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排序方式: 共有893条查询结果,搜索用时 171 毫秒
881.
Roderic E. Bosboom Guillaume Dupont-Nivet Alexander J.P. Houben Henk Brinkhuis Giuliana Villa Oleg Mandic Marius Stoica Willem Jan Zachariasse ZhaoJie Guo ChuanXin Li Wout Krijgsman 《Palaeogeography, Palaeoclimatology, Palaeoecology》2011,299(3-4):385-398
The Paleogene sediments of the southwest Tarim Basin along the West Kunlun Shan in western China include the remnants of the easternmost extent of a large epicontinental sea. This shallow sea once extended across the Eurasian continent before it retreated westward and eventually separated as the Paratethys Sea. Climate modeling results suggest that this sea retreat is an equally important forcing mechanism as the Tibetan plateau uplift in the aridification of the Asian continental interior and the intensification of the Asian monsoon system. The age and paleogeography of the retreat are poorly constrained, hindering the understanding of its cause and paleoenvironmental impacts. This study reports litho- and biostratigraphic results from two sections recording the last major regression out of the Tarim Basin that is expressed by a regional transition from marine clastics and limestones to continental red-beds. Rich micro- and macrofossil assemblages, including benthic foraminifera, ostracods, bivalves, calcareous nannofossils and organic walled dinoflagellate cysts (dinocysts), indicate a shallow, proximal and marine environment. Strong similarity to assemblages known from Central Asia and Europe confirms that surface–ocean connections extended across Eurasia from the Tarim Basin to the western Tethys during the latest Eocene. Moreover, the recovered fossil associations date the last marine sediments as earliest Priabonian in age (~ 37 Ma; overlap between dinoflagellate Mps Interval Zone and calcareous nannofossil Zone CP 14). The retreat of the sea from the Tarim Basin is time-equivalent with the sea level lowstand at the Bartonian–Priabonian boundary but pre-dates both the Oligocene–Miocene regional uplift of the Pamir mountains and Kunlun Shan and the major eustatic sea-level falls of the Eocene–Oligocene Transition (~ 34 Ma) and mid-Oligocene (~ 30 Ma), which are usually held responsible for the sea retreat. Furthermore, a concomitant and significant aridification step occurs at ~ 36.6 Ma (top of chron C17n.1n) as recorded by regional sedimentary records of the Xining Basin along the northeastern Tibetan Plateau, suggesting that the Tarim Sea served as a significant moisture contributor for the Asian interior. 相似文献
882.
A Klein J Branny M Sudol M Knycz C Drózd A Szuro 《Folia histochemica et cytochemica》1979,17(4):353-362
The non-dialysable sugar-peptide rich fraction of bovine blood plasma has been studied with regard to its influence on the amino acid incorporation of BHK-21 and BHK/RSV cells in vitro. The results indicate that the Nsp fraction contains a peptide factor(s) causing changes in activity for the protein and DNA synthethizing system in both the cell cultures examined. The biological activity of the factor(s) is regulated by interaction with blood serum components and this fact may play a leading role in its regulatory function. 相似文献
883.
Two serotype 1 strains ofLegionella pneumophila, Phildelphia 2 and Bellingham, were tested for their ability to metabolize five common substrates by measuring14CO2 released and14C-carbon incorporated into macromolecules. No major differences were noted between the two strains or preparations grown in
the yolk sac of chick embryos or agar-broth diphasic medium, following 2 or 14 pasaages on agar. Glutamate was the most actively
metabolized substrate, followed by glutamine. Acetate, glucose, and succinate were utilized at much more moderate rates. Changes
in cell density and substrate concentration altered the channeling of glutamate and glucose into CO2 and macromolecules. Specific CO2 felease from glutamate was greatest at low cell density and high substrate concentration, while carbon incorporation was
increased at high substrate concentration. A reciprocal relationship was noted with glucose: the proportion of carbon incorporation
was enhanced at low substrate concentration, but CO2 release paralleled increases in substrate concentration. The pH optimum for glutamate carbon incorporation and CO2 release was 5.5 and 6.1, respectively, but 25% of both activities were retained at pH 3.1. CO2 release from glucose was maximal at pH 7.5 with negligible activity at pH 3.1. Pathways of glucose metabolism were explored
by employing glucose, glucose-1-phosphate, and glucose-6-phosphate labeled in various carbon positions. The glycolytic pathway
appeared to play a lesser role than the pentose phosphate and/or Entner-Doudoroff pathways. Glucose-1-phosphate was metabolized
at a much higher rate than glucose or glucose-6-phosphate. We conclude that glutamate is utilized primarily as an energy source
while glucose may serve as an important metabolite for the nutrition ofL. pneumophila. 相似文献
884.
Marius Brazaitis Albertas Skurvydas Kazys Vadopalas Laura Daniusevičiūtė 《Journal of thermal biology》2010
The aim of this study was to investigate if voluntary activation and force variability during maximal voluntary contraction (MVC) depends more on muscle (local) or body (core) temperature. Ten volunteers performed a 2-min MVC of the knee extensors under the control (CON) conditions (ambient temperature (21 °C), relative humidity (30%), and air velocity (∼0.1 m/s)) as well as after heating (HT) and cooling (CL) of the lower body. During water manipulation procedure lower body was immersed up to the waist in a water bath at ∼44 °C for 45 min for HT experiment, and ∼15 °C for 30 min for CL experiment. Peak torque, torque variability, muscle voluntary activation and half-relaxation time were assessed during the exercise. HT increased muscle (2.8±0.2 °C) and rectal (1.9±0.1 °C) temperatures while CL lowered muscle (2.2±0.2 °C) temperature, but did not affect rectal temperature. During 2-min MVC, peak torque decreased (P<0.05; SP>90%) and to a lower level in HT compared to CON and CL experiments (52.6±2.3% versus 69.0±2.3% and 65.6±1.9% MVC, respectively, P<0.05; SP>90%). Torque variability increased significantly during exercise and was significantly larger in HT and lower in CL compared to CON experiment. Voluntary activation of exercising muscle was more depressed in HT (i.e. greater central fatigue) and the smallest effect was found in CL compared to CON. In conclusion increased core and muscle temperature impairs voluntary activation and increases force variability of the exercising muscles while a local muscle cooling decrease force variability but has a small effect on central fatigue. 相似文献
885.
