全文获取类型
收费全文 | 10930篇 |
免费 | 1046篇 |
国内免费 | 6篇 |
出版年
2023年 | 92篇 |
2022年 | 205篇 |
2021年 | 376篇 |
2020年 | 212篇 |
2019年 | 275篇 |
2018年 | 304篇 |
2017年 | 241篇 |
2016年 | 409篇 |
2015年 | 725篇 |
2014年 | 748篇 |
2013年 | 756篇 |
2012年 | 1059篇 |
2011年 | 965篇 |
2010年 | 543篇 |
2009年 | 399篇 |
2008年 | 564篇 |
2007年 | 596篇 |
2006年 | 463篇 |
2005年 | 423篇 |
2004年 | 410篇 |
2003年 | 324篇 |
2002年 | 308篇 |
2001年 | 71篇 |
2000年 | 61篇 |
1999年 | 61篇 |
1998年 | 82篇 |
1997年 | 44篇 |
1996年 | 42篇 |
1995年 | 31篇 |
1994年 | 35篇 |
1993年 | 41篇 |
1992年 | 64篇 |
1991年 | 50篇 |
1990年 | 58篇 |
1989年 | 39篇 |
1988年 | 35篇 |
1987年 | 40篇 |
1986年 | 34篇 |
1985年 | 51篇 |
1984年 | 46篇 |
1983年 | 42篇 |
1982年 | 39篇 |
1981年 | 39篇 |
1980年 | 42篇 |
1979年 | 31篇 |
1978年 | 43篇 |
1977年 | 30篇 |
1976年 | 37篇 |
1975年 | 28篇 |
1974年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Environmental adaptation in Chinook salmon (Oncorhynchus tshawytscha) throughout their North American range
下载免费PDF全文
![点击此处可从《Molecular ecology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Benjamin C. Hecht Andrew P. Matala Jon E. Hess Shawn R. Narum 《Molecular ecology》2015,24(22):5573-5595
Landscape genomics is a rapidly growing field with recent advances in both genotyping efficiency and statistical analyses that provide insight towards local adaptation of populations under varying environmental and selective pressure. Chinook salmon (Oncorhynchus tshawytscha) are a broadly distributed Pacific salmon species, occupying a diversity of habitats throughout the northeastern Pacific with pronounced variation in environmental and climate features but little is understood regarding local adaptation in this species. We used a multivariate method, redundancy analysis (RDA), to identify polygenic correlations between 19 703 SNP loci and a suite of environmental variables in 46 collections of Chinook salmon (1956 total individuals) distributed throughout much of its North American range. Models in RDA were conducted on both rangewide and regional scales by hierarchical partitioning of the populations into three distinct genetic lineages. Our results indicate that between 5.8 and 21.8% of genomic variation can be accounted for by environmental features, and 566 putatively adaptive loci were identified as targets of environmental adaptation. The most influential drivers of adaptive divergence included precipitation in the driest quarter of the year (Rangewide and North Coastal Lineage, anova P = 0.002 and 0.01, respectively), precipitation in the wettest quarter of the year (Interior Columbia River Stream‐Type Lineage, anova P = 0.03), variation in mean diurnal range in temperature (South Coastal Lineage, anova P = 0.005), and migration distance (Rangewide, anova P = 0.001). Our results indicate that environmental features are strong drivers of adaptive genomic divergence in this species, and provide a foundation to investigate how Chinook salmon might respond to global environmental change. 相似文献
992.
Greet De Coster Cristina Banks-Leite Jean Paul Metzger 《Proceedings. Biological sciences / The Royal Society》2015,282(1811)
Habitat loss often reduces the number of species as well as functional diversity. Dramatic effects to species composition have also been shown, but changes to functional composition have so far been poorly documented, partly owing to a lack of appropriate indices. We here develop three new community indices (i.e. functional integrity, community integrity of ecological groups and community specialization) to investigate how habitat loss affects the diversity and composition of functional traits and species. We used data from more than 5000 individuals of 137 bird species captured in 57 sites in the Brazilian Atlantic Forest, a highly endangered biodiversity hotspot. Results indicate that habitat loss leads to a decrease in functional integrity while measures of functional diversity remain unchanged or are even positively affected. Changes to functional integrity were caused by (i) a decrease in the provisioning of some functions, and an increase in others; (ii) strong within-guild species turnover; and (iii) a replacement of specialists by generalists. Hence, communities from more deforested sites seem to provide different but not fewer functions. We show the importance of investigating changes to both diversity and composition of functional traits and species, as the effects of habitat loss on ecosystem functioning may be more complex than previously thought. Crucially, when only functional diversity is assessed, important changes to ecological functions may remain undetected and negative effects of habitat loss underestimated, thereby imperiling the application of effective conservation actions. 相似文献
993.
