全文获取类型
收费全文 | 33706篇 |
免费 | 3926篇 |
国内免费 | 1308篇 |
专业分类
38940篇 |
出版年
2024年 | 36篇 |
2023年 | 217篇 |
2022年 | 563篇 |
2021年 | 1023篇 |
2020年 | 659篇 |
2019年 | 798篇 |
2018年 | 927篇 |
2017年 | 803篇 |
2016年 | 1027篇 |
2015年 | 1384篇 |
2014年 | 1661篇 |
2013年 | 1887篇 |
2012年 | 2162篇 |
2011年 | 2140篇 |
2010年 | 1291篇 |
2009年 | 1201篇 |
2008年 | 1394篇 |
2007年 | 1253篇 |
2006年 | 1224篇 |
2005年 | 1027篇 |
2004年 | 924篇 |
2003年 | 822篇 |
2002年 | 808篇 |
2001年 | 2547篇 |
2000年 | 2324篇 |
1999年 | 1707篇 |
1998年 | 582篇 |
1997年 | 572篇 |
1996年 | 508篇 |
1995年 | 466篇 |
1994年 | 393篇 |
1993年 | 310篇 |
1992年 | 805篇 |
1991年 | 648篇 |
1990年 | 555篇 |
1989年 | 443篇 |
1988年 | 355篇 |
1987年 | 269篇 |
1986年 | 210篇 |
1985年 | 155篇 |
1984年 | 104篇 |
1983年 | 76篇 |
1982年 | 52篇 |
1981年 | 43篇 |
1980年 | 29篇 |
1979年 | 31篇 |
1978年 | 27篇 |
1976年 | 31篇 |
1973年 | 30篇 |
1970年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Calcium ion (Ca2+) is essential secondary messenger in plant signaling networks. In this study, the effect of Ca2+ on oxidative damage caused by a high irradiance (HI) was investigated in the leaves of two cultivars of tall fescue (Arid3 and Houndog5). Pretreatment of the tall fescue leaves with a CaCl2 solution significantly increased Ca2+ content and intrinsic HI tolerance due to a decreased ion leakage and content of malondialdehyde, hydrogen peroxide, and superoxide radicals. Moreover, the activities of superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase increased in both the cultivars in the presence of Ca2+ under the HI stress. In contrast, treatments with a Ca2+ chelator ethylene glycol-bis(2-aminoethylether)-N,N,N′,N′-tetraacetic acid (EGTA) or a plasma membrane Ca2+ channel blocker LaCl3 reversed these effects. On the other hand, a pronounced increase in nitric oxide synthase-like activity and NO release by exogenous Ca2+ treatment was observed in the tolerant Arid3 plants after exposure to the HI, whereas only a small increase was observed in more sensitive Houndog5. Moreover, the inhibition of NO production by 2-(4-carboxy-2-phenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide or Nω-nitro-L-arginine blocked the protective effect of exogenous Ca2+, whereas the inhibition of Ca2+ by EGTA or LaCl3 had no influence on the protective effect of NO. The results indicate that NO might be involved in the Ca2+-induced activities of antioxidant enzymes further protecting against HI-induced oxidative damage. This protective mechanism was found to be more efficient in Arid3 than in Houndog5. 相似文献
992.
The roles of ethylene (ET) or salicylic acid (SA) in plant response to low temperature (LT, 5 °C) have been implicated. However, the combined effect of ET- and SA-signaling on plant growth and metabolism under LT remains to be evaluated. In this study, we comparatively analyzed the response of Arabidopsis ethylene insensitive (ein) 2-1 (an ET insensitive mutant), nonexprressor of pathogenesis relative (npr)1-1 (an SA insensitive mutant) and double mutant ein2-1/npr1-1 plants to LT. The results show that a LT of 5 °C induced plant growth retardation to a less degree in ein2-1, an intermediate degree in npr1-1, but a much larger in ein2-1/npr1-1 compared to the wild-type (WT) plants. The LT susceptibility of the ein2-1/npr1-1 plants was correlated to a lower net photosynthetic rate and proline content, and a higher content of H2O2 and malondialdehyde and electrolyte leakage relative to the WT plants. Lower activities of superoxide dismutase, peroxidase, and catalase, as well as a lower glutathione content and a ratio of its reduced form to its oxidized form were also observed in the double mutant plants as compared with the WT plants. However, at normal conditions (23 °C), all the tested physiological and biochemical parameters were comparable between the ein2-1/npr1-1 and WT plants, and plant growth was even better in the double mutant than in the WT plants. On the contrary, most of the above-mentioned parameters were advantageous in the ein2-1 and npr1-1 plants over the WT plants under the LT conditions. These data suggest that a parallel function or physiological redundancy of nonexpressor of pathogenesis relative 1 and ethylene insensitive 2 existed in the Arabidopsis plant response to the LT. On the other hand, an interaction between ET- and SA-signaling occurred during this process. 相似文献
993.
J. Wang Y. Zhang Y. Li X. Wang Z. Liu W. Nan C. Zhao F. Wang J. Ma Y. Bi 《Biologia Plantarum》2016,60(2):299-310
A wide range of microorganisms found in the rhizhosphere are able to regulate plant growth and development, but little is known about the mechanism by which epiphytic microbes inhibit plant growth. Here, an epiphytic bacteria Stenotrophomonas maltophilia, named as LZMBW216, were isolated and identified from the potato (Solanum tuberosum L. cv. Da Xi Yang) leaf surface. They could decrease primary root elongation and lateral root numbers in Arabidopsis seedlings. The inhibitory effects of LZMBW216 on plant growth were not due to a reduced indole-3-acetic acid (IAA) content, as exogenously applied IAA did not recover the inhibition. Furthermore, LZMBW216 did not affect the expression of DR5::GUS and CycB1;1::GUS. However, we found that LZMBW216 exhibited little effect on the primary root elongation in the pin2 mutant and on the lateral root numbers in the aux1-7 mutant. Moreover, LZMBW216 decreased expressions of AUX1 and PIN2 proteins. Together, these results suggest that root system architecture alterations caused by LZMBW216 may involve polar auxin transport. 相似文献
994.
995.
996.
997.
998.
999.
1000.