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   86670篇
  免费   5138篇
  国内免费   5847篇
林业   9421篇
农学   5939篇
基础科学   4533篇
  11382篇
综合类   38142篇
农作物   4338篇
水产渔业   2919篇
畜牧兽医   12386篇
园艺   2841篇
植物保护   5754篇
  2024年   719篇
  2023年   1787篇
  2022年   2701篇
  2021年   3127篇
  2020年   3137篇
  2019年   3525篇
  2018年   1957篇
  2017年   3121篇
  2016年   3855篇
  2015年   3277篇
  2014年   4749篇
  2013年   4694篇
  2012年   6531篇
  2011年   6429篇
  2010年   5176篇
  2009年   5129篇
  2008年   4595篇
  2007年   5205篇
  2006年   4495篇
  2005年   3615篇
  2004年   2971篇
  2003年   2549篇
  2002年   1916篇
  2001年   1885篇
  2000年   1717篇
  1999年   1326篇
  1998年   1060篇
  1997年   917篇
  1996年   835篇
  1995年   862篇
  1994年   743篇
  1993年   603篇
  1992年   557篇
  1991年   440篇
  1990年   352篇
  1989年   310篇
  1988年   226篇
  1987年   167篇
  1986年   90篇
  1985年   52篇
  1984年   39篇
  1983年   23篇
  1982年   39篇
  1981年   26篇
  1980年   29篇
  1979年   25篇
  1978年   16篇
  1976年   12篇
  1956年   13篇
  1955年   9篇
排序方式: 共有10000条查询结果,搜索用时 342 毫秒
101.
同期发情及腹腔内窥镜输精技术在肉羊产业中的广泛应用,对于改变肉羊产业的生产方式及经济结构,达到一年两产或两年三产的目的具有重要意义。在繁殖及非繁殖季节对内蒙古地区当地杂交羊进行了同期发情及腹腔内窥镜输精处理。结果表明,繁殖季节与非繁殖季节的发情率均在93%以上,差异不显著;对部分具有小尾寒羊血统的杂交羊同期发情处理后的第6天进行手术检查黄体,其排卵率分别为2.45个/只和1.68个/只。在受胎率方面,腹腔内窥镜输精的受胎率显著高于常规法人工授精的受胎率。  相似文献   
102.
本文通过对海北州草业发展现状的调研,进一步分析了当前草业发展存在的问题和困难,提出了今后发展草业的思路和建议。  相似文献   
103.
A 15 year-old Thoroughbred mare was examined for lethargy, fever, and inappetence of 1-day duration. A hard-bodied tick was removed from the horse. A complete blood count (CBC) demonstrated leukopenia with lymphopenia and thrombocytopenia. Morulae were visualized in circulating granulocytes. A polymerase chain reaction (PCR) confirmed the identity of these organisms as Anaplasma phagocytophilum. The horse was treated symptomatically for fever and inappetence with flunixin meglumine (1.1 mg/kg [0.5 mg/lb]) and oral electrolyte paste. Oxytetracycline (6.6 mg/kg [3 mg/lb] intravenously every 24 hours) treatment was begun as soon as a definitive diagnosis was determined. The mare responded to treatment, but she was switched to oral doxycycline (10 mg/kg [4.5 mg/lb] every 12 hours) after 5 days because of perivascular swelling at the injection site. Complete resolution of clinical signs was seen. There was no evidence of recurrence 1 year later. No additional horses at the farm were affected. The horse in this report presented for lethargy, inappetence, and fever, with limited other abnormalities. This represents a classical presentation of a mild to moderate case of anaplasmosis, which had not previously been reported in Virginia. The disease may be more widespread than has been previously reported, and it should warrant inclusion on a complete differential diagnosis list in a case of fever of unknown origin.  相似文献   
104.
Reasons for performing study: Insight into the loading pattern of the articular cartilage surface during the complete stride is important as biomechanical factors play a pivotal role in the pathogenesis of joint trauma and osteoarthritis (OA). Objectives: To determine the loading pattern in the equine MCP articulation in vitro during simulated walk. Methods: Eight cadaveric limbs from mature Dutch Warmblood horses were loaded in a pneumatic loading device in 6 different positions (A1‐A6). The pressure distribution on the articular surface of the proximal phalanx (P1) was measured at 7 sites (S1‐7) using intra‐articularly placed pressure sensitive films, which were analysed by scanning and densitometry. Results: Pressures recorded after mid‐stance (A4, 5, 6) were significantly (P<0.05) higher than those before (A1, 2, 3) and showed the biphasic loading pattern of the walk at all sites, except for the site halfway along the sagittal groove (S7). At S7, there was a linear increase in pressure during the progress of the stance phase of the stride in most horses. Medially (S4, 5, 6) the pressure was significantly higher than laterally (S1, 2, 3) (P<0.05). Conclusions and potential relevance: The heavier medial loading coincides with the location where articular cartilage degeneration in the process of OA in the equine MCP joint is known to start. The discrepancy between the loading of the central groove and the other parts of the joint may result in large stress differences at the end of the stance phase, which might be related to the pathogenesis of stress fractures in the first phalanx and distal third metacarpal bone.  相似文献   
105.
