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   269篇
  免费   36篇
林业   7篇
农学   6篇
  30篇
综合类   22篇
农作物   12篇
水产渔业   18篇
畜牧兽医   185篇
园艺   2篇
植物保护   23篇
  2024年   2篇
  2023年   3篇
  2022年   3篇
  2021年   8篇
  2020年   9篇
  2019年   11篇
  2018年   8篇
  2017年   11篇
  2016年   14篇
  2015年   13篇
  2014年   14篇
  2013年   11篇
  2012年   16篇
  2011年   15篇
  2010年   10篇
  2009年   9篇
  2008年   19篇
  2007年   10篇
  2006年   12篇
  2005年   8篇
  2004年   13篇
  2003年   7篇
  2002年   7篇
  2001年   10篇
  2000年   8篇
  1999年   2篇
  1998年   5篇
  1997年   2篇
  1996年   3篇
  1995年   2篇
  1994年   1篇
  1993年   2篇
  1992年   3篇
  1991年   2篇
  1990年   4篇
  1989年   5篇
  1987年   1篇
  1986年   3篇
  1985年   1篇
  1984年   2篇
  1983年   2篇
  1982年   1篇
  1981年   1篇
  1979年   2篇
  1978年   1篇
  1975年   2篇
  1974年   3篇
  1973年   2篇
  1964年   1篇
  1954年   1篇
排序方式: 共有305条查询结果,搜索用时 31 毫秒
81.
The present study intended to develop the hypoosmotic swelling (HOS) test in alpaca for its use in epididymal spermatozoa, to evaluate the membrane functional integrity and determine an appropriate hypoosmotic solution and whether the incubation time of 15 or 60 min is sufficient for the execution of the test. Hypoosmotic solutions (HS) with the following concentrations were used: 50, 100, 150, 200 and 275 mOsm/kg of sodium citrate tribasic dihydrate and d ‐fructose. Ten microlitres of epididymal sperm sample was mixed in 150 μL of the respective HS and incubated for 15 or 60 min at 38°C. From the proportion of reacted (swollen) spermatozoa, the 150 mOsm/kg HS was the most sensitive (p < 0.05). The exposure times (15 and 60 min) did not have significant differences (p > 0.05) in the proportion of both strong‐ and total‐coiled sperm tails. In conclusion, 150 mOsm/kg HS and 15 min exposure time are optimal to evaluate the plasma membrane functional integrity through the HOS test in alpaca epididymal spermatozoa.  相似文献   
82.
The objective of this study was to optimize protocols for the cryopreservation of sex‐sorted boar spermatozoa. In the experiment 1, we evaluated the effects of a standard boar sperm cryopreservation procedure (3% final glycerol concentration) on the in vitro characteristics of sex‐sorted sperm frozen at low sperm concentrations (20 × 106 sperm/ml; S20 group). Non‐sorted spermatozoa frozen at 1000 × 106 (C1000 group) and 20 × 106 (C20 group) sperm/ml were used as the freezing control groups. In experiment 2, the effects of different final glycerol concentrations (0.16%, 0.5%, 1.0%, 2.0% and 3.0%) on post‐thaw quality of the S20 and C20 groups were evaluated. In both experiments, the samples were evaluated prior to freezing (5°C) and at 30, 90 and 150 min after thawing. Experiment 1 indicated that freezing sperm at low concentrations decreased (p < 0.05) the total motility (TM) and progressive motility (PM) at 90 and 150 min after thawing regardless of whether the sperm were sorted or not. However, the sperm membrane integrity was not affected at any evaluation step. Inexperiment 2, significant effects on the TM and PM because of increased glycerol concentrations in the S20 and C20 groups were observed only at 90 and 150 min after thawing. The samples frozen in 3% glycerol showed lower (p < 0.05) TM and PM values when compared to those frozen in the presence of 0.5% and 1% glycerol. In both experiments, non‐sorted control samples displayed higher percentages of spermatozoa with damaged DNA than sorted spermatozoa. In conclusion, the optimization of cryopreservation conditions by decreasing the glycerol concentrations can improve post‐thaw motility of sex‐sorted spermatozoa frozen at low concentrations.  相似文献   
83.
Objective  To compare the analgesic and motor-blocking effects of epidurally administered levobupivacaine and bupivacaine in the conscious dog.
Study design  Prospective, randomized, cross-over study.
Animals  Six adult female Beagle dogs.
Methods  Each animal received three doses of levobupivacaine or bupivacaine (0.5, 1.0 and 1.5 mg kg−1; concentrations 0.25%, 0.50%, and 0.75%, respectively) in a total volume of 0.2 mL kg−1 by means of a chronically implanted epidural catheter. Onset, duration (through pinch response in the sacral, lumbar and toe areas) and degree of analgesia and motor-blocking status was determined with a scoring system and at regular intervals over 8.5 hours before (baseline) and after drug administration.
Results  Epidurally administered levobupivacaine and bupivacaine had a similar dose-dependent analgesic action with no significant differences in onset (range: 5–8 minutes), duration (bupivacaine: 42 ± 28, 135 ± 68 and 265 ± 68 minutes, and levobupivacaine: 28 ± 33, 79 ± 55 and 292 ± 133 minutes; 0.25%, 0.50%, and 0.75%, respectively) or maximum degree of analgesia. However, levobupivacaine tended to produce a shorter duration of motor block than bupivacaine and the difference in the motor to nociceptive blockade times was significant at the highest dose.
