全文获取类型
收费全文 | 2737篇 |
免费 | 221篇 |
国内免费 | 3篇 |
专业分类
2961篇 |
出版年
2023年 | 16篇 |
2022年 | 27篇 |
2021年 | 59篇 |
2020年 | 47篇 |
2019年 | 41篇 |
2018年 | 54篇 |
2017年 | 54篇 |
2016年 | 85篇 |
2015年 | 158篇 |
2014年 | 162篇 |
2013年 | 214篇 |
2012年 | 258篇 |
2011年 | 233篇 |
2010年 | 133篇 |
2009年 | 127篇 |
2008年 | 180篇 |
2007年 | 197篇 |
2006年 | 178篇 |
2005年 | 154篇 |
2004年 | 118篇 |
2003年 | 132篇 |
2002年 | 117篇 |
2001年 | 23篇 |
2000年 | 13篇 |
1999年 | 26篇 |
1998年 | 17篇 |
1997年 | 18篇 |
1996年 | 10篇 |
1995年 | 17篇 |
1994年 | 9篇 |
1993年 | 6篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1978年 | 2篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1968年 | 2篇 |
排序方式: 共有2961条查询结果,搜索用时 0 毫秒
21.
Eben Goodale Hari Sridhar Kathryn E. Sieving Priti Bangal Gabriel J. Colorado Z. Damien R. Farine Eckhard W. Heymann Harrison H. Jones Indrikis Krams Ari E. Martínez Flavia Montao‐Centellas Jenny Muoz Umesh Srinivasan Anne Theo Kartik Shanker 《Biological reviews of the Cambridge Philosophical Society》2020,95(4):889-910
Mixed‐species animal groups (MSGs) are widely acknowledged to increase predator avoidance and foraging efficiency, among other benefits, and thereby increase participants' fitness. Diversity in MSG composition ranges from two to 70 species of very similar or completely different phenotypes. Yet consistency in organization is also observable in that one or a few species usually have disproportionate importance for MSG formation and/or maintenance. We propose a two‐dimensional framework for understanding this diversity and consistency, concentrating on the types of interactions possible between two individuals, usually of different species. One axis represents the similarity of benefit types traded between the individuals, while the second axis expresses asymmetry in the relative amount of benefits/costs accrued. Considering benefit types, one extreme represents the case of single‐species groups wherein all individuals obtain the same supplementary, group‐size‐related benefits, and the other extreme comprises associations of very different, but complementary species (e.g. one partner creates access to food while the other provides vigilance). The relevance of social information and the matching of activities (e.g. speed of movement) are highest for relationships on the supplementary side of this axis, but so is competition; relationships between species will occur at points along this gradient where the benefits outweigh the costs. Considering benefit amounts given or received, extreme asymmetry occurs when one species is exclusively a benefit provider and the other a benefit user. Within this parameter space, some MSG systems are constrained to one kind of interaction, such as shoals of fish of similar species or leader–follower interactions in fish and other taxa. Other MSGs, such as terrestrial bird flocks, can simultaneously include a variety of supplementary and complementary interactions. We review the benefits that species obtain across the diversity of MSG types, and argue that the degree and nature of asymmetry between benefit providers and users should be measured and not just assumed. We then discuss evolutionary shifts in MSG types, focusing on drivers towards similarity in group composition, and selection on benefit providers to enhance the benefits they can receive from other species. Finally, we conclude by considering how individual and collective behaviour in MSGs may influence both the structure and processes of communities. 相似文献
22.
Caroline Ward Lindsay C. Stringer Eleanor Warren‐Thomas Fahmuddin Agus Keith Hamer Nathalie Pettorelli Bambang Hariyadi Jenny Hodgson Winda D. Kartika Jennifer Lucey Colin McClean Neneng L. Nurida Asmadi Saad Jane K. Hill 《Restoration Ecology》2020,28(4):817-827
Ecological restoration is considered to play an important role in mitigating climate change, protecting biodiversity, and preventing environmental degradation. Yet, there are often multiple perspectives on what outcomes restoration should be aiming to achieve, and how we should get to that point. In this study we interview a range of policymakers, academics, and non‐governmental organization (NGO) representatives to explore the range of perspectives on the restoration of Indonesia's tropical peatlands—key global ecosystems that have undergone large‐scale degradation. Thematic analysis suggests that participants agreed about the importance of restoration, but had differing opinions on how effective restoration activities to date have been and what a restored peatland landscape should look like. These results exemplify how ecological restoration can mean different things to different people, but also highlight important areas of consensus for moving forward with peatland restoration strategies. 相似文献
23.
John Fredrik Strøm Jenny L. A. Jensen Anna Nikolopoulos Eivind Nordli Pål Arne Bjørn Thomas Bøhn 《Journal of fish biology》2021,99(4):1280-1291
Anadromous brown trout (sea trout), Salmo trutta, is currently in decline throughout its range, largely due to anthropogenic stressors in freshwater and marine habitats. Acoustic telmetry was utilized to study the marine migration of sea trout post-smolts from three populations in a relatively pristine subarctic fjord system. While at sea, the sea trout spent a substantial part of their time close to their natal river, preferred near shore over pelagic habitats and were strongly surface oriented. Despite a fidelity towards local areas, the sea trout utilized various parts of the fjord system, with maximum dispersion >30 km and total migration distance >300 km. Almost half of the sea trout (44%) migrated between river outlets, indicating that a metapopulation approach may be appropriate when managing neighbouring sea trout populations at high latitudes. Furthermore, the different populations displayed different migratory behaviours in terms of distance migrated, dispersion from origin and the likelihood of leaving their home area. This variation in migratory behaviour is likely influenced by spatiotemporal differences in habitat quality between sites, indicating that local habitat variations may promote population-specific behavioural responses even in relatively confined fjord systems. 相似文献
24.
