全文获取类型
收费全文 | 430篇 |
免费 | 38篇 |
出版年
2022年 | 1篇 |
2021年 | 8篇 |
2020年 | 7篇 |
2019年 | 3篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 15篇 |
2015年 | 22篇 |
2014年 | 20篇 |
2013年 | 25篇 |
2012年 | 24篇 |
2011年 | 26篇 |
2010年 | 20篇 |
2009年 | 17篇 |
2008年 | 34篇 |
2007年 | 27篇 |
2006年 | 22篇 |
2005年 | 25篇 |
2004年 | 15篇 |
2003年 | 29篇 |
2002年 | 21篇 |
2001年 | 6篇 |
2000年 | 6篇 |
1999年 | 9篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 2篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1976年 | 1篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1965年 | 1篇 |
1953年 | 1篇 |
1946年 | 1篇 |
排序方式: 共有468条查询结果,搜索用时 62 毫秒
181.
The interaction between the plant hormones, brassinosteroids and auxins has been documented in various processes using a variety of plants and plant parts. In this study, detached inflorescences from brassinosteroid biosynthesis and signaling Arabidopsis mutants were evaluated for their gravitropic bending in response to epibrassinolide (EBR) and indole-3-acetic acid (IAA). EBR supplied to the base of detached inflorescences stimulated gravitropic bending in all BR biosynthetic mutants but there was no effect on the BR signaling mutant or wild type plants. When IAA was supplied to the base of BR mutant inflorescences both natural and EBR-induced gravitropic bending was inhibited. Treatment with the auxin inhibitors also decreased both natural and EBR-induced gravitropic bending. No gravitropic bending was observed when the apical tips of BR mutant inflorescences were removed. IAA treatment to the tips of decapitated BR mutant inflorescences restored gravitropic bending to values observed in the inflorescences with an apical tip, however, EBR applied to the tip had no effect. When decapitated inflorescences from BR mutants were treated with IAA to the base and either gel, EBR or IAA was applied to the tip; there was no gravitropic bending. These results show that brassinosteroids have a role in the gravitropic bending response in Arabidopsis and mutants serve to uncover this hidden contributor. 相似文献
182.
Leskov IL Whitsett J Vasquez-Vivar J Stokes KY 《Free radical biology & medicine》2011,51(12):2300-2308
Primary cytomegalovirus (CMV) infection promotes oxidative stress and reduces nitric oxide (NO) bioavailability in endothelial cells. These events are among the earliest vascular responses to cardiovascular risk factors. We assessed the roles of NAD(P)H oxidase and NO bioavailability in microvascular responses to persistent CMV infection alone or with hypercholesterolemia. Wild-type (WT) or gp91phox (NAD(P)H oxidase subunit) knockout mice received mock inoculum or 3 × 104 PFU murine CMV (mCMV) ip 5 weeks before placement on a normal or high-cholesterol diet (HC) for 4 weeks before assessment of arteriolar function and venular blood cell recruitment using intravital microscopy. Some WT groups received sepiapterin (a precursor of the nitric oxide synthase cofactor tetrahydrobiopterin) or apocynin (NAD(P)H oxidase inhibitor/antioxidant). Endothelium-dependent vasodilation was impaired in mCMV vs mock WT, regardless of diet. This was not affected by sepiapterin, and pharmacological inhibition of nitric oxide synthase reduced dilation similarly in mock and mCMV mice. Apocynin or deficiency of total, but not blood cell or vascular wall only (tested using bone marrow chimeras), gp91phox protected against arteriolar dysfunction. Blood cell recruitment was induced by mCMV–HC. Sepiapterin, but not NAD(P)H oxidase deficiency/apocynin, reduced leukocyte accumulation, whereas platelet adhesion was reduced by sepiapterin, apocynin, or total, platelet-specific, or vascular wall gp91phox deficiency. These data implicate activation of both hematopoietic and vessel wall NAD(P)H oxidase in mCMV-induced arteriolar dysfunction and platelet and vascular NAD(P)H oxidase in the thrombogenic phenotype induced by mCMV–HC. In contrast, findings with sepiapterin suggest that eNOS dysfunction, perhaps uncoupling, mediates venular, but not arteriolar, responses to mCMV–HC, thus indicating that NAD(P)H oxidase and eNOS differentially regulate microvascular responses to mCMV. 相似文献
183.
184.
Scofield DG Alfaro VR Sork VL Grivet D Martinez E Papp J Pluess AR Koenig WD Smouse PE 《Oecologia》2011,166(1):187-196
Landscape characteristics and social behavior can affect the foraging patterns of seed-dependent animals. We examine the movement of acorns from valley oak (Quercus lobata) trees to granaries maintained by acorn woodpeckers (Melanerpes formicivorus) in two California oak savanna-woodlands differing in the distribution of Q. lobata within each site. In 2004, we sampled Q. lobata acorns from 16 granaries at Sedgwick Reserve in Santa Barbara County and 18 granaries at Hastings Reserve in Monterey County. Sedgwick has lower site-wide density of Q. lobata than Hastings as well as different frequencies of other Quercus species common to both sites. We found acorn woodpeckers foraged from fewer Q. lobata seed source trees (K(g) = 4.1 ± 0.5) at Sedgwick than at Hastings (K(g) = 7.6 ± 0.6) and from fewer effective seed sources (N(em)* = 2.00 and 5.78, respectively). The differences between sites are due to a greater number of incidental seed sources used per granary at Hastings than at Sedgwick. We also found very low levels of seed source sharing between adjacent granaries, indicating that territoriality is strong at both sites and that each social group forages on its own subset of trees. We discovered an interesting spatial pattern in the location of granaries. At Sedgwick, acorn woodpeckers situated their granaries within areas of higher-than-average tree density, while at Hastings, they placed them within areas of lower-than-average tree density, with the outcome that granaries at the two sites were located in areas of similar valley oak density. Our results illustrate that landscape characteristics might influence the number of trees visited by acorn woodpeckers and the locations of territories, while woodpecker social behavior, such as territoriality, shapes which trees are visited and whether they are shared with other social groups. 相似文献
185.