Conclusion  Epidural levobupivacaine produced an analgesic action similar to that of bupivacaine.
Clinical relevance  Epidural levobupivacaine is suitable for clinical use in dogs, mostly at the highest dose if a high degree of analgesia is required.  相似文献   
84.
The first aim of the experiment was to study the effect of wheat (Triticum aestivum) particle size on the digestibility of starch in a pelleted diet given to broilers. The second aim was to study the consequences of food deprivation before the excreta collection period (from 21 to 24 d). Wheat from a strong hardness cultivar was incorporated at 546.1 g/kg in diets. The other main ingredients were soybean meal (353.5 g/kg) and rapeseed oil (55.0 g/kg). Diets were given as pellets. The experimental design was a 2 x 2 factorial design testing two particle sizes of wheat flour and two procedures of a balance experiment (with or without food deprivation). Birds given diet C (wheat coarse grinding before pelleting) had significantly greater gizzard weight than birds fed on diet F (wheat fine grinding before pelleting). Starch digestibility value was significantly increased when birds were fed on diet F. This effect was halved by food deprivation. No significant effect of grain particle size was observed for protein and lipid digestibility values. However, food deprivation decreased apparent protein digestibility, with an effect which was more pronounced for fine than for coarse grinding. AMEN of the diet was significantly improved by fine grinding of wheat and decreased by food deprivation. However, no significant differences in growth performance were induced by differences in wheat grinding. No significant effect of grinding was observed on the water excretion:feed intake ratio. No significant difference was observed for vent score between treatments. There was over-excretion of starch in the first hours of refeeding following food deprivation.  相似文献   
85.
OBJECTIVE: To identify factors affecting prognosis, outcome, and complications associated with pemphigus foliaceus in dogs. DESIGN: Retrospective study. ANIMALS: 43 dogs with pemphigus foliaceus. PROCEDURE: Medical records were reviewed for signalment, age at diagnosis, duration to diagnosis, body area affected, initial immunosuppressive regimens and concurrent use of antimicrobials and sucralfate or histamine receptor 2 blocking agent, adverse effects of treatment, duration of treatment, number of visits for follow-up care, cause of death, and credentials of the veterinarians responsible for continued care. RESULTS: The case fatality rate was 60.5%. Factors significantly correlated with survival time included concurrent use of antimicrobials during initiation of immunosuppressive treatment and a lower number of adverse effects to treatment. Treatment times lasting more than 10 months from diagnosis correlated significantly with survival. CONCLUSIONS AND CLINICAL RELEVANCE: Treatment with or prophylactic use of antimicrobials may be warranted during initial immunosuppressive treatment. The inverse correlation between survival time and number of adverse treatment effects was not unexpected because it was reflective of the owners' decision to euthanatize their dogs and of corticosteroid-related secondary diseases. Survival beyond the tenth month of treatment predicted long-term survival, which suggests that dogs require careful management during the early months of treatment.  相似文献   
86.
87.
Seventy-five 25-day-old broilers were divided into three groups: group I unmedicated and challenged with E coli 078:K80; group F infected and treated with 150 ppm of phosphomycin in their drinking water, and group C acted as a control. Their weights, feed intake, clinical signs, macroscopic lesions, E coli reisolation, and serum biochemistry were compared. Group F showed fewer symptoms and gross lesions than those from group I while the average daily gain, bodyweight, and feed intake were similar to the control group. E coli was reisolated in 32 per cent of the livers and spleens from group I, compared with 4 per cent of liver and 8 per cent of spleens from group F. There was an increase in the levels of total protein and globulins in group I but not in group F. These results provide evidence of the therapeutic efficacy of phosphomycin in the control of an experimental E coli infection in broiler chickens.  相似文献   
88.
The aim of this study was to evaluate if blastocysts arising from in vitro culture of Grade 3 bovine morulae produced in vivo can promote acceptable pregnancy rates when transferred into recipients. Embryos of different stages and qualities were recovered from superovulated Bos taurus and B. indicus donors. Grade 3 morulae were cultured in either Holding Plus® or TCM‐199 (supplemented with 10% bovine fetal serum) media for 24 h at 38.5°C. After this culture period, the resulting blastocysts were morphologically classified (Grades 1, 2 and 3) and transferred into recipients previously synchronized with the donors. Non‐cultured Grades 1 and 3 morulae were used as control. Pregnancy diagnosis was carried out 60 days after embryo transfer and the data were analysed by logistic regression, considering variables, such as embryo quality (Grade), donor breed, culture medium, donor‐recipient synchrony and seasonality. Embryo quality was the only variable, showing significant effect on the pregnancy rate. Pregnancy rates for non‐cultured Grade 1 and 3 morulae, and blastocysts arising from cultured Grade 3 morulae were 58.1% (n = 31), 17.1% (n = 35) and 51.1% (n = 47), respectively (p < 0.05). There were no statistical differences between non‐cultured Grade 1 morulae and cultured blastocysts. Pregnancy rates for Grades 1 (65.0%) and 2 (60.0%) were higher than Grade 3 (29.4%) cultured blastocysts (p < 0.05). It was concluded that short‐term in vitro culture is a very convenient method of identifying morphologically low quality morulae with higher chances of continuing development after the transfer into recipients.  相似文献   
89.
90.
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