首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   58篇
  免费   5篇
  国内免费   14篇
  2023年   2篇
  2022年   1篇
  2021年   5篇
  2020年   5篇
  2019年   1篇
  2018年   5篇
  2017年   2篇
  2016年   4篇
  2015年   3篇
  2014年   2篇
  2013年   4篇
  2012年   5篇
  2011年   3篇
  2010年   1篇
  2009年   2篇
  2008年   1篇
  2007年   1篇
  2006年   2篇
  2005年   1篇
  2003年   4篇
  2002年   1篇
  2001年   5篇
  2000年   1篇
  1997年   2篇
  1991年   1篇
  1990年   2篇
  1988年   1篇
  1987年   2篇
  1985年   1篇
  1981年   4篇
  1977年   2篇
  1974年   1篇
排序方式: 共有77条查询结果,搜索用时 15 毫秒
31.
《Anthrozo?s》2013,26(3):259-266
Abstract

Christian teaching has long held that only humans possess an immortal soul and it is commonly thought that this has had the effect of downgrading animal status. One item in each of two separate questionnaires investigated current attitudes to human and animal immortality. The first Survey (A), consisted of a 21-section questionnaire which focussed on the changing status of animals across three family-related generations. One hundred and one students, one of their parents and one of their grandparents were asked whether they believed in an afterlife for (a) humans and (b) all animals or (c) some animals (n = 303). The second survey (B) was a separate enquiry. It was sent both to principals of Christian ministerial courses (n = 22) and to those running university departments of philosophy. An extra item, asked of ministerial courses only, enquired what was the current teaching as to whether animals had the possibility of a life beyond this. Both questionnaires found that attitudes to animal immortality are changing.  相似文献   
32.
Among the factors that may reduce the predictability of evolution, chaos, characterized by a strong dependence on initial conditions, has received much less attention than randomness due to genetic drift or environmental stochasticity. It was recently shown that chaos in phenotypic evolution arises commonly under frequency‐dependent selection caused by competitive interactions mediated by many traits. This result has been used to argue that chaos should often make evolutionary dynamics unpredictable. However, populations also evolve largely in response to external changing environments, and such environmental forcing is likely to influence the outcome of evolution in systems prone to chaos. We investigate how a changing environment causing oscillations of an optimal phenotype interacts with the internal dynamics of an eco‐evolutionary system that would be chaotic in a constant environment. We show that strong environmental forcing can improve the predictability of evolution by reducing the probability of chaos arising, and by dampening the magnitude of chaotic oscillations. In contrast, weak forcing can increase the probability of chaos, but it also causes evolutionary trajectories to track the environment more closely. Overall, our results indicate that, although chaos may occur in evolution, it does not necessarily undermine its predictability.  相似文献   
33.
The relationship between androgens and paternal behavior is not straightforward, potentially because of the diversity of tasks a male must undertake to maximize reproductive success, notably alternating between courtship, aggression, and offspring care. In some species, these events are separated in time, but in others they are coincident. The endocrine profiles of species that simultaneously court, parent, and defend a nest, such as male bluebanded gobies (Lythrypnus dalli), are not well understood. We sampled a potent fish androgen, 11-ketotestosterone (KT), at different life history stages (experienced parenting males, experienced males not actively parenting, inexperienced males with their first clutch, and females), to examine this relationship. We found that experienced parenting L. dalli males have the highest KT levels of any group, while none of the other groups differed significantly. Males showed elevated KT levels when they had eggs compared to when they did not. Our data suggest that KT facilitates at least some aspects of parental care in L. dalli.  相似文献   
34.
Changes in protein conformation play key roles in facilitating various biochemical processes, ranging from signaling and phosphorylation to transport and catalysis. While various factors that drive these motions such as environmental changes and binding of small molecules are well understood, specific causative effects on the structural features of the protein due to these conformational changes have not been studied on a large scale. Here, we study protein conformational changes in relation to two key structural metrics: packing efficiency and disorder. Packing has been shown to be crucial for protein stability and function by many protein design and engineering studies. We study changes in packing efficiency during conformational changes, thus extending the analysis from a static context to a dynamic perspective and report some interesting observations. First, we study various proteins that adopt alternate conformations and find that tendencies to show motion and change in packing efficiency are correlated: residues that change their packing efficiency show larger motions. Second, our results suggest that residues that show higher changes in packing during motion are located on the changing interfaces which are formed during these conformational changes. These changing interfaces are slightly different from shear or static interfaces that have been analyzed in previous studies. Third, analysis of packing efficiency changes in the context of secondary structure shows that, as expected, residues buried in helices show the least change in packing efficiency, whereas those embedded in bends are most likely to change packing. Finally, by relating protein disorder to motions, we show that marginally disordered residues which are ordered enough to be crystallized but have sequence patterns indicative of disorder show higher dislocation and a higher change in packing than ordered ones and are located mostly on the changing interfaces. Overall, our results demonstrate that between the two conformations, the cores of the proteins remain mostly intact, whereas the interfaces display the most elasticity, both in terms of disorder and change in packing efficiency. By doing a variety of tests, we also show that our observations are robust to the solvation state of the proteins.  相似文献   
35.
