全文获取类型
收费全文 | 439篇 |
免费 | 19篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 14篇 |
2020年 | 5篇 |
2019年 | 5篇 |
2018年 | 7篇 |
2017年 | 14篇 |
2016年 | 12篇 |
2015年 | 18篇 |
2014年 | 18篇 |
2013年 | 27篇 |
2012年 | 31篇 |
2011年 | 36篇 |
2010年 | 45篇 |
2009年 | 18篇 |
2008年 | 23篇 |
2007年 | 35篇 |
2006年 | 27篇 |
2005年 | 18篇 |
2004年 | 23篇 |
2003年 | 16篇 |
2002年 | 10篇 |
2001年 | 6篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1971年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
1960年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有458条查询结果,搜索用时 15 毫秒
451.
452.
453.
454.
Jana Martínková Petr ?milauer Stanislav Mihulka Vít Latzel Jitka Klime?ová 《Annals of botany》2016,117(4):667-679
Background and Aims Senescence is the process of losing fitness when growing old, and is shaped by the trade-off between maintenance and reproduction that makes reproduction more unsure and maintenance more costly with age. In repeatedly reproducing plants, reductions in growth and fertility are signs of senescence. Disturbance, however, provides an opportunity to reset the ageing clock and consequently potentially ameliorate senescence.Methods To test the effects of disturbance on traits closely related to fitness and thus to senescence, a long-term garden experiment was established with two short-lived perennial congeners, Barbarea vulgaris and Barbarea stricta, that differ in their ability to resprout after injury. In the experiment, five damage treatments were applied to plants in four different phenophases.Key Results It was found that damage to the plant body significantly prolonged life span in B. vulgaris but decreased whole-life seed production in both species. High concentration of seed production in one growing season characterized short life spans. Both more severe damage and a more advanced phenological phase at the time of damage caused reproduction to be spread over more than one growing season and equalized per-season seed production. In terms of seed quality, average weight of a single seed decreased and seed germination rate increased with age regardless of damage.Conclusions Although disturbance is able to reset the ageing clock of plants, it is so harmful to plant fitness that resprouting serves, at best, only to alleviate slightly the signs of senescence. Thus, in terms of whole-life seed production, injured plants were not more successful than uninjured ones in the two studied species. Indeed, in these species, injury only slightly postponed or decelerated senescence and did not cause effective rejuvenation. 相似文献
455.
456.
Environmental stress leading to a decrease in growth may be compensated for later in ontogeny by a growth plastic response. Such response could be also transmitted to the next generation, which is called transgenerational plasticity. In this study, two Plantago species were used to test whether compensation for biomass loss after disturbance is driven by maternal effects (ME) due to nutrients and disturbance, i.e. by the form of transgenerational plasticity. Additionally, we tested whether ME could contribute to a different performance of progeny having different disturbance histories. We also tested whether ME are adaptive and whether they differ between related species. The degree of (over)compensation for biomass loss was affected by ME. Maternal effects resulted in different performance of disturbed over undisturbed progeny in relation to nutrient status of the progeny environment along with disturbance and nutrients experienced by mothers. Progeny of P. lanceolata grew more leaf biomass when grown in the same nutrient conditions as experienced by their mothers suggesting that maternal effects might be adaptive. Although overall, there was a consistent role of ME in biomass compensation after disturbance among the two species, there were also some species‐specific effects. We conclude that compensation for biomass loss is driven both by maternal effects and by progeny environment. This may lead to the different success of regenerative strategies in environments with contrasting nutrient levels. The different role of ME even between related species may contribute to ecological diversity among species. 相似文献
457.
Helena Kyseláková Jitka Prokopová Jan Nauš Ond?ej Novák Milan Navrátil Dana Šafá?ová Martina Špundová Petr Ilík 《Plant Physiology and Biochemistry》2011,49(11):1279-1289
We have investigated photosynthetic changes of fully expanded pea leaves infected systemically by pea enation mosaic virus (PEMV) that often attacks legumes particularly in northern temperate regions. A typical compatible virus–host interaction was monitored during 40 post-inoculation days (dpi). An initial PEMV-induced decrease in photosynthetic CO2 assimilation was detected at 15 dpi, when the virus appeared in the measured leaves. This decrease was not induced by stomata closure and corresponded with a decrease in the efficiency of photosystem II photochemistry (ΦPSII). Despite of a slight impairment of oxygen evolution at this stage, PSII function was not primarily responsible for the decrease in ΦPSII. Chlorophyll fluorescence imaging revealed that ΦPSII started to decrease from the leaf tip to the base. More pronounced symptoms of PEMV disease appeared at later stages, when a typical mosaic and enations appeared in the infected leaves and oxidative damage of cell membranes was detected. From 30 dpi, a degradation of photosynthetic pigments accelerated, stomata were closing and corresponding pronounced decline in CO2 assimilation was observed. A concomitant photoprotective responses, i.e. an increase in non-photochemical quenching and accumulation of de-epoxidized xanthophylls, were also detected. Interestingly, alternative electron sinks in chloroplasts were not stimulated by PEMV infection, which is in contradiction to earlier reports dealing with virus-induced plant stresses. The presented results show that the PEMV-induced alterations in mature pea leaves accelerated leaf senescence during which a decrease in ΦPSII took place in coordinated manner with an inhibition of CO2 assimilation. 相似文献
458.