全文获取类型
| 收费全文 | 261389篇 |
| 免费 | 15515篇 |
| 国内免费 | 1248篇 |
专业分类
| 林业 | 23834篇 |
| 农学 | 14330篇 |
| 基础科学 | 3203篇 |
| 43995篇 | |
| 综合类 | 27397篇 |
| 农作物 | 17314篇 |
| 水产渔业 | 16785篇 |
| 畜牧兽医 | 100611篇 |
| 园艺 | 6570篇 |
| 植物保护 | 24113篇 |
出版年
| 2021年 | 2686篇 |
| 2020年 | 3040篇 |
| 2019年 | 3805篇 |
| 2018年 | 4142篇 |
| 2017年 | 4624篇 |
| 2016年 | 4897篇 |
| 2015年 | 4517篇 |
| 2014年 | 5825篇 |
| 2013年 | 16444篇 |
| 2012年 | 6847篇 |
| 2011年 | 8908篇 |
| 2010年 | 7805篇 |
| 2009年 | 8255篇 |
| 2008年 | 8032篇 |
| 2007年 | 7103篇 |
| 2006年 | 7577篇 |
| 2005年 | 6877篇 |
| 2004年 | 6548篇 |
| 2003年 | 6370篇 |
| 2002年 | 5653篇 |
| 2001年 | 6060篇 |
| 2000年 | 5833篇 |
| 1999年 | 5385篇 |
| 1998年 | 4153篇 |
| 1997年 | 4179篇 |
| 1996年 | 3927篇 |
| 1995年 | 4440篇 |
| 1994年 | 3879篇 |
| 1993年 | 3575篇 |
| 1992年 | 4334篇 |
| 1991年 | 4632篇 |
| 1990年 | 4323篇 |
| 1989年 | 4245篇 |
| 1988年 | 3776篇 |
| 1987年 | 3842篇 |
| 1986年 | 3780篇 |
| 1985年 | 3966篇 |
| 1984年 | 3753篇 |
| 1983年 | 3514篇 |
| 1982年 | 2916篇 |
| 1981年 | 2818篇 |
| 1980年 | 2792篇 |
| 1979年 | 3294篇 |
| 1978年 | 2941篇 |
| 1977年 | 2684篇 |
| 1976年 | 2621篇 |
| 1975年 | 2428篇 |
| 1974年 | 2714篇 |
| 1973年 | 2609篇 |
| 1972年 | 2383篇 |
排序方式： 共有10000条查询结果，搜索用时 15 毫秒
991.
992.
993.
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
994.
995.
In a seminal article in 1946, S. S. Stevens noted that the numerical measures then in common use exhibited three admissible groups of transformations: similarity, affine, and monotonic. Until recently, it was unclear what other scale types are possible. For situations on the continuum that are homogeneous (that is, objects are not distinguishable by their properties), the possibilities are essentially these three plus another type lying between the first two. These types lead to clearly described classes of structures that can, in principle, be incorporated into the classical structure of physical units. Such results, along with characterizations of important special cases, are potentially useful in the behavioral and social sciences. 相似文献
996.
997.
998.
999.
L K 《Science (New York, N.Y.)》1987,237(4819):1237-1238
1000.
1. Brown egg layers were fed diets differing in oil content, oil source and linoleic acid concentration and the effect on performance from 22 to 69 weeks of age was studied.
2. The birds responded with an increasing mean egg weight up to a linoleic acid intake of 2.75 g/bird d.
3. Increasing the intake of readily absorbable oil without increasing linoleic acid concentration did not increase mean egg weight. 相似文献