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81.
We formulate and analyse a model for infectious diseases transmitted by asymptomatic carriers finding, that if harmless and pathogenic strains of the infected agent compete, frequent outbreaks of the pathogenic strains can occur. A counterintuitively high number of clustered outbreaks at low pathogenicity in our model compares well with observations in diseases with severe and often fatal results for the host, as for example in meningitis. These clustered outbreaks can be described by the typical scaling behaviour around criticality. The epidemic model is a susceptible-infected-recovered system (SIR) for the harmless infective agent, acting as a background to a mutant strain Y which occasionally creates severely affected hosts X. The full system of SIRYX is described in the master equation framework, confirming limiting assumptions about a reduced YX-system with the SIR-system in stationarity. In this limiting case we can analytically show convergence to power law scaling typical for critical states, as well as the divergence of the variance of outbreaks near criticality. These large fluctuations of outbreaks of accidental pathogens as mutants of otherwise harmless commensal organisms is the challenging new feature of our model for future epidemiology of diseases like meningococcal disease. 相似文献
82.
Smales CM Birch JR Racher AJ Marshall CT James DC 《Biochemical and biophysical research communications》2003,306(4):1050-1055
The relationship between spot volume and variation for all protein spots observed on large format 2D gels when utilising silver stain technology and a model system based on mammalian NSO cell extracts is reported. By running multiple gels we have shown that the reproducibility of data generated in this way is dependent on individual protein spot volumes, which in turn are directly correlated with the coefficient of variation. The coefficients of variation across all observed protein spots were highest for low abundant proteins which are the primary contributors to process error, and lowest for more abundant proteins. Using the relationship between spot volume and coefficient of variation we show it is necessary to calculate variation for individual protein spot volumes. The inherent limitations of silver staining therefore mean that errors in individual protein spot volumes must be considered when assessing significant changes in protein spot volume and not global error. 相似文献
83.
B. Reyers D.H.K. Fairbanks K.J. Wessels A.S. Van Jaarsveld 《Biodiversity and Conservation》2002,11(5):769-793
Existing complementarity-based reserve selection techniquesconcerned with maximal biodiversity representation within minimum landarea do not necessarily ensure the long-term maintenance ofbiodiversity. These approaches often ignore the maintenance of naturalprocesses, turnover of feature diversity and the need to minimisethreats within conservation areas. We address these three emergentissues in the identification of potential avian conservation areas inthe Northern Province of South Africa, by combining ordination andspatial autocorrelation analyses, as well as land transformation datainto complementarity-based reserve selection techniques. Existingconservation areas are biased and inefficient and complementarity-basedmethods do little to correct this skew. The inclusion of speciesassemblage structure as well as the underlying environmental gradientsensures a conservation area network that strives to maintain bothbiodiversity pattern and process. Spatial autocorrelation analysisallows for the identification of areas with high diversity,important areas for the long-term maintenance of biodiversity. Theinclusion of land transformation data leads to viable conservation areanetworks and highlights areas of potential conflict between biodiversityconservation interests and human land-use issues. These combinedimprovements on complementarity-based reserve selection techniques bringus a step closer to ensuring the long-term maintenance of biodiversitywithin conservation areas in the northern province. 相似文献
84.
Mariana N. São Pedro Mafalda S. Santos Michel H. M. Eppink Marcel Ottens 《Biotechnology journal》2023,18(1):2200332
A major challenge in the transition to continuous biomanufacturing is the lack of process analytical technology (PAT) tools which are able to collect real-time information on the process and elicit a response to facilitate control. One of the critical quality attributes (CQAs) of interest during monoclonal antibodies production is aggregate formation. The development of a real-time PAT tool to monitor aggregate formation is then crucial to have immediate feedback and process control. Miniaturized sensors placed after each unit operation can be a powerful solution to speed up an analytical measurement due to their characteristic short reaction time. In this work, a micromixer structure capable of mixing two streams is presented, to be employed in the detection of mAb aggregates using fluorescent dyes. Computational fluid dynamics (CFD) simulations were used to compare the mixing performance of a series of the proposed designs. A final design of a zigzag microchannel with 45° angle was reached and this structure was subsequently fabricated and experimentally validated with colour dyes and, later, with a FITC-IgG molecule. The designed zigzag micromixer presents a mixing index of around 90%, obtained in less than 30 seconds. Therefore, a micromixer channel capable of a fast and efficient mixing is hereby demonstrated, to be used as a real-time PAT tool for a fluorescence based detection of protein aggregation. 相似文献
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Mathieu Streefland Dirk E. Martens E. Coen Beuvery René H. Wijffels 《Engineering in Life Science》2013,13(3):212-223
The process analytical technology (PAT) initiative is now 10 years old. This has resulted in the development of many tools and software packages dedicated to PAT application on pharmaceutical processes. However, most applications are restricted to small molecule drugs, mainly for the relatively simple process steps like drying or tableting where only a limited number of parameters need to be controlled. A big challenge for PAT still lies in applications for biopharmaceuticals and then especially in the cultivation process step, where the quality of a biopharmaceutical product is largely determined. This review gives an overview of the currently available tools for monitoring and controlling the biopharmaceutical cultivation step and of the main challenges for the most common cell platforms (i.e. Escherichia coli, yeast, and mammalian cells) used in biopharmaceutical manufacturing. The real challenge is to understand how intracellular mechanisms (from synthesis to excretion) influence the quality of biopharmaceuticals and how these mechanisms can be monitored and controlled to yield the desired end product quality. Modern “omics” tools and advanced process analyzers have opened up the way for PAT applications for the biopharmaceutical cultivation process step. 相似文献
90.
Jeannette?Van?RijsoortEmail author Zhang?Jinfeng 《Biodiversity and Conservation》2005,14(11):2543-2573
Recent international forest policies stimulate involvement of communities in forest management as a strategy to improve biodiversity
conservation and the quality of local livelihoods. Increasingly, the role of local people in monitoring forest resources is
also acknowledged. This paper presents a participatory resources monitoring (PRM) system developed and implemented by representatives
of 12 villages, six each within and adjacent to two nature reserves in Yunnan, China. The short-term objectives are to monitor
resource and wildlife abundance, resource use, wildlife damage to crops, and land use. Main methods used by the village monitoring
team are: (1) observation through forest walk, (2) village interview, and (3) market survey. Monitoring is implemented throughout
the year to fit in the daily work of villagers. Staff from the nature reserve or forestry bureau provide support by visiting
the villages several days per year. Results indicate that participatory monitoring is a valuable tool for villagers to engage
in self-owned management actions. We discuss how monitoring is also a process which could lead to social change. Based on
narratives we suggest that participatory monitoring builds trust between stakeholders, changes perceptions and attitudes and
leads to more democratic and transparent decision-making. In discussing accuracy, we argue that all stakeholders perceive
and interpret nature differently based on different worldviews, knowledge systems, values and beliefs. We argue that if participatory
monitoring is to be sustainable, community-based monitoring – preferably linked to scientific monitoring and patrolling –
should be designed as a discursive institution where the process of building social capital and inter-actor learning is extremely
important. Finally, we briefly reflect upon efforts to scale up participatory monitoring. 相似文献