全文获取类型
收费全文 | 15689篇 |
免费 | 1137篇 |
国内免费 | 961篇 |
专业分类
林业 | 731篇 |
农学 | 959篇 |
基础科学 | 451篇 |
589篇 | |
综合类 | 5008篇 |
农作物 | 820篇 |
水产渔业 | 962篇 |
畜牧兽医 | 5723篇 |
园艺 | 664篇 |
植物保护 | 1880篇 |
出版年
2024年 | 71篇 |
2023年 | 294篇 |
2022年 | 451篇 |
2021年 | 618篇 |
2020年 | 599篇 |
2019年 | 707篇 |
2018年 | 429篇 |
2017年 | 578篇 |
2016年 | 634篇 |
2015年 | 610篇 |
2014年 | 807篇 |
2013年 | 853篇 |
2012年 | 1070篇 |
2011年 | 1010篇 |
2010年 | 859篇 |
2009年 | 874篇 |
2008年 | 794篇 |
2007年 | 813篇 |
2006年 | 748篇 |
2005年 | 596篇 |
2004年 | 562篇 |
2003年 | 448篇 |
2002年 | 373篇 |
2001年 | 415篇 |
2000年 | 398篇 |
1999年 | 331篇 |
1998年 | 237篇 |
1997年 | 196篇 |
1996年 | 180篇 |
1995年 | 199篇 |
1994年 | 156篇 |
1993年 | 140篇 |
1992年 | 162篇 |
1991年 | 106篇 |
1990年 | 98篇 |
1989年 | 92篇 |
1988年 | 58篇 |
1987年 | 50篇 |
1986年 | 27篇 |
1985年 | 19篇 |
1984年 | 10篇 |
1983年 | 14篇 |
1982年 | 19篇 |
1981年 | 10篇 |
1980年 | 20篇 |
1979年 | 18篇 |
1978年 | 7篇 |
1976年 | 8篇 |
1956年 | 6篇 |
1955年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 484 毫秒
41.
Modern biotechnology promises a number of new applications in animal breeding and production. Although conventional pig breeding has achieved a high level of efficiency and productivity numerous problems have been encountered with animal health and the loss of meat quality. Selection based on phenotypic performance data of individual animals does not take into account the importance of specific genes and their relevance within a complex regulatory system. In most cases it is therefore difficult to trace back the genetic origins of clinically important disorders. The application of genetic engineering techniques in pig production will facilitate diagnosis, improvement of productivity, and animal health by allowing direct genetic manipulation. Attention must be focussed on the physical and genetic analysis of the procine genome. The isolation and characterisation of genes, DNA-markers, polymorphic DNA-fragments, and their chromosomal assignment will be important prerequisites and tools for the elucidation of genetic disorders. Especially the detection of heterozygous carriers of recessive disorders and their elimination from the breeding stock will increase selection accuracy and decrease the generation intervals. But also the rapid and simple detection of infectious diseases, which is sometimes difficult if not impossible at present, will improve animal health and welfare. Although the production of transgenic animals either by DNA-microinjection into zygotes or the use of embryonal stem cells manipulated in vitro is less straightforward than DNA-based diagnosis it will play an important role in the direct manipulation of the porcine genome and genes. Breeding programmes including the use of transgenic livestock have already been developed. There is no doubt that genetic engineering has reached a degree of practical feasibility, allowing it to play an important role in pig breeding in particular and animal production in general. 相似文献
42.
本文通过层次分析法(Analytical Hierarchy Process,AHP),结合门源县当前畜禽疫病防治现状,对影响畜禽病防治的制约条件进行了研究,表明群众防疫意识的淡薄和防疫费收取困难是首要制约因素,基础设施建设和队伍建设滞后居次位,监督工作较弱也不容忽视。 相似文献
43.
以水貂阿留申病病毒对流免疫电泳(CIEP)细胞抗原为材料,经酶印迹(Westemblotting)测定,水貂阿留申病病毒CIEI细胞抗原与多克隆阳性血清反应,分子量为60000,50000和25000,而与CIEP阴性的抗水貂阿留申病病毒的单克隆抗体(Y—2—9)反应,分子量为60000,50000.因此初步确定水貂阿留申病病毒CIEP细胞抗原决定族位于分子25000蛋白上. 相似文献
44.
45.
46.
引种草坪草的适应性评价及病害和草害 总被引:10,自引:4,他引:6
1997~1998年,对引自丹麦的草地早熟禾、黑麦草、高羊茅、羊茅、紫羊茅、匍匐剪股颖和白三叶等草坪草的品种在兰州市进行了适应性评价。观测、记载了草坪的成坪期、密度、盖度、颜色、质地、越冬率、越夏率、返青期、枯黄期、青缘期等性状;调查了病害的发病率,并对病株进行了病原物的分离、培养和鉴定,统计了各品种带菌率和真菌的分离率;调查了草坪建植与生长过程中的杂草种类和危害程度。结果表明:除Pichwick和Juventus黑麦草以外的所有参试品种均可在兰州地区种植。其中,白三叶的综合性状最好,具有质地柔滑、成坪较快、覆盖度高、枯黄期晚等特点;其次为ORNAMENTAL和SPORT2个混配型草种,成坪快,但抗病性较差;其余各品种建坪后表现好,但成坪速度较慢。草坪生长过程中的主要病害为交链孢叶斑病、离蠕孢叶斑病、德氏霉叶斑病、壳二孢叶枯病、壳二孢叶斑病、镰刀菌枯萎病和叶点霉叶斑病。苗期主要杂革为狗尾草和田旋花。 相似文献
47.
48.
49.
M. Sandholm A. Vidovic A. Puotunen-Reinert S. Sankari K. Nyholm H. Rita 《Acta veterinaria Scandinavica》1995,36(2):255
The discriminating ability of 15 parameters alone or in combinations, including results from analysis of plasma endotoxin, the Nycomed plasma D-Dimer test and phospholipase A2, were analyzed to predict morbidity and mortality in equine gastrointestinal colic. Endotoxaemia was a characteristic feature of the colic horses. The problem of adequately predicting non-survivors among colic horses required several parameters to be included in the logistic model: if the “classical parameters”, (heart rate, respiratory rate, PCV, anion gap) were included in the model, addition of plasma D-dimer, phospholipase A2, and Cl- significantly improved the predictive value of the logistic model. Increasing heart rate and D-dimer together with decreasing chloride was a risk factor for nonsurvival. The sensitivity of this three-parameter logistic model to predict nonsurvival was 78% and specificity 77%. The Nycomed D-Dimer test is recommended as a horse-site test to predict disseminated intravascular coagulation and nonsurvival in equine colic. 相似文献
50.
采用种子处理方法可显著提高种子发芽率、降低发病率;其中以药剂浸种效果最好;药剂处理以多菌灵+福美双和多菌灵两个配方最佳。 相似文献