全文获取类型
收费全文 | 289463篇 |
免费 | 35796篇 |
国内免费 | 194篇 |
出版年
2016年 | 2786篇 |
2015年 | 4155篇 |
2014年 | 4844篇 |
2013年 | 6885篇 |
2012年 | 7754篇 |
2011年 | 7695篇 |
2010年 | 5287篇 |
2009年 | 4985篇 |
2008年 | 7002篇 |
2007年 | 7211篇 |
2006年 | 6839篇 |
2005年 | 6791篇 |
2004年 | 6612篇 |
2003年 | 6724篇 |
2002年 | 6392篇 |
2001年 | 11041篇 |
2000年 | 11155篇 |
1999年 | 9185篇 |
1998年 | 3559篇 |
1997年 | 3730篇 |
1996年 | 3715篇 |
1995年 | 3457篇 |
1994年 | 3458篇 |
1993年 | 3426篇 |
1992年 | 8170篇 |
1991年 | 7958篇 |
1990年 | 7755篇 |
1989年 | 7680篇 |
1988年 | 7245篇 |
1987年 | 7197篇 |
1986年 | 6662篇 |
1985年 | 6812篇 |
1984年 | 5711篇 |
1983年 | 5125篇 |
1982年 | 4092篇 |
1981年 | 3938篇 |
1980年 | 3574篇 |
1979年 | 5924篇 |
1978年 | 4634篇 |
1977年 | 4438篇 |
1976年 | 4235篇 |
1975年 | 4577篇 |
1974年 | 5036篇 |
1973年 | 4927篇 |
1972年 | 4585篇 |
1971年 | 4135篇 |
1970年 | 3643篇 |
1969年 | 3667篇 |
1968年 | 3270篇 |
1967年 | 2823篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
The ability of an invasive plant to occupy new areas is often attributed to both morphological and physiological plasticities
that allow them to remain viable over a wide range of environmental conditions. Studies addressing the ecological requirements
of Microstegium vimineum often consider soil moisture or soil moisture along with other factors as important explanatory components for the establishment
and persistence of this invasive monocot. However, controlled studies specifically targeting water relations in M. vimineum are needed. Therefore, the purpose of this study was to determine how different water availabilities influence the growth
and physiological performance of M. vimineum. This study utilized experimental microcosms to achieve different water availabilities including low soil moisture (<15%
water), moderate soil moisture (ca. 20–30%), and flooded conditions. While both flooded and low soil moisture resulted in
diminished growth, M. vimineum still survived under these conditions. Physiological processes including C4 metabolism, minimum stress under low water conditions, and the ability to increase tissue rigidity may confer some advantages
to M. vimineum during periods of limiting water conditions. Similarly, the proportionally low root biomass, shallow root structure, and
its ability to maintain stable water relations during flooding and/or soil waterlogging may facilitate M. vimineum’s ability to invade mesic habitats. It is likely, therefore, that the capacity to tolerate both low soil moistures and flooded
conditions has enhanced the ability of M. vimineum to populate disturbed systems in central North Carolina. 相似文献
162.
163.
The l-thyroxine binding site in human serum thyroxine-binding globulin was investigated by affinity labeling with N-bromoacetyl-l-thyroxine (BrAcT4). Competitive binding studies showed that, in the presence of 100 molar excess of BrAcT4, binding of thyroxine to thyroxine-binding globulin was nearly totally abolished. The reaction of BrAcT4 to form covalent binding was inhibited in the presence of thyroxine and the affinity-labeled thyroxinebinding globulin lost its ability to bind thyroxine. These results indicate BrAcT4 and thyroxine competed for the same binding site. Affinity labeling with 2 mol of BrAcT4/mol of thyroxine-binding globulin resulted in the covalent attachment of 0.7 mol of ligand. By amino acid analysis and high voltage paper electrophoresis, methionine was identified as the major residue labeled (75%). Lysine, tyrosine, and histidine were also found to be labeled to the extent of 8, 8, and 5%, respectively. 相似文献
164.
165.
166.
167.
W Van Beaumont 《Journal of applied physiology》1973,35(1):47-50
168.
169.
170.