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   5926篇
  免费   368篇
  国内免费   446篇
林业   818篇
农学   496篇
基础科学   281篇
  533篇
综合类   2487篇
农作物   275篇
水产渔业   276篇
畜牧兽医   1081篇
园艺   240篇
植物保护   253篇
  2024年   54篇
  2023年   97篇
  2022年   126篇
  2021年   224篇
  2020年   188篇
  2019年   235篇
  2018年   123篇
  2017年   223篇
  2016年   275篇
  2015年   211篇
  2014年   304篇
  2013年   356篇
  2012年   471篇
  2011年   468篇
  2010年   351篇
  2009年   426篇
  2008年   285篇
  2007年   298篇
  2006年   313篇
  2005年   272篇
  2004年   200篇
  2003年   165篇
  2002年   153篇
  2001年   135篇
  2000年   127篇
  1999年   100篇
  1998年   90篇
  1997年   62篇
  1996年   59篇
  1995年   50篇
  1994年   59篇
  1993年   46篇
  1992年   43篇
  1991年   44篇
  1990年   29篇
  1989年   33篇
  1988年   18篇
  1987年   9篇
  1986年   1篇
  1985年   1篇
  1984年   1篇
  1983年   1篇
  1982年   6篇
  1981年   3篇
  1980年   3篇
  1978年   1篇
  1956年   1篇
排序方式: 共有6740条查询结果,搜索用时 15 毫秒
61.
兔球虫病药物防治研究进展   总被引:2,自引:0,他引:2  
兔球虫病是严重危害养兔业发展的寄生虫病之一。长期以来,兔球虫病主要依靠化学药物和中草药等进行防治,由于球虫极易产生耐药性,给药物防治带来了困难。论文从兔球虫生物学特性、防治兔球虫病的药物等方面做一综述。  相似文献   
62.
Three, multiparous Holstein crossbred dairy cows with initial body weight of 385 ± 19 kg were randomly allocated to 3 treatments of rice straw (T1 = untreated rice straw; T2 = 5.5% urea-treated rice straw (5 g urea in 100 ml water to 100 g air-dry (91% DM) straw); T3 = 2.2% urea + 2.2% calcium hydroxide treated rice straw (2.0 g urea and 2.0 g Ca(OH)2 in 100 ml to 100 g air-dry (91% DM) straw) according to a 3 × 3 Latin square design. Each period lasted for 21 days in which feed, feces and rumen fluid were collected during the last 7 days for chemical analyses. The findings revealed significant improvements in dry matter intake and digestibility by using 5.5% urea-treated rice straw and 2.2% urea + 2.2% calcium hydroxide treated rice straw. Ruminal pH and NH3-N were found higher (P < 0.05) as compared with urea-treated rice straw fed group, while blood urea nitrogen and milk urea nitrogen were in normal ranges. Volatile fatty acid concentrations especially those of acetic acid were decreased (P < 0.05) and those of propionic acid were increased (P < 0.05), thus acetic acid:propionic acid was subsequently lowered (P < 0.05) in cows fed with 5.5% urea-treated rice straw and 2.2% urea + 2.2% calcium hydroxide treated rice straw, respectively. Moreover, ruminal viable and cellulolytic bacterial counts were enhanced by urea and calcium hydroxide treatments. Milk protein and fat concentrations were additionally increased by respective treatments while 3.5% fat-corrected milk was highest; ranking from 2.2% urea + 2.2% calcium hydroxide treated rice straw, 5.5% urea-treated rice straw and urea-treated rice straw fed groups. Based on this study, implications could be made that using 2.2% urea + 2.2% calcium hydroxide treated rice straw for straw treatment could be an alternative treatment to 5.5% urea treatment with regards to its effectiveness and treatment cost for lactating dairy cows.  相似文献   
63.
通过对福建省德化县早熟砂梨“黄叶病株”及“正常植株”叶片及土壤的营养诊断分析:黄叶病株叶片平均含镁量0.131%,极显著低于正常植株0.328%;黄叶症较重的果园土壤交换态镁含量低12.6~24.5㎎/㎏及土壤酸性强pH3.6~4.5,诊断结论砂梨叶片黄化现象为镁素缺乏所致。矫治试验效果,叶面喷施1%硝酸镁3次,可以叶色转绿;12月份土壤基施钙镁磷肥株1.3 kg,翌年5月份后有明显矫治效果。  相似文献   
64.
青蒿素及其衍生物抗寄生虫的研究进展   总被引:3,自引:0,他引:3  
本文介绍了青蒿素及其衍生物的基本研究状况和它们抗寄生虫病的研究进展,青蒿素及其衍生物主要的抗寄生虫作用表现为抗疟原虫和抗血吸虫,它们抗弓形虫、卡氏肺孢子虫、犬附红细胞体和球虫的作用也较强,对其进一步的研制和开发具有广阔的前号:  相似文献   
65.
In Burkina Faso, we assessed the efficacy of treating cattle with a footbath containing aqueous formulations of pyrethroids to control two tsetse-fly species, Glossina tachinoides Westwood, 1850 (Diptera, Glossinidae) and Glossina palpalis gambiensis Vanderplank 1949. Legs were the most targeted parts of the body for tsetse-fly blood meals: 81% (95% CI: 73, 89) for G. tachinoides and 88% (81, 95) for G. palpalis.

The in-stable efficacy of footbath treatments was compared with manual full spraying with a 0.005% alphacypermethrin (Dominex, FMC, Philadelphia, USA) formulation (250 mL versus 2 L). The proportions of knocked-down flies were the same with footbath and full spray but the latter was more protective against fly bites. In field use, the efficacy of both methods should be similar given the recommended treatment frequency: 3 days for footbath versus 7 days for full spray.

