全文获取类型
收费全文 | 83777篇 |
免费 | 4454篇 |
国内免费 | 2888篇 |
专业分类
林业 | 6073篇 |
农学 | 6050篇 |
基础科学 | 2422篇 |
11716篇 | |
综合类 | 14394篇 |
农作物 | 3651篇 |
水产渔业 | 4255篇 |
畜牧兽医 | 35996篇 |
园艺 | 1634篇 |
植物保护 | 4928篇 |
出版年
2022年 | 964篇 |
2021年 | 1409篇 |
2020年 | 1357篇 |
2019年 | 1410篇 |
2018年 | 1585篇 |
2017年 | 1966篇 |
2016年 | 1820篇 |
2015年 | 1927篇 |
2014年 | 2115篇 |
2013年 | 3684篇 |
2012年 | 3382篇 |
2011年 | 3865篇 |
2010年 | 3129篇 |
2009年 | 2874篇 |
2008年 | 3427篇 |
2007年 | 3372篇 |
2006年 | 3319篇 |
2005年 | 3017篇 |
2004年 | 2256篇 |
2003年 | 2171篇 |
2002年 | 2004篇 |
2001年 | 2773篇 |
2000年 | 2718篇 |
1999年 | 2354篇 |
1998年 | 1290篇 |
1997年 | 1123篇 |
1996年 | 1029篇 |
1995年 | 1097篇 |
1994年 | 989篇 |
1993年 | 938篇 |
1992年 | 1572篇 |
1991年 | 1660篇 |
1990年 | 1680篇 |
1989年 | 1516篇 |
1988年 | 1395篇 |
1987年 | 1327篇 |
1986年 | 1222篇 |
1985年 | 1128篇 |
1984年 | 936篇 |
1983年 | 752篇 |
1982年 | 548篇 |
1979年 | 796篇 |
1978年 | 616篇 |
1976年 | 524篇 |
1974年 | 624篇 |
1973年 | 605篇 |
1972年 | 633篇 |
1971年 | 601篇 |
1970年 | 588篇 |
1969年 | 537篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
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
62.
Inheritance process for β-glucan content in oat caryopsis
Due to the fact that there are only few studies concerning β-glucans in oat caryopsis with regard to plant-breeding aspects, three oat crosses were performed (cross 19 = low × high, cross 86 = low × low, cross 98 = high × high). In all of the three oat crosses, lower β-glucan content (% DM) was recorded in F, than in F, indicating that the β-glucan content (% DM) at a higher heterozygoty grade is lower than at a reduced heterozygoty grade. This points to a dominant inheritance of lower β-glucan content (% DM). A tendency towards the female β-glucan content (% DM) could not be proven. Thus, it can be started from a nuclear genetic inheritance of the β-glucan content (% DM). In most cases, the experiments showed a normal distribution of β-glucan content (% DM), indicating for several genes a quantitative inheritance of β-glucan content (% DM). By means of the regression of the F3 -lines to the F2 -plants, the narrow-sense heritability could be calculated for the cross 86 (h2 = 0.51***) and the cross 98 (h2 = 0.48***). The heritability for the cross 19 was not significant. 相似文献
Due to the fact that there are only few studies concerning β-glucans in oat caryopsis with regard to plant-breeding aspects, three oat crosses were performed (cross 19 = low × high, cross 86 = low × low, cross 98 = high × high). In all of the three oat crosses, lower β-glucan content (% DM) was recorded in F, than in F, indicating that the β-glucan content (% DM) at a higher heterozygoty grade is lower than at a reduced heterozygoty grade. This points to a dominant inheritance of lower β-glucan content (% DM). A tendency towards the female β-glucan content (% DM) could not be proven. Thus, it can be started from a nuclear genetic inheritance of the β-glucan content (% DM). In most cases, the experiments showed a normal distribution of β-glucan content (% DM), indicating for several genes a quantitative inheritance of β-glucan content (% DM). By means of the regression of the F
63.
64.
Experiments conducted m a phytotron on three rice varieties of different salinity tolerance revealed an increase in the content of endogenous abscisic acid (ABA) with increasing NaCl salinity in IR20 (semi salt-tolerant), but in Pokkali (salt-tolerant) and IR28 (salt-sensitive) the increase in ABA content was marginal. Under sahnity stress, in general, 5 weekly sprayings of ABA (10-4 mol L-1 ) decreased Na and K concentrations in the shoot to the extent of 29.5 % and 3.3 %, respectively. However, ABA application significantly improved the K/Na ratio as well as the chlorophyll fluorescence decrease ratio (Rfd, indicator for potential photosynthetic activity), the number of green leaves per plant and the shoot dry weight. The response of IR20 and IR28 to ABA application was significantly better than that of Pokkali. Increasing salinity caused marked nutrient imbalances, decreased Rfd values and shoot dry weight. The results are discussed in relation to possible mechanism of salinity tolerance. 相似文献
65.
L K 《Science (New York, N.Y.)》1986,234(4783):1595
66.
67.
Bott K 《Science (New York, N.Y.)》1989,246(4935):1331-1332
68.
69.
70.