全文获取类型
收费全文 | 94篇 |
免费 | 8篇 |
专业分类
林业 | 3篇 |
8篇 | |
综合类 | 10篇 |
农作物 | 2篇 |
水产渔业 | 4篇 |
畜牧兽医 | 69篇 |
园艺 | 4篇 |
植物保护 | 2篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2017年 | 5篇 |
2016年 | 2篇 |
2015年 | 1篇 |
2014年 | 5篇 |
2013年 | 5篇 |
2012年 | 3篇 |
2011年 | 5篇 |
2010年 | 3篇 |
2009年 | 7篇 |
2008年 | 6篇 |
2007年 | 2篇 |
2006年 | 2篇 |
2005年 | 1篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2002年 | 4篇 |
2001年 | 2篇 |
1999年 | 2篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1978年 | 1篇 |
排序方式: 共有102条查询结果,搜索用时 156 毫秒
21.
DL Jenkins LG Davis TW Stafford PF Campos B Hockett GT Jones LS Cummings C Yost TJ Connolly RM Yohe SC Gibbons M Raghavan M Rasmussen JL Paijmans M Hofreiter BM Kemp JL Barta C Monroe MT Gilbert E Willerslev 《Science (New York, N.Y.)》2012,337(6091):223-228
The Paisley Caves in Oregon record the oldest directly dated human remains (DNA) in the Western Hemisphere. More than 100 high-precision radiocarbon dates show that deposits containing artifacts and coprolites ranging in age from 12,450 to 2295 (14)C years ago are well stratified. Western Stemmed projectile points were recovered in deposits dated to 11,070 to 11,340 (14)C years ago, a time contemporaneous with or preceding the Clovis technology. There is no evidence of diagnostic Clovis technology at the site. These two distinct technologies were parallel developments, not the product of a unilinear technological evolution. "Blind testing" analysis of coprolites by an independent laboratory confirms the presence of human DNA in specimens of pre-Clovis age. The colonization of the Americas involved multiple technologically divergent, and possibly genetically divergent, founding groups. 相似文献
22.
S Chakraborty R Knoche H Schulze DC Rubie D Dobson NL Ross RJ Angel 《Science (New York, N.Y.)》1999,283(5400):362-365
Rates of cation diffusion (magnesium, iron, and nickel) have been determined in olivine and its high-pressure polymorph, wadsleyite, at 9 to 15 gigapascals and 1100 degrees to 1400 degreesC for compositions that are relevant to Earth's mantle. Diffusion in olivine becomes strongly dependent on composition at high pressure. In wadsleyite, diffusion is one to two orders of magnitude faster than in olivine, depending on temperature. Homogenization of mantle heterogeneities (chemical mixing) and mineral transformations involving a magnesium-iron exchange will therefore occur considerably faster in the transition zone than at depths of less than 410 kilometers. 相似文献
23.
24.
Development of Improved Feeding Methods in the Culture of Yellow Tang,Zebrasoma flavescens
下载免费PDF全文
![点击此处可从《Journal of the World Aquaculture Society》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Chatham K. Callan Aurora I. Burgess Cara R. Rothe Renee Touse 《Journal of the World Aquaculture Society》2018,49(3):493-503
Yellow tang, Zebrasoma flavescens, are one of the most heavily traded marine aquarium fish species, with nearly 400,000 individuals collected annually from Hawaii's reefs. Despite recent success culturing this species, significant challenges in the rearing processes remain to be overcome before commercialization is feasible. This study compared two feeding regimens, an original diet treatment, which was initially used to successfully culture yellow tang, and a revised diet, which differed in the timing of the introduction of feed items and weaning periods. Both diet regimens consisted of Parvocalanus crassirostris nauplii, enriched Brachionus rotundiformis rotifers, and Artemia nauplii, followed by a transition to dry and frozen feed items. The revised feeding regimen aimed to considerably reduce the amount of copepods and rotifers needed in the rearing process. Eggs were stocked at 40/L into replicate (n = 3) 200‐L tanks for the feeding regimen trial. A follow‐up rearing study, in which eggs were stocked at 19/L in a single 1000‐L tank, tested the revised feeding method at pilot scale. Fish reared on the revised feeding regimen were observed to grow faster in body length and body depth after 2 wk in culture and transitioned more quickly to juveniles as 41% had completed their transition to juvenile coloration by 70 d after hatch. None of the fish reared under the original feeding regimen attained full juvenile coloration during the study period. Survival was not significantly different between treatments and was 0.13% ± 0.13 and 0.29% ± 0.17 in the original and revised feeding regimens, respectively. In the pilot‐scale study, growth was comparable to that of both treatments in the 200‐L scale trial, but survival was much better at 1.9%. This study successfully shortened the copepod and rotifer feeding periods for yellow tang, while not jeopardizing growth or survival. This outcome enhances the commercialization potential for this and likely other Acanthuridae species. 相似文献
25.
26.
AE Pashitski A Gurevich AA Polyanskii DC Larbalestier A Goyal ED Specht DM Kroeger JA DeLuca JE Tkaczyk 《Science (New York, N.Y.)》1997,275(5298):367-369
Magneto-optical imaging was used to visualize the inhomogeneous penetration of magnetic flux into polycrystalline TlBa2Ca2Cu3Ox films with high critical current densities, to reconstruct the local two-dimensional supercurrent flow patterns and to correlate inhomogeneities in this flow with the local crystallographic misorientation. The films have almost perfect c-axis alignment and considerable local a- and b-axis texture because the grains tend to form colonies with only slightly misaligned a and b axes. Current flows freely over these low-angle grain boundaries but is strongly reduced at intermittent colony boundaries of high misorientation. The local (<10-micrometer scale) critical current density Jc varies widely, being up to 10 times as great as the transport Jc (scale of approximately 1 millimeter), which itself varies by a factor of about 5 in different sections of the film. The combined experiments show that the magnitude of the transport Jc is largely determined by a few high-angle boundaries. 相似文献
27.
28.
R Briante F La Cara M P Tonziello F Febbraio R Nucci 《Journal of agricultural and food chemistry》2001,49(7):3198-3203
The main reaction products obtainable by the hydrolysis of commercially available oleuropein by hyperthermophilic beta-glycosidase were purified and structurally characterized by UV and 1H and 13C NMR analyses. Their antioxidant activity, in particular their capacity to inhibit the fatty acid peroxidation rate, was studied. The molecular structures assigned revealed the presence of two elenolic acid forms presenting different antioxidant abilities closely correlated to their molecular structures, as well as an unstable elenolate which is a rearrangement product of the oleuropein aglycon. This molecule, under the reaction conditions (pH 7.0, 60 degrees C) required for beta-glycosidase activity, rapidly gives rise to 3,4-dihydroxy-phenylethanol (hydroxytyrosol). 相似文献
29.
de Cara MA Fernández J Toro MA Villanueva B 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2011,128(6):456-464
We study here the effect of using genome-wide marker data versus genealogical data in population management for the maintenance of diversity in conservation schemes using optimal contributions. We re-examine the benefits of using molecular data for different population and genome sizes and compare different management strategies according to the group of individuals where we take decisions (parents or offspring). We also study the consequences of using estimated genealogical coancestries calculated from molecular information. Using genome-wide marker data performed usually better than using genealogical data or estimated genealogical coancestry to maintain expected and observed heterozygosity. Furthermore, when we could take decisions acting on the offspring, a larger heterozygosity was maintained than when we based our decisions on the potential parents. 相似文献
30.