全文获取类型
收费全文 | 788篇 |
免费 | 55篇 |
国内免费 | 41篇 |
专业分类
林业 | 86篇 |
农学 | 40篇 |
基础科学 | 20篇 |
195篇 | |
综合类 | 264篇 |
农作物 | 29篇 |
水产渔业 | 80篇 |
畜牧兽医 | 121篇 |
园艺 | 19篇 |
植物保护 | 30篇 |
出版年
2024年 | 1篇 |
2023年 | 11篇 |
2022年 | 22篇 |
2021年 | 20篇 |
2020年 | 28篇 |
2019年 | 21篇 |
2018年 | 20篇 |
2017年 | 28篇 |
2016年 | 37篇 |
2015年 | 37篇 |
2014年 | 57篇 |
2013年 | 38篇 |
2012年 | 51篇 |
2011年 | 71篇 |
2010年 | 61篇 |
2009年 | 58篇 |
2008年 | 40篇 |
2007年 | 52篇 |
2006年 | 36篇 |
2005年 | 33篇 |
2004年 | 21篇 |
2003年 | 16篇 |
2002年 | 22篇 |
2001年 | 10篇 |
2000年 | 9篇 |
1999年 | 3篇 |
1998年 | 11篇 |
1997年 | 12篇 |
1996年 | 9篇 |
1995年 | 12篇 |
1994年 | 9篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1980年 | 1篇 |
排序方式: 共有884条查询结果,搜索用时 78 毫秒
91.
隐子草地上生物量以及营养价值季节动态研究 总被引:1,自引:0,他引:1
本文主要探讨了隐子草地上生物量和营养成分以及体内体外消化率及其季节性变化动态。隐子草产量高峰期为7、8月份并且生长初期(5、6月),它的枯黄部分较多而影响有机质和粗蛋白质含量以及体内体外消化率,到7月达最高值。并在8月份(隐子草的抽穗期)与其他牧草相比它的营养价值优良。 相似文献
92.
93.
Kazutaka Kanai Mariko Hino Yasutomo Hori Ruriko Nakao Fumio Hoshi Naoyuki Itoh Seiichi Higuchi 《Journal of veterinary science (Suw?n-si, Korea)》2008,9(4):421-423
The purpose of this study was to determine if salivary chromogranin a secretion in dogs exhibits a circadian rhythm. Saliva sampling was performed during three different sessions occurring in three nonconsecutive 24-h periods. Sixteen healthy adult beagle dogs (8 males and 8 females) were moved to a sampling room and housed individually in cages. Saliva samples were obtained every 4 h from 12:00 p.m. to 12:00 p.m. the following day. In the interest of habituation, saliva was obtained hourly from each dog 3 h before the experiment was started. Salivary chromogranin A concentrations were measured using an enzyme-linked immunosorbent assay. No circadian rhythm was detected for salivary chromogranin A secretion, and no differences in salivary chromogranin A concentrations measured every 4 h were demonstrated during the 24-h cycle in dogs. 相似文献
94.
通过DNA测序不仅可以更好地认识生命的本质,了解生物的差异性、进化及发展史,而且为重组DNA的研究提供了方向,在疾病诊断及基因分型方面具有非常重要的实用价值。首先从发现DNA是遗传物质开始,简要回顾了第一、二和三代测序技术的整个发展历程,以及各自的优缺点和主要测序技术或平台;其次,重点介绍了由PacBio公司开发的第三代测序典型技术--单分子实时测序技术(SMRT)和ONT纳米孔测序技术的原理、方法和技术流程,并总结了第三代测序技术的应用领域,包括基因组重测序、do novo测序、转录组研究、甲基化检测、与疾病相关的结构变异检测,以及流行病学中病毒准种分析等应用;再次,比较了三代测序技术在转录组测序和表观遗传学研究中的技术优势,第三代测序技术在基因组重复区域或结构变异等研究领域具有非常明显的优势,对多种疾病的研究意义重大,已成为未来重要的精准诊断工具,此外,凭借对重要经济物种遗传信息的解析,育种工作者通过建立基因与性状的关联,对持有优良性状基因的个体进行人工选育,大大缩短了育种年限;最后,对第三代测序技术在医疗、农业、环境等领域的应用前景进行了展望。 相似文献
95.
