全文获取类型
收费全文 | 1307101篇 |
免费 | 115565篇 |
国内免费 | 1411篇 |
专业分类
1424077篇 |
出版年
2021年 | 17786篇 |
2020年 | 12594篇 |
2019年 | 16152篇 |
2018年 | 17473篇 |
2017年 | 16292篇 |
2016年 | 27935篇 |
2015年 | 42349篇 |
2014年 | 50336篇 |
2013年 | 76636篇 |
2012年 | 35184篇 |
2011年 | 23180篇 |
2010年 | 43106篇 |
2009年 | 44553篇 |
2008年 | 22236篇 |
2007年 | 20212篇 |
2006年 | 25742篇 |
2005年 | 26834篇 |
2004年 | 26262篇 |
2003年 | 23854篇 |
2002年 | 22140篇 |
2001年 | 31291篇 |
2000年 | 28507篇 |
1999年 | 29381篇 |
1998年 | 25179篇 |
1997年 | 24962篇 |
1996年 | 24609篇 |
1995年 | 22753篇 |
1994年 | 22589篇 |
1993年 | 21634篇 |
1992年 | 25951篇 |
1991年 | 24184篇 |
1990年 | 22851篇 |
1989年 | 23761篇 |
1988年 | 21776篇 |
1987年 | 20688篇 |
1986年 | 19588篇 |
1985年 | 21543篇 |
1984年 | 21737篇 |
1983年 | 19289篇 |
1982年 | 20185篇 |
1981年 | 19405篇 |
1980年 | 18153篇 |
1979年 | 18115篇 |
1978年 | 17054篇 |
1977年 | 16545篇 |
1976年 | 15666篇 |
1975年 | 15015篇 |
1974年 | 15423篇 |
1973年 | 15904篇 |
1972年 | 13488篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
994.
Methods for production of containerized seedlings ofAlnus species were developed which permit nitrogen-fixing nodules to form on the root systems prior to outplanting, in order to provide an early nitrogen input during seedling establishment. The methods are based on procedures for inoculating root systems with suspensions ofFrankia (Actinomycetales), applied either directly in the container cell as a soil drench at the time of seeding, or as a root dip for seedlings transplanted into the containers. Germination of dried, stored seed was enhanced by light and by presoaking for 16 h in water. Pretreatments to overcome seed dormancy or to eliminate fungal pathogens did not further enhance germination. Some loss of seedlings was recorded in the early stages of growth shortly after germination, which is a factor in calculating projected seedling yield. Nodulation and seedling growth were evaluated in terms of growth media characteristics. Seedlings performed well in peat-vermiculite, at soil pH between 5.5 and 8.0. 相似文献
995.
Cultured porcine thoracic aorta endothelial cells were covalently labeled with 4-maleimido-2,2,6,6-tetramethylpiperidinooxyl. Electron paramagnetic resonance spectrometry revealed two major binding environments representing strongly and weakly immobilized species. The disorder parameter of weak/strong, determined from the respective peak amplitudes, was irreversibly elevated following incubation of endothelial cells with a superoxide-generating system, indicating increased membrane fluidity. The rate of increase in membrane disorder was dependent upon superoxide generation rates. Incorporation of the spin-label at concentrations less than 250 microM had no effect on cell viability. The cellular proteins reacting with the spin-label were predominantly membrane proteins, characterized by immunoblotting using a rabbit anti-4-maleimido-2,2,6,6-tetramethylpiperidinooxyl IgG, following sodium dodecyl sulfate-polyacrylamide gel electrophoresis and electrophorectic transfer to nitrocellulose. 相似文献
996.
997.
998.
999.
1000.