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   175篇
  免费   16篇
林业   3篇
农学   2篇
  1篇
综合类   19篇
农作物   2篇
水产渔业   8篇
畜牧兽医   149篇
植物保护   7篇
  2020年   3篇
  2019年   6篇
  2018年   6篇
  2017年   4篇
  2016年   4篇
  2015年   5篇
  2014年   9篇
  2013年   21篇
  2012年   2篇
  2011年   3篇
  2010年   11篇
  2009年   8篇
  2008年   1篇
  2007年   4篇
  2006年   3篇
  2005年   3篇
  2004年   1篇
  2003年   4篇
  2002年   2篇
  2001年   3篇
  1999年   4篇
  1998年   13篇
  1997年   17篇
  1996年   10篇
  1995年   5篇
  1994年   3篇
  1993年   3篇
  1992年   4篇
  1991年   3篇
  1990年   2篇
  1989年   3篇
  1988年   2篇
  1984年   1篇
  1983年   1篇
  1977年   1篇
  1976年   1篇
  1965年   1篇
  1963年   1篇
  1960年   2篇
  1959年   2篇
  1957年   2篇
  1956年   2篇
  1955年   1篇
  1954年   1篇
  1952年   1篇
  1950年   1篇
  1946年   1篇
排序方式: 共有191条查询结果,搜索用时 15 毫秒
51.
This study was conducted to determine the in vitro effects of three different concentrations (125, 187.5 and 250 microM in diluted semen) of zearalenone (zen) and alpha-zearalenol (alpha-zen) on boar sperm. Semen parameters such as motility, viability and spontaneous acrosome reaction were evaluated. From the results it was shown that both zen and alpha-zen affected the sperm characteristics significantly (p < 0.05), except for alpha-zen at the low concentration which did not decrease the percentage of live reacted spermatozoa significantly. In conclusion, zen and alpha-zen are directly toxic when they affect boar semen in vitro and consequently decrease the fertilization ability of the sperm. The higher the concentration of mycotoxin tested, the greater the decline of sperm parameters noticed. The influence of mycotoxins was found to be time- and dose-dependent.  相似文献   
52.
53.
54.
55.
56.
This short communication reports the impact of endometrial biopsies, uterine flushings and follicular fluid aspiration procedures at day 6 post artificial insemination (AI) on pregnancy rates. In Experiment 1, cows were timed AI (TAI) and assigned to the following treatment groups: control (n = 37), uterine flushing (n = 35) and endometrial biopsy (n = 38). On day 30 post AI, pregnancy rates were 40.5%, 33% and 28.5%, respectively (p > 0.1). Pregnancy rate on day 60 was lower (p < 0.004) in flushed cows than in the controls. In Experiment 2, oestrus was detected and cows were assigned to flushing (n = 32) or biopsy (n = 33) treatments 6 days after AI, which resulted in pregnancy rates of 31% and 36%, respectively (p > 0.1). In Experiment 3, cows were, 6 days after TAI, randomly assigned to the following treatments: control (n = 84) or aspiration of the largest follicle (n = 73). Pregnancy rates on day 30 post AI were 63.5% for the control group and 53% for the aspirated group (p > 0.1). In conclusion, uterine flushing and endometrial biopsy negatively affect pregnancy rates, but neither procedure can be considered to be incompatible with pregnancy maintenance. Follicular aspiration during pregnancy does not interact with pregnancy success. The amount and quality of samples obtained are compatible with the use of cellular and molecular analysis of uterine variables from cows that failed or succeeded on maintaining pregnancy.  相似文献   
57.
Flow cytometry is considered the only reliable method for the separation of X and Y chromosome bearing spermatozoa in equines. The MoFlo SX DP sorter is highly efficient, allowing the production of foals of the desired sex. However, to achieve acceptable pregnancy rates the currently used protocol requires working with fresh semen obtained close to, or at, the sorting facility. An alternative protocol was tested during two consecutive breeding seasons. Fresh stallion semen was cooled for 20 h, during which staining with Hoechst 33342 took place. On the following day, this sample was flow sorted and compared with spermatozoa from the same ejaculate that had been sexed on the previous day. All sperm parameters evaluated remained unchanged when fresh sorted and refrigerated sorted semen were compared. Pre‐sorting storage at 5°C did not alter sperm velocities nor kinetics, viability or membrane permeability, production of reactive oxygen species, mitochondrial membrane potential or DNA fragmentation index of the sorted sample. The findings open for the possibility of using semen from stallions housed far from the sorting facilities. Processed and stained sperm could be shipped refrigerated on the previous day, sorted and inseminated on the next day.  相似文献   
58.
Abstract. Simple body measurements were used to predict the fat content of Atlantic salmon parr. For three different sizes (wet weights 18–98g, 44–207g and 137-151·8g) at two times of year (November/December and July) the percentage body fat (as measured by lipid extraction) could be predicted accurately using multiple regressions based on a combination of the following measurements: wet weight, fork length, opercular height, dorsal height, opercular width, dorsal width, anal width, adipose fin length and condition factor. In every case predictions based on multiple regression equations were more accurate than condition factor alone. This biometric method is easily employed and can potentially be used both in biological studies and on fish farms to assess body condition of individual fish. Since it is non-destructive it has the additional advantage of allowing repeated monitoring of fat levels in the same fish.  相似文献   
59.
60.
Pain management is an important post-operative concern. Pain scales may rely on the observer's subjective assessment of the level of discomfort and may not correlate with physiologic or pharmacologic measures of pain. The purpose of this study was to develop an objective measure of behavior in healthy pain-free horses recovering from anesthesia that could be used for comparison with the behavior of horses recovering from a surgical procedure.
Focal sampling with videotape and observation was done on five healthy horses before anesthesia to establish baselines. Behavioral measures included head turns, tail swishes, eyelid aperture/size, ear position, angle of neck, weight shifts, and ambulation. Physiologic measures included heart rate, respiratory rate, and temperature. The horses were anesthetized for 2 hours with isoflurane, and in the recovery stall, data were collected continuously on videotape from the time of extubation to standing. Focal sampling of 15 minutes was repeated at 1, 2, 4, and 24 hours after the horses returned to their stalls. Video data were analyzed using the Noldus Observer Video Analysis System.
A wide variation in behavior was observed between horses in the recovery stall. Observations at 1, 2, and 4 hours revealed change from the up/forward ear position to the down ear position, and a decrease in weight bearing of the hind limb from a baseline of 11–12 minutes out of 15 minutes to 7–9 minutes with an increase in toe pointing. Time spent standing was similar to baseline of 93.8%, and the neck angle was not changed from baseline of 173.5°. Values had returned to baseline at 24 hours.
Changes in behavior were induced by anesthesia alone and must be taken into consideration when evaluating analgesic treatments.  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