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   16417篇
  免费   841篇
  国内免费   1726篇
林业   1486篇
农学   1829篇
基础科学   1172篇
  2131篇
综合类   6259篇
农作物   1101篇
水产渔业   800篇
畜牧兽医   2433篇
园艺   857篇
植物保护   916篇
  2024年   122篇
  2023年   255篇
  2022年   724篇
  2021年   732篇
  2020年   696篇
  2019年   698篇
  2018年   472篇
  2017年   713篇
  2016年   571篇
  2015年   806篇
  2014年   813篇
  2013年   1058篇
  2012年   1291篇
  2011年   1225篇
  2010年   1237篇
  2009年   1073篇
  2008年   1037篇
  2007年   926篇
  2006年   819篇
  2005年   638篇
  2004年   372篇
  2003年   263篇
  2002年   288篇
  2001年   290篇
  2000年   260篇
  1999年   231篇
  1998年   187篇
  1997年   122篇
  1996年   153篇
  1995年   150篇
  1994年   143篇
  1993年   115篇
  1992年   107篇
  1991年   93篇
  1990年   65篇
  1989年   71篇
  1988年   58篇
  1987年   31篇
  1986年   17篇
  1985年   9篇
  1984年   8篇
  1983年   7篇
  1982年   5篇
  1981年   13篇
  1980年   2篇
  1974年   2篇
  1970年   3篇
  1964年   3篇
  1963年   2篇
  1956年   3篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
In order to study the allergenicity of camel milk,cow milk and human milk,sixty BALB/c mice were randomly divided into β-lactoglobulin (β-lg) group (positive control group),cow milk group,camel milk group,human milk group and blank group (negative control group). Each group of mice received 1 mg/g BW samples and 0.3 μg/g cholera toxin (CT) per week,while mice in control group were received PBS and CT. After six weeks of intragastric administration,some allergic symptoms,the serum specific immunoglobulin E (IgE) and immunoglobulin G1 (IgG1) levels,plasma histamine levels and vascular permeability were detected. The results showed that the body weight of mice in camel milk,human milk and blank groups were normally increased,while that in β-lg and cow milk groups tended to slow down. The serum-specific IgE,IgG1 levels and histamine level in β-lg and cow milk groups were extremely significantly higher than blank group (P<0.01),the vascular permeability was increased,and the allergy symptoms were obvious. While the specific IgE and IgG1 levels of camel milk group were extremely significantly lower than cow milk group (P<0.01),but there were no significant difference with human milk group (P>0.05),and the allergy symptoms were mild. This study showed that the sensitization of camel milk was lower than cow milk,and similar to human milk.  相似文献   
82.
蒸汽压片处理因其在提高玉米淀粉消化率、改善反刍动物生产性能和畜产品品质、减少环境污染和降低饲养成本等方面功能越来越受到人们的重视,并随着在反刍动物日粮中进一步应用对其工艺技术和产品标准也提出更高要求。作者较全面地从蒸汽压片技术提高玉米淀粉利用率的作用机制、加工工艺及加工质量评价方法等方面进行综述,以期为蒸汽压片玉米研究提供参考。  相似文献   
83.
China was one of the first countries to use artificial insemination (AI) in equids, and it achieved international recognition for its widespread application of AI to commercial horse breeding. This article reviews the history of equine AI in China. The technique originated from the high demand for horses to be used in agriculture, transportation, and the military. Artificial insemination was identified as an ideal tool for Chinese horse breeding to improve the productivity of native horses, especially during 1950-1970. Presently, AI is still practiced commonly in China, and it includes the use of fresh semen and transported cooled semen. The use of frozen semen has also been resumed to broaden the range of elite Sporthorse stallions and to preserve threatened or endangered native breeds. Accurate prediction of the optimum time for insemination depended mainly on transrectal palpation of the mare's ovaries. In addition to controlled methods of insemination, factors like volume and number of spermatozoa in the inseminate and timing and frequency of insemination were optimized to accomplish high fertility rates in the field. Production of hinnies and mules for agricultural labor and donkeys for meat and hide gelatin stimulated a nationwide upsurge of research into the reproductive physiology of and AI technology in donkeys. In the future, there will be further increases in the use of traditional and modern AI techniques in the breeding of Chinese equids.  相似文献   
84.
子宫内膜炎是子宫黏膜的炎症;在子宫内贮留大量脓汁即子宫积脓症。  相似文献   
85.
