收费全文 | 113337篇 |
免费 | 4638篇 |
国内免费 | 167篇 |
118142篇 |
2022年 | 673篇 |
2021年 | 1425篇 |
2020年 | 1212篇 |
2019年 | 1200篇 |
2018年 | 2588篇 |
2017年 | 2412篇 |
2016年 | 3148篇 |
2015年 | 4102篇 |
2014年 | 4271篇 |
2013年 | 5550篇 |
2012年 | 6589篇 |
2011年 | 6096篇 |
2010年 | 3856篇 |
2009年 | 3174篇 |
2008年 | 4888篇 |
2007年 | 4690篇 |
2006年 | 4442篇 |
2005年 | 3853篇 |
2004年 | 3716篇 |
2003年 | 3369篇 |
2002年 | 3174篇 |
2001年 | 4183篇 |
2000年 | 3842篇 |
1999年 | 2880篇 |
1998年 | 1115篇 |
1997年 | 879篇 |
1996年 | 831篇 |
1995年 | 745篇 |
1994年 | 653篇 |
1993年 | 603篇 |
1992年 | 1823篇 |
1991年 | 1618篇 |
1990年 | 1505篇 |
1989年 | 1460篇 |
1988年 | 1332篇 |
1987年 | 1295篇 |
1986年 | 1154篇 |
1985年 | 1141篇 |
1984年 | 926篇 |
1983年 | 754篇 |
1982年 | 606篇 |
1979年 | 846篇 |
1978年 | 675篇 |
1975年 | 707篇 |
1974年 | 799篇 |
1973年 | 778篇 |
1972年 | 755篇 |
1971年 | 694篇 |
1970年 | 685篇 |
1969年 | 691篇 |
Reactive oxygen species (ROS) are formed in photosystem II (PSII) under various types of abiotic and biotic stresses. It is considered that ROS play a role in chloroplast-to-nucleus retrograde signaling, which changes the nuclear gene expression. However, as ROS lifetime and diffusion are restricted due to the high reactivity towards biomolecules (lipids, pigments, and proteins) and the spatial specificity of signal transduction is low, it is not entirely clear how ROS might transduce signal from the chloroplasts to the nucleus. Biomolecule oxidation was formerly connected solely with damage; nevertheless, the evidence appears that oxidatively modified lipids and pigments are be involved in chloroplast-to-nucleus retrograde signaling due to their long diffusion distance. Moreover, oxidatively modified proteins show high spatial specificity; however, their role in signal transduction from chloroplasts to the nucleus has not been proven yet. The review attempts to summarize and evaluate the evidence for the involvement of ROS in oxidative signaling in PSII.
相似文献One of the most remarkable natural plants is Vaccaria hispanica (Mill.) Rauschert, which has a high economic, medicinal and industrial potential due to its valuable compounds. However, it is mostly an underused plant worldwide. To implement doubled haploid technology in plant breeding programs and exploit its potential, first knowing the particulars of the species is necessary. This study was aimed to explore the androgenic potential of different wild Turkish V. hispanica genotypes collected from different Turkish regions, as a starting point to identify bottlenecks to solve in future studies. As to induction of microspore embryogenesis, nearly all of them responded, with efficiencies reaching 300 embryos/100 buds in some cases. However, we also found three main bottlenecks. First, the presence of foam-producing saponins in flowers prevented an efficient isolation of microspores. Second, embryos showed a reduced ability to germinate. Third, a dense network of hairy roots prevented the formation of a true, fully functional root system. Together, these drawbacks led to the production of very few DH plants. The presence of rhizogenic endophytes may be the cause of most of these problems, which opens the door for possible solutions.
相似文献