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   124篇
  免费   3篇
  国内免费   1篇
林业   6篇
农学   11篇
基础科学   1篇
  33篇
综合类   14篇
农作物   20篇
水产渔业   5篇
畜牧兽医   32篇
园艺   1篇
植物保护   5篇
  2023年   2篇
  2022年   6篇
  2021年   2篇
  2020年   6篇
  2019年   12篇
  2018年   11篇
  2017年   6篇
  2016年   7篇
  2015年   2篇
  2014年   5篇
  2013年   8篇
  2012年   4篇
  2011年   6篇
  2010年   8篇
  2009年   3篇
  2008年   7篇
  2007年   6篇
  2006年   2篇
  2005年   7篇
  2004年   5篇
  2002年   1篇
  2000年   2篇
  1999年   3篇
  1998年   1篇
  1997年   1篇
  1995年   1篇
  1994年   1篇
  1991年   1篇
  1984年   1篇
  1979年   1篇
排序方式: 共有128条查询结果,搜索用时 31 毫秒
1.
2.
Propofol is a potentially useful intravenous anesthetic agent for total intravenous anesthesia (TIVA) in horses. The purpose of this study was to compare the anesthetic and cardiorespiratory effects of TIVA following the administration of propofol alone(P–TIVA) and ketamine–medetomidine–propofol (KM–P–TIVA) in adult horses. The carotid artery was translocated to a subcutaneous position during TIVA with P–TIVA (n = 6) or KM–P–TIVA (n = 6). All horses were premedicated with medetomidine [0.005 mg kg–1, intravenously (IV)]. Anesthesia was induced with midazolam (0.04 mg kg–1 IV) and ketamine (2.5 mg kg IV). All horses were orotracheally intubated and breathed 100% oxygen. The KM drug combination (ketamine 40 mg mL–1 and medetomidine 0.05 mg mL–1) was infused at a rate of 0.025 mL kg–1 hour–1. Subsequently, a loading dose of propofol (0.5 mg kg–1, bolus IV) was administered to all horses; surgical anesthesia (determined by horse response to incision and surgical manipulation, positive response being purposeful or spontaneous movement of limbs or head) was maintained by varying the propofol infusion rate as needed. Arterial blood pressure and HR were also monitored. Both methods of producing TIVA provided excellent general anesthesia for the surgical procedure. Anesthesia time was 115 ± 17 (mean ± SD) and 112 ± 11 minutes in horses anesthetized with KM–P–TIVA and P–TIVA, respectively. The infusion rate of propofol required to maintain surgical anesthesia with KM–P–TIVA was significantly less than for P–TIVA (mean infusion rate of propofol during anesthesia; KM–P–TIVA 0.15 0.02 P–TIVA 0.23 ± 0.03 mg kg–1 minute–1, p = 0.004). Apnea occurred in all horses lasting 1–2 minutes and intermittent positive pressure ventilation was started. Cardiovascular function was maintained during both methods of producing TIVA. There were no differences in the time to standing after the cessation of anesthesia (KM–P–TIVA 62 ± 10 minutes versus P–TIVA 87 ± 36 minutes, p = 0.150). The quality of recovery was good in KM–P–TIVA and satisfactory in P–TIVA. KM–P–TIVA and P–TIVA produced clinically useful general anesthesia with minimum cardiovascular depression. Positive pressure ventilation was required to treat respiratory depression. Respiratory depression and apnea must be considered prior to the use of propofol in the horse.  相似文献   
3.
Fish Physiology and Biochemistry - This study presents the first incidence of intersex associated with testis-ova in spotted scat (Scatophagus argus) reared in a controlled environment. The...  相似文献   
4.
