全文获取类型
收费全文 | 834篇 |
免费 | 74篇 |
国内免费 | 1篇 |
出版年
2021年 | 7篇 |
2020年 | 10篇 |
2019年 | 6篇 |
2018年 | 5篇 |
2017年 | 8篇 |
2016年 | 16篇 |
2015年 | 16篇 |
2014年 | 26篇 |
2013年 | 35篇 |
2012年 | 27篇 |
2011年 | 33篇 |
2010年 | 31篇 |
2009年 | 24篇 |
2008年 | 29篇 |
2007年 | 33篇 |
2006年 | 20篇 |
2005年 | 24篇 |
2004年 | 23篇 |
2003年 | 20篇 |
2002年 | 20篇 |
2001年 | 29篇 |
2000年 | 29篇 |
1999年 | 32篇 |
1998年 | 17篇 |
1997年 | 12篇 |
1996年 | 14篇 |
1995年 | 13篇 |
1994年 | 11篇 |
1993年 | 15篇 |
1992年 | 16篇 |
1991年 | 17篇 |
1990年 | 19篇 |
1989年 | 16篇 |
1988年 | 17篇 |
1987年 | 9篇 |
1986年 | 11篇 |
1985年 | 22篇 |
1984年 | 9篇 |
1983年 | 14篇 |
1981年 | 5篇 |
1979年 | 9篇 |
1978年 | 7篇 |
1977年 | 9篇 |
1975年 | 9篇 |
1974年 | 7篇 |
1973年 | 8篇 |
1969年 | 6篇 |
1967年 | 5篇 |
1923年 | 5篇 |
1888年 | 4篇 |
排序方式: 共有909条查询结果,搜索用时 609 毫秒
31.
32.
33.
Alastair D. MacKenzie Ross Martin G. Cook Heung Chong Mehnaz Hossain Hardev S. Pandha Dorothy C. Bennett 《Pigment cell & melanoma research》2013,26(2):226-235
The best‐established function of the melanoma‐suppressor p16 is mediation of cell senescence, a permanent arrest following cell proliferation or certain stresses. The importance of p16 in melanoma suggests indolence of the other major senescence pathway through p53. Little or no p53 is expressed in senescent normal human melanocytes, but p16‐deficient melanocytes can undergo p53‐mediated senescence. As p16 expression occurs in nevi but falls with progression toward melanoma, we here investigated whether p53‐dependent senescence occurs at some stage and, if not, what defects were detectable in this pathway, using immunohistochemistry. Phosphorylated checkpoint kinase 2 (CHEK2) can mediate DNA‐damage signaling, and under some conditions senescence, by phosphorylating and activating p53. Remarkably, we detected no prevalent p53‐mediated senescence in any of six classes of lesions. Two separate defects in p53 signaling appeared common: in nevi, lack of p53 phosphorylation by activated CHEK2, and in melanomas, defective p21 upregulation by p53 even when phosphorylated. 相似文献
34.
Nicholas S. Kirkby Anne K. Zaiss Paula Urquhart Jing Jiao Philip J. Austin Malak Al-Yamani Martina H. Lundberg Louise S. MacKenzie Timothy D. Warner Anna Nicolaou Harvey R. Herschman Jane A. Mitchell 《PloS one》2013,8(7)
There are two schools of thought regarding the cyclooxygenase (COX) isoform
active in the vasculature. Using urinary prostacyclin markers some groups have
proposed that vascular COX-2 drives prostacyclin release. In contrast, we and
others have found that COX-1, not COX-2, is responsible for vascular
prostacyclin production. Our experiments have relied on immunoassays to detect
the prostacyclin breakdown product, 6-keto-PGF1α and antibodies to
detect COX-2 protein. Whilst these are standard approaches, used by many
laboratories, antibody-based techniques are inherently indirect and have been
criticized as limiting the conclusions that can be drawn. To address this
question, we measured production of prostanoids, including
6-keto-PGF1α, by isolated vessels and in the circulation
in vivo using liquid chromatography tandem mass
spectrometry and found values essentially identical to those obtained by
immunoassay. In addition, we determined expression from the
Cox2 gene using a knockin reporter mouse in which
luciferase activity reflects Cox2 gene expression. Using this
we confirm the aorta to be essentially devoid of Cox2 driven
expression. In contrast, thymus, renal medulla, and regions of the brain and gut
expressed substantial levels of luciferase activity, which correlated well with
COX-2-dependent prostanoid production. These data are consistent with the
conclusion that COX-1 drives vascular prostacyclin release and puts the sparse
expression of Cox2 in the vasculature in the context of the
rest of the body. In doing so, we have identified the thymus, gut, brain and
other tissues as target organs for consideration in developing a new
understanding of how COX-2 protects the cardiovascular system. 相似文献
35.
