全文获取类型
收费全文 | 3355篇 |
免费 | 620篇 |
国内免费 | 1323篇 |
出版年
2024年 | 3篇 |
2023年 | 115篇 |
2022年 | 86篇 |
2021年 | 146篇 |
2020年 | 179篇 |
2019年 | 236篇 |
2018年 | 211篇 |
2017年 | 233篇 |
2016年 | 228篇 |
2015年 | 210篇 |
2014年 | 215篇 |
2013年 | 263篇 |
2012年 | 223篇 |
2011年 | 246篇 |
2010年 | 215篇 |
2009年 | 189篇 |
2008年 | 196篇 |
2007年 | 229篇 |
2006年 | 223篇 |
2005年 | 160篇 |
2004年 | 129篇 |
2003年 | 142篇 |
2002年 | 131篇 |
2001年 | 128篇 |
2000年 | 106篇 |
1999年 | 100篇 |
1998年 | 86篇 |
1997年 | 71篇 |
1996年 | 77篇 |
1995年 | 68篇 |
1994年 | 54篇 |
1993年 | 54篇 |
1992年 | 55篇 |
1991年 | 61篇 |
1990年 | 33篇 |
1989年 | 37篇 |
1988年 | 16篇 |
1987年 | 25篇 |
1986年 | 12篇 |
1985年 | 17篇 |
1984年 | 26篇 |
1983年 | 16篇 |
1982年 | 14篇 |
1981年 | 4篇 |
1980年 | 8篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1958年 | 2篇 |
排序方式: 共有5298条查询结果,搜索用时 15 毫秒
1.
This study was conducted to study the long-term impact of bioinoculants, Azotobacter chroococcum and arbuscular mycorrhizal fungi (AMF) on growth and biomass yield of Jatropha curcas grown in nursery and in field conditions. The experiment was set up in a randomized block design, and the following treatments was designed (T1 = control, T2 = Azotobacter, T3 = inoculation with AMF, and T4 = inoculation with Azotobacter + AMF). Data on various growth attributes (shoot height and shoot diameter) and biochemical parameters [leaf relative water content (LRWC), sugars, protein, and photosynthetic pigments] were recorded up to 6 months in the nursery and in the field (18 months). Results pertaining to morpho-physiological traits showed Azotobacter and AMF consortia increase shoot height, shoot diameter, LRWC, sugars, proteins, and photosynthetic pigments over control under nursery conditions. Besides enhancing the plant growth, these bioinoculants helped in better establishment of Jatropha plants under field conditions. A significant improvement in the shoot height, shoot diameter, fruit yield/plant, and seed yield (g)/plant was evident in 18-month-old Jatropha plants under field conditions when Azotobacter and AMF were co-inoculated. This work supports the application of bioinoculants for establishment of Jatropha curcas in semi-arid regions. 相似文献
2.
3.
4.
5.
6.
Abstract The growth, biomass δ13C values, and ability to accumulate titratable acidity at night were compared in eight environmental treatments for Cremnophila linguifolia, Sedum greggii, and their F1 hybrid. In the phytotron, differences in treatment daylength, day/night temperature and water availability were all found to have effects on total plant dry weight, nocturnal accumulation of titratable acidity and biomass δ13C value of at least some of the genotypes. However, there were differences between the genotypes both in the magnitude and direction of response of the phenotypic properties to the treatment variables. The phytotron δ13C values ranged from -12.9 to -19.2‰ for C. linguifolia, from -22.2 to -33.4‰ for S. greggii, and from -19.2 to -24.9‰ for the hybrid. After with-holding water for 76 h both C. linguifolia and the hybrid had midday Ψleaf values of -0.23 MPa; however, S. greggii had a value of -1.05 MPa. In contrast to past observations of other species, the daily watered plants of C. linguifolia had less negative δ13C values than did the plants watered only weekly. 相似文献
7.
8.
9.
10.
The application of light reflectance for estimating biomass concentration was investigated on oxidative chemostat culture of Saccharomyces cerevisiae. A correlation between light reflectance and dry weight was established for biomass concentrations from 0.5 to 10 g l–1. The light reflectance signal was stable during the course of chemostat culture and proved to be sensitive to slight but fast changes in biomass concentration following shift-up in dilution rate, acetate pulse or during an oscillation. On-line estimated biomass revealed a larger time window of the biological response during spontaneous oscillations and could be used to predict carbohydrate storage. 相似文献