Zargham Khan, M., Muhammad, G., Umar, A. and Ali Khan, S., 1997. A preliminary comparison of plasma fibrinogen concentrations, leukocyte numbers and erythrocyte sedimentation rate as non-specific indicators of inflammatory conditions in buffalo (Bubalis bubalis). Veterinary Research Communications, 21 (4), 265-271The plasma fibrinogen concentration (Fib), total leukocyte count (TLC), neutrophil, lymphocyte and monocyte numbers, and the erythrocyte sedimentation rate (ESR) were determined in 153 buffaloes suffering from different clinical conditions. Fib increased significantly (p < 0.05) in chronic mastitis, pyrexia, pyometra, cutaneous abscesses, tail gangrene and acute indigestion, whereas in most of the other conditions studied it varied non-significantly. TLC increased significantly in chronic mastitis, pyrexia, endometritis, cutaneous abscesses and infected skin wounds. An increase in neutrophils was associated with an increased TLC. Numbers of lymphocytes varied non-significantly in most of the conditions. Monocytes decreased significantly in most of the acute conditions. ESR was significantly elevated in all clinical conditions. Significantly increased mean Fib values in the different conditions varied from 703 ± 119 to 725 ± 140 mg/dl, while the maximum individual value was 1510 mg/dl in a case of cutaneous myiasis. The significantly increased mean TLC ranged from 9.48 ± 2.91 to 11.1 ± 3.5 × 103/µl, while it was 21.7 × 103/µl in a case of meningitis. ESR values in sick buffaloes varied from 57 to 111 mm in the first hour.  相似文献   
5.
The objectives of this study were to investigate the effect of a saponin-based surfactant, Grain Prep surfactant (GP), and hot flake aging time on starch characteristics and ruminal DM and starch degradability of steam-flaked corn grain. In 2 experiments, the moisture content of incoming corn was automatically adjusted using the Grain Prep Auto Delivery System to 19.8% (Exp. 1) and 18.5% (Exp. 2). The application rate of GP was 22 mg/kg (as-is basis). Control corn was treated with water alone. Processed corn in Exp. 2 was stored in insulated containers for 0, 4, 8, or 16 h. Flaked corn samples were incubated in the rumen of lactating dairy cows for 0, 2, 4, 6, 16, or 24 h. In Exp. 1, GP increased, compared with the control, the soluble fraction and effective degradability (ED) of DM by 17.2 and 8.6%, respectively. The ED of cornstarch was increased by 6.7%. In Exp. 2, the concentration of soluble DM and starch were increased by GP by 15 and 24% compared with the control. The ED of DM and starch were also increased by 3 and 4%, respectively. No differences in gelatinization temperatures were observed due to treatment, except that GP-treated grain had a slightly greater mean gelatinization enthalpy in Exp. 2. In a pilot study, DM degradability parameters were not affected by germination of the corn kernels. Aging of the hot flakes for up to 16 h resulted in a quadratic decrease in DM and starch ruminal degradability. The aging process affected starch gelatinization enthalpy values of flaked grain in a manner opposite to that observed for ruminal DM and starch degradation. This phenomenon was most likely explained by increased starch intramolecular associations or crystallinity associated with starch annealing, or both. This study confirmed our previous observations that Grain Prep surfactant increases flaked corn DM and starch degradability in the rumen. Because the rate of degradation was not affected by the surfactant, the increase in degradability was attributed mainly to increases in DM and starch solubility.  相似文献   
6.
In a two years field study on effect of irrigation at vegetative and flowering stages occurring at 40 and 60 days after sowing, respectively alongwith straw mulch ca. 5 t/ha were found to have beneficial effect on growth, yield attributes and seed yield of horsegram ( Dolichos biflorus Roxb.). Application of mulches significantly increased pods/plants, seeds/pod, test weight and seed yield and maintained better soil moisture during crop growth in semi-arid lateritic region of Indian sub-tropics. Mulches proved useful to conserve more moisture in soil profile and thereby increased the water use efficiency of the crop; straw mulch was found superior to leaf mulch.  相似文献   
7.
If they could be easily exfoliated, layered materials would become a diverse source of two-dimensional crystals whose properties would be useful in applications ranging from electronics to energy storage. We show that layered compounds such as MoS(2), WS(2), MoSe(2), MoTe(2), TaSe(2), NbSe(2), NiTe(2), BN, and Bi(2)Te(3) can be efficiently dispersed in common solvents and can be deposited as individual flakes or formed into films. Electron microscopy strongly suggests that the material is exfoliated into individual layers. By blending this material with suspensions of other nanomaterials or polymer solutions, we can prepare hybrid dispersions or composites, which can be cast into films. We show that WS(2) and MoS(2) effectively reinforce polymers, whereas WS(2)/carbon nanotube hybrid films have high conductivity, leading to promising thermoelectric properties.  相似文献   
8.
