全文获取类型
收费全文 | 288篇 |
免费 | 30篇 |
专业分类
318篇 |
出版年
2024年 | 4篇 |
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 5篇 |
2015年 | 11篇 |
2014年 | 10篇 |
2013年 | 15篇 |
2012年 | 17篇 |
2011年 | 14篇 |
2010年 | 7篇 |
2009年 | 15篇 |
2008年 | 13篇 |
2007年 | 10篇 |
2006年 | 13篇 |
2005年 | 14篇 |
2004年 | 13篇 |
2003年 | 16篇 |
2002年 | 12篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 7篇 |
1998年 | 2篇 |
1997年 | 9篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 8篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1983年 | 5篇 |
1980年 | 2篇 |
1979年 | 8篇 |
1977年 | 5篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1971年 | 1篇 |
1968年 | 1篇 |
1966年 | 2篇 |
1963年 | 1篇 |
1953年 | 1篇 |
排序方式: 共有318条查询结果,搜索用时 15 毫秒
311.
312.
313.
Yuanyuan Feng Michael Y. Roleda Evelyn Armstrong Tina C. Summerfield Cliff S. Law Catriona L. Hurd Philip W. Boyd 《Global Change Biology》2020,26(10):5630-5645
Ongoing ocean global change due to anthropogenic activities is causing multiple chemical and physical seawater properties to change simultaneously, which may affect the physiology of marine phytoplankton. The coccolithophore Emiliania huxleyi is a model species often employed in the study of the marine carbon cycle. The effect of ocean acidification (OA) on coccolithophore calcification has been extensively studied; however, physiological responses to multiple environmental drivers are still largely unknown. Here we examined two‐way and multiple driver effects of OA and other key environmental drivers—nitrate, phosphate, irradiance, and temperature—on the growth, photosynthetic, and calcification rates, and the elemental composition of E. huxleyi. In addition, changes in functional gene expression were examined to understand the molecular mechanisms underpinning the physiological responses. The single driver manipulation experiments suggest decreased nitrate supply being the most important driver regulating E. huxleyi physiology, by significantly reducing the growth, photosynthetic, and calcification rates. In addition, the interaction of OA and decreased nitrate supply (projected for year 2100) had more negative synergistic effects on E. huxleyi physiology than all other two‐way factorial manipulations, suggesting a linkage between the single dominant driver (nitrate) effects and interactive effects with other drivers. Simultaneous manipulation of all five environmental drivers to the conditions of the projected year 2100 had the largest negative effects on most of the physiological metrics. Furthermore, functional genes associated with inorganic carbon acquisition (RubisCO, AEL1, and δCA) and calcification (CAX3, AEL1, PATP, and NhaA2) were most downregulated by the multiple driver manipulation, revealing linkages between responses of functional gene expression and associated physiological metrics. These findings together indicate that for more holistic projections of coccolithophore responses to future ocean global change, it is necessary to understand the relative importance of environmental drivers both individually (i.e., mechanistic understanding) and interactively (i.e., cumulative effect) on coccolithophore physiology. 相似文献
314.
The molecular organization of the beta-globin complex of the deer mouse, Peromyscus maniculatus 总被引:1,自引:0,他引:1
Padgett RW; Loeb DD; Snyder LR; Edgell MH; Hutchison CA d 《Molecular biology and evolution》1987,4(1):30-45
Recombinant DNA clones have been isolated that contain 80 kb of the
beta-globin complex from the deer mouse, Peromyscus maniculatus.