25.
Jenny G. Parvani Amy J. Galliher-Beckley Barbara J. Schiemann William P. Schiemann 《Molecular biology of the cell》2013,24(21):3449-3459
Mammary tumorigenesis and epithelial–mesenchymal transition (EMT) programs cooperate in converting transforming growth factor-β (TGF-β) from a suppressor to a promoter of breast cancer metastasis. Although previous reports associated β1 and β3 integrins with TGF-β stimulation of EMT and metastasis, the functional interplay and plasticity exhibited by these adhesion molecules in shaping the oncogenic activities of TGF-β remain unknown. We demonstrate that inactivation of β1 integrin impairs TGF-β from stimulating the motility of normal and malignant mammary epithelial cells (MECs) and elicits robust compensatory expression of β3 integrin solely in malignant MECs, but not in their normal counterparts. Compensatory β3 integrin expression also 1) enhances the growth of malignant MECs in rigid and compliant three-dimensional organotypic cultures and 2) restores the induction of the EMT phenotypes by TGF-β. Of importance, compensatory expression of β3 integrin rescues the growth and pulmonary metastasis of β1 integrin–deficient 4T1 tumors in mice, a process that is prevented by genetic depletion or functional inactivation of β3 integrin. Collectively our findings demonstrate that inactivation of β1 integrin elicits metastatic progression via a β3 integrin–specific mechanism, indicating that dual β1 and β3 integrin targeting is necessary to alleviate metastatic disease in breast cancer patients. 相似文献
26.
Paul H. Morris Jenny White Edward R. Morrison Kayleigh Fisher 《Evolution and human behavior》2013,34(3):176-181
There is a strong contemporary association between high heels and female sexuality. We investigated the hypothesis that one motivation for women wearing high heels is that it artificially increases the femininity of gait. We isolated the effects of heels on gait using point-light methodology. Females were recorded walking in flat shoes and high heels. Participants viewed point-light videos of the women wearing the two types of shoe. Participants judged the females in the heels condition as significantly more attractive (with a large effect size) than the females in the flat shoe condition. Biomechanical analyses revealed that wearing high heels led to increased femininity of gait including reduced stride length and increased rotation and tilt of the hips. We conclude that high heels exaggerate sex specific aspects of female gait and women walking in high heels could be regarded as a supernormal stimulus. 相似文献
27.
Kathleen M. Maloney Jenny Ancca‐Juarez Renzo Salazar Katty Borrini‐Mayori Malwina Niemierko Joshua O. Yukich Cesar Naquira Joseph A. Keating Michael Z. Levy 《Journal of vector ecology》2013,38(1):6-11
The vector of Chagas disease, Triatoma infestans, is largely controlled by the household application of pyrethroid insecticides. Because effective, large‐scale insecticide application is costly and necessitates numerous trained personnel, alternative control techniques are badly needed. We compared the residual effect of organophosphate‐based insecticidal paint (Inesfly 5A IGR? (I5A)) to standard deltamethrin, and a negative control, against T. infestans in a simulated natural environment. We evaluated mortality, knockdown, and ability to take a blood meal among 5th instar nymphs. I5A paint caused significantly greater mortality at time points up to nine months compared to deltamethrin (Fisher's Exact Test, p < 0.01 in all instances). A year following application, mortality among nymphs in the I5A was similar to those in the deltamethrin (χ2 = 0.76, df=1, p < 0.76). At months 0 and 1 after application, fewer nymphs exposed to deltamethrin took a blood meal compared to insects exposed to paint (Fisher's Exact Tests, p < 0.01 and p < 0.01, respectively). Insecticidal paint may provide an easily‐applied means of protection against vectors of Chagas disease. 相似文献
28.
Ekatherina Serysheva Hebist Berhane Luca Grumolato Kubilay Demir Sophie Balmer Maxime Bodak Michael Boutros Stuart Aaronson Marek Mlodzik Andreas Jenny 《EMBO reports》2013,14(8):718-725
Wnt/β-catenin signalling is central to development and its regulation is essential in preventing cancer. Using phosphorylation of Dishevelled as readout of pathway activation, we identified Drosophila Wnk kinase as a new regulator of canonical Wnt/β-catenin signalling. WNK kinases are known for regulating ion co-transporters associated with hypertension disorders. We demonstrate that wnk loss-of-function phenotypes resemble canonical Wnt pathway mutants, while Wnk overexpression causes gain-of-function canonical Wnt-signalling phenotypes. Importantly, knockdown of human WNK1 and WNK2 also results in decreased Wnt signalling in mammalian cell culture, suggesting that Wnk kinases have a conserved function in ensuring peak levels of canonical Wnt signalling. 相似文献
29.
30.
Alphonse Ouédraogo Alfred B. Tiono Désiré Kargougou Jean Baptiste Yaro Esperance Ouédraogo Youssouf Kaboré David Kangoye Edith C. Bougouma Adama Gansane Noelie Henri Amidou Diarra Souleymane Sanon Issiaka Soulama Amadou T. Konate Nora L. Watson Valerie Brown Jenny Hendriks Maria Grazia Pau Isabella Versteege Edison Wiesken Jerald Sadoff Issa Nebie Sodiomon B. Sirima 《PloS one》2013,8(11)