186.
The yeast PH domain proteins Slm1 and Slm2 are targets of sphingolipid signaling during the response to heat stress 下载免费PDF全文
The PH domain-containing proteins Slm1 and Slm2 were previously identified as effectors of the phosphatidylinositol-4,5-bisphosphate (PI4,5P(2)) and TORC2 signaling pathways. Here, we demonstrate that Slm1 and Slm2 are also targets of sphingolipid signaling during the heat shock response. We show that upon depletion of cellular sphingolipid levels, Slm1 function becomes essential for survival under heat stress. We further demonstrate that Slm proteins are regulated by a phosphorylation/dephosphorylation cycle involving the sphingolipid-activated protein kinases Pkh1 and Pkh2 and the calcium/calmodulin-dependent protein phosphatase calcineurin. By using a combination of mass spectrometry and mutational analysis, we identified serine residue 659 in Slm1 as a site of phosphorylation. Characterization of Slm1 mutants that mimic dephosphorylated and phosphorylated states demonstrated that phosphorylation at serine 659 is vital for survival under heat stress and promotes the proper polarization of the actin cytoskeleton. Finally, we present evidence that Slm proteins are also required for the trafficking of the raft-associated arginine permease Can1 to the plasma membrane, a process that requires sphingolipid synthesis and actin polymerization. Together with previous work, our findings suggest that Slm proteins are subject to regulation by multiple signals, including PI4,5P(2), TORC2, and sphingolipids, and may thus integrate inputs from different signaling pathways to temporally and spatially control actin polarization. 相似文献
187.
Daniel Laporte Jeannette Vera Nancy P. Chandía Elisa A. Zúñiga Betty Matsuhiro Alejandra Moenne 《Journal of applied phycology》2007,19(1):79-88
Tobacco plants were treated with structurally unrelated oligosaccharides obtained from Chilean marine macroalgae. These oligosaccharides
were prepared by chemical depolymerization of native polysaccharides extracted from brown and red algae and correspond to
pure polymers of around 20 units of guluronic acid (Poly-Gu), mannuronic acid (Poly-Ma) and sulphated galactan (Poly-Ga).
These oligosaccharides were solubilized in water, at a final concentration of 500 μg mL−1, and sprayed on tobacco leaves, once a week for a month. Their effects on the stimulation of growth and defense against tobacco
mosaic virus (TMV) were determined 7 and 15 days after the final spraying, respectively. The activities of several defense
and antioxidant enzymes and the levels of water-soluble antioxidant compounds were determined. Plants treated with Poly-Ga
and Poly-Ma showed an increase in height of 23% and 49%, respectively, whereas Poly-Gu did not stimulate growth. Plants treated
with Poly-Gu, Poly-Ma and Poly-Ga showed an increase in defense against TMV corresponding to decreases in the number of necrotic
lesions of 9%, 22% and 74%, respectively. The stimulation of plant growth correlates with activation of the antioxidant enzyme
ascorbate peroxidase (AP) and with a decrease in ascorbate level. On the other hand, the stimulation of defense against TMV
is correlated with the activation of the defense enzyme phenylalanine ammonia-lyase (PAL). These results indicate that algal
oligosaccharides differentially stimulate growth and defense against TMV in tobacco plants and that these processes involve
the activation of the enzymes AP and PAL, respectively. 相似文献
188.
Elevated spinal monoamine neurotransmitters after antenatal hypoxia–ischemia in rabbit cerebral palsy model 下载免费PDF全文
Alexander Drobyshevsky Silvia Honda Takada Kehuan Luo Matthew Derrick Lei Yu Katharina A. Quinlan Jeannette Vasquez‐Vivar Maria Inês Nogueira Sidhartha Tan 《Journal of neurochemistry》2015,132(4):394-402
We hypothesized that a deficiency in the descending serotonergic input to spinal cord may underlie postnatal muscle hypertonia after global antenatal hypoxic‐ischemic injury in a rabbit model of cerebral palsy. Neurotransmitter content was determined by HPLC in the spinal cord of newborns with and without muscle hypertonia after fetal global hypoxic‐ischemic brain injury and naïve controls. Contrary to our hypothesis, serotonin levels in both cervical and lumbar expansions and norepinephrine in cervical expansion were increased in hypertonic kits relative to non‐hypertonic kits and controls, with unchanged number of serotonergic cells in caudal raphe by stereological count. Serotonergic fiber length per unit of volume was also increased in hypertonic kits’ cervical and lumbar spinal cord, both in dorsal and ventral horns. Gene expression of serotonin transporter was increased and 5‐HTR2 receptors were decreased in hypertonic kits relative to controls in cervical and lumbar cord. Intrathecal administration of non‐selective serotonin receptor inhibitor methysergide decreased muscle tone in hypertonic kits only. Conversely, intrathecal administration of serotonin solution increased muscle tone only in non‐hypertonic kits. We speculate that maturation of serotonergic system in spinal cord may be directly affected by decreased corticospinal connectivity after antenatal hypoxic‐ischemic brain injury.
189.
190.
Odelia Koh Jeannette Lee Maudrene L. S. Tan E-Shyong Tai Ce Jin Foo Kok Joon Chong Su-Yen Goh Yong Mong Bee Julian Thumboo Yin-Bun Cheung Avjeet Singh Hwee-Lin Wee 《PloS one》2014,9(12)