全文获取类型
收费全文 | 62535篇 |
免费 | 2834篇 |
国内免费 | 42篇 |
专业分类
林业 | 2516篇 |
农学 | 1645篇 |
基础科学 | 429篇 |
6150篇 | |
综合类 | 14758篇 |
农作物 | 2461篇 |
水产渔业 | 2346篇 |
畜牧兽医 | 31047篇 |
园艺 | 643篇 |
植物保护 | 3416篇 |
出版年
2017年 | 553篇 |
2016年 | 536篇 |
2014年 | 540篇 |
2013年 | 1863篇 |
2012年 | 1202篇 |
2011年 | 1436篇 |
2010年 | 913篇 |
2009年 | 877篇 |
2008年 | 1427篇 |
2007年 | 1389篇 |
2006年 | 1371篇 |
2005年 | 1386篇 |
2004年 | 1318篇 |
2003年 | 1391篇 |
2002年 | 1354篇 |
2001年 | 1493篇 |
2000年 | 1473篇 |
1999年 | 1206篇 |
1998年 | 531篇 |
1997年 | 538篇 |
1995年 | 596篇 |
1994年 | 573篇 |
1993年 | 561篇 |
1992年 | 1309篇 |
1991年 | 1395篇 |
1990年 | 1449篇 |
1989年 | 1488篇 |
1988年 | 1399篇 |
1987年 | 1356篇 |
1986年 | 1400篇 |
1985年 | 1373篇 |
1984年 | 1150篇 |
1983年 | 1005篇 |
1982年 | 718篇 |
1981年 | 688篇 |
1980年 | 644篇 |
1979年 | 1127篇 |
1978年 | 916篇 |
1977年 | 819篇 |
1976年 | 768篇 |
1975年 | 860篇 |
1974年 | 1126篇 |
1973年 | 1063篇 |
1972年 | 1128篇 |
1971年 | 1080篇 |
1970年 | 1022篇 |
1969年 | 874篇 |
1968年 | 710篇 |
1967年 | 844篇 |
1966年 | 693篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
Germinating seeds and young plants of winter rape var. Górczañski were vernalized for 56–63 days under conditions of 9-hour day, at the temperature 2 and 5 °C and in continuous darkness at the temperature 2 °C. After vernalization the plants grew under conditions enabling to complete vernalization: in a glass-house at the temperature day/night 15/10 °C and in semi natural conditions of open vegetation hall in the period from June till August. After sub-optimal vernalization further growth of the plants at lowered temperature increased its effectiveness (completion of vernalization). Depending on the degree of the vernalization of the plants the completion of their vernalization was both obligatory, i.e. conditioning the acquisition of the ability of generative development, and facultative i.e. accelerating this development. It has been demonstrated that the population of plants of the examined variety is strongly differentiated not only with respect of vernalization requirements in the particular plants, but also what regards the effectiveness of vernalization completion. New observations have been made indicating that the mechanisms controlling the successive phases of generative development, i.e. phase of forming flower buds and the flowering phase are not identical which may be interpreted as indicating that the "flowering factor" is polymorphous. 相似文献
52.
53.
The determination of differentiation and transplantation antigens will be of growing importance in immune diagnosis for individual animals as well as for breeding purposes in populations. Differentiation antigens characterize subsets of cell populations and indicate their functional capacity while transplantation antigens represent markers of individuals of a species. Occurrence and significance of these antigenic systems are briefly reviewed. 相似文献
54.
There is only limited information on sheep interferon available. Recent publications have reported on: 1. an interferon (IFN) alpha subtype, which is secreted by the fetal trophectoderm into the lumen of the uterus between the 10th and 21st day of gestation. It was therefore named ovine trophoblast protein (oTP-1), and is responsible for signalling pregnancy to the ewe via high affinity receptors in the endometrium. It is thought that oTP-1 acts by directly influencing prostaglandin metabolism. 2. the role of lentivirus-induced interferon (LV-IFN) in the pathogenesis of Maedi/Visna. The results indicate that LV-IFN limits viral replication and therefore contributes to virus persistence and is also responsible for a chronic inflammatory process. 3. the mitogen- or antigen-dependent induction of ovine interferon gamma (IFN gamma) and its characterization. 相似文献
55.
56.
57.
58.
W R Hause 《Modern veterinary practice》1984,65(6):461-465
Pleural effusions can cause dyspnea and cyanosis, and are caused by cardiomyopathy, pyothorax, FIP, FeLV-related disease and trauma. Thoracentesis is used to obtain fluid samples for cytologic examination and culture. Radiographs made after thoracentesis may reveal the cause. Lymphosarcoma causes a sterile exudate containing neoplastic cells. Congestive cardiomyopathy causes a transudate or modified transudate. The sterile exudate of FIP has a proteinaceous background on cytologic examination. The exudate of pyothorax is septic. Treatment depends on the cause but generally includes thoracentesis and supportive care. Cardiomyopathy causes dyspnea, cyanosis, murmurs, gallop rhythms and other arrhythmias. Radiography reveals a globoid heart in the congestive form and a "valentine-shaped" heart in the hypertrophic form. Treatment of congestive cardiomyopathy involves use of furosemide, but is usually unrewarding. Hypertrophic cardiomyopathy is treated with propranolol. Fever may be caused by infection, immune-mediated disease, neoplasia and unknown causes. Treatment is aimed at removal of the underlying cause. 相似文献
59.
Roof WC 《Science (New York, N.Y.)》1984,223(4637):691
60.