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   1197篇
  免费   161篇
  国内免费   95篇
林业   49篇
农学   11篇
基础科学   4篇
  11篇
综合类   294篇
农作物   16篇
水产渔业   847篇
畜牧兽医   135篇
园艺   5篇
植物保护   81篇
  2024年   7篇
  2023年   12篇
  2022年   15篇
  2021年   28篇
  2020年   38篇
  2019年   48篇
  2018年   48篇
  2017年   59篇
  2016年   59篇
  2015年   43篇
  2014年   43篇
  2013年   64篇
  2012年   59篇
  2011年   72篇
  2010年   57篇
  2009年   64篇
  2008年   82篇
  2007年   62篇
  2006年   57篇
  2005年   52篇
  2004年   63篇
  2003年   50篇
  2002年   37篇
  2001年   45篇
  2000年   43篇
  1999年   39篇
  1998年   28篇
  1997年   33篇
  1996年   27篇
  1995年   29篇
  1994年   17篇
  1993年   17篇
  1992年   18篇
  1991年   15篇
  1990年   7篇
  1989年   4篇
  1988年   5篇
  1987年   4篇
  1986年   1篇
  1984年   1篇
  1977年   1篇
排序方式: 共有1453条查询结果,搜索用时 15 毫秒
61.
取闽南地区牛、羊消化道常见的8种线虫幼虫,对它们进行了形态学观察及比较,以期提供用于生前诊断的参考资料,  相似文献   
62.
本研究通过改变雄性卵与幼虫的孵化和哺育状态,观察工蜂对这些卵和幼虫的接受情况,探讨工蜂对卵和幼虫性别的识别能力。结果表明,工蜂对卵和大龄幼虫性别的识别能力较强,而对1-3日龄小幼虫的性别的识别能力较弱。  相似文献   
63.
A study was carried out on a ranch in the semi-arid area of Kajiado District in Kenya during the period July 2000 to June 2001 to determine the seasonal patterns of development and survival of gastrointestinal nematodes of sheep on pastures. A series of plots were contaminated with sheep faeces every month and pasture samples were collected weekly for the recovery and identification of larvae. The availability of infective larvae on naturally contaminated pastures was also monitored on the paddocks grazed by sheep and around the night pen and the watering point every month from July 2000 to June 2001. The results from the examination of the pasture samples indicated that rainfall distribution was the major factor governing the development and survival of the pre-parasitic stages. No parasitic larvae were detected from the plots contaminated during the dry months from July to October 2000, but development and translocation of infective larvae on pastures occurred on plots contaminated during the rainy seasons and soon after when relatively high moisture was present in the herbage (November 2000 to June 2001). During this period, peak larval counts occurred between the first and the second week post contamination, then declined to undetectable levels between week 4 and 16 post contamination. The lack of development of infective larvae during the dry season and the relatively rapid decline of their population during the wet season presents an opportunity for the use of pasture spelling as a means of helminth control in the study area. The availability of infective larvae on naturally contaminated pastures, around the night pen and around the watering point also followed the rainfall distribution pattern. Infective larvae were consistently recovered around the watering point throughout the study period. This indicated that the point is an important source of infection for sheep, especially during the dry season when other pastures are non-infective.  相似文献   
64.
综述了鳞翅目昆虫幼虫的取食抑制素味觉神经元及其感受模式的研究进展,为防治鳞翅目害虫提供参考。  相似文献   
65.
本研究旨在探讨不同家蝇幼虫制品对黄羽肉仔鸡营养物质可利用率、肠道菌群和血清生化指标的影响。选取 1日龄的黄羽肉仔鸡 252只,随机分成 7组,每组 3个重复,每个重复 12只鸡。对照组饲喂基础饲粮,其余 6组饲喂分别用 0.2%、0.5%的家蝇幼虫肽,0.2%、0.5%的家蝇幼虫酶解物,0.2%、0.5%的脱脂家蝇幼虫粉等量替代基础饲粮中鱼粉的试验饲粮。结果表明:1)添加家蝇幼虫肽有提高干物质、粗蛋白质和能量的可利用率的趋势(P>0.05),且随着添加剂量的增加而提高;添加 0.5%的家蝇幼虫肽可显著提高粗脂肪、钙、磷和粗灰分的可利用率(P<0.05)。2)添加家蝇幼虫肽可显著提高试验第2周和第4周肠道乳酸杆菌和双歧杆菌的数量(P<0.05),显著降低大肠杆菌和沙门氏菌的数量(P<0.05)。3)添加家蝇幼虫肽可显著降低试验第 2周血清谷丙转氨酶活性(P<0.05)和显著提高血清总蛋白含量(P<0.05),且以0.5%的家蝇幼虫肽组效果最优。在饲粮中添加不同家蝇幼虫制品均能显著降低黄羽肉仔鸡血清尿素氮含量(P<0.05)。由此得出,家蝇幼虫肽具有改善黄羽肉仔鸡肠道菌群、提高营养物质可利用率的作用,且以 0.5%的添加量效果较好。  相似文献   
66.
2008―2010年,对寄生于新疆卡拉麦里与普氏野马同域生活的家马体内的黑腹胃蝇(Gasterophilus pecorum)进行了实验室培养和野外行为观察。将收集到的920只3龄幼虫进行室内培养,结果成功化蛹35个(3.80%),化蛹期为13~27 d,巅峰期为18~20 d(42.86%);17个(48.57%)个体羽化,羽化期为15~27 d,巅峰期为21~22 d(22.86%)。在这些羽化的成蝇当中雄性占11.76%,雌性占88.24%,雄雌比为0.13;其存活期为2~8 d,较大存活率发生在第4-6天(58.82%)。3龄幼虫体长(13.2±7.0) mm,体宽(5.1±4.0) mm,体质量(241±30) mg。相关性分析表明,幼虫的体长、体宽和体质量与成蝇的性别无相关性。交尾行为没有在野外或者靠近的马体的周围环境中发现,羽化初期有梳理和寻求寄主行为。黑腹胃蝇的卵在马的体表和植物茎叶上也均未发现。  相似文献   
67.
刘长月  赵莉  倪亦非 《草业科学》2013,30(2):281-286
本研究将当年收获的苜蓿(Medicago sativa)种子储存于4个温度条件下,采用定期剖种的方法,调查苜蓿籽蜂(Bruchophagus roddi)的越冬虫态及其存活情况。结果表明,苜蓿籽蜂主要以3龄幼虫在苜蓿种子内滞育越冬。10月从田间将苜蓿种子收回,储存温度在18.0 ℃、平均湿度为27.2%(10―12月)时,越冬幼虫于当年12月下旬开始化蛹;储存温度在9.9 ℃,平均湿度为40.1%(10月―次年2月)时,越冬幼虫于次年2月下旬开始化蛹。不同温度和不同时间梯度处理苜蓿种子结果表明,在50 ℃、-30 ℃条件下处理1 d,籽蜂幼虫的死亡率均达100%,苜蓿种子的发芽率分别为93.33%和88.33%。  相似文献   
68.
Abstract

