全文获取类型
收费全文 | 3888篇 |
免费 | 374篇 |
国内免费 | 4篇 |
出版年
2023年 | 28篇 |
2022年 | 57篇 |
2021年 | 76篇 |
2020年 | 61篇 |
2019年 | 85篇 |
2018年 | 126篇 |
2017年 | 92篇 |
2016年 | 145篇 |
2015年 | 188篇 |
2014年 | 214篇 |
2013年 | 236篇 |
2012年 | 319篇 |
2011年 | 277篇 |
2010年 | 210篇 |
2009年 | 170篇 |
2008年 | 204篇 |
2007年 | 176篇 |
2006年 | 164篇 |
2005年 | 143篇 |
2004年 | 154篇 |
2003年 | 136篇 |
2002年 | 132篇 |
2001年 | 67篇 |
2000年 | 74篇 |
1999年 | 57篇 |
1998年 | 40篇 |
1997年 | 30篇 |
1996年 | 28篇 |
1995年 | 29篇 |
1994年 | 29篇 |
1993年 | 36篇 |
1992年 | 43篇 |
1991年 | 38篇 |
1990年 | 35篇 |
1989年 | 40篇 |
1988年 | 36篇 |
1987年 | 31篇 |
1986年 | 25篇 |
1985年 | 24篇 |
1984年 | 20篇 |
1983年 | 25篇 |
1982年 | 9篇 |
1981年 | 21篇 |
1980年 | 13篇 |
1979年 | 17篇 |
1978年 | 11篇 |
1977年 | 10篇 |
1974年 | 13篇 |
1973年 | 13篇 |
1966年 | 8篇 |
排序方式: 共有4266条查询结果,搜索用时 31 毫秒
91.
Blanca Domenech‐Ximenos Victor Cuba Pepus Daunis‐i‐Estadella Santiago Thi‐Henestrosa Francisco Jaldo Carles Biarnes Xavier Molina Gemma Xifra Wifredo Ricart Anton Bardera Imma Boada Marco Essig Salvador Pedraza Massimo Federici Jos Manuel Fernndez‐Real Josep Puig 《Obesity (Silver Spring, Md.)》2020,28(9):1663-1670
92.
Francesco Rovero Jorge Ahumada Patrick A. Jansen Douglas Sheil Patricia Alvarez Kelly Boekee Santiago Espinosa Marcela Guimarães Moreira Lima Emanuel H. Martin Timothy G. O'Brien Julia Salvador Fernanda Santos Melissa Rosa Alexander Zvoleff Chris Sutherland Simone Tenan 《Ecography》2020,43(1):75-84
The understanding of global diversity patterns has benefitted from a focus on functional traits and how they relate to variation in environmental conditions among assemblages. Distant communities in similar environments often share characteristics, and for tropical forest mammals, this functional trait convergence has been demonstrated at coarse scales (110–200 km resolution), but less is known about how these patterns manifest at fine scales, where local processes (e.g. habitat features and anthropogenic activities) and biotic interactions occur. Here, we used standardized camera trapping data and a novel analytical method that accounts for imperfect detection to assess how the functional composition of terrestrial mammal communities for two traits – trophic guild and body mass – varies across 16 protected areas in tropical forests and three continents, in relation to the extent of protected habitat and anthropogenic pressures. We found that despite their taxonomic differences, communities generally have a consistent trophic guild composition, and respond similarly to these factors. Insectivores were found to be sensitive to the size of protected habitat and surrounding human population density. Body mass distribution varied little among communities both in terms of central tendency and spread, and interestingly, community average body mass declined with proximity to human settlements. Results indicate predicted trait convergence among assemblages at the coarse scale reflects consistent functional composition among communities at the local scale, suggesting that broadly similar habitats and selective pressures shaped communities with similar trophic strategies and responses to drivers of change. These similarities provide a foundation for assessing assemblages under anthropogenic threats and sharing conservation measures. 相似文献
93.
Loss of function of Arabidopsis NADP‐malic enzyme 1 results in enhanced tolerance to aluminum stress
94.
95.
