全文获取类型
收费全文 | 4677篇 |
免费 | 242篇 |
国内免费 | 13篇 |
专业分类
林业 | 283篇 |
农学 | 165篇 |
基础科学 | 38篇 |
875篇 | |
综合类 | 793篇 |
农作物 | 263篇 |
水产渔业 | 411篇 |
畜牧兽医 | 1622篇 |
园艺 | 143篇 |
植物保护 | 339篇 |
出版年
2023年 | 39篇 |
2022年 | 26篇 |
2021年 | 91篇 |
2020年 | 105篇 |
2019年 | 107篇 |
2018年 | 93篇 |
2017年 | 93篇 |
2016年 | 100篇 |
2015年 | 71篇 |
2014年 | 116篇 |
2013年 | 202篇 |
2012年 | 275篇 |
2011年 | 309篇 |
2010年 | 198篇 |
2009年 | 161篇 |
2008年 | 253篇 |
2007年 | 281篇 |
2006年 | 245篇 |
2005年 | 258篇 |
2004年 | 242篇 |
2003年 | 232篇 |
2002年 | 210篇 |
2001年 | 61篇 |
2000年 | 60篇 |
1999年 | 67篇 |
1998年 | 43篇 |
1997年 | 33篇 |
1996年 | 46篇 |
1995年 | 37篇 |
1994年 | 35篇 |
1993年 | 50篇 |
1992年 | 39篇 |
1991年 | 46篇 |
1990年 | 38篇 |
1989年 | 44篇 |
1988年 | 42篇 |
1987年 | 30篇 |
1986年 | 35篇 |
1985年 | 33篇 |
1984年 | 40篇 |
1983年 | 27篇 |
1982年 | 20篇 |
1981年 | 24篇 |
1979年 | 19篇 |
1978年 | 17篇 |
1977年 | 18篇 |
1976年 | 17篇 |
1975年 | 23篇 |
1974年 | 22篇 |
1973年 | 22篇 |
排序方式: 共有4932条查询结果,搜索用时 46 毫秒
11.
12.
13.
14.
15.
Landscape-ecological mapping of the Netherlands 总被引:1,自引:0,他引:1
Kees J. Canters Cees P. den Herder Aart A. de Veer Paul W. M. Veelenturf Rein W. de Waal 《Landscape Ecology》1991,5(3):145-162
The Landscape-ecological Mapping of the Netherlands project (LMN project) started in 1983 with the aim of establishing a landscape-ecological database for use in developing and evaluating national land-use plans. The project, working with grid cells of 1 km2, has four working objectives: a) development of mapping potential for basic landscape-ecological data, b) assessment of susceptibility to interventions, c) evaluation of significance for nature conservation and d) production of vulnerability maps, as a combination of susceptibility and significance. In addition to information on soil, groundwater, ecotopes, flora and fauna, the database also incorporates information on physiographical features and entire landscapes. The resulting database is a geographic information system (GIS). This article describes the second phase of the project (1985–1989), covering the Randstad area, and focusses on the methods and the applications potential of the database. 相似文献
16.
The T.M.E. System of Feed Evaluation. I.R. Sibbald, Animal Research Centre Contribution 83‐1, Animal Research Centre, Ottawa, Ontario, Canada.
Physiology and Behaviour of the Pigeon, edited by M. Abs. 1983. 360 pages, illustrated. London, Academic Press Ltd. Price £34.00. ISBN 0 12 042950 0. 相似文献
17.
A strategy for control of bovine leukemia virus infection: test and corrective management 总被引:2,自引:2,他引:0
下载免费PDF全文
![点击此处可从《The Canadian veterinary journal. La revue veterinaire canadienne》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ruppanner R Behymer DE Paul S Miller JM Theilen GH 《The Canadian veterinary journal. La revue veterinaire canadienne》1983,24(6):192-195
Test and corrective management was applied in one dairy herd (130 milking cows) to control bovine leukemia virus infection. It consisted of: raising uninfected calves in order to establish a pool of uninfected replacement heifers, preventing transmission of bovine leukemia virus through transfer of blood from animal to animal and closing the herd. Regular herd testing was combined with selected changes in herd management. These procedures have been followed since January 1979. Prevalence of antibodies (as determined by gel-immunodiffusion) has declined markedly since the program was implemented. 相似文献
18.
The influence of cottonseed oil and of linseed oil upon the fatty-acid composition of milk fat was each studied in one sow. Each oil was added to the basic diet in an amount of 6.3 % for two periods of the lactation. As cottonseed oil has a fatty-acid composition that is similar to that of the basic diet, the supplement with this oil will, in general, increase the same kind of fat in the diet. The linoleic-acid content in the milk fat will be nearly redoubled (11.7 % to 20.5 %) when the cottonseed oil is added. The supplement with linseed oil (of which linolenic acid constitutes about 58 %) to the food raised the linolenic-acid level in the milk fat from 1.1 % to 18.3 %. The increase of linoleic and linolenic acid is counterbalanced by a decrease of shorter fatty acids (G 14 and G 16 acids). The fatty-acid composition of the milk fat adjusts itself to the dietary changes within two or three days.By feeding a diet containing 16.7 % cottonseed oil to a sow, about 27 % linoleic acid was obtained in the sow’s milk fat.The influence of 30 hours of starvation upon the fatty-acid composition was studied in two sows. The content of G 18 acids rose during starvation and that of shorter acids (C14 and C16) diminished. 相似文献
19.
20.
Williams TD Rebar AH Teclaw RF Yoos PE 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》1992,21(4):106-110
Hematologic and/or serum chemical analyses were done on a total of 27 non-tranquilized adult and juvenile wild sea otters, 66 tranquilized adult and juvenile wild sea otters, and 26 wild sea otter pups. The median and inner 90 percentile range were determined for the adult, juvenile, and pup groups and for the following subgroups: adult male versus adult female, juvenile male versus juvenile female, pup male versus pup female, captured with dip net versus captured with Wilson trap, and tranquilized adults and juveniles versus non-tranquilized adults and juveniles. When values for adults were compared to values for juveniles and pups, hematocrits, red blood cell counts, and hemoglobin levels were significantly lower in pups. This is consistent with documented findings in other species. White cell counts were also somewhat lower in younger animals. Among the subgroups, significantly higher hemoglobin levels, white cell counts and neutrophil counts were found in adult females than in adult males. This is in direct contrast to what is seen in other mammalian species and warrants further documentation. Method of capture and tranquilization did not appear to influence either hematologic or serum biochemical determinations from a clinical perspective. 相似文献