全文获取类型
收费全文 | 506篇 |
免费 | 35篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 16篇 |
2021年 | 17篇 |
2020年 | 12篇 |
2019年 | 7篇 |
2018年 | 11篇 |
2017年 | 11篇 |
2016年 | 22篇 |
2015年 | 35篇 |
2014年 | 38篇 |
2013年 | 37篇 |
2012年 | 35篇 |
2011年 | 32篇 |
2010年 | 28篇 |
2009年 | 16篇 |
2008年 | 30篇 |
2007年 | 24篇 |
2006年 | 15篇 |
2005年 | 22篇 |
2004年 | 22篇 |
2003年 | 11篇 |
2002年 | 19篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1998年 | 8篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 7篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1977年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1968年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有541条查询结果,搜索用时 15 毫秒
501.
502.
Devaleena S. Pradhan Tessa K. Solomon-Lane Madelyne C. Willis Matthew S. Grober 《Proceedings. Biological sciences / The Royal Society》2014,281(1786)
While systemic steroid hormones are known to regulate reproductive behaviour, the actual mechanisms of steroidal regulation remain largely unknown. Steroidogenic enzyme activity can rapidly modulate social behaviour by influencing neurosteroid production. In fish, the enzyme 11β-hydroxysteroid dehydrogenase (11β-HSD) synthesizes 11-ketotestosterone (KT, a potent teleost androgen) and deactivates cortisol (the primary teleost glucocorticoid), and both of these steroid hormones can regulate behaviour. Here, we investigated the role of neurosteroidogenesis in regulating parenting in a haremic bidirectionally hermaphroditic fish, Lythrypnus dalli, where males provide all requisite parental care. Using an in vitro assay, we found that an 11β-HSD inhibitor, carbenoxolone (CBX), reduced brain and testicular KT synthesis by 90% or more. We modulated neurosteroid levels in parenting males via intracerebroventricular injection of CBX. Within only 20 min, CBX transiently eliminated parenting behaviour, but not other social behaviour, suggesting an enzymatic mechanism for rapid neurosteroidal regulation of parenting. Consistent with our proposed mechanism, elevating KT levels rescued parenting when paired with CBX, while cortisol alone did not affect parenting. Females paired with the experimental males opportunistically consumed unattended eggs, which reduced male reproductive success by 15%, but some females also exhibited parenting behaviour and these females had elevated brain KT. Brain KT levels appear to regulate the expression of parenting behaviour as a result of changes in neural 11β-HSD activity. 相似文献
503.
Alissa D. Guarnaccia Kristie L. Rose Jing Wang Bin Zhao Tessa M. Popay Christina E. Wang Kiana Guerrazzi Salisha Hill Chase M. Woodley Tyler J. Hansen Shelly L. Lorey J. Grace Shaw William G. Payne April M. Weissmiller Edward T. Olejniczak Stephen W. Fesik Qi Liu William P. Tansey 《Cell reports》2021,34(3):108636
504.
505.
506.
507.
Tessa Richards 《BMJ (Clinical research ed.)》2008,336(7658):1408
508.
Injection of a silicon rubber compound has been used to demonstrate the microvascular architecture of various tissues and organs (Reynolds 1968, Cortel 1969, Beeuwkes 1971, Beeuwkes and Bonventre 1975, Plyley and Groom 1975). 相似文献
509.
Ellie Bergstrom Jelle Lahnstein Helen Collins Tessa M. Page Vincent Bulone Guillermo Diaz-Pulido 《Journal of phycology》2023,59(1):111-125
Crustose coralline algae (CCA) are one of the most important benthic substrate consolidators on coral reefs through their ability to deposit calcium carbonate on an organic matrix in their cell walls. Discrete polysaccharides have been recognized for their role in biomineralization, yet little is known about the carbohydrate composition of organic matrices across CCA taxa and whether they have the capacity to modulate their organic matrix constituents amidst environmental change, particularly the threats of ocean acidification (OA) and warming. We simulated elevated pCO2 and temperature (IPCC RCP 8.5) and subjected four mid-shelf Great Barrier Reef species of CCA to 2 months of experimentation. To assess the variability in surficial monosaccharide composition and biomineralization across species and treatments, we determined the monosaccharide composition of the polysaccharides present in the cell walls of surficial algal tissue and quantified calcification. Our results revealed dissimilarity among species' monosaccharide constituents, which suggests that organic matrices are composed of different polysaccharides across CCA taxa. We also observed that species differentially modulate composition in response to ocean acidification and warming. Our findings suggest that both variability in composition and ability to modulate monosaccharide abundance may play a crucial role in surficial biomineralization dynamics under the stress of OA and global warming. 相似文献
510.
Erin R. Ricketts James P. Kennett Tessa M. Hill James P. Barry 《Marine Micropaleontology》2009,72(3-4):165-175
Deep-sea sequestration of CO2 is being considered as a possible mitigation tool to decrease atmospheric CO2 concentrations and its associated negative effects. This study investigated potential effects of liquid carbon dioxide (CO2) injection on deep-sea foraminiferal assemblages. Foraminifera are ideal for this ecological impact investigation because of differing test composition (calcareous and non-calcareous) and thickness, and diverse epifaunal and infaunal depth preferences. The experiment was conducted on August–September 2003, at 3600 m off the coast of Monterey Bay, California, aboard the R/V Western Flyer using the ROV Tiburon. The pH of the site was monitored throughout the experiment. Sediment push-cores were collected (both from the experimental and control sites) and stained to distinguish live (stained) from dead (unstained) individuals. Effects of CO2 injection on assemblages have been tracked both vertically (to 10 cm depth below sea floor) and horizontally (up to 10 m from CO2 injection sites), as well as between live and dead individuals. Within corrals (containing the injected CO2) and their underlying sediments, severe pH changes (near 4.0 units) were recorded. This compares with a record of small average reductions in ocean pH (− 0.05 units) combined with large episodic excursions (− 1.7 units) over the experimental area due to the injection of CO2. Exposure to this gradient of low pH caused increased mortality and dissolution of calcareous forms within corrals, as far as 5 m from the injection site, and to at least 10 cm depth in the sediments.This experiment revealed several major effects of CO2 injection on foraminiferal assemblages in surficial sediments: 1) total number of foraminifera in a sample decreases; 2) foraminiferal species richness decreases in both stained and unstained specimens; and 3) relative percentage of stained (live) forms in the remaining tests increases. Down-core trends (to 10 cm below sea floor) have revealed: 1) percent agglutinated forms decline and calcareous forms increase with depth; 2) agglutinated species richness decreases with depth; and 3) experimental core assemblages become increasingly similar with depth to those in control cores not subjected to CO2 injection. These results imply almost complete initial mortality and dissolution in the upper 10 cm throughout the corrals following liquid CO2 injection. Since calcareous foraminifera represent more than 50% of the total assemblages, this clearly indicates that emplacement of CO2 will result in negative effects to diversity and survivorship of the deep-sea benthic meiofauna. 相似文献