnolopha) kept in captivity. Thirty pregnant agoutis that ranged in size from small to medium and weighed between 2.5 and 3 kg underwent B‐mode and Doppler ultrasonography for the biometric evaluation of the foetal organs. The foetal aortic blood flow proved to be predominantly systolic, and the measured flow velocity was 78.89 ± 2.95 cm/s, with a maximum pressure gradient of 2.12 ± 0.27 mmHg. The liver was characterized by its large volume, occupying the entire cranial aspect of the abdominal cavity, and it was associated cranially with the diaphragm and caudally with the stomach. The flow velocity in the portal vein was estimated to equal 12.17 ± 2.37 cm/s, with a resistivity index of 0.82 ± 0.05. The gallbladder was centrally located and protruded cranially towards the diaphragm. The spleen was visualized as an elongated structure with tapered cranial and caudal extremities, and the foetal kidneys were visualized bilaterally in the retroperitoneal region, with the right kidney positioned slightly more cranially than the left. The morphological characterization and hemodynamic analysis of the foetal organs of black‐rumped agoutis via B‐mode and Doppler ultrasonography allow determination of the vascular network and of reference values for the blood flow required for perfusing the anatomical elements essential for maintaining the viability of foetuses at different gestational ages.  相似文献   
10.
Micrometeorological variables measured in the BIOSPHERE-2 Center (B2C) enclosed rain forest biome for 1 year were compared with similar measurements made in the Amazon rain forest. In the B2C rain forest, the overlying glass and supporting structure significantly reduces (by approximately a factor of two) the incoming solar radiation. Monthly mean values of above-canopy and within-canopy air temperature, vapor pressure, and vapor pressure deficit are reasonably similar to those of the Amazon rain forest, but there are marked differences in the above-canopy values of these variables in the Arizona summer. Monthly mean diurnal trends also show significant differences. Measurements of vertical air temperature gradient clearly showed two very distinct environments in the 27.4 m high rain forest dome during daylight hours. There is a comparatively cool and fairly well-mixed environment (which is reasonably similar to that found in a natural rain forest) below about 10 m and a hot, thermally stable environment above about 15 m. The nature of the atmospheric turbulence within the B2C rain forest also is significantly different from that normally found in natural rain forests. There is little turbulent mixing above the forest canopy in this enclosed environment. These findings are important for guiding the operation and use of this experimental rain forest facility in future research and for understanding how the rain forest biome functions in an enclosed environment.  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