全文获取类型
收费全文 | 3673篇 |
免费 | 257篇 |
国内免费 | 307篇 |
专业分类
林业 | 379篇 |
农学 | 279篇 |
基础科学 | 82篇 |
366篇 | |
综合类 | 1459篇 |
农作物 | 215篇 |
水产渔业 | 308篇 |
畜牧兽医 | 657篇 |
园艺 | 325篇 |
植物保护 | 167篇 |
出版年
2024年 | 22篇 |
2023年 | 71篇 |
2022年 | 136篇 |
2021年 | 155篇 |
2020年 | 170篇 |
2019年 | 212篇 |
2018年 | 120篇 |
2017年 | 195篇 |
2016年 | 184篇 |
2015年 | 198篇 |
2014年 | 198篇 |
2013年 | 199篇 |
2012年 | 259篇 |
2011年 | 247篇 |
2010年 | 172篇 |
2009年 | 200篇 |
2008年 | 204篇 |
2007年 | 191篇 |
2006年 | 136篇 |
2005年 | 108篇 |
2004年 | 94篇 |
2003年 | 80篇 |
2002年 | 68篇 |
2001年 | 63篇 |
2000年 | 60篇 |
1999年 | 54篇 |
1998年 | 48篇 |
1997年 | 47篇 |
1996年 | 40篇 |
1995年 | 37篇 |
1994年 | 46篇 |
1993年 | 35篇 |
1992年 | 30篇 |
1991年 | 39篇 |
1990年 | 38篇 |
1989年 | 18篇 |
1988年 | 24篇 |
1987年 | 15篇 |
1986年 | 8篇 |
1985年 | 1篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有4237条查询结果,搜索用时 15 毫秒
1.
2.
3.
根据大豆理想株型的概念,分析了大豆的主要生理性状和形态性状与产量的关系,并提出了大豆高产理想株型的合理构成,以期为大豆育种的田间选择和株型育种提供理论依据和实践指导。 相似文献
4.
描记滑胸茧蜂属属征和褐滑胸茧蜂形态,并提供该蜂的形态图。 相似文献
5.
合理调整我国人民的食物结构是提高全民族身体素质,推进社会文明进步,具有深远的战略意义的一项国策。调整国民食物结构是一个科学性,政策性很强,社会涉及面广,地区人群民食习惯差别大的极为复杂的动态系统工程。作者针对山西省情实际,从追朔我国饮食传统,膳食民习,食物资源及演变趋向探求,提出合理调整山西人民食物结构的策略与途径。 相似文献
6.
7.
Although agronomically interesting, selection of creeping-rootedness inlucerne, that is, the ability to form adventitious shoots on horizontal,spreading roots, remains difficult because of the complex and still unclear geneticcontrol of this character, coupled with the possible occurrence of external factorsthat affect unpredictably its expression. Two experiments were undertaken onprogenies of creeping-rooted plants, to verify previous findings and inferences,and test novel hypotheses, concerning the effect of various plant factors on theexpression of creeping-rootedness. The ultimate aim was to provide information onthe most appropriate germplasm, procedures, or indirect selection criteria, that wouldimprove the efficiency of breeding for this character. The factors here examinedincluded genotype, age, kind of progeny, vigour, spreading ability, and undergroundmorphology. Some genotypes appeared to be good donors of the character, whereasothers did not. The proportion of creeping-rooted plants increased in allcases with the plant age. Selfing consistently depressed the expression ofthe character compared with clonal propagation or crossing. It is suggestedthat the effect of age and selfing on the penetrance of creeping-rootedness ismediated through their effect on plant vigour. Both aerial and root vigour showedindeed an effect per se on the presence of the character. Beside thevigour, possible indirect selection criteria were identified in the frequenciesof swollen zones and latent stem primordia on horizontal roots. Proportion ofcreeping-rooted plants in progenies after one year of growth appeared as a simple anduseful criterion to predict future trends. Consistent with previous conclusions, theresults provided evidence that a combination of family and individualselection may enhance the character expression. 相似文献
8.
After about 25 years of intensive research a substantial moment of information has accumulated on the basic biology of Prostephanus truncatus in stored products. This article reviews the literature on the geographical distribution, biotypes, symbiotic associations, mating and flight behaviour, oviposition, and development on both agricultural and non-agricultural hosts. The current knowledge about the nutritional biology (including the role of symbionts) and host finding behaviour (including the inter-linked roles of plant chemicals and the insect's own pheronones) are highlighted as research areas which deserve future attention. In addition, few studies have been conducted to determine the extent to which the biology of P. truncatus permits it to survive and reproduce in non-agricultural environments. These areas of study should be pursued as possible routes to providing more effective integrated pest managements strategies for the larger grain borer. 相似文献
9.
许多固氮树种速生丰产,萌生能力强,叶片,木屑含氮率较高,可为食用菌栽培提供理想原料,而且固氮树种在绿花荒山,保持水土,提高地力方面作用显著,以固氮树种发展短轮伐期食用菌专用林,具有较高的经济效益和生态效益,本文介绍了银合欢,黑荆,大叶相思,银荆,桤木,南洋楹和马占相思等在食用菌栽培上的应用概况,各地可因地制宜栽培合适的固氮树种作为食用菌专用林。 相似文献
10.