全文获取类型
收费全文 | 1961篇 |
免费 | 170篇 |
出版年
2023年 | 8篇 |
2022年 | 33篇 |
2021年 | 57篇 |
2020年 | 33篇 |
2019年 | 43篇 |
2018年 | 50篇 |
2017年 | 38篇 |
2016年 | 74篇 |
2015年 | 118篇 |
2014年 | 127篇 |
2013年 | 129篇 |
2012年 | 185篇 |
2011年 | 166篇 |
2010年 | 112篇 |
2009年 | 80篇 |
2008年 | 117篇 |
2007年 | 112篇 |
2006年 | 98篇 |
2005年 | 95篇 |
2004年 | 102篇 |
2003年 | 71篇 |
2002年 | 69篇 |
2001年 | 21篇 |
2000年 | 10篇 |
1999年 | 26篇 |
1998年 | 18篇 |
1997年 | 16篇 |
1996年 | 12篇 |
1995年 | 11篇 |
1994年 | 13篇 |
1993年 | 6篇 |
1992年 | 8篇 |
1991年 | 7篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1975年 | 2篇 |
1974年 | 5篇 |
1973年 | 3篇 |
1966年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有2131条查询结果,搜索用时 515 毫秒
41.
Kathleen B?rner Dominik Niopek Gabriella Cotugno Michaela Kaldenbach Teresa Pankert Joschka Willemsen Xian Zhang Nina Schürmann Stefan Mockenhaupt Andrius Serva Marie-Sophie Hiet Ellen Wiedtke Mirco Castoldi Vytaute Starkuviene Holger Erfle Daniel F. Gilbert Ralf Bartenschlager Michael Boutros Marco Binder Konrad Streetz Hans-Georg Kr?usslich Dirk Grimm 《Nucleic acids research》2013,41(21):e199
As the only mammalian Argonaute protein capable of directly cleaving mRNAs in a small RNA-guided manner, Argonaute-2 (Ago2) is a keyplayer in RNA interference (RNAi) silencing via small interfering (si) or short hairpin (sh) RNAs. It is also a rate-limiting factor whose saturation by si/shRNAs limits RNAi efficiency and causes numerous adverse side effects. Here, we report a set of versatile tools and widely applicable strategies for transient or stable Ago2 co-expression, which overcome these concerns. Specifically, we engineered plasmids and viral vectors to co-encode a codon-optimized human Ago2 cDNA along with custom shRNAs. Furthermore, we stably integrated this Ago2 cDNA into a panel of standard human cell lines via plasmid transfection or lentiviral transduction. Using various endo- or exogenous targets, we demonstrate the potential of all three strategies to boost mRNA silencing efficiencies in cell culture by up to 10-fold, and to facilitate combinatorial knockdowns. Importantly, these robust improvements were reflected by augmented RNAi phenotypes and accompanied by reduced off-targeting effects. We moreover show that Ago2/shRNA-co-encoding vectors can enhance and prolong transgene silencing in livers of adult mice, while concurrently alleviating hepatotoxicity. Our customizable reagents and avenues should broadly improve future in vitro and in vivo RNAi experiments in mammalian systems. 相似文献
42.
Michaela Ecker Hervé Bocherens Marie-Anne Julien Florent Rivals Jean-Paul Raynal Marie-Hélène Moncel 《Journal of human evolution》2013
The Middle Palaeolithic site of Payre in southeastern France yields abundant archaeological material associated with fossil hominid remains. With its long sequence of Middle Pleistocene deposits, Payre is a key site to study the Middle Palaeolithic chronology of this region. This study is the first to investigate carbon and oxygen isotope contents of Neanderthal tooth enamel bioapatite, together with a wide range of herbivorous and carnivorous species. The aim is to contribute to the understanding of hunting behaviour, resource partitioning, diet and habitat use of animals and Neanderthals through a palaeoecological reconstruction. 相似文献
43.
