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排序方式: 共有71条查询结果,搜索用时 15 毫秒
1.
Tissue-specific and developmental regulation of rod opsin chimeric genes in transgenic mice. 总被引:13,自引:0,他引:13
Chimeric gene fusions between 4.4 kb of rod opsin 5' flanking sequence fused to a diphtheria toxin gene and 4.4 kb or 500 bp of rod opsin 5' flanking sequence fused to the E. coli IacZ gene were used to generate transgenic mice for analysis of cell type-specific expression and temporal and spatial distribution of reporter gene product during retinal development. Opsin-diphtheria toxin transgene expression evoked photoreceptor-specific cell death. The 4.4 kb opsin-IacZ transgene followed temporal and spatial gradients of expression that approximate opsin expression. The 500 bp opsin fragment targeted expression to photoreceptors, but expression was weaker and nonuniform, suggesting that elements located upstream may be required for enhanced and uniform spatial expression. 相似文献
2.
3.
Michelle Lem Jason B. Coe Derek B. Haley Elizabeth Stone William O'Grady 《Anthrozo?s》2016,29(1):123-136
Street-involved youth represent a particularly vulnerable subsection of the homeless population and are at increased risk of health problems, substance abuse, and depression. Qualitative research has demon- strated that animal companions help homeless youth cope with loneliness, are motivators for positive change, such as decreasing drug or alcohol use, provide unconditional love without judgement, and improve youths’ sense of health. To quantitatively investigate the association between depression and pet ownership among street-involved youth, a cross-sectional study was per- formed with a convenience sample of 189 street-involved youths who were surveyed in four cities in Ontario, Canada, 89 of whom were pet owners and 100 of whom were not. Logistic regression modelling found pet ownership to be negatively associated with depression in the study population (controlling for gender, regular use of drugs, and time since youth left home), with the odds of being depressed three times greater for youths who did not own pets. While pet ownership among street-involved youth has many liabilities, includ- ing impairing youths’ ability to access shelter, services, and housing and employment opportunities, companion animals may offer both physical and psychosocial benefits that youth have difficult attaining. This finding highlights the importance of increased awareness among youth service providers of the potential impacts of pet ownership for street-involved youth. 相似文献
4.
Elodie Poiroux Christine Cavaro-Ménard Stéphanie Leruez Jean Michel Lemée Isabelle Richard Mickael Dinomais 《PloS one》2015,10(11)
Many of the brain structures involved in performing real movements also have increased activity during imagined movements or during motor observation, and this could be the neural substrate underlying the effects of motor imagery in motor learning or motor rehabilitation. In the absence of any objective physiological method of measurement, it is currently impossible to be sure that the patient is indeed performing the task as instructed. Eye gaze recording during a motor imagery task could be a possible way to “spy” on the activity an individual is really engaged in. The aim of the present study was to compare the pattern of eye movement metrics during motor observation, visual and kinesthetic motor imagery (VI, KI), target fixation, and mental calculation. Twenty-two healthy subjects (16 females and 6 males), were required to perform tests in five conditions using imagery in the Box and Block Test tasks following the procedure described by Liepert et al. Eye movements were analysed by a non-invasive oculometric measure (SMI RED250 system). Two parameters describing gaze pattern were calculated: the index of ocular mobility (saccade duration over saccade + fixation duration) and the number of midline crossings (i.e. the number of times the subjects gaze crossed the midline of the screen when performing the different tasks). Both parameters were significantly different between visual imagery and kinesthesic imagery, visual imagery and mental calculation, and visual imagery and target fixation. For the first time we were able to show that eye movement patterns are different during VI and KI tasks. Our results suggest gaze metric parameters could be used as an objective unobtrusive approach to assess engagement in a motor imagery task. Further studies should define how oculomotor parameters could be used as an indicator of the rehabilitation task a patient is engaged in. 相似文献
5.
Bonhomme J Le Goff L Lemée V Gargala G Ballet JJ Favennec L 《Parasitology international》2011,60(3):327-330
The intestinal protozoan Giardia duodenalis includes 2 genetically distinct assemblages, A and B, which are responsible for human infections. Little is known so far on the genotypes of G. duodenalis human isolates in France. The present characterization of 19 French clinical isolates was aimed at determining their genotype patterns and associations with clinical symptoms, and in vivo metronidazole resistance, respectively. Based on both triose-phosphate isomerase (tpi) and β-giardin (bg) gene sequences, twelve isolates were identified as assemblage A, and 7 as assemblage B for the 2 gene loci. Sub-genotyping heterogeneities were observed in 15/19 isolates attributed to either A or B assemblage. They include frequent mismatches and intra-assemblage discordances and mixed positions, which were found more frequently in tpi than in bg sequences, and in assemblage B than in assemblage A sequences. No association was found between sub-genotypes, clinical symptoms and metronidazole sensitivity. Present data underline the need for improvements in the standardization of G. duodenalis multilocus genotyping approach for further molecular epidemiologic studies of giardiasis. 相似文献
6.
