全文获取类型
收费全文 | 525篇 |
免费 | 27篇 |
专业分类
552篇 |
出版年
2023年 | 4篇 |
2022年 | 11篇 |
2021年 | 12篇 |
2020年 | 10篇 |
2019年 | 9篇 |
2018年 | 14篇 |
2017年 | 4篇 |
2016年 | 16篇 |
2015年 | 14篇 |
2014年 | 29篇 |
2013年 | 31篇 |
2012年 | 38篇 |
2011年 | 22篇 |
2010年 | 20篇 |
2009年 | 11篇 |
2008年 | 17篇 |
2007年 | 19篇 |
2006年 | 16篇 |
2005年 | 13篇 |
2004年 | 12篇 |
2003年 | 10篇 |
2002年 | 16篇 |
2001年 | 15篇 |
2000年 | 18篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 7篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1987年 | 3篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1979年 | 13篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1975年 | 6篇 |
1974年 | 5篇 |
1972年 | 3篇 |
1971年 | 3篇 |
1970年 | 6篇 |
1967年 | 4篇 |
1966年 | 5篇 |
1962年 | 3篇 |
排序方式: 共有552条查询结果,搜索用时 0 毫秒
541.
Maryam Zarepour Kristina Simon Moritz Wilch Ute Niel?nder Tomokazu Koshiba Mitsunori Seo Thomas Lindel Florian Bittner 《Plant molecular biology》2012,80(6):659-671
Plant aldehyde oxidases (AOs) have gained great attention during the last years as they catalyze the last step in the biosynthesis of the phytohormone abscisic acid by oxidation of abscisic aldehyde. Furthermore, oxidation of indole-3-acetaldehyde by AOs is likely to represent one route to produce another phytohormone, indole-3-acetic acid, and thus, AOs play important roles in many aspects of plant growth and development. In the present work we demonstrate that heterologously expressed AAO1 and AAO3, two prominent members of the AO family from Arabidopsis thaliana, do not only generate hydrogen peroxide but also superoxide anions by transferring aldehyde-derived electrons to molecular oxygen. In support of this, superoxide production has also been found for native AO proteins in Arabidopsis leaf extracts. In addition to their aldehyde oxidation activity, AAO1 and AAO3 were found to exhibit NADH oxidase activity, which likewise is associated with the production of superoxide anions. According to these results and due to the fact that molecular oxygen is the only known physiological electron acceptor of AOs, the production of hydrogen peroxide and/or superoxide has to be considered in any physiological condition in which aldehydes or NADH serve as substrate for AOs. In this respect, conditions such as natural senescence and stress-induced stomatal movement, which both require simultaneously elevated levels of abscisic acid and hydrogen peroxide/superoxide, are likely to benefit from AOs in two ways, namely by formation of abscisic acid and by concomitant formation of reactive oxygen species. 相似文献
542.
Önder Gürcan Kemal S. Türker Jean-Pierre Mano Carole Bernon Oğuz Dikenelli Pierre Glize 《Journal of computational neuroscience》2014,36(2):235-257
We present a novel computational model that detects temporal configurations of a given human neuronal pathway and constructs its artificial replication. This poses a great challenge since direct recordings from individual neurons are impossible in the human central nervous system and therefore the underlying neuronal pathway has to be considered as a black box. For tackling this challenge, we used a branch of complex systems modeling called artificial self-organization in which large sets of software entities interacting locally give rise to bottom-up collective behaviors. The result is an emergent model where each software entity represents an integrate-and-fire neuron. We then applied the model to the reflex responses of single motor units obtained from conscious human subjects. Experimental results show that the model recovers functionality of real human neuronal pathways by comparing it to appropriate surrogate data. What makes the model promising is the fact that, to the best of our knowledge, it is the first realistic model to self-wire an artificial neuronal network by efficiently combining neuroscience with artificial self-organization. Although there is no evidence yet of the model’s connectivity mapping onto the human connectivity, we anticipate this model will help neuroscientists to learn much more about human neuronal networks, and could also be used for predicting hypotheses to lead future experiments. 相似文献
543.
Dario Kremer Ivna Dragojević Müller Valerija Dunkić Dubravka Vitali Edith Stabentheiner Andreas Oberländer Nada Bezić Ivan Kosalec 《Central European Journal of Biology》2012,7(5):941-947
Chemical composition of the essential oil (analysed by GC-FID and GC-MS), the content of macroelements and trace elements (analysed by ICP-AES), and antimicrobial activities were investigated in Teucrium arduini L. from Mt Biokovo (Croatia). Additionally, a study on the types and distribution of glandular trichomes which produce essential oils was investigated. The oil was characterized by a high concentration of sesquiterpene hydrocarbons (68.5%) of which β-caryophyllene (32.9%) and germacrene D (16.4%) being the major compounds. Among the macroelements, the content of calcium was the highest (9772 mg/kg), while the content of sodium was the smallest (117.74 mg/kg). Among the micronutrients, the most represented element was iron (72.07 mg/kg). The content of each investigated toxic metal (As, Hg, Pb, Cd and Cr) was below permissible levels. The essential oils showed antimicrobial activity against bacterial species tested, with MIC values ranging from 6.25 mg/mL to 37.50 mg/mL. Fungal species were susceptible with MIC values from 7.81 mg/mL and 25.00 mg/mL. 相似文献
544.