无芒雀麦草地营养物质生产量季节动态的研究 总被引:3,自引:0,他引:3
采用在生长季节内按照不同生长发育时期共取15次样品分析牧草营养成分含量的方法,研究了无芒雀麦人工草地牧草营养万分含量和营养物质生产量的季节动态,了在高寒地区无氮浸出物含量呈中间低两头高的特殊性。 相似文献
96.
Seasonal and photoperiodic regulation of secretion of hormones associated with reproduction in Magang goose ganders 总被引:1,自引:0,他引:1
Shi ZD Huang YM Liu Z Liu Y Li XW Proudman JA Yu RC 《Domestic animal endocrinology》2007,32(3):190-200
This study examined the reproductive endocrine profile under natural and artificial photoperiods in Magang goose ganders. Group 1 ganders (n=8) served as non-treated controls and were exposed to natural photoperiod throughout the experiment from 13th January to 17th December 2004. Group 2 ganders (n=8) were exposed to 18 h long daily photoperiod for 60 days from 13 January till 15 March 2004 and again to 16 h photoperiod for 75 days till 10th October 2004, and the 11h short photoperiod in the remainder periods of the experiment. In control ganders, plasma LH concentrations were high in normal breeding seasons (August-March) and decreased to low levels in non-breeding season from April to July. Testosterone concentrations changed similarly to that of LH throughout the seasons. Seasonal pattern of PRL concentrations was opposite to those of LH and testosterone, with low values in breeding season and high values in non-breeding season. In artificial photoperiod treated ganders, increasing photoperiod increased PRL and decreased LH and testosterone concentrations, while decreasing photoperiod reversed these changes. There were no seasonal or photoperiod caused changes in plasma T3 concentrations in both control ganders and artificial photoperiod treated ganders. These results demonstrated that in Magang goose ganders that long photoperiod stimulates PRL secretion and decreases LH secretion, which terminates reproductive season in spring and early summer, and short photoperiod stimulates LH secretion and inhibits PRL secretion rendering ganders enter into reproductive season. 相似文献
97.
98.
通过对西北黄土高原旱区所属三省一区78县饲草资源及其利用改良现状的调查研究,结果表明:该区现已超载875万个羊单位。文章分析了超载过牧的根源及严重性,并对草场气候生产潜力进行了框算,提出了解决问题和挖掘出生产潜力的基本思路。 相似文献
99.
本文报告了三明市区家鼠寄生革螨的种类、组成、季节消长情况。观察一周年,共捕鼠711只,带螨鼠143只,带螨率为20.11%,检集革螨871只,鼠革蛲指数为1.23只/鼠,鉴定为3属4种即毒厉螨、纳氏厉螨、柏氏禽刺螨和鼠颚毛厉螨;毒厉螨为优势种,占81.86%,平均螨指数为1.00只/鼠,各宿主动物间带情况存在差异。以褐家鼠最高,达37.20%,螨指数为2.72只/鼠,革螨常年活动,以4-6月、83 相似文献
100.
In relevance to osmoregulatory and reproductive functions, activity of hypothalamic neurosecretory neurons may also vary seasonally. The current study was performed to determine annual changes in ir-AVT neurons of hypothalamus and adrenal gland function. We examined changes in ir-AVT neuron by immunohistochemical method and plasma testosterone was measured by enzyme immunoassay. The steroidogenic interrenal activity was studied by histological and biochemical methods. Birds were sampled in February (quiescent), April (recrudescent), June (breeding) and November (regressive). A significant and gradual increase in the number of ir-AVT neurons was observed from quiescent to breeding phase which decreased during regressive phase of annual gonadal cycle. The gradual increase in ir-AVT neurons along with annual gonadal activity of quail were accompanied by increase in plasma levels of testosterone. These results indicate a functional interaction between sex steroid and AVT synthesizing neurons. Adrenal activity (as judged by weight, ascorbic acid content, cortical cord width and cortico-medullary ratio) was also maximum during breeding phase. It is thus postulated that domesticated quail when exposed to natural day length (NDL), exhibits seasonal/annual cyclicity in vastocinergic activity and adrenal function which may be due to difference in sex steroid hormone. 相似文献