Schistosomiasis vector snails are subjected to extreme seasonal changes, particularly in ephemeral rivers and lentic waterbodies. In the tropics, aestivation is one of the adaptive strategies for survival and is used by snails in times of extremely high temperatures and desiccation. Aestivation therefore plays an important role in maintaining the transmission of schistosomiasis. This review assesses the possible impacts of climate change on the temporal and spatial distribution of schistosomiasis-transmitting snails with special emphasis on aestivation, and discusses the effect of schistosome infection on aestivation ability. The impacts of parasite development on snails, as well as physiological changes, are discussed with reference to schistosomiasis transmission. This review shows that schistosome-infected snails have lower survival rates during aestivation, and that those that survive manage to get rid of the infection. In general, snail aestivation ability is poor and survival chances diminish with time. Longer dry periods result in fewer, as well as uninfected, snails. However, the ability of the surviving snails to repopulate the habitats is high. 相似文献
36.
Attenuation of pattern recognition receptor signaling is mediated by a MAP kinase kinase kinase
下载免费PDF全文
![点击此处可从《EMBO reports》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Sharon C Mithoe Christina Ludwig Michiel JC Pel Mara Cucinotta Alberto Casartelli Malick Mbengue Jan Sklenar Paul Derbyshire Silke Robatzek Corné MJ Pieterse Ruedi Aebersold Frank LH Menke 《EMBO reports》2016,17(3):441-454
Pattern recognition receptors (PRRs) play a key role in plant and animal innate immunity. PRR binding of their cognate ligand triggers a signaling network and activates an immune response. Activation of PRR signaling must be controlled prior to ligand binding to prevent spurious signaling and immune activation. Flagellin perception in Arabidopsis through FLAGELLIN‐SENSITIVE 2 (FLS2) induces the activation of mitogen‐activated protein kinases (MAPKs) and immunity. However, the precise molecular mechanism that connects activated FLS2 to downstream MAPK cascades remains unknown. Here, we report the identification of a differentially phosphorylated MAP kinase kinase kinase that also interacts with FLS2. Using targeted proteomics and functional analysis, we show that MKKK7 negatively regulates flagellin‐triggered signaling and basal immunity and this requires phosphorylation of MKKK7 on specific serine residues. MKKK7 attenuates MPK6 activity and defense gene expression. Moreover, MKKK7 suppresses the reactive oxygen species burst downstream of FLS2, suggesting that MKKK7‐mediated attenuation of FLS2 signaling occurs through direct modulation of the FLS2 complex. 相似文献
37.