Jos Manuel Ugalde Philippe Fuchs Thomas Nietzel Edoardo A Cutolo Maria Homagk Ute C Vothknecht Loreto Holuigue Markus Schwarzlnder Stefanie J Müller-Schüssele Andreas J Meyer 《Plant physiology》2021,186(1):125
Metabolic fluctuations in chloroplasts and mitochondria can trigger retrograde signals to modify nuclear gene expression. Mobile signals likely to be involved are reactive oxygen species (ROS), which can operate protein redox switches by oxidation of specific cysteine residues. Redox buffers, such as the highly reduced glutathione pool, serve as reservoirs of reducing power for several ROS-scavenging and ROS-induced damage repair pathways. Formation of glutathione disulfide and a shift of the glutathione redox potential (EGSH) toward less negative values is considered as hallmark of several stress conditions. Here we used the herbicide methyl viologen (MV) to generate ROS locally in chloroplasts of intact Arabidopsis (Arabidopsis thaliana) seedlings and recorded dynamic changes in EGSH and H2O2 levels with the genetically encoded biosensors Grx1-roGFP2 (for EGSH) and roGFP2-Orp1 (for H2O2) targeted to chloroplasts, the cytosol, or mitochondria. Treatment of seedlings with MV caused rapid oxidation in chloroplasts and, subsequently, in the cytosol and mitochondria. MV-induced oxidation was significantly boosted by illumination with actinic light, and largely abolished by inhibitors of photosynthetic electron transport. MV also induced autonomous oxidation in the mitochondrial matrix in an electron transport chain activity-dependent manner that was milder than the oxidation triggered in chloroplasts by the combination of MV and light. In vivo redox biosensing resolves the spatiotemporal dynamics of compartmental responses to local ROS generation and provides a basis for understanding how compartment-specific redox dynamics might operate in retrograde signaling and stress acclimation in plants. Methyl viologen-induced photo-oxidative stress increases hydrogen peroxide and oxidation of glutathione in chloroplasts, cytosol, and mitochondria, as well as autonomous oxidation in mitochondria. 相似文献
545.
546.
547.
548.
E. K. Garger V. Kashpur G. Belov V. Demchuk J. Tschiersch F. Wagenpfeil H. G. Paretzke F. Besnus W. Holländer J. Martinez-Serrano I. Vintersved 《Radiation and environmental biophysics》1997,36(3):139-148
Results of measurements of the resuspended radioactive aerosols in the Chernobyl area are presented which were obtained soon
after the Chernobyl reactor accident and in a European project in 1992–1993. The measurements were carried out with the intention
of obtaining a data base for dose assessment of resuspended radioactive particles. Potential significant dose contributions
may result from inhalation and secondary contamination due to resuspended radionuclides. In this first article of a series
of three papers, the instrumentation and the measurement uncertainties are discussed. An effort was made to sample quantitatively
giant aerosol particles (particles larger than 10 μm aerodynamic diameter) as well. The comparison of the samplers shows,
in general, an agreement of concentration measurements of 137Cs and 7Be within a factor of two. One sampler was identified with larger discrepancies and needs additional investigation of its
sampling characteristics; for another device, the recalibration of the analysing system is recommended. Ordinary integrating
samplers have a loss of about 30% in 137Cs activity compared to an isokinetic sampler collecting giant particles as well. The mean ratio of 137Cs activity concentration between an instrument sampling only particles larger than 10 μm and an ordinary integrating sampler
is 0.39 ± 0.15 during anthropogenic-enhanced resuspension. These findings demonstrate the significant contribution of giant
particles to resuspended airborne radioactivity. The results of this study concerning integral measurements during wind-driven
resuspension proved to be in good agreement with previously published data on resuspension.
Received: 15 May 1997 / Accepted: 4 August 1997 相似文献
549.
Alfred Bürgi Patrizia Frei Gaston Theis Evelyn Mohler Charlotte Braun‐Fahrländer Jürg Fröhlich Georg Neubauer Matthias Egger Martin Röösli 《Bioelectromagnetics》2010,31(3):226-236
We present a geospatial model to predict the radiofrequency electromagnetic field from fixed site transmitters for use in epidemiological exposure assessment. The proposed model extends an existing model toward the prediction of indoor exposure, that is, at the homes of potential study participants. The model is based on accurate operation parameters of all stationary transmitters of mobile communication base stations, and radio broadcast and television transmitters for an extended urban and suburban region in the Basel area (Switzerland). The model was evaluated by calculating Spearman rank correlations and weighted Cohen's kappa (κ) statistics between the model predictions and measurements obtained at street level, in the homes of volunteers, and in front of the windows of these homes. The correlation coefficients of the numerical predictions with street level measurements were 0.64, with indoor measurements 0.66, and with window measurements 0.67. The kappa coefficients were 0.48 (95%‐confidence interval: 0.35–0.61) for street level measurements, 0.44 (95%‐CI: 0.32–0.57) for indoor measurements, and 0.53 (95%‐CI: 0.42–0.65) for window measurements. Although the modeling of shielding effects by walls and roofs requires considerable simplifications of a complex environment, we found a comparable accuracy of the model for indoor and outdoor points. Bioelectromagnetics 31:226–236, 2010. © 2009 Wiley‐Liss, Inc. 相似文献
550.
Herlânder Azevedo Alberto Dias Rui Manuel Tavares 《Plant Cell, Tissue and Organ Culture》2008,93(1):115-121
We report the establishment of a Pinus pinaster (Ait.) cell suspension culture in a modified MS medium supplemented with 2 mg ml−1 2,4-D and 1 mg ml−1 BA. Calli were obtained from seedling root segments and established a friable isodiametric cell suspension, suitable for in vitro studies
of maritime pine at the cellular level. Growth (dry weight), cell viability, pH, and nutrient consumption: carbon source (sucrose,
fructose and glucose), nitrogen source (ammonia and nitrate) and phosphate were monitored over 24 h. Suspension cells exhibited
a 15-day exponential growth stage, during which a biphasic consumption profile was observed for all nutrients. Phosphate was
the first limiting nutrient and preferable consumption was observed for glucose over fructose and nitrate over ammonium. 相似文献