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排序方式: 共有537条查询结果,搜索用时 234 毫秒
91.
92.
Stefano P. Marelli Michela Beccaglia Alessandro Bagnato Maria G. Strillacci 《Reproduction in domestic animals》2020,55(Z2):4-9
Pedigree dogs and cats are bred aiming to conform breed standards with very poor consideration for breeding stock fertility. At the same time, the genetic asset underlining reproductive traits could be effectively analysed like in other species under selection. The definition of selection targets is very important in breeding protocols determination. The aim of the present work is to present an overview of the different correlations between reproduction and genetics, starting from selection procedure and inbreeding coefficient moving to genomic and the application of SNPs and GWAS on population study and identification of genes involved in phenotypical variation of reproductive traits in dogs. Particular relevance has been given to the concept of inbreeding which effects on canine reproduction have been presented. The use of genomic information in inbreeding coefficient calculation can be considered an improved effective procedure in the evaluation of the genetic variability loss in canine population and its negative effects on reproductive traits. 相似文献
93.
94.
曹屯贻 《浙江大学学报(农业与生命科学版)》1994,(5)
采用SCL-90症状自评量表,以整群抽样法,对3所农业院校248名大学生的心理健康状况进行了测评,结果表明,总均分为1.18±0.18,阳性均分为2.34±0.22,阳性项目数为44.3±6.3.各因子分中以强迫、人际关系敏感、抑郁为前三位。强迫、人际关系敏感、偏执的症状痛苦水平达中度-重度的人数比例分别为10.5%,8.1%,6%。心理反应异常的检出率12.9%,以偏执、抑郁、焦虑为多。 相似文献
95.
1953-2010年黄土洼天然淤地坝内洪水沉积物粒度旋回特征 总被引:2,自引:1,他引:1
利用137Cs断代技术进行沉积物的测年,结合1953年以来的降雨资料,对黄土洼天然聚湫坝淤地的水成沉积物粒度旋回特征进行了分析。结果表明,坝淤地4 m沉积物是在近百年内形成的,物源比较单一,主要为洪水沉积物;降雨是影响沉积物粒度的主要因素;淤地坝内洪水沉积物粒度以粗粉砂为主,中砂含量很少,没有粗砂;沉积物剖面具有良好的沉积层理,剖面粒度旋回至少记录了42次较大的洪水事件,不同期次洪水沉积物之间粒度变化明显,反映了该区近百年内年流域侵蚀和降水量的变化。 相似文献
96.
Isatis tinctoria L. (woad) is a dye plant whose cultivation is increasing because of its adaptability to marginal conditions and increasing
demand for natural products. Suitable breeding schemes need to be set up in order to obtain woad varieties for each proposed
environment. Presently, no data about the reproductive system are available. The effects of selfing and crossing on setting
and progeny vigour were assessed. Results showed the existence of an outcrossing system in I. tinctoria. Obligate self-pollinated plants produced fewer siliques (7.1 g per plant) with lower weight (6.0 mg) and lower seed germinability
(8.2%) than outcrossing plants (44.1 g, 8.0 mg and 46.0% for each character, respectively). Self-pollinated progenies also
generally showed lower vigour than outcrossing progenies. 相似文献
97.
地下水系统的演化是在天然或人为因素影响下,以新的宏观状态取代旧的宏观状态的耗散过程。提出基于耗散结构理论研究地下水系统演化机制的新思路。地下水系统是一个复杂的开放系统,其演化过程处于非平衡有序状态且不可逆,与地下水系统相关的各子系统之间的作用是非线性的,强烈的人为因素对地下水系统演变的影响显著。华北平原中部“冀枣衡”深层地下水漏斗是人类活动强烈干扰下地下水系统异常涨落的产物。大规模超量开采地下水导致衡水市地下水动力场、水化学场和含水介质空间结构变异等问题,地下水系统进入人为活动强烈干扰下的新的演化时期。 相似文献
98.
99.
Y Li H N Kadarmideen J C M Dekkers 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2008,125(5):320-329
The purpose of this study was to develop and investigate selection strategies that aim at maximizing long-term genetic response while conserving gene diversity and controlling inbreeding in populations of limited effective size, assuming complete knowledge of all genes affecting a quantitative trait. Three selection strategies were proposed to select on 100 quantitative trait loci (QTL) and compared with truncation selection on breeding value. Alternative selection strategies aimed at maximizing the average breeding value of parents with a penalty on (1) the number of unfavourable QTL genotypes among parents (OS-I), (2) the negative of the logarithm of the frequency of the favourable allele at each QTL among parents (OS-II), and (3) the average pedigree relationship among parents (OS-III). When all QTL and their effects were known, the strategies examined were able to obtain extra long-term responses, conserve QTL diversity and reduce inbreeding, compared with truncation selection. Strategy OS-II was the most effective in conserving QTL diversity and OS-III in reducing inbreeding. By changing the magnitude of the penalties applied, the impact on long-term response, inbreeding and diversity can be controlled. Extra long-term responses over truncation selection of OS-I and OS-II were even greater when effects of QTL were estimated rather than assumed known, indicating the applicability of results to practical strategies for marker-assisted selection. Extra responses are expected to be reduced for larger population sizes. 相似文献
100.
反式脂肪酸降低乳脂合成的机理 总被引:3,自引:0,他引:3
乳中的反式脂肪酸直接来源于日粮脂肪或由瘤胃微生物氢化生成,本文重点介绍了反10-油酸和反10,顺12-共轭亚油酸两种不同反式脂肪酸对乳脂合成的影响,讨论了反式脂肪酸影响乳脂合成的机理,可能是反式脂肪酸通过抑制乳腺中脂肪酸合成的关键酶乙酰辅酶A羧化酶和脂肪酸合成酶的活性,进而导致乳脂合成的减少。 相似文献