全文获取类型
收费全文 | 724篇 |
免费 | 63篇 |
出版年
2021年 | 5篇 |
2020年 | 8篇 |
2019年 | 7篇 |
2018年 | 18篇 |
2017年 | 7篇 |
2016年 | 13篇 |
2015年 | 30篇 |
2014年 | 34篇 |
2013年 | 32篇 |
2012年 | 48篇 |
2011年 | 48篇 |
2010年 | 34篇 |
2009年 | 34篇 |
2008年 | 36篇 |
2007年 | 34篇 |
2006年 | 36篇 |
2005年 | 26篇 |
2004年 | 39篇 |
2003年 | 44篇 |
2002年 | 28篇 |
2001年 | 15篇 |
2000年 | 6篇 |
1999年 | 11篇 |
1998年 | 23篇 |
1997年 | 6篇 |
1996年 | 12篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 8篇 |
1991年 | 7篇 |
1990年 | 9篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 12篇 |
1983年 | 7篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1980年 | 3篇 |
1979年 | 8篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1973年 | 7篇 |
1972年 | 2篇 |
1958年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有787条查询结果,搜索用时 14 毫秒
111.
Lihua Sun Jari Per?kyl? Anselmi Kovalainen Keith H. Ogawa Pekka J. Karhunen Kaisa M. Hartikainen 《PloS one》2016,11(2)
Transcranial extraocular light affects the brains of birds and modulates their seasonal changes in physiology and behavior. However, whether the human brain is sensitive to extraocular light is unknown. To test whether extraocular light has any effect on human brain functioning, we measured brain electrophysiology of 18 young healthy subjects using event-related potentials while they performed a visual attention task embedded with emotional distractors. Extraocular light delivered via ear canals abolished normal emotional modulation of attention related brain responses. With no extraocular light delivered, emotional distractors reduced centro-parietal P300 amplitude compared to neutral distractors. This phenomenon disappeared with extraocular light delivery. Extraocular light delivered through the ear canals was shown to penetrate at the base of the scull of a cadaver. Thus, we have shown that extraocular light impacts human brain functioning calling for further research on the mechanisms of action of light on the human brain. 相似文献
112.
113.
Pekka H. Mäenpää 《Biochimica et Biophysica Acta (BBA)/General Subjects》1977,498(2):294-305
The phosphorylation of phosvitin in vitro by a cyclic nucleotide-independent protein kinase (phosvitin kinase) derived from rooster liver is markedly stimulated by the divalent cation, Mg2+. In addition, the activity is further stimulated by low concentrations of the polyamines putrescine, spermidine and spermine leading to higher rates of phosphate incorporation than could be obtained at any concentration of Mg2+. Spermine is inhibitory at higher concentrations. The polyamines shift the Mg2+ requirement for maximal activity to lower concentrations. The activity of a cyclic AMP-dependent histone kinase from beef heart is not altered by the presence of polyamines. Heparin is a potent inhibitor of phosvitin kinase but has no effect on histone kinase. Polyribonucleotides (polyadenylic acid and transfer RNA) inhibit both types of kinases, but the degree of inhibition of phosvitin kinase is variable and depends upon the type of the polyanion present. Spermidine and spermine, but not Mg2+, efficiently counteract the inhibitory action of heparin and tRNA. The results suggest that, also in vivo, naturally occurring polyamines and polyanions such ass tRNA may have a regulatory function on protein kinases. 相似文献
114.
115.
116.
Rob Tinch Rob Bugter Malgorzata Blicharska Paula Harrison John Haslett Pekka Jokinen Laurence Mathieu Eeva Primmer 《Biodiversity and Conservation》2018,27(7):1763-1788
Making a strong case for biodiversity protection is central to meeting the biodiversity targets in international agreements such as the CBD and achieving the UN Sustainable Development Goals. Effective arguments are needed to convince diverse actors that protection is worthwhile, and can play a crucial role in closing the implementation gap between biodiversity policy targets and outcomes. Drawing on a database of arguments from 11 European case studies, along with additional interview and case study material from all 13 case studies of the BESAFE project, we analysed relationships between potential and observed effectiveness of arguments. Our results show that strong logic, robustness, and timing of arguments are necessary but not sufficient conditions for arguments to be effective. We find that use of multiple and diverse arguments can enhance effectiveness by broadening the appeal to wider audiences, especially when arguments are repeated and refined through constructive dialogue. We discuss the role of framing, bundling and tailoring arguments to audiences in increasing effectiveness. Our results provide further support for the current shift towards recognition of value pluralism in biodiversity science and decision-making. We hope our results will help to demonstrate more convincingly the value of biodiversity to stakeholders in decision processes and thus build better cases for its conservation. 相似文献
117.