Formaldehyde is endogenously produced in the human body and brain levels of this compound are elevated in neurodegenerative conditions. Although the toxic potential of an excess of formaldehyde has been studied, little is known on the molecular mechanisms underlying its neurotoxicity as well as on the ability of neurons to metabolize formaldehyde. To address these topics, we have used cerebellar granule neuron cultures as model system. These cultures express mRNAs of various enzymes that are involved in formaldehyde metabolism and were remarkably resistant toward acute formaldehyde toxicity. Cerebellar granule neurons metabolized formaldehyde with a rate of around 200 nmol/(h × mg) which was accompanied by significant increases in the cellular and extracellular concentrations of formate. In addition, formaldehyde application significantly increased glucose consumption, almost doubled the rate of lactate release from viable neurons and strongly accelerated the export of the antioxidant glutathione. The latter process was completely prevented by inhibition of the known glutathione exporter multidrug resistance protein 1. These data indicate that cerebellar granule neurons are capable of metabolizing formaldehyde and that the neuronal glycolysis and glutathione export are severely affected by the presence of formaldehyde. 相似文献
44.
45.
Sina Berger Inyoung Jang Juyoung Seo Hojeong Kang Gerhard Gebauer 《Biogeochemistry》2013,115(1-3):317-332
Rice is staple food of half of mankind and paddy soils account for the largest anthropogenic wetlands on earth. Ample of research is being done to find cultivation methods under which the integrative greenhouse effect caused by emitted CH4 and N2O would be mitigated. Whereas most of the research focuses on quantifying such emissions, there is a lack of studies on the biogeochemistry of paddy soils. In order to deepen our mechanistic understanding of N2O and CH4 fluxes in rice paddies, we also determined NO3 ? and N2O concentrations as well as N2O isotope abundances and presence of O2 along soil profiles of paddies which underwent three different water managements during the rice growing season(s) in (2010 and) 2011 in Korea. Largest amounts of N2O (2 mmol m?2) and CH4 (14.5 mol m?2) degassed from the continuously flooded paddy, while paddies with less flooding showed 30–60 % less CH4 emissions and very low to negative N2O balances. In accordance, the global warming potential (GWP) was lowest for the Intermittent Irrigation paddy and highest for the Traditional Irrigation paddy. The N2O emissions could the best be explained (*P < 0.05) with the δ15N values and N2O concentrations in 40–50 cm soil depth, implying that major N2O production/consumption occurs there. No significant effect of NO3 ? on N2O production has been found. Our study gives insight into the soil of a rice paddy and reveals areas along the soil profile where N2O is being produced. Thereby it contributes to our understanding of subsoil processes of paddy soils. 相似文献
46.
Petr Veselý Dana Luhanová Michaela Prášková Roman Fuchs 《Ethology : formerly Zeitschrift fur Tierpsychologie》2013,119(2):138-145
Current research of imperfect mimicry brings ambiguous results. Experiments simulating more natural conditions rather than laboratory experiments show lower willingness of avian predators to attack less perfect mimics. We decided to simulate a natural situation by testing responses of wild‐caught adult avian predators (Great tit – Parus major) to variously perfect mimics of the red firebug (Pyrrhocoris apterus), which were in previous studies shown to elicit avoidance in Great tits. Presented mimics were perfect in all traits (firebug with its own colour pattern), imperfect in colour pattern (firebug with modified colour pattern), perfect in colour pattern, but imperfect in other visual traits (cockroach with firebug colour pattern), and imperfect in colour pattern as well as in other visual traits (cockroach with modified colour patterns). Modification of the pattern focused on the rounded spots on firebug's hemielytra, which is a conspicuous trait within the pattern. The pattern modification had no influence on the number of birds attacking the prey; nevertheless, birds spent more time observing the cockroaches that displayed the perfect firebug colour pattern than in the case of any other prey. Moreover, firebugs that displayed the perfect firebug colour pattern were observed for the shortest time (equal to that of the model – unmodified firebug). Cockroaches were attacked more often than firebugs, which suggest that birds were able to use additional visual cues (shape of legs and antennae) in prey recognition. Given these result, we conclude that differences in morphological traits characteristic for used prey taxa (true bugs, cockroaches) seem to be more important in the prey's protection than its colour pattern. 相似文献
47.
