全文获取类型
收费全文 | 661篇 |
免费 | 2篇 |
国内免费 | 6篇 |
专业分类
系统科学 | 9篇 |
教育与普及 | 2篇 |
理论与方法论 | 20篇 |
现状及发展 | 69篇 |
研究方法 | 100篇 |
综合类 | 381篇 |
自然研究 | 88篇 |
出版年
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 9篇 |
2015年 | 4篇 |
2014年 | 3篇 |
2013年 | 10篇 |
2012年 | 43篇 |
2011年 | 147篇 |
2010年 | 28篇 |
2009年 | 4篇 |
2008年 | 50篇 |
2007年 | 49篇 |
2006年 | 44篇 |
2005年 | 56篇 |
2004年 | 59篇 |
2003年 | 53篇 |
2002年 | 45篇 |
2001年 | 1篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 4篇 |
1988年 | 3篇 |
1986年 | 2篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1982年 | 2篇 |
1980年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有669条查询结果,搜索用时 15 毫秒
401.
402.
Hinch AG Tandon A Patterson N Song Y Rohland N Palmer CD Chen GK Wang K Buxbaum SG Akylbekova EL Aldrich MC Ambrosone CB Amos C Bandera EV Berndt SI Bernstein L Blot WJ Bock CH Boerwinkle E Cai Q Caporaso N Casey G Cupples LA Deming SL Diver WR Divers J Fornage M Gillanders EM Glessner J Harris CC Hu JJ Ingles SA Isaacs W John EM Kao WH Keating B Kittles RA Kolonel LN Larkin E Le Marchand L McNeill LH Millikan RC Murphy A Musani S Neslund-Dudas C Nyante S Papanicolaou GJ Press MF Psaty BM 《Nature》2011,476(7359):170-175
Recombination, together with mutation, gives rise to genetic variation in populations. Here we leverage the recent mixture of people of African and European ancestry in the Americas to build a genetic map measuring the probability of crossing over at each position in the genome, based on about 2.1 million crossovers in 30,000 unrelated African Americans. At intervals of more than three megabases it is nearly identical to a map built in Europeans. At finer scales it differs significantly, and we identify about 2,500 recombination hotspots that are active in people of West African ancestry but nearly inactive in Europeans. The probability of a crossover at these hotspots is almost fully controlled by the alleles an individual carries at PRDM9 (P?value 10(-245)). We identify a 17-base-pair DNA sequence motif that is enriched in these hotspots, and is an excellent match to the predicted binding target of PRDM9 alleles common in West Africans and rare in Europeans. Sites of this motif are predicted to be risk loci for disease-causing genomic rearrangements in individuals carrying these alleles. More generally, this map provides a resource for research in human genetic variation and evolution. 相似文献
403.
Cognitive deficits are now recognized widely as core features of schizophrenia, and as major contributors to the clinical outcome of the disorder. They are also studied widely as ‘endophenotypes’, reflecting a growing consensus that schizophrenia is a broader, more multidimensional illness than the diagnostic criteria required for its formal diagnosis. This evolving view of cognition underlies its utilization in recent initiatives for intervention and assessment in schizophrenia. Two of these initiatives ar... 相似文献
404.
405.
406.
Boomsma JJ Beekman M Cornwallis CK Griffin AS Holman L Hughes WO Keller L Oldroyd BP Ratnieks FL 《Nature》2011,471(7339):E4-5; author reply E9-10
Arising from M. A. Nowak, C. E. Tarnita & E. O. Wilson 466, 1057-1062 (2010); Nowak et al. reply. The paper by Nowak et al. has the evolution of eusociality as its title, but it is mostly about something else. It argues against inclusive fitness theory and offers an alternative modelling approach that is claimed to be more fundamental and general, but which, we believe, has no practical biological meaning for the evolution of eusociality. Nowak et al. overlook the robust empirical observation that eusociality has only arisen in clades where mothers are associated with their full-sibling offspring; that is, in families where the average relatedness of offspring to siblings is as high as to their own offspring, independent of population structure or ploidy. We believe that this omission makes the paper largely irrelevant for understanding the evolution of eusociality. 相似文献
407.
408.
<正>作为一门组织完善的科学学科,生态学已迈入它的第二个世纪:生态学通过大量的实验和丰富的观察,让人类对自然界的运行规律有了基本的理解。今天,环境科学家拥有一系列强有力的工具和技术来测量和监督环境,并解读一大堆各种各样的数据。然而,尽管新信息海量般地涌现,生态学家们却常常无法将他们的知识有效地转化给公众和政策制定者。除非生态科学的发现能 相似文献
409.
How broadly tuned olfactory receptors equally recognize their agonists. Human OR1G1 as a test case 总被引:1,自引:1,他引:0
Landry Charlier Jérémie Topin Catherine Ronin Soo-Kyung Kim William A. Goddard III Roman Efremov Jér?me Golebiowski 《Cellular and molecular life sciences : CMLS》2012,69(24):4205-4213
The molecular features that dominate the binding mode of agonists by a broadly tuned olfactory receptor are analyzed through a joint approach combining cell biology, calcium imaging, and molecular modeling. The odorant/receptor affinities, estimated through statistics accrued during molecular dynamics simulations, are in accordance with the experimental ranking. Although in many systems receptors recognize their target through a network of oriented interactions, such as H-bonding, the binding by broadly tuned olfactory receptors is dominated by non-polar terms. We show how such a feature allows chemicals belonging to different chemical families to similarly activate the receptors through compensations of interactions within the binding site. 相似文献
410.
William G. Simpson 《西北部美国博物学家》2011,69(2)
It has been suggested that Nearctic pikas ( Ochotona spp.) are good biogeographic indicators of regions containing rocky, mesic, and cool habitat characterized by long winters and short summers. I examined whether populations of pikas inhabiting distinct low-elevation locales (121–255 m) are faithfully restricted to long-winter and shortsummer conditions by monitoring the climate associated with American pikas ( Ochotona princeps ) in the southern part of the Columbia River Gorge, Oregon. Ambient air temperatures and weather conditions in the vicinity of 4 pika-occupied rockslides were monitored with remote temperature loggers and weather stations from June 2000 to June 2001. Temperatures were compared to long-term averages recorded within the area. I detected pikas inhabiting locales where some temperatures lie outside of the limiting climatic values previously calculated for regions containing pikas. Mild winter temperatures at these pika locations show that long-winter temperatures and snow accumulation associated with typical habitat may not be requirements for pikas in some low-elevation habitat. When using climatic conditions experienced by extant pikas to estimate local paleoenvironments surrounding fossil sites and to anticipate effects of climate change on future pika distributions, I determined that pika sites in the Columbia River Gorge indicate that the association of pikas with long-winter habitat should be considered uncertain. These results highlight the need for further investigation into how local temperatures affect the distribution, behavior, and persistence of low-elevation pikas. 相似文献