Pekka Jokinen Malgorzata Blicharska Eeva Primmer Ann Van Herzele Leena Kopperoinen Outi Ratamäki 《Biodiversity and Conservation》2018,27(7):1725-1740
Arguments in the formulation, implementation and evaluation of biodiversity policy frame conservation in a range of ways and express interests that can be conflicting. Policy processes are cyclic and iterative by nature and as policies are constantly reformulated, argumentation has an important role at each policy stage. In this paper, we utilise the policy cycle model to shed light on biodiversity-related policy processes and the ways in which argumentation generates effects at different stages of these processes. The paper first draws on literature and the theory-driven assumptions are then illustrated with insights from four European case studies on different policy processes in which biodiversity conservation plays a role. The analysis shows that argumentation tends to evolve over the course of the policy cycle, and framing has a key role across the different policy stages. It is concluded that the ways in which arguments persist, accumulate, diffuse, and replace old arguments, should be the target of increased attention in policy analysis. 相似文献
118.
119.
Joseph Billingsley Jan Antfolk Pekka Santtila Debra Lieberman 《Evolution and human behavior》2018,39(3):290-299
Despite the profound influence of relatedness on mating and cooperative behavior in humans, the cues men use to assess paternity and guide offspring-directed behavior have yet to be fully resolved. According to leading theories of kin detection, kinship cues should influence both sexual and altruistic motivations because of fitness consequences associated with inbreeding and welfare tradeoff decisions, respectively. Prior work with paternity assessment, however, has generally evaluated candidate cues solely by demonstrating associations with altruism. Here we (i) replicate past work that found effects of phenotypic resemblance and perceived partner fidelity on offspring investment; and (ii) evaluate whether both phenotypic resemblance and perceived partner fidelity meet the more stringent criteria suggested by theory—that is, whether they also predict inbreeding aversions. We report on two studies, one from a population-based sample of Finnish fathers (N?=?390), the other from a Mechanical Turk sample (N?=?700), and furnish evidence in strong support of perceived partner fidelity as a cue to paternity. Support for resemblance as a cue to paternity was decidedly weaker. We discuss a non-kin-based role that resemblance might play in altruistic decision-making, consider whether men might use additional kinship cues to meet the computational challenges associated with paternity assessment, and provide suggestions for future research. 相似文献
120.
Community structure of insect herbivores is driven by conservatism,escalation and divergence of defensive traits in Ficus 下载免费PDF全文
Martin Volf Scott E. Miller Brus Isua Mentap Sisol Gibson Aubona Petr Šimek Martin Moos Juuso Laitila Jorma Kim Jan Zima Jr Jadranka Rota George D. Weiblen Stewart Wossa Juha‐Pekka Salminen Yves Basset Vojtech Novotny 《Ecology letters》2018,21(1):83-92
Escalation (macroevolutionary increase) or divergence (disparity between relatives) in trait values are two frequent outcomes of the plant‐herbivore arms race. We studied the defences and caterpillars associated with 21 sympatric New Guinean figs. Herbivore generalists were concentrated on hosts with low protease and oxidative activity. The distribution of specialists correlated with phylogeny, protease and trichomes. Additionally, highly specialised Asota moths used alkaloid rich plants. The evolution of proteases was conserved, alkaloid diversity has escalated across the studied species, oxidative activity has escalated within one clade, and trichomes have diverged across the phylogeny. Herbivore specificity correlated with their response to host defences: escalating traits largely affected generalists and divergent traits specialists; but the effect of escalating traits on extreme specialists was positive. In turn, the evolution of defences in Ficus can be driven towards both escalation and divergence in individual traits, in combination providing protection against a broad spectrum of herbivores. 相似文献