丁壮素的特点及其作用   总被引:5,自引:0,他引:5  
章亮  罗云  周斌华 《饲料广角》2006,(10):47-48
丁酸是短链脂肪酸的一种,其抗菌抑菌作用已被广泛认知和接受。抗菌抑菌原理如图1。图1丁酸抗菌抑菌原理由于丁酸脂臭味重、闪点低和挥发性强的特点,工业归类上将其按危险品管理。常温下丁酸呈液态,饲料生产中操作不便,且由于易挥发、计量不好把控,生产上往往把丁酸转化为丁酸盐  相似文献   
86.
油毡纸作为蜂箱大盖防雨层已被广泛应用于养蜂生产中,虽然解决了蜂箱防雨问题,但也在很大程度上降低了养蜂生产效率。本研究经过多年的蜂场实地测试,发现在夏季最高气温37℃天气里,10~14时,1组油毡纸大盖上面温度为60.5℃~63℃;2组油毡纸上遮草帘大盖上温度为34.7℃~37.5℃;3组木板大盖上温度为52℃~57℃。尽管各部位温度差异较大,但子脾间温度差异很小。l组蜂群的有效产卵量和群势、产蜜量均低于2、3组,饲料消耗量高于2、3组。由此表明油毡纸蜂箱大盖吸收日光热源对蜂群繁殖效率及产蜜量具有明显的影响。  相似文献   
87.
通过显微镜检查对来源于全国各地的37种出口观赏鸟进行了血液原虫调查。共检查血样1144份,结果为:血液原虫的检出率为2.1%,主要是血变原虫和/或疟原虫。感染季节以秋冬两季为主,易感鸟品种主要是白腰文鸟、红喉歌鸲、蓝歌鸲、暗绿绣眼鸟、豆冠、白燕、情侣鹦鹉。  相似文献   
88.
浅谈我国养鹿业可持续发展的对策   总被引:2,自引:2,他引:2  
针对我国养鹿业面临入世后的严峻挑战 ,基于国内和国际区域性养鹿业的现状和形势 ,从几方面扼要阐述了我国养鹿业可持续发展应采取的对策。  相似文献   
89.
许正福  颜亮东  马扶林  马玉芳 《草业科学》2011,28(11):1924-1928
积温是作物与品种特性的重要指标之一,对积温农业气象重要指标的研究,对于指导农牧业生产具有十分重要的现实意义。本研究通过利用青海省海南藏族自治州共和、兴海、贵南、同德和贵德5县气象站的地面观测资料,对该地区近30年来≥0 ℃年积温的变化,主要农作物、牧草生育期的变化及其生育期≥0 ℃的积温变化做了分析,得出该地区大部分农作物及牧草的生育期有所缩短,开始期有所提前。由于近10年该地区升温明显,热量条件充足,各地≥0 ℃年积温有所增加,农作物及牧草发育期的积温增多,为该地区农作物及牧草的生长发育提供了充足的热量条件,对于该地区适时调整农牧业结构提供了依据。  相似文献   
90.
Spermatozoa are highly specialized cells, and energy metabolism plays an important role in modulating sperm viability and function. Rosiglitazone is an antidiabetic drug in the thiazolidinedione class that regulates metabolic flexibility and glucose uptake in various cell types, but its effects on boar sperm metabolism are unknown. In this study, we investigated the potential effect of rosiglitazone against time‐dependent deterioration of boar spermatozoa during liquid preservation at 17°C. Freshly ejaculated semen was diluted with Beltsville Thawing Solution (BTS) containing different concentrations of rosiglitazone, and the motility, membrane and acrosome integrity of sperm were detected. Besides, we measured glucose uptake capacity, l ‐lactate production level, mitochondrial membrane potential, adenosine triphosphate (ATP) content and mitochondrial reactive oxygen species (mROS) production of sperm after boar semen had been incubated with or without rosiglitazone, iodoacetate (glycolysis inhibitor) and rotenone (electron transport chain inhibitor) for 5 days. The addition of rosiglitazone significantly enhanced sperm quality and had a strong protective effect on the sperm membrane and acrosome integrity during storage. BTS containing 50 μM rosiglitazone maintained the total motility of liquid‐preserved sperm above 60% for 7 days. Rosiglitazone improved sperm quality by regulating energy metabolism manner of preserved sperm, protected the sperm mitochondrial membrane potential, enhanced sperm ATP production and in the meanwhile reduced mROS through enhancing glycolysis but not oxidative phosphorylation. The data suggested the practical feasibility of using rosiglitazone for improving boar spermatozoa quality during semen preservation.  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