Improved white spruce (Picea glauca) genome assemblies and annotation of large gene families of conifer terpenoid and phenolic defense metabolism
下载免费PDF全文
![点击此处可从《The Plant journal : for cell and molecular biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
René L. Warren Christopher I. Keeling Macaire Man Saint Yuen Anthony Raymond Greg A. Taylor Benjamin P. Vandervalk Hamid Mohamadi Daniel Paulino Readman Chiu Shaun D. Jackman Gordon Robertson Chen Yang Brian Boyle Margarete Hoffmann Detlef Weigel David R. Nelson Carol Ritland Nathalie Isabel Barry Jaquish Alvin Yanchuk Jean Bousquet Steven J. M. Jones John MacKay Inanc Birol Joerg Bohlmann 《The Plant journal : for cell and molecular biology》2015,83(2):189-212
994.
995.
Benjamin L. S. Furman Adam J. Bewick Tia L. Harrison Eli Greenbaum Václav Gvoždík Chifundera Kusamba Ben J. Evans 《Molecular ecology》2015,24(4):909-925
The African clawed frog Xenopus laevis has a large native distribution over much of sub‐Saharan Africa and is a model organism for research, a proposed disease vector, and an invasive species. Despite its prominent role in research and abundance in nature, surprisingly little is known about the phylogeography and evolutionary history of this group. Here, we report an analysis of molecular variation of this clade based on 17 loci (one mitochondrial, 16 nuclear) in up to 159 individuals sampled throughout its native distribution. Phylogenetic relationships among mitochondrial DNA haplotypes were incongruent with those among alleles of the putatively female‐specific sex‐determining gene DM‐W, in contrast to the expectation of strict matrilineal inheritance of both loci. Population structure and evolutionarily diverged lineages were evidenced by analyses of molecular variation in these data. These results further contextualize the chronology, and evolutionary relationships within this group, support the recognition of X. laevis sensu stricto, X. petersii, X. victorianus and herein revalidated X. poweri as separate species. We also propose that portions of the currently recognized distributions of X. laevis (north of the Congo Basin) and X. petersii (south of the Congo Basin) be reassigned to X. poweri. 相似文献
996.
Spatial Intensity Distribution Analysis Reveals Abnormal Oligomerization of Proteins in Single Cells
Antoine?G. Godin Benjamin Rappaz Laurent Potvin-Trottier Timothy?E. Kennedy Yves De?Koninck Paul?W. Wiseman 《Biophysical journal》2015,109(4):710-721
Knowledge of membrane receptor organization is essential for understanding the initial steps in cell signaling and trafficking mechanisms, but quantitative analysis of receptor interactions at the single-cell level and in different cellular compartments has remained highly challenging. To achieve this, we apply a quantitative image analysis technique—spatial intensity distribution analysis (SpIDA)—that can measure fluorescent particle concentrations and oligomerization states within different subcellular compartments in live cells. An important technical challenge faced by fluorescence microscopy-based measurement of oligomerization is the fidelity of receptor labeling. In practice, imperfect labeling biases the distribution of oligomeric states measured within an aggregated system. We extend SpIDA to enable analysis of high-order oligomers from fluorescence microscopy images, by including a probability weighted correction algorithm for nonemitting labels. We demonstrated that this fraction of nonemitting probes could be estimated in single cells using SpIDA measurements on model systems with known oligomerization state. Previously, this artifact was measured using single-step photobleaching. This approach was validated using computer-simulated data and the imperfect labeling was quantified in cells with ion channels of known oligomer subunit count. It was then applied to quantify the oligomerization states in different cell compartments of the proteolipid protein (PLP) expressed in COS-7 cells. Expression of a mutant PLP linked to impaired trafficking resulted in the detection of PLP tetramers that persist in the endoplasmic reticulum, while no difference was measured at the membrane between the distributions of wild-type and mutated PLPs. Our results demonstrate that SpIDA allows measurement of protein oligomerization in different compartments of intact cells, even when fractional mislabeling occurs as well as photobleaching during the imaging process, and reveals insights into the mechanism underlying impaired trafficking of PLP. 相似文献
997.