AIM: To determine whether the fungicide, carbendazim, as applied to pastures for controlling facial eczema (FE), would inhibit development of the free-living stages of the gastrointestinal nematode parasite Trichostrongylus colubriformis.

METHODS: Two studies were conducted, using sheep faeces containing eggs of T. colubriformis. In the first, the faeces were either exposed or not to an application of carbendazim sprayed at the recommended rate for FE control. After spraying, dishes containing the faeces were incubated at 20°C for 14 days, and the resulting third-stage infective larvae (L3) extracted by baermannisation and counted. In addition, naturally infested pasture was also sprayed, and the number of L3 present 7 days later was assessed by cutting herbage samples and extracting larvae by soaking in water and baermannisation. In the second, the faeces were incubated at 20°C for 0, 3 or 7 days before being exposed to no, one or two applications of carbendazim. After further incubation for 14, 11 or 7 days, L3 were similarly extracted by baermannisation and counted.

RESULTS: In the first study, there was a 74% reduction in the number of T. colubriformis larvae recovered from faeces exposed to carbendazim compared with faeces not exposed, but there was no reduction in the number of L3 recovered from herbage. In the second study, faeces incubated for 0 or 3 days prior to exposure to a single application of carbendazim yielded 98% or 89% fewer larvae, respectively, than faeces not exposed. Faeces incubated for 7 days prior to exposure yielded similar numbers of larvae to faeces not exposed.

CONCLUSION: Treatment of pastures with carbendazim for FE control is likely to result in reduced development of the larvae of T. colubriformis, and by inference those of other species, where the application coincides with the presence of freshly deposited faeces containing eggs and developing larvae. However, no effect of treatment on L3 was indicated. The significance of this for on-farm nematode parasite control remains to be determined, as does any potential for strategic applications of carbendazim to pasture aimed at reducing numbers of parasite larvae on pasture. The latter should not be contemplated without due consideration of the implications for the development of anthelmintic resistance.  相似文献   
69.
Yellow catfish (Pelteobagrus fulvidraco) is an important commercial species with high aquaculture potential in China. To better understand the process of digestive functioning of gastric gland development during the larval from 1 dph (day post‐hatching) to 30 dph, real‐time PCR was used to detect and quantify the pepsinogen and H+/K+‐ATPase gene expression in P. fulvidraco. These data were also compared with the adult situation. The results showed that the expression of pepsinogen and H+/K+‐ATPase genes in P. fulvidraco larvae both started at 1 dph, though the expression level was very low until 3 dph. The quantification of pepsinogen gene expression increased significantly from 4 to 8 dph, increased fluctuantly from 8 to 23 dph and rose sharply from 23 to 30 dph. In comparison with adult fish, there were no significant differences with larvae at 5 and 23 dph. However, data of 10 and 30 dph larvae were obviously higher than those of adult group. H+/K+‐ATPase gene expression increased linearly from 1 to 30 dph. However, it was significantly lower than that of adult. The results show that P. fulvidraco larvae have an earlier functional stomach, though the function of the stomach is still not perfect. There is a gradual acidification environment within the stomach during the P. fulvidraco larvae development. Based on these results, we suggest that the weaning time for P. fulvidraco larvae would be much better after 23 dph.  相似文献   
70.
研究了黄颡鱼(Pelteobagrus fulvidraco)受精卵孵化及仔鱼发育阶段鱼体磷脂含量的变化规律.采用常规化学分析方法对黄颡鱼从鱼卵受精开始至仔鱼孵化后未投饵的7d内的磷脂含量进行测定.结果表明,孵化期间受精卵磷脂含量在受精后16h略有增加;仔鱼孵化后,鱼体磷脂含量急剧下降,从0日龄的1.32%降低到7日龄的0.14%.说明磷脂是黄颡鱼仔鱼发育阶段代谢的重要能源,是仔鱼正常生长和发育所必需的重要营养素,仔鱼对磷脂的需求量很大.  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