Comparisons of this complex with that from the laboratory mouse, Mus
domesticus (with an order 5'-Hbby, Hbb-bhO, Hbb-bhl, Hbb-bh2, Hbb-bh3,
Hbb-bl, Hbb-b2 3') highlight organizational trends in the beta-globin
complex since the two species diverged. Unlike other mammals studied thus
far, the deer mouse possesses three adult genes. Partial sequence analysis
indicates that each of the three adult genes is intact and hence may be
functional. Hybridization of one of the two Mus pseudogenes, Hbb-bh3, to
genomic blots from Peromyscus reveals that it has a homologous counterpart
in Peromyscus. Homologous genes to the two gamma-like Mus genes, Hbb-bhO
and Hbb-bhl, are also found in Peromyscus. The strong hybridization between
the Hbb-bhl genes and significant nucleotide similarity between the Hbb-bhO
genes suggest that both pairs are important for the ontogeny of these mice
although no known product has been identified for the Hbb-bhO genes. The
presence of Hbb-bhO and Hbb-bhl in Peromyscus suggests that the duplication
that created this related gene set occurred before the two lineages
diverged. A single gene for Hbb-y has been isolated from Peromyscus. The
adult region in Peromyscus has undergone significant divergence from the
same region in Mus, having three rather than two adult genes, the
acquisition of at least 15 kb of extra DNA relative to Mus, and possibly
the loss of the Hbb-bh2 pseudogene. The nonadult region of the complex, in
contrast, contains the same set of genes apparently distributed over the
same amount of DNA as in the Mus beta- globin complex. This observation
suggests that the embryonic region of the complex is more evolutionarily
stable than the adult region.
相似文献
315.
Formation of cluster roots and mycorrhizal status of Comptonia peregrina and Myrica pensylvanica in Maine, USA 总被引:1,自引:0,他引:1
Extent of cluster (proteoid) root formation in the field was examined in relation to availability of P and successional status of the site in two actinorhizal, N2 -fixing shrubs. Comptonia peregrina (L.) Coult. and Myrica pensylvanica Loisel. In C. peregrina cluster roots were present at all 13 sites and comprised between 0.2 and 19% of total fine root dry weight. Cluster root formation was most extensive at recently disturbed sites and was negatively correlated with cover of associated woody species (r =−0.85), litter depth (r =−0.81) and available (extractable) soil P (r =−0.75). In M. pensylvanica cluster roots were present at all 11 sites and comprised between 6 and 20% of total fine root dry weight. On mineral soils (n = 6), extent of cluster root formation was negatively correlated (r =−0.86) with cover of associated woody species and with litter depth (r =−0.78; P = 0.07). Comptonia peregrina and M. pensylvanica lack functional mycorrhizae at these sites because only intracellular infections were found and these lacked arbuscules. None of 22 non-N2 -fixing, dominant woody species associated with C. peregrina and M. pensylvanica formed cluster roots. Cluster roots probably allow C. peregrina and M. pensylvanica to obtain sufficient P from nutrient-poor soils in the absence of functional mycorrhizae. Extensive cluster root formation on disturbed, early successional sites may aid these species in colonizing these sites because they have to form only one symbiosis (with Frankia ) and not two (with Frankia and a mycorrhizal fungus). 相似文献
316.
317.
318.
Transpiration rates of potted spray carnation plants Cerise Royalette decreased about 0.04% per vpm CO2 between ambient atmospheric CO2 concentration and 1500 vpm CO2 at several light flux densities and leaf temperatures. Measurements of daily water losses of potted spray carnation plants placed under high solar radiation conditions in two minigreenhouses with 300 and 5000 vpm CO2 demonstrated that elevated CO2 concentrations reduced water losses by 20–30%. The effect of the increase in global CO2 concentration on stomatal closure was calculated to have decreased the yearly transpiration rate of an outdoor crop by 1.6% in this century and is expected to cause a decrease of 10% within the next 50 years if all other factors remain unchanged. From a model of CO2 uptake of carnation plants it was calculated that the expected water use efficiency (net photosynthesis rate/transpiration rate) will increase by about 40–50% over the next 50 years due to the expected increase in global CO2 concentration.Contribution No. 205-E, 1979 series.Presented at the Eighth International Congress of Biometeorology 8–14 September 1979, Shefayim, Israel. 相似文献