全文获取类型
收费全文 | 268篇 |
免费 | 30篇 |
国内免费 | 1篇 |
专业分类
林业 | 10篇 |
基础科学 | 1篇 |
28篇 | |
综合类 | 72篇 |
农作物 | 9篇 |
水产渔业 | 11篇 |
畜牧兽医 | 158篇 |
园艺 | 4篇 |
植物保护 | 6篇 |
出版年
2023年 | 3篇 |
2021年 | 2篇 |
2020年 | 7篇 |
2019年 | 3篇 |
2018年 | 9篇 |
2017年 | 5篇 |
2016年 | 8篇 |
2015年 | 10篇 |
2014年 | 8篇 |
2013年 | 18篇 |
2012年 | 8篇 |
2011年 | 17篇 |
2010年 | 6篇 |
2009年 | 7篇 |
2008年 | 4篇 |
2007年 | 8篇 |
2006年 | 13篇 |
2005年 | 9篇 |
2004年 | 7篇 |
2003年 | 4篇 |
2002年 | 2篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1998年 | 7篇 |
1997年 | 8篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1971年 | 3篇 |
1967年 | 2篇 |
1966年 | 2篇 |
1946年 | 2篇 |
1945年 | 2篇 |
1944年 | 8篇 |
1942年 | 2篇 |
1941年 | 2篇 |
1932年 | 2篇 |
排序方式: 共有299条查询结果,搜索用时 312 毫秒
31.
32.
Physical and chemical anal ysis of pottery fragments, including a crucible shard and ore samples from Tal-i-Iblis, Iran, suggests that copper smelting may have been well advantced late in the fifth millennium B.C. 相似文献
33.
34.
Treusch S Hamamichi S Goodman JL Matlack KE Chung CY Baru V Shulman JM Parrado A Bevis BJ Valastyan JS Han H Lindhagen-Persson M Reiman EM Evans DA Bennett DA Olofsson A DeJager PL Tanzi RE Caldwell KA Caldwell GA Lindquist S 《Science (New York, N.Y.)》2011,334(6060):1241-1245
Aβ (beta-amyloid peptide) is an important contributor to Alzheimer's disease (AD). We modeled Aβ toxicity in yeast by directing the peptide to the secretory pathway. A genome-wide screen for toxicity modifiers identified the yeast homolog of phosphatidylinositol binding clathrin assembly protein (PICALM) and other endocytic factors connected to AD whose relationship to Aβ was previously unknown. The factors identified in yeast modified Aβ toxicity in glutamatergic neurons of Caenorhabditis elegans and in primary rat cortical neurons. In yeast, Aβ impaired the endocytic trafficking of a plasma membrane receptor, which was ameliorated by endocytic pathway factors identified in the yeast screen. Thus, links between Aβ, endocytosis, and human AD risk factors can be ascertained with yeast as a model system. 相似文献
35.
Benjamin M. Rau Dale W. Johnson Robert R. Blank Annmarrie. Lucchesi Todd G. Caldwell Eugene W. Schupp 《Strength and Conditioning Journal》2011,64(2):139-147
Vegetation changes associated with climate shifts and anthropogenic disturbance have major impacts on biogeochemical cycling. Much of the interior western United States currently is dominated by sagebrush (Artemisia tridentata Nutt.) ecosystems. At low to intermediate elevations, sagebrush ecosystems increasingly are influenced by cheatgrass (Bromus tectorum L.) invasion. Little currently is known about the distribution of belowground organic carbon (OC) on these changing landscapes, how annual grass invasion affects OC pools, or the role that nitrogen (N) plays in carbon (C) retention. As part of a Joint Fire Sciences-funded project called the Sagebrush Treatment Evaluation Project (SageSTEP), we quantified the depth distribution of soil OC and N at seven sites experiencing cheatgrass invasion. We sampled plots that retained sagebrush, but represented a continuum of cheatgrass invasion into the understory. Eighty-four soil cores were taken using a mechanically driven diamond-tipped core drill to a depth of 90 cm, or until bedrock or a restrictive layer was encountered. Samples were taken in 15-cm increments, and soil, rocks, and roots were analyzed for OC and total N. We determined that cheatgrass influences the vertical distribution of OC and N within the soil profile and might result in decreased soil OC content below 60 cm. We also found that OC and total N associated with coarse fragments accounted for at least 10% of belowground pools. This emphasizes the need for researchers to quantify nutrients in deep soil horizons and coarse fragments. 相似文献
36.
Rumen contents of 2 heifers with acute polioencephalomalacia (cerebrocortical necrosis) were compared with rumen contents from a healthy steer fed a fibrous diet. Also examined were (i) the quantitative nature of the predominant rumen microflora, (ii) the distribution of morphologic types of bacteria in the rumen contents, (iii) the extent that morphologic groups produced or degraded thiamine, and (iv) the cumulative effects of metabolic activities of the predominant rumen bacteria concerning the net production or degradation of thiamine. The differences in the frequency of occurrence of particular bacterial morphologic groups, the extent of growth, and the amount of thiamine metabolism in relationship to growth were also evaluated. The cumulative thiamine metabolism of the predominant bacteria associated with the rumen of polioencephalomalacia-affected heifers led to substantial net thiamine destruction, whereas metabolism associated with the rumen of a normal steer led to thiamine production. Polioencephalomalacia may occur as a consequence of alteration of the metabolic activities of the predominant resident ruminal bacteria associated with diseased cattle. 相似文献
37.
38.
39.
40.
Phylogenetic characterisation of bluetongue viruses from naturally-infected insects, cattle and sheep in Australia 总被引:1,自引:0,他引:1
KA McCOLL AR GOULD LI PRITCHARD L MEL VILLE† G. BELLIS† 《Australian veterinary journal》1994,71(4):102-105
SUMMARY The polymerase chain reaction was used to detect the presence of blue-tongue virus (BTV) in a number of clinical and insect samples collected in the Northern Territory of Australia. Sequence analyses of the amplified BTV genes differentiated endemic Australian and exotic viruses. Two potential exotic BTV were detected as a result of PCR analyses of blood from sentinel animals and of the insect vector, Culicoides wadai. The detection of BTV in C wadai was the first direct demonstration of the presence of BTV in this potential vector. This new technology can significantly reduce the time taken for a diagnosis from a clinical sample and increase the amount of useful information obtained on a BTV isolate by using rapid sequencing techniques. Sequence data were used to differentiate between BTV20 isolated in 1975 and two isolates of the same serotype, isolated in 1992, and indicated that the latter were probably a recent incursion into Australia from Indonesia due to their greater VP3 sequence homology to the BTV9 (Java) than to Australian BTV isolates. 相似文献