Caroline R. Cummings Sonia M. Hernandez Maureen Murray Taylor Ellison Henry C. Adams Robert E. Cooper Shannon Curry Kristen J. Navara 《Ecology and evolution》2020,10(15):8416-8428
When wildlife forage and/or live in urban habitats, they often experience a shift in resource availability and dietary quality. Some species even use human handouts, such as bread, as well as human refuse, as a large part of their new diets; yet the influences of this nutritional shift on health and survival remain unclear. American white ibises are increasingly being seen in urban areas in Florida; they collect handouts, such as bread and other food items, from humans in parks, and are also found foraging on anthropogenic sources in trash heaps. We hypothesized that the consumption of these new anthropogenic food sources may trigger increases in indicators of physiological challenge and dampen immune responses. We tested this experimentally by raising 20 white ibis nestlings in captivity, and exposing 10 to a simulated anthropogenic diet (including the addition of white bread and a reduction in seafood content) while maintaining 10 on a diet similar to what ibises consume in more natural environments. We then tested two indicators of physiological challenge (corticosterone and heat shock protein 70), assessed innate immunity in these birds via bactericidal assays and an in vitro carbon clearance assay, and adaptive immunity using a phytohemagglutinin skin test. The anthropogenic diet depressed the development of the ability to kill Salmonella paratyphi in culture. Our results suggest that consuming an anthropogenic diet may be detrimental in terms of the ability to battle a pathogenic bacterial species, but there was little effect on indicators of physiological challenge and other immunological measures. 相似文献
96.
Studies have found that mutant, misfolded superoxide dismutase [Cu–Zn] (SOD1) can convert wild type SOD1 (wtSOD1) in a prion-like fashion, and that misfolded wtSOD1 can be propagated by release and uptake of protein aggregates. In developing a prion-like mechanism for this propagation of SOD1 misfolding we have previously shown how enervation of the SOD1 electrostatic loop (ESL), caused by the formation of transient non-obligate SOD1 oligomers, can lead to an experimentally observed gain of interaction (GOI) that results in the formation of SOD1 amyloid-like filaments. It has also been shown that freedom of ESL motion is essential to catalytic function. This work investigates the possibility that restricting ESL mobility might not only compromise superoxide catalytic activity but also serve to promote the peroxidase activity of SOD1, thus implicating the formation of SOD1 oligomers in both protein misfolding and in protein oxidation. 相似文献
97.
98.
Santiago Herrera-lvarez Elinor Karlsson Oliver A Ryder Kerstin Lindblad-Toh Andrew J Crawford 《Molecular biology and evolution》2021,38(5):1715
Gigantism results when one lineage within a clade evolves extremely large body size relative to its small-bodied ancestors, a common phenomenon in animals. Theory predicts that the evolution of giants should be constrained by two tradeoffs. First, because body size is negatively correlated with population size, purifying selection is expected to be less efficient in species of large body size, leading to increased mutational load. Second, gigantism is achieved through generating a higher number of cells along with higher rates of cell proliferation, thus increasing the likelihood of cancer. To explore the genetic basis of gigantism in rodents and uncover genomic signatures of gigantism-related tradeoffs, we assembled a draft genome of the capybara (Hydrochoerus hydrochaeris), the world’s largest living rodent. We found that the genome-wide ratio of nonsynonymous to synonymous mutations (ω) is elevated in the capybara relative to other rodents, likely caused by a generation-time effect and consistent with a nearly neutral model of molecular evolution. A genome-wide scan for adaptive protein evolution in the capybara highlighted several genes controlling postnatal bone growth regulation and musculoskeletal development, which are relevant to anatomical and developmental modifications for an increase in overall body size. Capybara-specific gene-family expansions included a putative novel anticancer adaptation that involves T-cell-mediated tumor suppression, offering a potential resolution to the increased cancer risk in this lineage. Our comparative genomic results uncovered the signature of an intragenomic conflict where the evolution of gigantism in the capybara involved selection on genes and pathways that are directly linked to cancer. 相似文献
99.
100.
Hashemzadeh Segherloo Iraj Ghojoghi Fariborz Tabatabaei Seyedeh Narjes Normandeau Eric Hernandez Cecilia Hallerman Eric Boyle Brian Bernatchez Louis 《Hydrobiologia》2021,848(2):345-361
Hydrobiologia - The genus Rutilus is widespread in the western and central Palearctic region. In the Caspian Sea, the taxonomic status of different populations of Rutilus lacustris has... 相似文献