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   7405篇
  免费   362篇
  国内免费   616篇
林业   601篇
农学   438篇
基础科学   1008篇
  1171篇
综合类   3086篇
农作物   315篇
水产渔业   165篇
畜牧兽医   725篇
园艺   261篇
植物保护   613篇
  2024年   45篇
  2023年   146篇
  2022年   214篇
  2021年   213篇
  2020年   231篇
  2019年   253篇
  2018年   210篇
  2017年   313篇
  2016年   380篇
  2015年   295篇
  2014年   434篇
  2013年   435篇
  2012年   622篇
  2011年   590篇
  2010年   457篇
  2009年   485篇
  2008年   413篇
  2007年   567篇
  2006年   392篇
  2005年   356篇
  2004年   271篇
  2003年   211篇
  2002年   128篇
  2001年   105篇
  2000年   101篇
  1999年   72篇
  1998年   79篇
  1997年   51篇
  1996年   52篇
  1995年   62篇
  1994年   36篇
  1993年   43篇
  1992年   32篇
  1991年   25篇
  1990年   19篇
  1989年   14篇
  1988年   16篇
  1987年   12篇
  1986年   2篇
  1956年   1篇
排序方式: 共有8383条查询结果,搜索用时 15 毫秒
21.
研究了国产替米考星注射用药对人工感染多杀性巴氏杆菌病猪的治疗效果,用断奶仔猪进行试验,为临床使用提供了依据.结果表明,替米考星治疗急性猪肺疫效果确实, 推荐剂量为10 mg/kg体重.  相似文献   
22.
多花黑麦草品种比较试验   总被引:9,自引:2,他引:9  
通过对现行生产中常用的4个多花黑麦草品种在昆明地区的物候期、株高、草产量、生长率、净同化率等指标的规定表明,在生长初期,特高的生产性能比其余3个品种都好,但生长一段时间后,邦德的生产性能明显超过特高(P<0.05),抗锈王略高于特高(P>0.05),旺饲的生产性能最差(P<0.05)。因此,邦德是一个在生产中值得推广应用的品种。  相似文献   
23.
MB22木聚糖酶发酵条件的研究   总被引:2,自引:0,他引:2  
通过因素轮换试验和正交试验,对MB22菌产木聚糖酶的培养基配方和发酵条件进行了研究。结果显示最佳培养基组成是:以玉米芯粉和麸皮为碳源,麸皮120g/l,玉米芯280g/l,(NH4)2SO44g/l,CaCO31.5g/l,Tween80,2.0g/l,MgSO4·7H2O1.5g/l;最佳发酵条件为:起始pH5.0,摇床培养温度30℃,转速160r/min,振荡培养84h。在最佳发酵条件下,MB22菌的最高产酶活力可达898.23U/ml。虽然与一些高产菌株相比该菌株的产酶能力还有待于进一步提高,但该试验结果为进一步进行微生物生产木聚糖酶的研究提供了理论依据。  相似文献   
24.
秀珍菇营养配方的试验   总被引:3,自引:0,他引:3  
本研究通过三因素三水平的正交试验表明 ,在培养基中添加VB1(2× 10 -6) ,N P K (0 1% ) ,NAA(10× 10 -6) ,最适合秀珍菇菌丝的生长  相似文献   
25.
引诱剂在综合防治桔小实蝇作用中的评估   总被引:5,自引:1,他引:5  
以使用引诱剂为主 ,坚持在杨桃园挂引诱笼 2 - 3年后 ,大量降低田间桔小实蝇BactroceradorsalisHendel雄虫数量和卵的受精率 ,配合其它的综防措施 ,防效逐年提高。三个综防点试验实践表明 :杨桃每果虫口数 ,卵孵化率及受害果率大大降低 ,防效达 92 5%。对桔小实蝇的防治初见成效。  相似文献   
26.