Judith S. Renes Maria A. J. de Ridder Petra E. Breukhoven Annemieke J. Lem Anita C. S. Hokken-Koelega 《PloS one》2012,7(12)
Background
Growth hormone (GH) treatment has become a frequently applied growth promoting therapy in short children born small for gestational age (SGA). Children born SGA have a higher risk of developing attention deficit hyperactivity disorder (ADHD). Treatment of ADHD with methylphenidate (MP) has greatly increased in recent years, therefore more children are being treated with GH and MP simultaneously. Some studies have found an association between MP treatment and growth deceleration, but data are contradictory.Objective
To explore the effects of MP treatment on growth in GH-treated short SGA childrenMethods
Anthropometric measurements were performed in 78 GH-treated short SGA children (mean age 10.6 yr), 39 of whom were also treated with MP (SGA-GH/MP). The SGA-GH/MP group was compared to 39 SGA-GH treated subjects. They were matched for sex, age and height at start of GH, height SDS at start of MP treatment and target height SDS. Serum insulin-like growth factor-I (IGF-I) and IGF binding protein-3 (IGFBP-3) levels were yearly determined. Growth, serum IGF-I and IGFBP-3 levels during the first three years of treatment were analyzed using repeated measures regression analysis.Results
The SGA-GH/MP group had a lower height gain during the first 3 years than the SGA-GH subjects, only significant between 6 and 12 months of MP treatment. After 3 years of MP treatment, the height gain was 0.2 SDS (±0.1 SD) lower in the SGA-GH/MP group (P = 0.17). Adult height was not significantly different between the SGA-GH/MP and SGA-GH group (−1.9 SDS and −1.9 SDS respectively, P = 0.46). Moreover, during the first 3 years of MP treatment IGF-I and IGFBP-3 measurements were similar in both groups.Conclusion
MP has some negative effect on growth during the first years in short SGA children treated with GH, but adult height is not affected. 相似文献7.
G. Lemée 《Plant Ecology》1953,4(4):237-238
Sans résumé 相似文献
8.
Interactive controls of herbivory and fluvial dynamics on landscape vegetation patterns on the Tanana River floodplain, interior Alaska 总被引:2,自引:0,他引:2
Lem G. Butler † Knut Kielland T. Scott Rupp Thomas A. Hanley 《Journal of Biogeography》2007,34(9):1622-1631
Aim We examined the interactive effects of mammalian herbivory and fluvial dynamics on vegetation dynamics and composition along the Tanana River in interior Alaska.
Location Model parameters were obtained from field studies along the Tanana River, Alaska between Fairbanks (64°50.50' N, 147°43.30' W) and Manley Hot Springs (65°0.0' N, 150°36.0' W).
Methods We used a spatially explicit model of landscape dynamics (ALFRESCO) to simulate vegetation changes on a 1-year time-step. The model was run for 250 years and was replicated 100 times.
Results Increases in herbivory decreased the proportion of early successional vegetation and increased the proportion of late successional vegetation on the simulated landscape. Erosion and accretion worked as antagonists to herbivory, increasing the amount of early successional vegetation and decreasing the amount of late successional vegetation. However, the interactive effects of herbivory and erosion/accretion were especially important in determining system response, particularly in early seral vegetation types. High erosion rates, when coupled with low herbivory, greatly increased the proportion of willow on the landscape. When coupled with high herbivory, however, they greatly increased the proportion of alder on the landscape. At low levels of herbivory, alder abundance peaked at intermediate levels of erosion/accretion.
Main conclusions Neither erosion/accretion nor herbivory produced consistent landscape patterns that could be predicted independently of the other. These findings underscore the importance of the interactive effects of biotic and abiotic disturbances in shaping large-scale landscape vegetation patterns in boreal floodplain ecosystems – systems traditionally thought to be driven primarily by abiotic disturbance alone. 相似文献
Location Model parameters were obtained from field studies along the Tanana River, Alaska between Fairbanks (64°50.50' N, 147°43.30' W) and Manley Hot Springs (65°0.0' N, 150°36.0' W).
