全文获取类型
收费全文 | 7763篇 |
免费 | 576篇 |
国内免费 | 1篇 |
出版年
2023年 | 51篇 |
2022年 | 96篇 |
2021年 | 160篇 |
2020年 | 149篇 |
2019年 | 156篇 |
2018年 | 205篇 |
2017年 | 199篇 |
2016年 | 279篇 |
2015年 | 439篇 |
2014年 | 417篇 |
2013年 | 552篇 |
2012年 | 609篇 |
2011年 | 598篇 |
2010年 | 428篇 |
2009年 | 374篇 |
2008年 | 453篇 |
2007年 | 441篇 |
2006年 | 449篇 |
2005年 | 379篇 |
2004年 | 371篇 |
2003年 | 318篇 |
2002年 | 298篇 |
2001年 | 76篇 |
2000年 | 66篇 |
1999年 | 80篇 |
1998年 | 68篇 |
1997年 | 61篇 |
1996年 | 43篇 |
1995年 | 52篇 |
1994年 | 36篇 |
1993年 | 41篇 |
1992年 | 27篇 |
1991年 | 29篇 |
1990年 | 30篇 |
1989年 | 18篇 |
1988年 | 17篇 |
1987年 | 25篇 |
1986年 | 21篇 |
1985年 | 19篇 |
1984年 | 23篇 |
1983年 | 24篇 |
1982年 | 19篇 |
1981年 | 19篇 |
1980年 | 12篇 |
1979年 | 10篇 |
1977年 | 16篇 |
1976年 | 10篇 |
1975年 | 12篇 |
1974年 | 14篇 |
1973年 | 11篇 |
排序方式: 共有8340条查询结果,搜索用时 31 毫秒
1.
Sacramento Doralice Rodrigues Coelho Rosalie Reed Rodrigues Wigg Márcia Dutra Toledo Luna Linhares Luiz Fernando de Matos dos Santos Marta Gonçalves Azevedo Soares Semêdo Luzia Teixeira de Ribeiro da Silva Antonio Jorge 《World journal of microbiology & biotechnology》2004,20(3):225-229
A promising producer of bioactive compounds isolated from a Brazilian tropical soil was tested for its range of antimicrobial
activities. Strain 606, classified as Streptomyces sp., could not be identified up to species level, suggesting a possible new taxon. The supernatant and 10 extracts and fractions,
obtained by extraction and chromatographic techniques, presented antimicrobial activity using antibiograms. The methanolic
fraction was highly active against pathogenic bacteria, phytopathogenic fungi and the human pathogenic yeast Candida albicans. It also possessed high antiviral activity inhibiting the propagation of an acyclovir-resistant herpes simplex virus type
1 strain on HEp-2 cells at non-cytotoxic concentration. The strong cytotoxic effect suggests an antitumour action.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
HIF-1 expression in healing wounds: HIF-1alpha induction in primary inflammatory cells by TNF-alpha 总被引:12,自引:0,他引:12
3.
Carlo L. Seifert Martin Volf Leonardo R. Jorge Tomokazu Abe Grace Carscallen Pavel Drozd Rajesh Kumar Greg P.A. Lamarre Martin Libra Maria E. Losada Scott E. Miller Masashi Murakami Geoffrey Nichols Petr Pyszko Martin igut David L. Wagner Vojtch Novotný 《Ecology and evolution》2020,10(24):14137
- Assemblages of insect herbivores are structured by plant traits such as nutrient content, secondary metabolites, physical traits, and phenology. Many of these traits are phylogenetically conserved, implying a decrease in trait similarity with increasing phylogenetic distance of the host plant taxa. Thus, a metric of phylogenetic distances and relationships can be considered a proxy for phylogenetically conserved plant traits and used to predict variation in herbivorous insect assemblages among co‐occurring plant species.
- Using a Holarctic dataset of exposed‐feeding and shelter‐building caterpillars, we aimed at showing how phylogenetic relationships among host plants explain compositional changes and characteristics of herbivore assemblages.
- Our plant–caterpillar network data derived from plot‐based samplings at three different continents included >28,000 individual caterpillar–plant interactions. We tested whether increasing phylogenetic distance of the host plants leads to a decrease in caterpillar assemblage overlap. We further investigated to what degree phylogenetic isolation of a host tree species within the local community explains abundance, density, richness, and mean specialization of its associated caterpillar assemblage.
- The overlap of caterpillar assemblages decreased with increasing phylogenetic distance among the host tree species. Phylogenetic isolation of a host plant within the local plant community was correlated with lower richness and mean specialization of the associated caterpillar assemblages. Phylogenetic isolation had no effect on caterpillar abundance or density. The effects of plant phylogeny were consistent across exposed‐feeding and shelter‐building caterpillars.
- Our study reveals that distance metrics obtained from host plant phylogeny are useful predictors to explain compositional turnover among hosts and host‐specific variations in richness and mean specialization of associated insect herbivore assemblages in temperate broadleaf forests. As phylogenetic information of plant communities is becoming increasingly available, further large‐scale studies are needed to investigate to what degree plant phylogeny structures herbivore assemblages in other biomes and ecosystems.
4.
Rosalem Gabriel Santos Las Casas Estevam Barbosa Lima Thiago Parente González-Torres Libardo Andrés 《Biomechanics and modeling in mechanobiology》2020,19(5):1537-1549
Biomechanics and Modeling in Mechanobiology - Cell migration is a process of crucial importance for the human body. It is responsible for important processes such as wound healing and tumor... 相似文献
5.
6.
