全文获取类型
收费全文 | 630282篇 |
免费 | 63613篇 |
国内免费 | 400篇 |
出版年
2018年 | 6503篇 |
2017年 | 6482篇 |
2016年 | 10134篇 |
2015年 | 15243篇 |
2014年 | 16728篇 |
2013年 | 21511篇 |
2012年 | 23206篇 |
2011年 | 21300篇 |
2010年 | 14901篇 |
2009年 | 13851篇 |
2008年 | 17481篇 |
2007年 | 18039篇 |
2006年 | 16934篇 |
2005年 | 21774篇 |
2004年 | 20425篇 |
2003年 | 17985篇 |
2002年 | 15294篇 |
2001年 | 29423篇 |
2000年 | 28656篇 |
1999年 | 23287篇 |
1998年 | 7377篇 |
1997年 | 7697篇 |
1996年 | 7064篇 |
1995年 | 6565篇 |
1994年 | 6303篇 |
1993年 | 6265篇 |
1992年 | 18609篇 |
1991年 | 17861篇 |
1990年 | 17339篇 |
1989年 | 16853篇 |
1988年 | 15501篇 |
1987年 | 14400篇 |
1986年 | 13329篇 |
1985年 | 13187篇 |
1984年 | 10622篇 |
1983年 | 8815篇 |
1982年 | 6448篇 |
1981年 | 5808篇 |
1980年 | 5479篇 |
1979年 | 9845篇 |
1978年 | 7482篇 |
1977年 | 6818篇 |
1976年 | 6187篇 |
1975年 | 6941篇 |
1974年 | 7593篇 |
1973年 | 7387篇 |
1972年 | 6749篇 |
1971年 | 6204篇 |
1970年 | 5355篇 |
1969年 | 5129篇 |
排序方式: 共有10000条查询结果,搜索用时 828 毫秒
961.
962.
Reuben S.E. Young Andrew P. Bowman Kaylyn D. Tousignant Berwyck L.J. Poad Jennifer H. Gunter Lisa K. Philp Colleen C. Nelson Shane R. Ellis Ron M.A. Heeren Martin C. Sadowski Stephen J. Blanksby 《Journal of lipid research》2022,63(6):100223
The cellular energy and biomass demands of cancer drive a complex dynamic between uptake of extracellular FAs and their de novo synthesis. Given that oxidation of de novo synthesized FAs for energy would result in net-energy loss, there is an implication that FAs from these two sources must have distinct metabolic fates; however, hitherto, all FAs have been considered part of a common pool. To probe potential metabolic partitioning of cellular FAs, cancer cells were supplemented with stable isotope-labeled FAs. Structural analysis of the resulting glycerophospholipids revealed that labeled FAs from uptake were largely incorporated to canonical (sn-) positions on the glycerol backbone. Surprisingly, labeled FA uptake also disrupted canonical isomer patterns of the unlabeled lipidome and induced repartitioning of n-3 and n-6 PUFAs into glycerophospholipid classes. These structural changes support the existence of differences in the metabolic fates of FAs derived from uptake or de novo sources and demonstrate unique signaling and remodeling behaviors usually hidden from conventional lipidomics. 相似文献
963.
Marine phytoplankton can evolve rapidly when confronted with aspects of climate change because of their large population sizes and fast generation times. Despite this, the importance of environment fluctuations, a key feature of climate change, has received little attention—selection experiments with marine phytoplankton are usually carried out in stable environments and use single or few representatives of a species, genus or functional group. Here we investigate whether and by how much environmental fluctuations contribute to changes in ecologically important phytoplankton traits such as C:N ratios and cell size, and test the variability of changes in these traits within the globally distributed species Ostreococcus. We have evolved 16 physiologically distinct lineages of Ostreococcus at stable high CO2 (1031±87 μatm CO2, SH) and fluctuating high CO2 (1012±244 μatm CO2, FH) for 400 generations. We find that although both fluctuation and high CO2 drive evolution, FH-evolved lineages are smaller, have reduced C:N ratios and respond more strongly to further increases in CO2 than do SH-evolved lineages. This indicates that environmental fluctuations are an important factor to consider when predicting how the characteristics of future phytoplankton populations will have an impact on biogeochemical cycles and higher trophic levels in marine food webs. 相似文献
964.
965.
966.
967.
968.
969.
Paracoccidioides brasiliensis Interferes on Dendritic Cells Maturation by Inhibiting PGE2 Production
Reginaldo K. Fernandes Tatiana F. Bachiega Daniela R. Rodrigues Marjorie de A. Golim Luciane A. Dias-Melicio Helanderson de A. Balderramas Ramon Kaneno ?ngela M. V. C. Soares 《PloS one》2015,10(3)
Paracoccidioidomycosis (PCM) is a systemic mycosis, endemic in most Latin American countries, especially in Brazil, whose etiologic agent is the thermodimorphic fungus of the genus Paracoccidioides, comprising cryptic species of Paracoccidioides brasiliensis, S1, PS2, PS3 and Paracoccidioides lutzii. The mechanisms involved in the initial interaction of the fungus with cells of the innate immune response, as dendritic cells (DCs), deserve to be studied. Prostaglandins (PGs) are eicosanoids that play an important role in modulating functions of immune cells including DCs. Here we found that human immature DCs derived from the differentiation of monocytes cultured with GM-CSF and IL-4 release substantial concentrations of PGE2, which, however, were significantly inhibited after challenge with P. brasiliensis. In vitro blocking of pattern recognition receptors (PRRs) by monoclonal antibodies showed the involvement of mannose receptor (MR) in PGE2 inhibition by the fungus. In addition, phenotyping assays showed that after challenge with the fungus, DCs do not change their phenotype of immature cells to mature ones, as well as do not produce IL-12 p70 or adequate concentrations of TNF-α. Assays using exogenous PGE2 confirmed an association between PGE2 inhibition and failure of cells to phenotypically mature in response to P. brasiliensis. We conclude that a P. brasiliensis evasion mechanism exists associated to a dysregulation on DC maturation. These findings may provide novel information for the understanding of the complex interplay between the host and this fungus. 相似文献
970.