Fiona M. Soper Richard A. MacKenzie Sahadev Sharma Thomas G. Cole Creighton M. Litton Jed P. Sparks 《Global Change Biology》2019,25(12):4315-4326
Mangrove forests play an important role in climate change adaptation and mitigation by maintaining coastline elevations relative to sea level rise, protecting coastal infrastructure from storm damage, and storing substantial quantities of carbon (C) in live and detrital pools. Determining the efficacy of mangroves in achieving climate goals can be complicated by difficulty in quantifying C inputs (i.e., differentiating newer inputs from younger trees from older residual C pools), and mitigation assessments rarely consider potential offsets to CO2 storage by methane (CH4) production in mangrove sediments. The establishment of non‐native Rhizophora mangle along Hawaiian coastlines over the last century offers an opportunity to examine the role mangroves play in climate mitigation and adaptation both globally and locally as novel ecosystems. We quantified total ecosystem C storage, sedimentation, accretion, sediment organic C burial and CH4 emissions from ~70 year old R. mangle stands and adjacent uninvaded mudflats. Ecosystem C stocks of mangrove stands exceeded mudflats by 434 ± 33 Mg C/ha, and mangrove establishment increased average coastal accretion by 460%. Sediment organic C burial increased 10‐fold (to 4.5 Mg C ha?1 year?1), double the global mean for old growth mangrove forests, suggesting that C accumulation from younger trees may occur faster than previously thought, with implications for mangrove restoration. Simulations indicate that increased CH4 emissions from sediments offset ecosystem CO2 storage by only 2%–4%, equivalent to 30–60 Mg CO2‐eq/ha over mangrove lifetime (100 year sustained global warming potential). Results highlight the importance of mangroves as novel systems that can rapidly accumulate C, have a net positive atmospheric greenhouse gas removal effect, and support shoreline accretion rates that outpace current sea level rise. Sequestration potential of novel mangrove forests should be taken into account when considering their removal or management, especially in the context of climate mitigation goals. 相似文献
38.
Therese C. Frauendorf Richard A. MacKenzie Ralph W. Tingley Abby G. Frazier Michael H. Riney Rana W. El‐Sabaawi 《Global Change Biology》2019,25(4):1344-1357
Climate change is expected to alter precipitation patterns worldwide, which will affect streamflow in riverine ecosystems. It is vital to understand the impacts of projected flow variations, especially in tropical regions where the effects of climate change are expected to be one of the earliest to emerge. Space‐for‐time substitutions have been successful at predicting effects of climate change in terrestrial systems by using a spatial gradient to mimic the projected temporal change. However, concerns have been raised that the spatial variability in these models might not reflect the temporal variability. We utilized a well‐constrained rainfall gradient on Hawaii Island to determine (a) how predicted decreases in flow and increases in flow variability affect stream food resources and consumers and (b) if using a high temporal (monthly, four streams) or a high spatial (annual, eight streams) resolution sampling scheme would alter the results of a space‐for‐time substitution. Declines in benthic and suspended resource quantity (10‐ to 40‐fold) and quality (shift from macrophyte to leaf litter dominated) contributed to 35‐fold decreases in macroinvertebrate biomass with predicted changes in the magnitude and variability in the flow. Invertebrate composition switched from caddisflies and damselflies to taxa with faster turnover rates (mosquitoes, copepods). Changes in resource and consumer composition patterns were stronger with high temporal resolution sampling. However, trends and ranges of results did not differ between the two sampling regimes, indicating that a suitable, well‐constrained spatial gradient is an appropriate tool for examining temporal change. Our study is the first to investigate resource to community wide effects of climate change on tropical streams on a spatial and temporal scale. We determined that predicted flow alterations would decrease stream resource and consumer quantity and quality, which can alter stream function, as well as biomass and habitat for freshwater, marine, and terrestrial consumers dependent on these resources. 相似文献
39.
The ability of the wild-type XIAP BIR3 domain as well as its Trp323Ser variant in inhibition of human caspase-9, binding to AVPFVASLPN (SMAC-peptide), SMAC protein, and mature caspase-9 was investigated. In order to investigate the role of W323 on these interactions, this residue was mutated to Serine. Circular dichroism as well as thermal denaturation studies showed that W323S mutation did not hamper proper folding of the protein. The dissociation constants for the interaction of the wild type BIR3 as well as its mutant to Smac-type peptide were found to be 1.8 and 27 muM, respectively. The inhibition of and binding to caspase-9 by wild-type BIR3 and its mutant were also compared. While the wild-type protein potently inhibited the enzyme, the mutant failed to do so. The lack of caspase-9 inhibition was due to absence of interaction of the mutant BIR3 with mature caspase-9. These results indicate that Trp323 of BIR3 plays a pivotal role both in maintaining necessary conformation for caspase-9 interaction and to a lesser extent, recognition of Smac-type peptide. Moreover, decreased stability of the mutant compared with the wild type indicates that W323 is essential for maintaining the stability BIR3-Smac-peptide complex. 相似文献
40.