One‐dimensional (1D) (spherically averaged) powder diffraction diagrams are commonly used to determine the degree of cellulose crystallinity in biomass samples. Here, it is shown using molecular modeling how disorder in cellulose fibrils can lead to considerable uncertainty in conclusions drawn concerning crystallinity based on 1D powder diffraction data alone. For example, cellulose microfibrils that contain both crystalline and noncrystalline segments can lead to powder diffraction diagrams lacking identifiable peaks, while microfibrils without any crystalline segments can lead to such peaks. This leads to false positives, that is, assigning disordered cellulose as crystalline, and false negatives, that is, categorizing fibrils with crystalline segments as amorphous. The reliable determination of the fraction of crystallinity in any given biomass sample will require a more sophisticated approach combining detailed experiment and simulation. © 2014 Wiley Periodicals, Inc. Biopolymers 103: 67–73, 2015. 相似文献
998.
Bioprocessing analysis of Pyrococcus furiosus strains engineered for CO2‐based 3‐hydroxypropionate production
下载免费PDF全文
![点击此处可从《Biotechnology and bioengineering》网站下载免费的PDF全文](/ch/ext_images/free.gif)
999.
Spatial analysis of Listronotus maculicollis immature stages demonstrates strong associations with conspecifics and turfgrass damage but not with optimal hosts on golf course fairways
下载免费PDF全文
![点击此处可从《Entomologia Experimentalis et Applicata》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Benjamin A. McGraw Albrecht M. Koppenhöfer 《Entomologia Experimentalis et Applicata》2015,157(3):307-316
For insects that develop on few hosts and/or have immobile immature stages, optimal oviposition theory suggests that females should seek high‐quality hosts that maximize larval development and reduce competition from conspecifics. However, there is a growing amount of evidence that suggests female choice may often be at odds with their offspring's development. Listronotus maculicollis (Kirby) (Coleoptera: Curculionidae) is a serious pest of golf course turfgrass in eastern North America. The weevil develops on few hosts and demonstrates improved fitness traits when developing on Poa annua L. (Poaceae). However, previous population studies observed either weak or no correlations between the spatial dispersion of larval populations and P. annua in the field. In this study, populations on three golf course fairways were monitored over a 4‐year period (2009–2012) to determine whether the lack of spatial associations between preferred hosts and immatures was a result of spatial scale or the density and distribution of conspecifics. Spatial Analysis by Distance IndicEs (SADIE) was used to characterize the spatial dispersion of populations of individual stages (larvae and pupae), P. annua, and turfgrass damage. Life stages were aggregated in each observation, independent of population density or the spatial dispersion of hosts. The distribution of consecutive and non‐consecutive immature stages was found to be correlated in all years, suggesting that females do not avoid patches already occupied by conspecific eggs. Surprisingly, significant spatial associations were not found between larvae and P. annua when the host plant was relatively abundant. Hence, multiple mechanisms may drive L. maculicollis oviposition site‐selection behavior, and a flexible strategy may allow the weevil to persist in areas where P. annua is not the dominant species. Future studies are required to determine what other factors (e.g., natural enemy‐free space, egg or time limitations) influence oviposition behavior. 相似文献
1000.
Benjamin M. Peter Montgomery Slatkin 《Evolution; international journal of organic evolution》2015,69(3):721-734
The gradual loss of diversity and the establishment of clines in allele frequencies associated with range expansions are patterns observed in many species, including humans. These patterns can result from a series of founder events occurring as populations colonize previously unoccupied areas. We develop a model of an expanding population and, using a branching process approximation, show that spatial gradients reflect different amounts of genetic drift experienced by different subpopulations. We then use this model to measure the net average strength of the founder effect, and we demonstrate that the predictions from the branching process model fit simulation results well. We further show that estimates of the effective founder size are robust to potential confounding factors such as migration between subpopulations. We apply our method to data from Arabidopsis thaliana. We find that the average founder effect is approximately three times larger in the Americas than in Europe, possibly indicating that a more recent, rapid expansion occurred. 相似文献