全文获取类型
收费全文 | 750篇 |
免费 | 58篇 |
专业分类
林业 | 15篇 |
农学 | 23篇 |
基础科学 | 3篇 |
52篇 | |
综合类 | 140篇 |
农作物 | 20篇 |
水产渔业 | 36篇 |
畜牧兽医 | 486篇 |
园艺 | 5篇 |
植物保护 | 28篇 |
出版年
2023年 | 5篇 |
2021年 | 5篇 |
2020年 | 11篇 |
2019年 | 18篇 |
2018年 | 13篇 |
2017年 | 7篇 |
2016年 | 15篇 |
2015年 | 9篇 |
2014年 | 8篇 |
2013年 | 37篇 |
2012年 | 14篇 |
2011年 | 21篇 |
2010年 | 26篇 |
2009年 | 23篇 |
2008年 | 15篇 |
2007年 | 33篇 |
2006年 | 35篇 |
2005年 | 35篇 |
2004年 | 22篇 |
2003年 | 24篇 |
2002年 | 27篇 |
2001年 | 23篇 |
2000年 | 19篇 |
1999年 | 20篇 |
1998年 | 21篇 |
1997年 | 15篇 |
1996年 | 13篇 |
1995年 | 10篇 |
1994年 | 6篇 |
1993年 | 6篇 |
1992年 | 21篇 |
1991年 | 17篇 |
1990年 | 15篇 |
1989年 | 16篇 |
1988年 | 13篇 |
1987年 | 14篇 |
1986年 | 7篇 |
1985年 | 14篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1980年 | 5篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1977年 | 9篇 |
1976年 | 6篇 |
1973年 | 6篇 |
1971年 | 10篇 |
1969年 | 5篇 |
1914年 | 4篇 |
1902年 | 4篇 |
排序方式: 共有808条查询结果,搜索用时 531 毫秒
41.
42.
Daniel J. Archambault Eduardo Marentes Wayne Buckley John Clarke Gregory J. Taylor 《Euphytica》2001,117(2):175-182
We have developed a seedling-based bioassay that iscapable of identifying low Cd-accumulating phenotypes(homozygous and heterozygous) after 96–120 h ofexposure. Our experiments were conducted using109Cd as a tracer at subtoxic concentrations tosimulate conditions that might be experienced in thefield. Supply of Cd (10-11 M) to 4-d oldseedlings for 0–8 h resulted in no differences in rootand leaf Cd content between the low (TL05) and high(TL04) Cd-accumulating isolines. Increasing time ofexposure produced significant differences in leaf Cdaccumulation between isolines, with differencesbecoming most pronounced after the bulk of appliedcadmium ( 95%) was depleted from absorption solutions( 72 h). Similar results were obtained with8-d old seedlings, where differences between genotypeswere more pronounced in young leaves (2nd leaf) orshoot bases. Individuals from five low and highCd-accumulating near isogenic pairs (50individuals/isoline) were screened using Cdconcentration of shoot bases as the screeningcriterion. Mean scores within each isoline pair weresignificantly different, although overlap ofindividual scores was observed at intermediate foliarCd concentrations. The 2nd leaf to root Cdcontent ratio, which reflects root to shoottranslocation, provided a better parameter todistinguish low from high Cd-accumulating isolines. Plants used for this bioassay could also be rescuedfor subsequent experimental crosses, providing a rapidand cost-effective tool for early detection of the lowCd-accumulating phenotype. 相似文献
43.
Summary A CODASYL type database has been created for plant propagation records. The existence and history of plants can be recorded in such a way that details of parentage and offspring can be traced. Plants that have undergone similar treatments and events or that have similar characteristics can be located and other information assisting the management of the propagation experiments is recorded. Containing this information, the database is a model of experimental plant propagation. 相似文献
44.
Pre-harvest sprouting of wheat grain can cause economic losses especially in cultivars with low levels of seed dormancy. The
aim of this study was to determine genotype differences in embryo sensitivity to germination in response to exogenous (+/–)
cis-trans ABA treatments at different concentrations. Six white and four red seed-colored bread wheat genotypes that differed in dormancy
were grown in a field near Swift Current, Saskatchewan in 2000 as a randomized complete block design with four replicates.
The seed samples from this experiment were germinated in a controlled environment at 20 °C without light. The exogenous ABA
treatments were 0 μM – whole seed (control), 0 μM-embryos, 25 μM – embryos and 50 μM – embryos. The ABA experiment was a factorial
design with four randomized complete blocks with four ABA treatments in all combinations with the ten genotypes. A weighted
(by day) germination index (WGI) was calculated for each genotype in each ABA treatment. Genotypes differed in response to
ABA. The genotypes, ABA concentration and genotype by ABA concentration interaction effects were significant (p ≤ 0.05). Excised embryos showed significantly decreased dormancy in most of the experimental genotypes. The addition of exogenous
ABA enhanced embryo dormancy of most genotypes.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
45.
Breeding territoriality in birds means that a certain proportion of the adult population may breed in suboptimal habitats or not breed at all. Non-breeding birds, or floaters, can have a `buffer effect' on breeding population size. Farmland bird declines in Britain are measured and analysed in terms of numbers of territory-holding birds. We use a population dynamics model to illustrate how, because of the buffer effect of floaters, there can be a time lag between the start of total population decline and detectable breeding population decline. Differences in the timing of declines of closely related farmland birds could therefore be due to slight differences in their population dynamics, rather than differences in their response to agricultural change. 相似文献
46.
Effect of gamma-irradiation on beef myoglobin 总被引:1,自引:0,他引:1
47.
48.
An important, but often limiting step in marker-assisted breeding is the efficient isolation of plant DNA for polymerase chain reaction (PCR) amplification. A simple method using an alkali treatment to extract wheat DNA for marker-assisted selection (MAS) in wheat breeding programs was compared to a commercial kit and cetyltrimethylammonium bromide (CTAB) extraction. DNA concentration from the alkali extraction was higher than the other two methods but purity was lower than CTAB extraction. The alkali extraction method was used on breeding lines to determine its usefulness. The alkali-extracted DNA samples were suitable for several PCR-based procedures, including random amplified polymorphic DNA (RAPD), microsatellite (simple sequence repeat, i.e., SSR) and sequence characterized amplified region (SCAR)analyses. 相似文献
49.
Self-incompatibility: a self-recognition system in plants 总被引:18,自引:0,他引:18
V Haring J E Gray B A McClure M A Anderson A E Clarke 《Science (New York, N.Y.)》1990,250(4983):937-941
Self-incompatibility (SI), a genetically controlled mechanism to prevent inbreeding in plants, offers a relatively simple model system for studying the interactions between plant cells or between a plant cell and the secreted product or products of another cell. Examples of two major types of SI, gametophytic and sporophytic, have been studied by cloning cDNAs corresponding to glycoproteins of the female tissues that segregate with particular variants encoded by the putative S locus. These secreted glycoproteins are envisaged to interact with the currently undescribed pollen component to cause arrest of pollen tube growth. 相似文献
50.
A method for dating geological samples which uses fission product xenon in a manner similar to the use of radiogenic argon in the 40Ar-39Ar technique has been developed. The results of stepwise heating experiments for a zircon from the Ahaggar region in the Sahara are compared to the geochronology determined by the rubidiumstrontium, uranium-thorium-lead, and potassium-argon dating methods. 相似文献