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   2176篇
  免费   102篇
  国内免费   69篇
林业   76篇
农学   68篇
基础科学   25篇
  154篇
综合类   1035篇
农作物   47篇
水产渔业   32篇
畜牧兽医   862篇
园艺   22篇
植物保护   26篇
  2024年   12篇
  2023年   24篇
  2022年   33篇
  2021年   54篇
  2020年   65篇
  2019年   82篇
  2018年   41篇
  2017年   50篇
  2016年   83篇
  2015年   78篇
  2014年   150篇
  2013年   145篇
  2012年   161篇
  2011年   163篇
  2010年   144篇
  2009年   142篇
  2008年   115篇
  2007年   124篇
  2006年   108篇
  2005年   88篇
  2004年   129篇
  2003年   95篇
  2002年   30篇
  2001年   27篇
  2000年   24篇
  1999年   23篇
  1998年   16篇
  1997年   16篇
  1996年   15篇
  1995年   20篇
  1994年   17篇
  1993年   21篇
  1992年   14篇
  1991年   13篇
  1990年   5篇
  1988年   2篇
  1987年   4篇
  1986年   1篇
  1985年   5篇
  1984年   2篇
  1983年   4篇
  1980年   2篇
排序方式: 共有2347条查询结果,搜索用时 15 毫秒
91.
Summary The author recalls that the late Professor Mercury S. Ghilarov, from the Institute of Animal Morphology and Ecology in Moscow, was a great pioneer in soil zoology and a far-sighted scientist in the evolution of terrestrial faunas. Professor Ghilarov agreed that during their evolution insects passed through the soil as a transitional medium from aquatic to terrestrial habitats. His theory, which is based on morphological and physiological observations, fits the thermodynamics of soil water the author describes when considering all porous bodies (porosphere), such as soil and other media, permitting a slow and gradual transition from an aquatic towards a xeric aerial system. In conclusion, a general concept of water accessibility for soil animals is formulated.Dedicated to the late Prof. Dr. M.S. Ghilarov  相似文献   
92.
In recent years the fate of human and animal pathogen microorganisms as a potential pollutant of the environment has been paid increased attention. Substantial quantities of these compounds and their metabolites are excreted, flushed down the drain, discarded as waste, or left over in animal feedlots. After passing to the sewer, several of these compounds are not adequately eliminated by the methods that are currently used in sewage treatment. Substantial quantities of biosolids and livestock manure end up on agricultural land. Effective sanitation of the environment, particularly of some of its special parts, which can be a source of spreading of diseases, plays an important role in prevention of infectious diseases. In this respect special attention should be paid to the disinfection of infected farm animal excrements. Sanitation of excrements should, on the one hand, ensure effective inhibition of infectious agents and, on the other hand, comply with the requirement of preserving the composition of the manure so it can be used in agricultural production.  相似文献   
93.
A study was undertaken to evaluate the effects of incorporating high (HMS) and low (LMS) maturity maize silages into diets based on low (LGS) and high (HGS) feed value grass silages offered to beef cattle. Seventy-two continental cross-bred steers were used in a 14-week continuous design, randomised block experiment. The six treatments were arranged as a 2 × 3 factorial design incorporating the LGS and HGS offered as the sole forage, along with each of the two grass silages offered in a 60:40 ratio (DM basis) with the HMS and LMS. All diets were supplemented with 3 kg/head/day concentrates. Total daily DM and metabolisable energy intakes were higher (P < 0.001) for diets based on HGS compared to those based on LGS. Intakes were similar (P > 0.05) between diets containing LMS and HMS, both of which were higher (P < 0.001) than diets containing grass silage as the sole forage. Highest DM intakes were recorded with a mixture of HGS and HMS (P < 0.05 or greater). Cattle offered diets containing HGS had higher live-weight gain (P < 0.05), final live weight, carcass gain and carcass weight (P < 0.001) than those offered diets containing LGS. Feed conversion efficiency, assessed on a carcass gain basis, was poorer (P < 0.05) with diets containing LGS compared with those containing HGS, though differences between diets containing either LMS or HMS and GS as the sole forage were not significant (P > 0.05).  相似文献   
94.
动物应激的研究进展   总被引:2,自引:0,他引:2  
对动物应激的研究已有几十年,但有关应激的基础理论体系仍不健全,对于应激的概念及其应用也有很多模糊的地方,致使很多时候人们对应激研究的结果不能进行准确解释。本文对应激的概念、应激的一般反应及应激反应的机理等几个方面进行了综述,希望能引起人们对有关应激理论的思考。  相似文献   
95.
本文通过对兴海县气温、降水等气象观测资料的分析,得出气候变化对畜牧业生产造成的影响,认为当前制约兴海县畜牧业可持续发展的主要因素是气候变化,并针对气候变化的制约条件提出了草地可持续发展对策。  相似文献   
96.
饲用莫能菌素的研究进展   总被引:2,自引:0,他引:2  
莫能菌素是聚醚类离子载体抗生素,是目前欧盟唯一允许使用的抗生素饲料添加剂。本文通过其作用机理、畜禽生产中的添加效果及使用剂量等方面的综合论述,证明了在畜禽生产中饲用莫能菌素的可行性,并为其今后的广泛应用做了研究展望。  相似文献   
97.
根据生态畜牧业的理念,结合凉山地区畜牧业生产和生态环境现状,提出凉山地区发展生态畜牧业的技术措施,推动凉山畜牧业健康持续发展。  相似文献   
98.
天峻县北部地区因受气候干旱、鼠虫危害等因素的影响,畜牧业生产逐年下降,通过对存在问题的分析,提出了北部地区今后走退牧还草或休牧育草路子的设想。  相似文献   
99.
The extensive pig production in Spain is traditionally characterised by: the use of the Iberian pig, an autochthonous breed perfectly integrated into the environment in which they have developed; a long duration of the productive cycle for about 23–24 months; a high level of animal welfare level, specially in the fattening process with freedom of movement and feeding base on natural sources: acorns and grass, and an equilibrated “dehesa” agro-forestry system where this activity has been developed. Nowadays, the introduction of more intensificated methods due to the increasing demand led to important changes, such as: the shortening of the productive cycle (10–12 months); freeing from the territorial base; changes during the fattening period, fattening with mixed feed and less animal freedom. All these facts may implicate a loss of the animal welfare condition. These circumstances lead us to question it from an ethical point of view.  相似文献   
100.
动物科学专业本科人才培养目标是确定动物科学专业本科课程教学方案的依据,是培养什么质量的动物科学专业本科人才的指导思想。动物科学专业的人才培养目标应包含如下几个重要方面。首先,动物科学专业人才培养目标应着眼于人文精神和合作精神的培养。其二,应注重基础课的教学,使学生获得终生学习的能力。其三,应促进学生的主动性思维,而不是让学生被动地接受知识的传授。其四,应提高学生的实践动手能力。最后,应在本科教学阶段继续提高动物科学专业本科生的语言技能。本文对如上方面逐一进行了阐述。  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