全文获取类型
收费全文 | 1420篇 |
免费 | 192篇 |
出版年
2022年 | 17篇 |
2021年 | 29篇 |
2020年 | 17篇 |
2019年 | 37篇 |
2018年 | 43篇 |
2017年 | 34篇 |
2016年 | 49篇 |
2015年 | 66篇 |
2014年 | 66篇 |
2013年 | 77篇 |
2012年 | 89篇 |
2011年 | 78篇 |
2010年 | 79篇 |
2009年 | 57篇 |
2008年 | 70篇 |
2007年 | 78篇 |
2006年 | 69篇 |
2005年 | 58篇 |
2004年 | 58篇 |
2003年 | 41篇 |
2002年 | 49篇 |
2001年 | 26篇 |
2000年 | 44篇 |
1999年 | 28篇 |
1998年 | 21篇 |
1997年 | 9篇 |
1996年 | 18篇 |
1995年 | 10篇 |
1994年 | 15篇 |
1993年 | 12篇 |
1992年 | 19篇 |
1991年 | 22篇 |
1990年 | 21篇 |
1989年 | 17篇 |
1988年 | 13篇 |
1987年 | 9篇 |
1986年 | 14篇 |
1985年 | 15篇 |
1984年 | 12篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1980年 | 9篇 |
1977年 | 12篇 |
1976年 | 8篇 |
1975年 | 6篇 |
1973年 | 8篇 |
1972年 | 9篇 |
1971年 | 5篇 |
1969年 | 9篇 |
1967年 | 7篇 |
排序方式: 共有1612条查询结果,搜索用时 15 毫秒
161.
Joel Vega‐Rodriguez Davinia Perez‐Barreto Antonio Ruiz‐Reyes Marcelo Jacobs‐Lorena 《Cellular microbiology》2015,17(11):1594-1604
Malaria remains one of the most devastating infectious diseases, killing up to a million people every year. Whereas much progress has been made in understanding the life cycle of the parasite in the human host and in the mosquito vector, significant gaps of knowledge remain. Fertilization of malaria parasites, a process that takes place in the lumen of the mosquito midgut, is poorly understood and the molecular interactions (receptor–ligand) required for Plasmodium fertilization remain elusive. By use of a phage display library, we identified FG1 (Female Gamete peptide 1), a peptide that binds specifically to the surface of female Plasmodium berghei gametes. Importantly, FG1 but not a scrambled version of the peptide, strongly reduces P. berghei oocyst formation by interfering with fertilization. In addition, FG1 also inhibits P. falciparum oocyst formation suggesting that the peptide binds to a molecule on the surface of the female gamete whose structure is conserved. Identification of the molecular interactions disrupted by the FG1 peptide may lead to the development of novel malaria transmission‐blocking strategies. 相似文献
162.
Gustavo Ciudad Isaac Reyes Milko A. Jorquera Laura Azócar Lukas Y. Wick Rodrigo Navia 《World journal of microbiology & biotechnology》2011,27(11):2505-2512
A novel three-phase solid–gas–liquid bioreactor (SGLB) concept using gaseous alcohol and liquid rapeseed oil with immersed
microorganisms overlying a nutrient agar phase (solid) is proposed for biodiesel (fatty acid alkyl esters, FAAE) production
based on the high hydrophobicity and negative surface charge showed by the fungi Rhizopus oryzae. This novel bioreactor was thought to increase oil bioavailability and decrease alcohol toxicity for effective microbial
growth, reaching high yields of FAAE production without any pretreatment. High growth rates were reached for R. oryzae using a SGLB simultaneously reaching a high FAAE production yield, up to 50% using methanol and up to 70% using ethanol at
144 h of incubation at 20°C. To compare the effect of gaseous alcohol, the same experiments were carried out in a three-phase
solid–liquid–liquid bioreactor (SLLB), where the alcohol was added in liquid phase, showing significant R. oryzae growth but no FAAE formation. This suggests that the inhibitory effect of alcohol is more significant in lipase activity
than in R. oryzae growth, and the use of alcohol in gaseous phase may decrease both of them. The experimental procedure using SGLB showed that
when R. oryzae is maintained alive, it can catalyze at the same time the hydrolysis, esterification and transesterification of triglycerides
from rapeseed oil, but its activity strongly depends on the used growth media. Therefore, the application of gaseous alcohol
coupled with R. oryzae as immobilized whole cell catalysts may be a potential alternative to the use of commercial lipases for biodiesel production. 相似文献
163.
164.
