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   215篇
  免费   7篇
林业   14篇
农学   4篇
  28篇
综合类   19篇
农作物   7篇
水产渔业   20篇
畜牧兽医   119篇
园艺   2篇
植物保护   9篇
  2024年   1篇
  2022年   3篇
  2021年   3篇
  2020年   7篇
  2019年   9篇
  2018年   8篇
  2017年   2篇
  2016年   2篇
  2015年   2篇
  2014年   10篇
  2013年   7篇
  2012年   9篇
  2011年   14篇
  2010年   7篇
  2009年   12篇
  2008年   18篇
  2007年   13篇
  2006年   18篇
  2005年   6篇
  2004年   3篇
  2003年   10篇
  2002年   10篇
  2001年   1篇
  2000年   4篇
  1999年   4篇
  1998年   5篇
  1997年   2篇
  1996年   1篇
  1995年   2篇
  1993年   1篇
  1992年   1篇
  1991年   1篇
  1990年   4篇
  1989年   2篇
  1988年   2篇
  1987年   2篇
  1986年   5篇
  1985年   8篇
  1984年   1篇
  1981年   1篇
  1969年   1篇
排序方式: 共有222条查询结果,搜索用时 0 毫秒
31.
32.
蛋鸡生产者应基于沙门氏菌感染的风险和后果来评估预防其感染的成本和收益. 控制沙门氏菌感染如今正成为食用禽蛋生产的一个重要成本因素.欧盟出台的一系列旨在减少消费者感染沙门氏菌的法令,目的就是对整个生产链的操作流程进行评估.鸡蛋生产商应该利用现有的关于感染流行病学和控制措施方面的知识来制定禽舍建造、管理系统和禽群饲养(包括从饲料原料的质控到鸡蛋的产后处理、储存和运输)的决策.他们也应该评估在生产区域内由于沙门氏菌感染的风险和后果而采取的预防措施的成本和潜在效益.  相似文献   
33.
34.
Recent technologic advances have allowed the production and marketing of cage-side blood gas analyzers to private practitioners. The widespread use of cage-side portable blood gas analyzers in veterinary practices has increased the need to develop the basic skills of blood gas analysis as part of a tool kit for practicing veterinarians. Rapid expansion of emergency and critical care medicine as a specialty and increased numbers of veterinary emergency and veterinary specialty practices have occurred concurrently with the availability of blood gas analyzers that are affordable for private practitioners. As a result, evaluation of blood gas results is no longer an activity confined to academic institutions and has become a daily part of many practicing veterinarians' activities.  相似文献   
35.
As one of the few felids that is predominantly diurnal, cheetahs (Acinonyx jubatus) can be exposed to high heat loads in their natural habitat. Little is known about long‐term patterns of body temperature and activity (including hunting) in cheetahs because long‐term concurrent measurements of body temperature and activity have never been reported for cheetahs, or, indeed, for any free‐living felid. We report here body temperature and locomotor activity measured with implanted data loggers over 7 months in 5 free‐living cheetahs in Namibia. Air temperature ranged from a maximum of 39 °C in summer to ?2 °C in winter. Cheetahs had higher (~0.4 °C) maximum 24‐h body temperatures, later acrophase (~1 h), with larger fluctuations in the range of the 24‐h body temperature rhythm (approximately 0.4 °C) during a hot‐dry period than during a cool‐dry period, but maintained homeothermy irrespective of the climatic conditions. As ambient temperatures increased, the cheetahs shifted from a diurnal to a crepuscular activity pattern, with reduced activity between 900 and 1500 hours and increased nocturnal activity. The timing of hunts followed the general pattern of activity; the cheetahs hunted when they were on the move. Cheetahs hunted if an opportunity presented itself; on occasion they hunted in the midday heat or in total darkness (new moon). Biologging revealed insights into cheetah biology that are not accessible by traditional observer‐based techniques.  相似文献   
36.
37.