孟凡超  郭军  周莉  熊明明  张雷 《生态学杂志》2017,28(12):4117-4126
气温、大气CO2浓度和降水等气候因子是影响作物生长发育的关键因子,而不同的气候因子对作物的影响并非独立的,多气候因子交互作用对作物的影响目前已成为研究的焦点问题.研究不同气候因子交互作用的影响,其结果更接近作物生长的实际情况,有助于了解作物甚至作物生态系统对气候变化的真实响应.国内外关于不同气候因子对作物影响的报道较多,要全面总结不同气候因子交互作用对作物的影响是非常困难的.因此,本文只对近年来有关气温升高、大气CO2浓度增加和降水变化交互作用对作物生长发育、光合生理及产量影响的研究进展做一简要评述,并提出目前研究的不足和需要解决的关键问题,以期为气候变化对作物生长发育及产量影响的研究提供参考.  相似文献   
36.
37.
Under the 1G condition, the increase in antipain-sensitive protease activity promptly after UV (mainly 254 nm wavelength) irradiation in cultured human cells is detected and found to be one of the intriguing events involved in suppression of cell mutability. It was found that two cell lines, RSa and its variant UVAP-1 cells are applicable; the former is hypermutable and not susceptible to protease activation, while the latter is hypomutable and susceptible. In the present study it was investigated whether the increase in protease activity by UV irradiation is also observed in hypomutable human UVAP-1 cells exposed to gravity-changing stress and whether the increase is involved in suppression of UV mutagenicity. Exposure of human UVAP-1 cells to gravity-changing stress such as free-fall and parabolic flight prior to UV irradiation resulted in a pronounced increase in protease activity, but not to hypergravity conditions (2 and 10G) prior to UV irradiation. To characterize the proteases, components of lysates from the cells exposed to free-fall prior to UV irradiation were fractionated by high performance liquid chromatography, indicating two separate fractions with highly increased levels of E-64-sensitive protease activity. In the cells treated with E-64 during their exposure to free-fall, K-ras codon 12 base substitution mutation was detected after UV irradiation, although the mutation was not detected after UV irradiation alone. Thus, the increase in E-64-sensitive protease activity may be involved in the suppression of UV mutagenicity in UVAP-1 cells exposed to free-fall.  相似文献   
38.
* Plants must cope with environmental variation in space and time. Phenotypic plasticity allows them to adjust their form and function to small-scale variations in habitat quality. Empirical studies have shown that stoloniferous plants can exploit heterogeneous habitats through plastic ramet specialization and internal resource exchange (division of labour). * Here we present a spatially explicit simulation model to explore costs and benefits of plasticity in spatio-temporally heterogeneous environments. We investigated the performance of three plant strategies in pairwise competition. The nonplastic strategy was unable to specialize. The autonomous plastic strategy displayed localized responses to external resource signals. In the coordinated plastic strategy, localized responses could be modified by internal demand signals from connected modules. * Plasticity in resource uptake proved beneficial in a broad range of environments. Modular coordination was beneficial under virtually all realistic conditions, especially if resource supplies did not closely match resource needs. * The benefits of division of labour extend considerably beyond the parameter combination covered by empirical studies. Our model provides a general framework for evaluating the benefits, costs and limits of plasticity in spatio-temporally heterogeneous habitats.  相似文献   
39.
【目的】飞蝗Locusta migratoria(Linnaeus)是我国乃至全世界广泛发生的重要农业害虫,其种群暴发会给农作物造成重大为害和减产。飞蝗种群发生动态受低温及变温的影响,但低温和变温如何作用于胚胎发育和是否诱导胚胎滞育的发生,目前尚不清楚。【方法】本文在对飞蝗胚胎发育特点观察鉴定的基础上,研究了胚胎发育中期恒定低温诱导、诱导后恢复、发育中期变温诱导及发育早期低温诱导等条件对胚胎发育进程的影响。【结果】研究发现,胚胎发育起点温度下非致死温度7.5℃处理促使胚胎发育历期变异增加,而25~30℃高温下胚胎发育整齐。7.5℃处理时间长短对胚胎发育影响不明显,但该低温培育时间长短影响后期常温下的胚胎发育,即7.5℃下长期低温可能促进25℃或30℃下的胚胎的发育。25℃以下变温温度影响胚胎发育进展,但影响胚胎发育的限制因子主要是发育起点以上温度。【结论】因此,温度作为单一环境因子,其特定的低温和变温处理不仅没有诱导胚胎滞育的发生,反而促进后期胚胎在常温下的发育。本研究结果对揭示温度变化对个体发育和种群动态影响及预测飞蝗种群发生有重要的指导意义。  相似文献   
40.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号