全文获取类型
收费全文 | 1051篇 |
免费 | 33篇 |
专业分类
林业 | 407篇 |
农学 | 8篇 |
85篇 | |
综合类 | 49篇 |
农作物 | 41篇 |
水产渔业 | 31篇 |
畜牧兽医 | 401篇 |
园艺 | 16篇 |
植物保护 | 46篇 |
出版年
2018年 | 20篇 |
2017年 | 18篇 |
2016年 | 22篇 |
2014年 | 11篇 |
2013年 | 13篇 |
2012年 | 24篇 |
2011年 | 18篇 |
2010年 | 13篇 |
2009年 | 15篇 |
2008年 | 21篇 |
2007年 | 25篇 |
2006年 | 23篇 |
2005年 | 29篇 |
2004年 | 20篇 |
2003年 | 16篇 |
2002年 | 17篇 |
2001年 | 22篇 |
2000年 | 18篇 |
1999年 | 12篇 |
1992年 | 16篇 |
1991年 | 16篇 |
1990年 | 23篇 |
1989年 | 20篇 |
1988年 | 16篇 |
1986年 | 19篇 |
1985年 | 22篇 |
1984年 | 23篇 |
1983年 | 21篇 |
1982年 | 20篇 |
1981年 | 19篇 |
1980年 | 15篇 |
1979年 | 22篇 |
1978年 | 24篇 |
1977年 | 10篇 |
1976年 | 11篇 |
1975年 | 10篇 |
1974年 | 15篇 |
1973年 | 22篇 |
1972年 | 11篇 |
1971年 | 19篇 |
1970年 | 20篇 |
1969年 | 13篇 |
1968年 | 10篇 |
1965年 | 12篇 |
1956年 | 13篇 |
1941年 | 7篇 |
1937年 | 13篇 |
1936年 | 7篇 |
1934年 | 9篇 |
1930年 | 9篇 |
排序方式: 共有1084条查询结果,搜索用时 15 毫秒
1.
1. This paper addresses the possibility of using a monthly model for the genetic evaluation of laying hens, based on the definition of a test day model with fixed regression as used in dairy cattle, in which monthly records were treated as repeated measurements of the same trait. 2. Production records of 6450 hens, daughters of 180 sires and 1335 dams were analysed using an animal model with restricted maximum likelihood (REML). The traits considered were individual monthly egg production and cumulative egg production in 11 months. Four different models were fitted to various combinations of monthly and cumulative records. The covariates were derived from the regression of Ali and Schaeffer (1987). 3. Spearman rank correlations were computed to compare breeding values from different models. Two types of correlations were computed: between individual breeding values and between sire breeding values based on subsets of full-sib records. 4. The results indicated that a monthly model with nested covariates produced higher heritability and permanent environmental variance than the models with non-nested or without covariates. The estimates of heritability obtained from monthly model were lower than the estimates from the cumulative model. The monthly model resulted in higher correlations of sire breeding values between two subsets of full-sib records than those from cumulative models. 5. In conclusion, the monthly model with nested covariates appears to be better than the model with non-nested covariates or without covariate. Although the heritability estimates obtained from the monthly model were lower, the monthly model with nested covariates could be better than the cumulative model for genetic evaluation of laying hens in the 1st cycle of laying period when using either full or part records. The use of information from odd months of production could be of interest for the evaluation of full records. 相似文献
2.
We report on an outbreak of enzootic abortion in a herd of goats with high losses caused by mixed infection with Coxiella burnetii and Chlamydia psittaci. Both agents could be detected by microscopic investigation of smears from afterbirths by Giménez staining and by a capture enzyme-linked immunofluorescence assay (Capture ELIFA). Additionally, Coxiella burnetii was isolated from the same tissues in BGM cell cultures. Serological investigations with CF, indirect ELIFA, and IF tests revealed high antibody titers against both agents in most animals. Coxiella antigen was still detected 91 days later in milk samples of two infected goats by Capture ELIFA. 相似文献
3.
P Sch?ss 《Berliner und Münchener tier?rztliche Wochenschrift》1989,102(11):387-389
Atrophic rhinitis is caused by toxigenic Pasteurella multocida strains. The infection is supported by Bordetella bronchiseptica and other widespread agents and by non-infectious factors damaging the nasal epithelium. The term "infectious multifactorial disease" means in German, that ubiquitous low-virulent agents cause disease when intensified by non-infectious factors. Atrophic rhinitis does not belong to this group but is an infectious disease, caused by a specific agent and influenced by several factors. 相似文献
4.
H T?nhardt J Dorst B Schülke H Sajonski 《Archiv fuer experimentelle veterinaermedizin》1976,30(5):733-738
Testicular tissue and blood samples (V. spermatica interna) were taken from 32 boars during castration. The animals were different age groups. Against this background, studies were conducted into the correlations between testicular and plasma testosterone, on the one hand, and the amount of interstitial cells of Leydig in testicular tissue as well as the latters' cell nuclei volumes, on the other. The results seemed to support the conclusion that any age-dependent increase of testicular and plasma testosterone concentrations was caused unambigously by an absolute increase in volume of androgenic testicular tissue, in concomitance with testicular growth, in other words, by rise in the total number of interstitial cells of Leydig. 相似文献
5.
J. Schäler R. Wellmann J. Bennewitz G. Thaller D. Hinrichs 《Acta Agriculturae Scandinavica, Section A - Animal Sciences》2018,68(2):63-72
Recovering native uniqueness has major importance for breeds with historic introgression. The aim of the study was to estimate population genetic parameters for two local red cattle breeds from Northern Germany and to study possibilities to reverse introgression. Genealogical information consisted of 90,783 individuals for German Angler and 187,255 individuals for Red Dual-Purpose cattle breed, with additional information on sex, born, breed, status, and conventional breeding values. It is concluded that the native genetic contribution could be included as an additional trait in the total merit index in order to recover a part of the native genetic background. Native contributions should be estimated in the long term from marker data in order to account for Mendelian sampling. The maintenance of a sufficient genetic diversity of native alleles can be achieved by an advanced OCS with appropriate constraints. 相似文献
6.
Longitudinal analysis of allergen‐specific IgE and IgG subclasses as potential predictors of insect bite hypersensitivity following first exposure to Culicoides in Icelandic horses
下载免费PDF全文
![点击此处可从《Veterinary dermatology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
7.
Reducing copper use in the environment: the use of larixol and larixyl acetate to treat downy mildew caused by Plasmopara viticola in viticulture
下载免费PDF全文
![点击此处可从《Pest management science》网站下载免费的PDF全文](/ch/ext_images/free.gif)
8.
9.
10.