Wild blueberry (Vaccinium angustifolium Ait.) fields in the north east Canada are naturally grown in a course textured thin layer of soil and below this layer is a soilless layer of gravel. The root zone depth of this crop varies from 10 to 15 cm. Investigating the depth to the gravel layer below the course textured soil is advantageous, as it affects the water holding capacity of the root zone. Water and nutrient management are the two primary determinants of crop yield and the amount of leaching. The objective of this study was to estimate the depth to the gravel layer using DualEM-2 instrument. A C++ program written in Visual Studio 2010 was used to develop mathematical models for estimating the depth to the gravel layer from the outputs of DualEM-2 sensor. Two wild blueberry fields were selected in central Nova Scotia, Canada to evaluate the performance of DualEM-2 instrument in estimating the rootzone depth above the gravel layer. The mid points of squares created by grid lines were used as the sampling points at each experimental site. The actual depth to the interface was measured manually at selected grid points (n = 50). The apparent ground conductivity (ECa) values of DualEM-2 were recorded and the depth to the interface was estimated for the same sampling points within the selected fields. The fruit yield samples were also collected from the same grid points to identify the impact of the depth to the gravel layer on crop yield. After calibrations, comprehensive surveys were conducted and the actual and estimated depths to the interface were established. The interpolated maps of fruit yield, and the actual (zin) and estimated (\( {\text{z}}_{\text{in}}^{*} \)) depths to the interface were created in ArcGIS 10 software. Results indicated that the zin was significantly correlated with \( {\text{z}}_{\text{in}}^{*} \) for the North River (R 2 = 0.73; RMSE = 0.27 m) and the Carmel (R 2 = 0.45; RMSE = 0.20 m) sites. Results revealed that the areas with shallow depth to the gravel layer were low yielding, indicating that the variation in the depth to the gravel layer can have an impact on crop productivity. Non-destructive estimations of the depth to the gravel layer can be used to develop erosion control strategies, which will result in an increased crop production.  相似文献   
9.
Accurate prediction of soil N availability requires a sound understanding of the effects of environmental conditions and management practices on the microbial activities involved in N mineralization. We determined the effects of soil temperature and moisture content and substrate type and quality (resulting from long-term pasture management) on soluble organic C content, microbial biomass C and N contents, and the gross and net rates of soil N mineralization and nitrification. Soil samples were collected at 0–10 cm from two radiata pine (Pinus radiata D. Don) silvopastoral treatments (with an understorey pasture of lucerne, Medicago sativa L., or ryegrass, Lolium perenne L.) and bare ground (control) in an agroforestry field experiment and were incubated under three moisture contents (100, 75, 50% field capacity) and three temperatures (5, 25, 40 °C) in the laboratory. The amount of soluble organic C released at 40 °C was 2.6- and 2.7-fold higher than the amounts released at 25 °C and 5 °C, respectively, indicating an enhanced substrate decomposition rate at elevated temperature. Microbial biomass C:N ratios varied from 4.6 to 13.0 and generally increased with decreasing water content. Gross N mineralization rates were significantly higher at 40 °C (12.9 g) than at 25 °C (3.9 g) and 5 °C (1.5 g g–1 soil day–1); and net N mineralization rates were also higher at 40 °C than at 25 °C and 5 °C. The former was 7.5-, 34-, and 29-fold higher than the latter at the corresponding temperature treatments. Gross nitrification rates among the temperature treatments were in the order 25 °C >40 °C >5 °C, whilst net nitrification rates were little affected by temperature. Temperature and substrate type appeared to be the most critical factors affecting the gross rates of N mineralization and nitrification, soluble organic C, and microbial biomass C and N contents. Soils from the lucerne and ryegrass plots mostly had significantly higher gross and net mineralization and nitrification rates, soluble organic C, and microbial biomass C and N contents than those from the bare ground, because of the higher soil C and N status in the pasture soils. Strong positive correlations were obtained between gross and net rates of N mineralization, between soluble organic C content and the net and gross N mineralization rates, and between microbial biomass N and C contents.  相似文献   
10.
A three-tiered survey was devised comprising a detailed questionnaire, a serological survey and a sentinel herd scheme for disease surveillance. The survey was carried out in the traditional farming sector in 7 districts of Zambia to obtain background information on cattle management and productivity, data on the prevalence of tick-borne and other disease problems in these areas and to monitor changes in individual herds.In the questionnaire survey, 288 farmers were interviewed. They owned a total of 15 360 head of cattle, representing approximately one percent of the national herd. Mean herd sizes ranged from 31 to 114 for each district. Mean calving percentages were 44–80%. Average national offtake from these herds was 10%. Calf mortality rates ranged from 4 to 32%, while adult yearly mortality rates ranged from 4 to 16%. Factors affecting the regional variation of these figures are discussed.  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