Among 96 cattle drinking at the same water point in Dafinso (Burkina Faso), 68 (71%) were treated with a footbath containing a 0.005% deltamethrin formulation (Vectocid, CEVA SA, Libourne, France). We observed the effect of this live-bait technique on the one hand on released cohorts of reared, irradiated flies, and on the other hand on wild tsetse flies. In both cases, the footbath treatment was associated with a reduction of the apparent fly density probably related to an increased mortality.  相似文献   

66.
Reasons for performing study: Assessing patients' quality of life (QOL) is a core part of clinical decision making. Various methodologies for assessing patients' QOL have been developed in human medicine and small animal veterinary disciplines. In contrast, the lack of aids for QOL assessment in equine veterinary practice leaves practitioners reliant on subjective assessments of QOL, which may be prone to avoidable errors. Objectives: This paper suggests pragmatic ways in which QOL may be enhanced, while remaining appropriate for the time, financial and owner‐based constraints within equine practice. Methods: Through interdisciplinary research, this paper identifies, adapts and applies insights from several areas of research and practical experience in order to develop an overarching approach to making QOL‐based decisions in clinical cases. Results: The paper identifies 6 steps involved in QOL‐based decision making and provides examples of how these steps may be practically applied. These include deciding what each clinician feels is important; deciding how to evaluate it, including taking owners' views into consideration; making decisions about each case and achieving the desired clinical outcomes. Conclusions: Practitioners can draw their own conclusions on how they may improve QOL assessment in practice and may usefully share these with colleagues. Reporting cases and sharing practical examples of QOL tools used on the ground are vital to the development of this field and appropriate methodologies. Potential relevance: Improvements in QOL assessment are relevant to all areas of equine veterinary practice, and several areas of research. Further research may develop QOL assessment in practice, but more important are the personal improvements that each practitioner may achieve. See also correspondence by Grove  相似文献   
67.
肉牛呼吸系统疾病是由环境因素(如断奶、运输、混群、阉割、拥挤和通风不良)、宿主自身因素和病原体等诸多因素相互作用引发的呼吸系统综合症。罹病牛日增重减少、饲料转化率降低、胴体质量下降和防治成本增加。在肉牛养殖业中,该病发病率和死亡率均较高,对世界肉牛养殖业造成巨大经济损失。文章介绍了发达国家和我国对肉牛呼吸系统疾病诊断、治疗和预防的近期研究进展,旨在为其有效防治提供参考。  相似文献   
68.
为了改造低产桑园、建立密植高产桑园,研究建立了提高压条苗生产效率的压条苗甲醛处理法,研究结果表明压条苗甲醛处理的生根数比环割处理增加130%,比非环割增加190%;压条苗甲醛处理的新根的生长比环割处理高1.5倍,比非环割处理高1.3倍;成苗率也是压条苗甲醛处理最好。该方法是一种高效成苗的方法。  相似文献   
69.
REASON FOR PERFORMING STUDY: Although there is anecdotal evidence of clinical effectiveness of chiropractic in treatment of equine back pain, little scientific work has been reported on the subject. OBJECTIVES: To quantify the effect of chiropractic manipulations on back and limb kinematics in horse locomotion. METHODS: Kinematics of 10 Warmblood horses were measured over ground at walk and trot at their own, preferred speed before, and one hour and 3 weeks after chiropractic treatment that consisted of manipulations of the back, neck and pelvic area. Speed was the same during all measurements for each horse. RESULTS: Chiropractic manipulations resulted in increased flexion-extension range of motion (ROM) (P<0.05) at trot in the vertebral angular segments: T10-T13-T17 (0.3 degrees ) and T13-T17-L1 (0.8 degrees ) one hour after treatment, but decreased ROM after 3 weeks. The angular motion patterns (AMPs) of the same segments showed increased flexion at both gaits one hour after treatment (both angles 0.2 degrees at walk and 0.3 degrees at trot, P<0.05) and 3 weeks after treatment (1.0 degrees and 2.4 degrees at walk and 1.9 degrees and 2.9 degrees at trot, P<0.05). The lumbar (L3 and L5) area showed increased flexion after one hour (both angles 0.3 degrees at walk and 0.4 degrees at trot P<0.05), but increased extension after 3 weeks (1.4 degrees and 1.2 degrees , at trot only, P<0.05). There were no detectable changes in lateral bending AMPs. The inclination of the pelvis was reduced at trot one hour (1.6 degrees ) and 3 weeks (3 degrees ) after treatment (P<0.05). The mean axial rotation of the pelvis was more symmetrical 3 weeks after the treatment at both gaits (P<0.05). There were no changes in limb angles at walk and almost no changes at trot. CONCLUSIONS: The main overall effect of the chiropractic manipulations was a less extended thoracic back, a reduced inclination of the pelvis and improvement of the symmetry of the pelvic motion pattern. POTENTIAL RELEVANCE: Chiropractic manipulations elicit slight but significant changes in thoracolumbar and pelvic kinematics. Some of the changes are likely to be beneficial, but clinical trials with increased numbers of horses and longer follow-up are needed.  相似文献   
70.
2013年山东滨州市某兔场发生仔兔高病死率、母兔流产的疾病。为了诊断治疗该病,本试验采集病死兔肺脏进行病原的分离,通过病原分离、形态学观察、生理生化试验、溶血试验、药敏试验等试验,证实分离菌为肺炎双球菌。该菌具有α-溶血性,对青霉素、头孢吡肟、阿米卡星等药物敏感;动物回归试验成功复制出兔肺炎双球菌病,症状典型,病理剖检变化明显。根据临床症状和药敏试验结果,用青霉素等药物进行治疗,病情得到有效控制。  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