The efficacy of the commercial glyphosate [( N -phosphonomethyl) glycine] formulations Roundup Ultra, Touchdown and Engame were compared for the control of prickly sida ( Sida spinosa L.), morningglory ( Ipomeae hederacea var. integriuscula Gray), sicklepod ( Senna obtusifolia L.) and purple nutsedge ( Cyperus rotundus L.). Engame is a new formulation of glyphosate that contains glyphosate acid and 1-aminomethanamide dihydrogen tetraoxosulfate (AMADS), a proprietary mixture of sulfuric acid and urea, other than glyphosate salt and surfactants. Injury by Engame differed from Roundup Ultra and Touchdown in that necrotic lesions formed on leaves several hours after treatment. Leaves of very susceptible species, such as prickly sida, were rapidly, although incompletely, desiccated and then became chlorotic and died in a manner typical of other glyphosate formulations. Engame was 2–3 times more active to growth inhibition than either the Roundup Ultra or Touchdown formulations, based on GR50 comparisons expressed on an acid equivalent basis. The GR50 estimates did not change over the 3 week evaluation period for prickly sida and purple nutsedge, and after 2 weeks after treatment for morningglory. The GR50 estimates for sicklepod decreased over the 3 week evaluation period indicating a slower response to glyphosate. The application of AMADS alone caused minute necrotic lesions on sicklepod and purple nutsedge, and lesions up to 3 mm in diameter on prickly sida and morningglory. Further injury from AMADS was not noted and plants resumed growth without apparent delay. At glyphosate rates above 1120 g ha−1, greater than 80% control was achieved at 7 days after treatment. These results demonstrate that glyphosate efficacy can be further enhanced by formulations that apparently improve uptake and translocation.  相似文献   
27.
28.
Amoxicillin has become a major antimicrobial substance in pig medicine for the treatment and control of severe, systemic infections such as Streptococcus suis. The minimum inhibitory concentration 90% (MIC 90) is 0.06 μg amoxicillin/ml, and the proposed epidemiological cut‐off value (ECOFF) is 0.5 μg/ml, giving only 0.7% of isolates above the ECOFF or of reduced susceptibility. Clinical breakpoints have not been set for amoxicillin against porcine pathogens yet, hence the use of ECOFFs. It has also been successfully used for bacterial respiratory infections caused by Actinobacillus pleuropneumoniae and Pasteurella multocida. The ECOFF for amoxicillin against A. pleuropneumoniae is also 0.5 μg/ml demonstrating only a reduced susceptibility in 11.3% of isolates. Similarly, P. multocida had an ECOFF of 1.0 μg/ml and a reduced susceptibility in only 2.6% of isolates. This reduced susceptibility disappears when combined with the beta‐lactamase inhibitor, clavulanic acid, demonstrating that it is primarily associated with beta‐lactamase production. In contrast, amoxicillin is active against Escherichia coli and Salmonella species but using ECOFFs of 8.0 and 4.0 μg/ml, respectively, reduced susceptibility can be seen in 70.9% and 67.7% of isolates. These high levels of reduced susceptibility are primarily due to beta‐lactamase production also, and most of this resistance can be overcome by the combination of amoxicillin with clavulanic acid. Currently, amoxicillin alone is considered an extremely valuable antimicrobial in both human and animal medicine and remains in the critically important category of antibiotics alongside the fluoroquinolones and macrolides by the World Health Organization as well as the third‐ and fourth‐generation cephalosporins, but these cephalosporins show marked resistance to basic beta‐lactamase production and are only destroyed by the extended‐spectrum beta‐lactamases. Amoxicillin alone and in combination with clavulanic acid are currently classed together in Category 2 in the European Union. By reviewing the pharmacodynamic data and comparing this with pharmacokinetic data from healthy and infected animals and clinical trial data, it can be seen that the product has a good efficacy against S. suis and A. pleuropneumoniae, in spite of usage over many years. However, it may be much less efficacious on its own against E. coli, due to reduced susceptibility and resistance associated with beta‐lactamase production, which is largely overcome by the use of clavulanic acid. It is felt that this differentiation may be useful in future classification of amoxicillin alone, in comparison with its combined use with clavulanic acid and thereby preserve the use of the more critically important antibiotics in veterinary medicine and reducing the risk of their resistance being transmitted to human.  相似文献   
29.
采用了文献资料法、问卷调查法、数理统计法、逻辑分析法对影响我国大学城体育场地资源共享的因素进行了分析与总结,研究结果表明,影响大学城高校体育场地资源共享的主要因素包括:场地客观因素、学校领导因素、学校教师因素、学生因素、地理位置因素、相关政策因素、课程安排因素、经济因素、社会因素、比赛安排因素。根据木桶效应,在构建大学体育场地资源共享模式的时候,需要对课程进行合理的安排,并做好场地对内和对外开放的时间以及方式合理安排,以提供我国高校体育场地资源的利用率,促进我国高等体育教育和社会体育的发展。  相似文献   
30.
本试验引进了沪绿68、沪绿88和沪绿118共3个西兰花新品种,与当地主栽品种——耐寒优秀进行比较试验,试图筛选出适应当地种植的西兰花新品种。试验结果表明,沪绿68花球紧实度不高且蕾粒容易掉;沪绿118植株侧枝很多且花球有空心;沪绿88品种长势好、商品性好,适宜在如东地区种植。  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