Daniela Morick Michaela Schatz Raphael Hubrich Helen Hoffmeister Anya Krefft Ralph Witzgall Claudia Steinem 《Biochemical and biophysical research communications》2013
Polycystin-2 (PC2) trafficking has been proposed to be a result of the interaction of PIGEA14 with PC2 as a function of the phosphorylation state of PC2. Here, we investigated the interaction of PIGEA14 with the C-terminal part of polycystin-2 wild type (cPC2wt) and the pseudophosphorylated mutant (cPC2S812D) to first, quantify the binding affinity between cPC2 and PIGEA14 and second, to elucidate the influence of PC2 phosphorylation on PIGEA14 binding. Solid supported membranes composed of octanethiol/1,2-dioleoyl-sn-glycero-3-phosphocholine doped with the receptor lipid DOGS–NTA–Ni were used to attach PIGEA14 to the membrane via its hexahistidine tag. By means of the quartz crystal microbalance technique, binding affinities as well as kinetic constants of the interaction were extracted in a label-free manner by applying the scaled particle theory. The results show that the dissociation constant of cPC2 to PIGEA14 is in the 10 nM regime providing strong evidence of a very specific interaction of cPC2 with PIGEA14. The interaction of cPC2wt is twofold larger than that of cPC2S812D. The moderate higher binding affinity of cPC2wt to PIGEA14 is discussed in light of PC2 trafficking to the plasma membrane. 相似文献
48.
Tibor Maliar Mária Maliarová Ján Kraic Miroslav Ondrejovič Ivana Pšenáková Michaela Havrlentová 《Biologia》2013,68(1):99-104
Beneficial effects of whole grains of cereals and pseudocereals and their fractions to human physiology are well known and broadly published. Especially secondary metabolites, dominantly from the category of phenolics (or polyphenols), beneficially influence the health physiology and/or prevent disease progress. Within the frame of this study, ten genotypes of four cereals or pseudocereals, respectively, were chosen for their antioxidant activity, determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP) and β-carotene-linoleic acid bleaching model (BCLM) mechanisms. Tested genotypes were selected from primary collection based on their antioxidant activity values, as well as higher level of flavonoids or phenolic acids. The stability of antioxidant properties after thermic, acidic, and basic treatments was evaluated. The oat cultivar Sirene and buckwheat cultivar Bogatyr expressed high level of the antioxidant activity, but they lost it due to all types of treatment. Oppositely, treatments increased antioxidant activities in some samples, especially in oat cultivar Maris Oberon, wheat cultivar Ines and Karolinum, or partially in barley cultivars Kompakt (after basic treatment) and Jubilant (acidic and basic treatments). The lack of the antioxidant activity could be observed due to destruction of the key compounds responsible for the antioxidant effect, whereas the increasing activity could be seen due to release of the aglycons from glycosidic forms after treatment. The stability of antioxidant properties could be a valuable parameter of the raw material for manufacturing special foods with functional properties. 相似文献
49.
50.
Elizabeth Bilsland Andrew Sparkes Kevin Williams Harry J. Moss Michaela de Clare P?nar Pir Jem Rowland Wayne Aubrey Ron Pateman Mike Young Mark Carrington Ross D. King Stephen G. Oliver 《Open biology》2013,3(2)
We have developed a robust, fully automated anti-parasitic drug-screening method that selects compounds specifically targeting parasite enzymes and not their host counterparts, thus allowing the early elimination of compounds with potential side effects. Our yeast system permits multiple parasite targets to be assayed in parallel owing to the strains’ expression of different fluorescent proteins. A strain expressing the human target is included in the multiplexed screen to exclude compounds that do not discriminate between host and parasite enzymes. This form of assay has the advantages of using known targets and not requiring the in vitro culture of parasites. We performed automated screens for inhibitors of parasite dihydrofolate reductases, N-myristoyltransferases and phosphoglycerate kinases, finding specific inhibitors of parasite targets. We found that our ‘hits’ have significant structural similarities to compounds with in vitro anti-parasitic activity, validating our screens and suggesting targets for hits identified in parasite-based assays. Finally, we demonstrate a 60 per cent success rate for our hit compounds in killing or severely inhibiting the growth of Trypanosoma brucei, the causative agent of African sleeping sickness. 相似文献