Kinga Michno David Knight Jorge M. Campussano Diana van de Hoef Gabrielle L. Boulianne 《PloS one》2009,4(9)
Much of our current understanding about neurodegenerative diseases can be attributed to the study of inherited forms of these disorders. For example, mutations in the presenilin 1 and 2 genes have been linked to early onset familial forms of Alzheimer''s disease (FAD). Using the Drosophila central nervous system as a model we have investigated the role of presenilin in one of the earliest cellular defects associated with Alzheimer''s disease, intracellular calcium deregulation. We show that expression of either wild type or FAD-mutant presenilin in Drosophila CNS neurons has no impact on resting calcium levels but does give rise to deficits in intracellular calcium stores. Furthermore, we show that a loss-of-function mutation in calmodulin, a key regulator of intracellular calcium, can suppress presenilin-induced deficits in calcium stores. Our data support a model whereby presenilin plays a role in regulating intracellular calcium stores and demonstrate that Drosophila can be used to study the link between presenilin and calcium deregulation. 相似文献
7.
Presented a choice between conspecific males and 2 congeneric males, virgin females ofMelittobia australica andM. digitata chose conspecific males disproportionately more often, whereasM. femorata females distributed themselves evenly among the choices. Empty tubes, provided as the fourth choice in the test apparatus,
were entered much less often than tubes containing live males. Females of all species chose “wrong” males about equally frequently.
These observations suggest that even non-conspecific males possess some degree of attractiveness to virgin females. Chemicals
in the sex pheromone of the males are presumed to be the source of the males' attractancy. The incomplete species specificity
is interpreted in light of the life history of this genus, and it is suggested that specific recognition cues operate primarily
after the sexes come together.
Supported by a grant from Kagoshima Prefecture in Japan under the exchange program of faculty members between Kagoshima University
and the University of Georgia. 相似文献
8.
Jorge E. Ramos Gretta T. Pecl Natalie A. Moltschaniwskyj Jan M. Strugnell Rafael I. León Jayson M. Semmens 《PloS one》2014,9(8)
Understanding the response of any species to climate change can be challenging. However, in short-lived species the faster turnover of generations may facilitate the examination of responses associated with longer-term environmental change. Octopus tetricus, a commercially important species, has undergone a recent polewards range shift in the coastal waters of south-eastern Australia, thought to be associated with the southerly extension of the warm East Australian Current. At the cooler temperatures of a polewards distribution limit, growth of a species could be slower, potentially leading to a bigger body size and resulting in a slower population turnover, affecting population viability at the extreme of the distribution. Growth rates, body size, and life span of O. tetricus were examined at the leading edge of a polewards range shift in Tasmanian waters (40°S and 147°E) throughout 2011. Octopus tetricus had a relatively small body size and short lifespan of approximately 11 months that, despite cooler temperatures, would allow a high rate of population turnover and may facilitate the population increase necessary for successful establishment in the new extended area of the range. Temperature, food availability and gender appear to influence growth rate. Individuals that hatched during cooler and more productive conditions, but grew during warming conditions, exhibited faster growth rates and reached smaller body sizes than individuals that hatched into warmer waters but grew during cooling conditions. This study suggests that fast growth, small body size and associated rapid population turnover may facilitate the range shift of O. tetricus into Tasmanian waters. 相似文献
9.
Miguel Gandra Jorge Assis Manuel Ramos Martins David Abecasis 《Molecular biology and evolution》2021,38(4):1402
Knowledge on genetic structure is key to understand species connectivity patterns and to define the spatiotemporal scales over which conservation management plans should be designed and implemented. The distribution of genetic diversity (within and among populations) greatly influences species ability to cope and adapt to environmental changes, ultimately determining their long-term resilience to ecological disturbances. Yet, the drivers shaping connectivity and structure in marine fish populations remain elusive, as are the effects of fishing activities on genetic subdivision. To investigate these questions, we conducted a meta-analysis and compiled genetic differentiation data (FST/ΦST estimates) for more than 170 fish species from over 200 published studies globally distributed. We modeled the effects of multiple life-history traits, distance metrics, and methodological factors on observed population differentiation indices and specifically tested whether any signal arising from different exposure to fishing exploitation could be detected. Although the myriad of variables shaping genetic structure makes it challenging to isolate the influence of single drivers, results showed a significant correlation between commercial importance and genetic structure, with widespread lower population differentiation in commercially exploited species. Moreover, models indicate that variables commonly used as proxy for connectivity, such as larval pelagic duration, might be insufficient, and suggest that deep-sea species may disperse further. Overall, these results contribute to the growing body of knowledge on marine genetic connectivity and suggest a potential effect of commercial fisheries on the homogenization of genetic diversity, highlighting the need for additional research focused on dispersal ecology to ensure long-term sustainability of exploited marine species. 相似文献
10.
Martha L. Bohórquez Alonso Jorge Martínez Cotrina David Aguilar Pardo Enrique Font Miguel Molina-Borja 《Journal of Ethology》2010,28(2):305-311
Many vertebrate species show display behaviors when predators are in their vicinity. Some of these displays may inform the
predator of the improbability of capturing the prey (i.e., pursuit-deterrent displays) and are potentially advantageous to
both predator and prey. Here we present data on a tail display performed by Gonatodes albogularis, a diurnal tropical gecko. We performed transect surveys in three habitats near Bogotá in Colombia. Geckos detected during
transects were approached by the observer in a standardized way, and details of their tail-waving displays were recorded.
In control recordings animals were watched from a distant site without approaching them. Results showed sexual differences
in tail-waving display: when approached by the observer, males performed this behavior more frequently than females. We found
no significant differences between males and females in flight-initiation distances and height above the substratum when they
were initially located. Results also showed that males displayed more frequently when approached than when the simulated predator
remained stationary. We interpret these results as evidence that the display functions as a pursuit-deterrent signal to potential
predators. However, as some tail displays were performed in the presence of conspecifics, the display may also have a social
function. 相似文献