全文获取类型
收费全文 | 9195篇 |
免费 | 634篇 |
国内免费 | 50篇 |
专业分类
林业 | 578篇 |
农学 | 471篇 |
基础科学 | 83篇 |
1637篇 | |
综合类 | 642篇 |
农作物 | 471篇 |
水产渔业 | 720篇 |
畜牧兽医 | 4290篇 |
园艺 | 127篇 |
植物保护 | 860篇 |
出版年
2023年 | 85篇 |
2022年 | 154篇 |
2021年 | 289篇 |
2020年 | 288篇 |
2019年 | 350篇 |
2018年 | 334篇 |
2017年 | 351篇 |
2016年 | 352篇 |
2015年 | 251篇 |
2014年 | 332篇 |
2013年 | 527篇 |
2012年 | 526篇 |
2011年 | 587篇 |
2010年 | 294篇 |
2009年 | 339篇 |
2008年 | 461篇 |
2007年 | 446篇 |
2006年 | 404篇 |
2005年 | 375篇 |
2004年 | 350篇 |
2003年 | 316篇 |
2002年 | 342篇 |
2001年 | 244篇 |
2000年 | 246篇 |
1999年 | 208篇 |
1998年 | 58篇 |
1997年 | 61篇 |
1996年 | 55篇 |
1995年 | 54篇 |
1994年 | 39篇 |
1993年 | 41篇 |
1992年 | 80篇 |
1991年 | 54篇 |
1990年 | 65篇 |
1989年 | 68篇 |
1988年 | 66篇 |
1987年 | 53篇 |
1986年 | 49篇 |
1985年 | 59篇 |
1984年 | 40篇 |
1983年 | 42篇 |
1982年 | 30篇 |
1980年 | 23篇 |
1979年 | 37篇 |
1978年 | 21篇 |
1977年 | 21篇 |
1974年 | 23篇 |
1973年 | 25篇 |
1972年 | 24篇 |
1970年 | 26篇 |
排序方式: 共有9879条查询结果,搜索用时 31 毫秒
101.
102.
103.
104.
105.
106.
Alana Batista dos Santos Mara Lúcia Albuquerque Pereira Herymá Giovane de Oliveira Silva Gleidson Giordano Pinto de Carvalho Taiala Cristina de Jesus Pereira Leandro Sampaio Oliveira Ribeiro José Augusto Gomes Azevêdo Maria das Graças Conceição Parada Costa Silva Larisse Borges Sousa Leandro Borges Sousa Daiane de Oliveira Alencar 《Tropical animal health and production》2016,48(3):509-515
107.
108.
109.
Amália Turner Giannico Elaine Mayumi Ueno Gil Daniela Aparecida Ayres Garcia Marlos Gonçalves Sousa Tilde Rodrigues Froes 《Veterinary research communications》2016,40(1):11-19
The aim of this study was to develop regression models for correlation of canine fetal heart development with body size to characterize normal development or suggest cardiac anomalies. Twenty clinically healthy pregnant bitches, either brachycephalic and non-brachycephalic, were examined ultrasonographically. Transabdominal fetal echocardiography was conducted every 4 days from the beginning of cardiac chambers differentiation until parturition. Ten cardiac parameters were measured: length, width and diameter of the heart; heart area; left and right ventricular dimensions; left and right atrial dimensions; and aortic and pulmonary artery diameter. Femoral length, biparietal diameter and abdominal cross-sectional area were also recorded. Regression equations were developed for each parameter of fetal body size, and linear and logarithmic models were compared. The model with the highest correlation coefficient was chosen to produce equations to calculate relative dimensions based on the correlations. Only the left-ventricular chamber differed between the two racial groups. Biparietal diameter was the independent parameter that produced the highest correlation coefficient for the most fetal cardiac dimensions, although good correlations were also observed using femoral length and abdominal cross-sectional area. Heart width and heart diameter were used as surrogates of cardiac development, as these measurements showed the best statistical correlation. Quantitative evaluation of fetal cardiac structures can be used to monitor normal and abnormal cardiac development. 相似文献
110.