886.
887.
Felix Horlamus Andreas Wittgens Philipp Noll Jan Michler Inga Müller Fabiola Weggenmann Claudia Oellig Frank Rosenau Marius Henkel Rudolf Hausmann 《Global Change Biology Bioenergy》2019,11(1):260-268
The purpose of this study was to evaluate Cellvibrio japonicus as a potential host strain for one‐step bioconversion of hemicellulose polymers to value‐added products. C. japonicus could be cultivated on all main lignocellulose monosaccharides as well as xylan polymers as a sole carbon source. This is particularly interesting as most industrially relevant bacteria are neither able to depolymerize wood polymers nor metabolize most hemicellulose monosaccharides. As a result, lignocellulose raw materials typically have to be degraded employing additional processes while the complete conversion of all lignocellulose sugars remains a challenge. Exemplary for a value‐added product, a one‐step conversion of xylan polymers to mono‐rhamnolipid biosurfactants with C. japonicus after transformation with the plasmid pSynPro8oT carrying the genes rhlAB was demonstrated. As achieved product yields in this one‐step bioconversion process are comparably low, many challenges remain to be overcome for application on an industrial scale. Nonetheless, this study provides a first step in the search for establishing a future host strain for bioeconomy, which will ideally be used for bioconversion of lignocellulose polymers with as little exhaustive pretreatment as possible. 相似文献
888.
Anke Schmidberger Marius Henkel Rudolf Hausmann Thomas Schwartz 《Applied microbiology and biotechnology》2014,98(15):6725-6737
Bioprocesses based on sustainable resources and rhamnolipids in particular have become increasingly attractive in recent years. These surface-active glycolipids with various chemical and biological properties have diverse biotechnological applications and are naturally produced by Pseudomonas aeruginosa. Their production, however, is tightly governed by a complex growth-dependent regulatory network, one of the major obstacles in the way to upscale production. P. aeruginosa PAO1 was grown in shake flask cultures using varying concentrations of ferric iron. Gene expression was assessed using quantitative PCR. A strong increase in relative expression of the genes for rhamnolipid synthesis, rhlA and rhlC, as well as the genes of the pqs quorum sensing regulon was observed under iron-limiting conditions. Iron repletion on the other hand caused a down-regulation of those genes. Furthermore, gene expression of different iron regulation-related factors, i.e. pvdS, fur and bqsS, was increased in response to iron limitation. Ensuing from these results, a batch cultivation using production medium without any addition of iron was conducted. Both biomass formation and specific growth rates were not impaired compared to normal cultivation conditions. Expression of rhlA, rhlC and pvdS, as well as the gene for the 3-oxo-C12-HSL synthetase, lasI, increased until late stationary growth phase. After this time point, their expression steadily decreased. Expression of the C4-HSL synthetase gene, rhlI, on the other hand, was found to be highly increased during the entire process. 相似文献
889.
Marijana Samardzija Andrea Corna Raquel Gomez-Sintes Mohamed Ali Jarboui Angela Armento Jerome E. Roger Eleni Petridou Wadood Haq Francois Paquet-Durand Eberhart Zrenner Pedro de la Villa Günther Zeck Christian Grimm Patricia Boya Marius Ueffing Dragana Trifunovi 《Cell death and differentiation》2021,28(4):1317
Cone photoreceptor cell death in inherited retinal diseases, such as Retinitis Pigmentosa (RP), leads to the loss of high acuity and color vision and, ultimately to blindness. In RP, a vast number of mutations perturb the structure and function of rod photoreceptors, while cones remain initially unaffected. Extensive rod loss in advanced stages of the disease triggers cone death by a mechanism that is still largely unknown. Here, we show that secondary cone cell death in animal models for RP is associated with increased activity of histone deacetylates (HDACs). A single intravitreal injection of an HDAC inhibitor at late stages of the disease, when the majority of rods have already degenerated, was sufficient to delay cone death and support long-term cone survival in two mouse models for RP, affected by mutations in the phosphodiesterase 6b gene. Moreover, the surviving cones remained light-sensitive, leading to an improvement in visual function. RNA-seq analysis of protected cones demonstrated that HDAC inhibition initiated multi-level protection via regulation of different pro-survival pathways, including MAPK, PI3K-Akt, and autophagy. This study suggests a unique opportunity for targeted pharmacological protection of secondary dying cones by HDAC inhibition and creates hope to maintain vision in RP patients even in advanced disease stages.Subject terms: Neuroscience, Neurological disorders 相似文献
890.
Marius Mihăşan 《Biologia》2010,65(5):760-768
Based on similarity searches, two putative pathways were previously described as being encoded by the pAO1 megaplasmid of
Arthrobacter nicotinovorans: an almost fully established nicotine-degrading pathway and a yet unknown putative sugar-catabolic pathway. The general organization
of the open reading frames (ORFs) of the latter indicated possible gene products as targets for docking experiments, aimed
at identifying possible sugar substrates of this pathway. Homology modelling and docking results with the deduced proteins
of three ORFs of the putative sugar catabolic pathway indicated D-tagatose-1,6-bisphosphate as a common ligand and thus as
substrate of the pathway. 相似文献