Zeins, the prolamin storage proteins found in maize (Zea mays), accumulate in accretions called protein bodies inside the endoplasmic reticulum (ER) of starchy endosperm cells. We found that genes encoding zeins, α-globulin, and legumin-1 are transcribed not only in the starchy endosperm but also in aleurone cells. Unlike the starchy endosperm, aleurone cells accumulate these storage proteins inside protein storage vacuoles (PSVs) instead of the ER. Aleurone PSVs contain zein-rich protein inclusions, a matrix, and a large system of intravacuolar membranes. After being assembled in the ER, zeins are delivered to the aleurone PSVs in atypical prevacuolar compartments that seem to arise at least partially by autophagy and consist of multilayered membranes and engulfed cytoplasmic material. The zein-containing prevacuolar compartments are neither surrounded by a double membrane nor decorated by AUTOPHAGY RELATED8 protein, suggesting that they are not typical autophagosomes. The PSV matrix contains glycoproteins that are trafficked through a Golgi-multivesicular body (MVB) pathway. MVBs likely fuse with the multilayered, autophagic compartments before merging with the PSV. The presence of similar PSVs also containing prolamins and large systems of intravacuolar membranes in wheat (Triticum aestivum) and barley (Hordeum vulgare) starchy endosperm suggests that this trafficking mechanism may be common among cereals. 相似文献
165.
Ana E Bergues Pupo Juan Bory Reyes Luis E Bergues Cabrales Jesús M Bergues Cabrales 《Biomedical engineering online》2011,10(1):1-14
Background
During the cardiac cycle, the heart normally produces repeatable physiological sounds. However, under pathologic conditions, such as with heart valve stenosis or a ventricular septal defect, blood flow turbulence leads to the production of additional sounds, called murmurs. Murmurs are random in nature, while the underlying heart sounds are not (being deterministic).Innovation
We show that a new analytical technique, which we call Digital Subtraction Phonocardiography (DSP), can be used to separate the random murmur component of the phonocardiogram from the underlying deterministic heart sounds.Methods
We digitally recorded the phonocardiogram from the anterior chest wall in 60 infants and adults using a high-speed USB interface and the program Gold Wave http://www.goldwave.com. The recordings included individuals with cardiac structural disease as well as recordings from normal individuals and from individuals with innocent heart murmurs. Digital Subtraction Analysis of the signal was performed using a custom computer program called Murmurgram. In essence, this program subtracts the recorded sound from two adjacent cardiac cycles to produce a difference signal, herein called a "murmurgram". Other software used included Spectrogram (Version 16), GoldWave (Version 5.55) as well as custom MATLAB code.Results
Our preliminary data is presented as a series of eight cases. These cases show how advanced signal processing techniques can be used to separate heart sounds from murmurs. Note that these results are preliminary in that normal ranges for obtained test results have not yet been established.Conclusions
Cardiac murmurs can be separated from underlying deterministic heart sounds using DSP. DSP has the potential to become a reliable and economical new diagnostic approach to screening for structural heart disease. However, DSP must be further evaluated in a large series of patients with well-characterized pathology to determine its clinical potential. 相似文献166.
167.
The responses of neurons in sensory cortex depend on the summation of excitatory and inhibitory synaptic inputs. How the excitatory and inhibitory inputs scale with stimulus depends on the network architecture, which ranges from the lateral inhibitory configuration where excitatory inputs are more narrowly tuned than inhibitory inputs, to the co-tuned configuration where both are tuned equally. The underlying circuitry that gives rise to lateral inhibition and co-tuning is yet unclear. Using large-scale network simulations with experimentally determined connectivity patterns and simulations with rate models, we show that the spatial extent of the input determined the configuration: there was a smooth transition from lateral inhibition with narrow input to co-tuning with broad input. The transition from lateral inhibition to co-tuning was accompanied by shifts in overall gain (reduced), output firing pattern (from tonic to phasic) and rate-level functions (from non-monotonic to monotonically increasing). The results suggest that a single cortical network architecture could account for the extended range of experimentally observed response types between the extremes of lateral inhibitory versus co-tuned configurations. 相似文献
168.
Molecular cloning of IGF-1 and IGF-1 receptor and their expression pattern in the Chilean flounder (Paralichthys adspersus) 总被引:1,自引:0,他引:1
169.
Angela Taboada D. Johan Kotze José M. Salgado Reyes Tárrega 《Journal of Insect Conservation》2011,15(4):573-590
Species rich semi-natural grasslands are disappearing across Europe, affecting invertebrate diversity negatively. In NW Spain,
the recent abandonment of traditional farming practices and the gradual decrease in grazing pressures are reducing the number
and extent of montane grasslands. In this context, we investigated the composition of carabid beetle (Coleoptera, Carabidae)
assemblages that inhabit semi-natural grasslands situated in long-term managed oak and beech forested landscapes. According
to their spatial arrangement, the studied grasslands were classified into: (1) interior or gap grasslands (small and completely
surrounded by continuous forest) and (2) exterior grasslands (large and connected to a variety of habitat types). Our results
indicate that, within each forested landscape, the gap and exterior grasslands harboured particular carabid assemblages (i.e.
exclusive or abundantly collected species), which were also distinct from the surrounding forest carabid fauna. Dissimilarities
between gap and exterior grasslands in each landscape suggest great carabid diversity at the regional scale. We also detected
species-specific responses as several carabids were mainly associated with gap or exterior grasslands. Consequently, in highly
modified forested landscapes, semi-natural grassland remnants may constitute great value for the protection of the carabid
fauna. Specifically, we recommend conservation strategies that preserve variety in grassland features and maintain proper
management activities to prevent the loss of specialised species and a decrease in regional carabid diversity. 相似文献
170.