Objective

To compare the efficacy and quality of analgesia provided by constant rate infusions (CRIs) of hydromorphone and fentanyl in dogs in the intensive care unit (ICU).

Study design

Prospective, randomized, blinded, clinical trial.

Animals

A total of 29 client-owned dogs.

Methods

Dogs prescribed a μ-opioid agonist infusion for postsurgical or medical pain were randomized to be administered either hydromorphone (0.025 or 0.05 mg kg?1 bolus, followed by a 0.03 mg kg?1 hour?1 infusion) or fentanyl (2.5 or 5 μg kg?1 bolus, followed by a 3 μg kg?1 hour?1 infusion). The technical staff and clinicians were blinded as to which drug was administered. Pain scores, using the Colorado State University Canine Acute Pain Scale, sedation scores and nausea scores were assigned at regular intervals and compared between groups. Dose escalation and de-escalation of the study drug were performed according to set protocols. Adverse clinical signs and all other medications administered were recorded and compared between groups. The study drug was discontinued if the animal remained painful despite dose escalations, or if adverse effects were noted.

Results

The pain scores were of low magnitude and were not significantly different between groups. The use of concurrent analgesia, sedation/anxiolytic medications and antacid/antiemetic medications was not different between groups. Sedation and nausea scores were not statistically different between groups.

Conclusions and clinical relevance

Hydromorphone and fentanyl CRIs appear to be equally effective for adequate pain relief in dogs, with no significant differences in adverse effects. Therefore, either drug may be chosen for control of postsurgical or medical pain in an ICU setting.  相似文献   
38.
Methyl mercury (Hg) was determined in rainbow trout (Oncorhynchus mykiss) and organisms in the lower tropic levels: smelts (Retropinna retropinna), bullies (Gobiomorphus cotidianus), koura (Paranephrops planifrons); and zooplankton (Daphnia carinata and Calamoecia lucasi) in Lakes Okareka, Okaro, Tarawera, Rotorua and Rotomahana, New Zealand. Water concentrations of total Hg (HgT) and methyl Hg were also measured. Mean methyl Hg concentrations in the trout, the prey species (smelts, bullies and koura) and zooplankton increased linearly with mean HgT and methyl Hg chloride (CH3HgCl) concentrations in water. Most of the bio-magnification of methyl Hg occurred in the lower trophic levels of the trout food web (104.72) between the zooplankton and water. The bioaccumulation factors between the forage fish and zooplankton were 100.73 for bullies and 101.06 for smelt. Methyl Hg was 100.41 to 100.95 times greater in the trout then their prey.  相似文献   
39.
40.
Recreational fishing is a popular sport and leisure activity in many countries worldwide. There has been growing interest by recreational fishing groups and researchers in the perceived physical and psychological health and social (or ‘biopsychosocial’) benefits of recreational fishing. However, quantifying the key subjective ‘human dimensions’ of fishing that satisfy both the needs of recreational fishing groups and fishery managers is a major obstacle. We propose the use of psychometrically valid health‐related quality of life (HRQOL) measures widely used in the medical and health sciences – namely the Short‐Form Health Survey (SF‐36) – as rapid, reliable and cost‐effective instruments for quantifying HRQOL of recreational fishers. The widespread use of SF‐36 and availability of population normative data allows comparisons of the HRQOL of recreational fishers across multiple temporal and spatial scales, with participants of other activities, and the general population. The use of such measures in periodic surveys allows the biopsychosocial status of a recreational fishery's participants to be assessed using a modified Kobe plot, a graphical format that is easily interpretable and consistent with existing reporting formats used in fisheries stock assessment. Future biopsychosocial research in recreational fisheries can further benefit from interdisciplinary collaboration to develop a suite of standardized psychometrically valid and reliable instruments for assessing specific issues that commonly affect recreational fisheries from regional to international scales, such as drivers of fisher motivation, behaviour and satisfaction.  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