对咸阳地区的畜禽养殖状况,畜禽粪便的污染程度,畜禽粪便治理的现状与存在的问题,提出了治理的措施及治理后的前景,以期为政府部门在研究制定咸阳市规范时提供考虑。  相似文献   
106.
Zhang Q  Li D  Liu X  Liu Z  Cai X  Wu G  Qi S  Yang S  Yan X  Shang Y  He J  Ma J  Li J  Ma W  Han R  Liu X  Zhang J  Xie Q  Zhang Z 《Research in veterinary science》2008,85(2):368-371
This study was carried out to investigate the biological characteristics of the foot-and-mouth disease (FMD) virus strain Asia-1 China/2005, which is responsible for the 2005 epidemic in China. The result showed that this strain is not host restricted, and could not only cause FMD in cattle and sheep but also in pigs by either inoculation or direct contact.  相似文献   
107.
3个产地板蓝根多糖作用的比较研究   总被引:6,自引:0,他引:6  
通过小鼠吞噬试验、脾淋巴细胞增殖试验和最低抑菌与最低杀菌浓度的检测,对不同产地板蓝根多糖功能进行比较研究。结果表明,3个产地板蓝根多糖均使小鼠吞噬能力增强,并协同促进淋巴细胞增殖,具有一定的杀菌和抑菌效果。  相似文献   
108.
从广东四会某猪场分离到一株疑为猪伪狂犬病病毒(PRV)的病毒,病毒在猪肾细胞上出现细胞变圆、拉网、融合等典型病变,并具有细胞泛嗜性特点。在MDCK细胞上测得其TCID50值为10-8/0.1mL,能被伪狂犬病病毒标准阳性血清中和。将0.1mL病毒液接种小鼠后发生奇痒并麻痹致死,接种猪3天后发病,7天死亡,从攻毒病死猪的脑组织病理切片上观察到典型的病毒性脑膜脑炎及血管套现象。通过PCR扩增到PRVgD基因,由此进一步证明所分离病毒为猪伪狂犬病毒,并命名为GDSH株。根据GenBank中发表的序列,设计一对扩增PRVgE基因的特异性引物,建立可以区分PRV野毒株与疫苗株的PCR诊断方法。以此方法对病毒的细胞培养液进行检测,结果证实所分毒株为PRV野毒株,经克隆测序后与GenBank收录的其它PRVgE基因序列进行比较,发现所测毒株的核苷酸序列与其它PRV毒株的同源性介于98.3%~99.9%之间,其中与PRVEa株的亲缘关系最近为99.9%。  相似文献   
109.
110.
Survey and analysis of common diseases of laboratory monkeys are great significance to understand disease epidemiology, and formulate a set of scientific and reasonable measures for prevention and control disease, to improve the quantity and quality of laboratory monkeys, to ensure the accuracy of the animal experiment results. Through the investigation of the sick and dead animals of a large-scale laboratory monkeys breeding facility in Kunming area in 2014, the animals were classified depends on the main diseases, and the diseases were classified according to adult and juvenile animals, data were analyzed by Excel Office 2010 software. The results showed the common diseases of laboratory monkeys included the digestive system, respiratory system, trauma, reproductive system, and locomotor system disease, which were 47.45%, 13.06%, 12.10%, 11.46% and 8.92% separately; Common diseases included diarrhoea, soft tissue injuries, abortion, lobar pneumonia, dysentery, arthritis, intestinal pneumatosis, chronic colitis, and extreme bad nutrition, the ratio were 18.47%, 11.15%, 8.91%, 8.28%, 8.28%, 7.96%, 5.10%, 5.10% and 5.09% separately. Comprehensive analysis of common diseases and disease occurrence causes of the laboratory monkeys, suggesting that providing better quality laboratory monkeys for scientific research only by constantly improving the scientific breeding management level, constantly strengthening veterinary capacity, mastering the theoretical knowledge and scientific diagnosis method.  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