Methods We used a spatially explicit model of landscape dynamics (ALFRESCO) to simulate vegetation changes on a 1-year time-step. The model was run for 250 years and was replicated 100 times.
Results Increases in herbivory decreased the proportion of early successional vegetation and increased the proportion of late successional vegetation on the simulated landscape. Erosion and accretion worked as antagonists to herbivory, increasing the amount of early successional vegetation and decreasing the amount of late successional vegetation. However, the interactive effects of herbivory and erosion/accretion were especially important in determining system response, particularly in early seral vegetation types. High erosion rates, when coupled with low herbivory, greatly increased the proportion of willow on the landscape. When coupled with high herbivory, however, they greatly increased the proportion of alder on the landscape. At low levels of herbivory, alder abundance peaked at intermediate levels of erosion/accretion.
Main conclusions Neither erosion/accretion nor herbivory produced consistent landscape patterns that could be predicted independently of the other. These findings underscore the importance of the interactive effects of biotic and abiotic disturbances in shaping large-scale landscape vegetation patterns in boreal floodplain ecosystems – systems traditionally thought to be driven primarily by abiotic disturbance alone. 相似文献
9.
William J. Foley Allen McIlwee Ivan Lawler Lem Aragones Andrew P. Woolnough Nils Berding 《Oecologia》1998,116(3):293-305
Many ecological studies rely heavily on chemical analysis of plant and animal tissues. Often, there is limited time and money
to perform all the required analyses and this can result in less than ideal sampling schemes and poor levels of replication.
Near infrared reflectance spectroscopy (NIRS) can relieve these constraints because it can provide quick, non-destructive
and quantitative analyses of an enormous range of organic constituents of plant and animal tissues. Near infrared spectra
depend on the number and type of CH, NH and OH bonds in the material being analyzed. The spectral features are then combined with reliable compositional or functional
analyses of the material in a predictive statistical model. This model is then used to predict the composition of new or unknown
samples. NIRS can be used to analyze some specific elements (indirectly – e.g., N as protein) or well-defined compounds (e.g.,
starch) or more complex, poorly defined attributes of substances (e.g., fiber, animal food intake) have also been successfully
modeled with NIRS technology. The accuracy and precision of the reference values for the calibration data set in part determines
the quality of the predictions made by NIRS. However, NIRS analyses are often more precise than standard laboratory assays.
The use of NIRS is not restricted to the simple determination of quantities of known compounds, but can also be used to discriminate
between complex mixtures and to identify important compounds affecting attributes of interest. Near infrared reflectance spectroscopy
is widely accepted for compositional and functional analyses in agriculture and manufacturing but its utility has not yet
been recognized by the majority of ecologists conducting similar analyses. This paper aims to stimulate interest in NIRS and
to illustrate some of the enormous variety of uses to which it can be put. We emphasize that care must be taken in the calibration
stage to prevent propagation of poor analytical work through NIRS, but, used properly, NIRS offers ecologists enormous analytical
power.
Received: 10 October 1997 / Accepted: 12 May 1998 相似文献
10.
Keqing Huang Lichun Chang Yihui Hou Wenzhong Ji Thành Trần-Phú Anh Dinh Bui Azul Osorio Mayon Wei Wang Olivier Lee Cheong Lem Dang-Thuan Nguyen Grace Dansoa Tabi Leiping Duan Yun Liu Heping Shen Junliang Yang Thomas P. White Kylie R. Catchpole Klaus J. Weber The Duong 《Liver Transplantation》2024,14(17):2304073
Due to the limited interface contact and weak interfacial interaction, planar heterojunction perovskite solar cells (PSCs) have space for further improvement. Herein, a structural and chemical crosslinking interface is proposed and constructed by introducing an extra layer, which blends tin dioxide (SnO2) nanoparticles with chloride salts. Since the incorporated materials can be dissolved during the fabrication of perovskite, the quality of perovskite films is improved, leading to larger grain size and reduced trap-state density. Also, more chloride ions at the SnO2/perovskite interface are observed and the interaction between Cl− and Sn4+ is confirmed. It results in more pronounced n-type SnO2 with better conductivity and deeper conduction bands, leading to preferable energy level alignment between SnO2 and perovskite. Consequently, the open-circuit voltage and fill factor of the devices increase, and target cells present better stability, retaining 98% of initial efficiencies after >10 000 h storage in dry air (≈5% relative humidity) and maintaining 85.50% of the initial efficiency after 1000 h of operation under light. This strategy enables the achievement of 25.28% efficiency with a low bandgap (1.53 eV) perovskite composition, and it is confirmed to be universal when other related materials are utilized. 相似文献